Fellow in Advanced Rhinology and Anterior Skull Base Surgery  University of Miami Miller School of Medicine   Director of Rhinology and Endoscopic Skull Base Surgery  Department of Otolaryngology—Head and Neck Surgery  Virginia Mason Medical Center   Director, Rhinology and Endoscopic Skull Base Program  Professor and Vice Chairman   Chief of Pediatric Otolaryngology  Residency Program Director  Department of Otolaryngology  University of Florida College of Medicine  Gainesville, Florida   Co-Director, Endoscopic Skull Base Surgery Program  Department of Otolaryngology—Head and Neck Surgery  Professor of Neurological Surgery   Professor of Ophthalmology and Visual Science  Neurological Institute of New Jersey   Director, Rhinology and Endoscopic Skull Base Surgery  Department of Otolaryngology—Head and Neck Surgery  Department of Neurosurgery   Rhinology & Endoscopic Skull Base Surgery  Otolaryngology—Head and Neck Surgery Department  Faculty of Medicine, Zagazig University   Consultant of Rhinology & Endoscopic Skull Base Surgery  ORL-H&N and Skull Base Surgery Center    Arjuna B. Kuperan, MD  Houston Plastic Craniofacial & Sinus Surgery  Houston, Texas   Department of Otolaryngology—Head and Neck Surgery  Louisiana State University Health Sciences Center  Shreveport, Louisiana   Rhinology and Endoscopic Skull Base Surgery  Department of Otolaryngology-Head and Neck Surgery  New York University School of Medicine   Associate Professor of Otolaryngology—Head and Neck Surgery  Director, Center for Skull Base and Pituitary Surgery  Department of Neurological Surgery   Department of Otolaryngology—Head and Neck Surgery  Rutgers New Jersey Medical School   Rhinology, Sinus, and Endoscopic Skull Base Surgery Fellow  Department of Otolaryngology—Head and Neck Surgery  Neurological Institute of New Jersey   Fellow in Advanced Rhinology and Anterior Skull Base Surgery  University of Miami Miller School of Medicine    Transnasal sinus surgery began in 1886, when Miculitz! reported  on the endonasal fenestration of the maxillary sinus. A transnasal  approach to performing an ethmoidectomy was first reported in  1915 by Halle.’ Even then, it was immediately apparent that a  transnasal ethmoidectomy posed significant inherent risks for  the patient. Indeed, these risks were reported by Mosher? in 1929,  when he described intranasal ethmoidectomy as being “one of  the easiest operations to kill a patient.” Further reports have also  shown the wide variability in distances and dimensions among  virtually all the intranasal anatomic structures.*""   Hirschmann made the first attempt at nasal and sinus endoscopy  in 1901 using a modified cystoscope.'' In 1925, Maltz,'? a New  York rhinologist, used the term sinoscopy and advocated the  technique for diagnosis. However, endoscopic sinus surgery (ESS)  was introduced in the European literature in 1967 by Messerk-  linger,'? and was then further popularized by others.'*-?' In 1985,  Kennedy et al”? introduced the technique of functional endoscopic  sinus surgery (FESS) in the United States. Since then, there has  been an ongoing effort to refine and redefine the ESS technique  and to identify consistent anatomic landmarks to navigate within  the ethmoid sinuses and facilitate safe entry into the maxillary,  sphenoid, and frontal sinuses.?*-* This has led to further refinement  in transnasal endoscopic surgical technique beyond the confines  of the sinus cavities to address complicated inflammatory and  neoplastic processes of the skull base and orbit.   Although exceptions do exist, nowadays most rhinologists agree  that ESS for chronic rhinosinusitis should be a “disease-directed”  and a mucosal-sparing operation, recognizing the potential for  reestablishing drainage and mucosal recovery of the dependent  sinuses.'?'*'© The ostiomeatal complex theory states that most  inflammatory conditions of the maxillary, ethmoid, and frontal  sinuses arise from this common drainage pathway.'° Therefore,  the surgical procedure, when combined with appropriate medical  management, can be limited to an absolute minimum, and cor-  rection of ethmoid disease usually results in reestablishment of  drainage and mucosal recovery of the larger (dependent) sinuses.   In more advanced disease states (revision sinus surgery, sig-  nificant polyp disease, or neoplastic disease) mucosal preservation  may not always be possible, or even indicated. In such cases, severe  distortion of anatomy requires an enhanced understanding of  critical anatomic landmarks as one navigates endoscopically  through the nose and paranasal sinuses along the orbit and skull  base. Anatomic structures typically used in less diseased states  may not be appropriately used or even dependable when applied  to these types of cases. This dissection manual defines time-tested,    consistent, and reliable anatomic landmarks, which will keep  surgeons oriented as they proceed anteroposteriorly through the  nose, paranasal sinuses, skull base, and orbit.    1 Miculitz JV. Zur operativen Behandlung des Empyems der Highmorshohle. Dtsch Arch  Klin Med 1886;34:626-634.   2 Halle M. Die intranasalen operationen bei eitrigen erkrankungen der nebenhohlen  der nase. Arch Laryngol Rhinol 1915;29:73-112.   3 Mosher HP. The surgical anatomy of the ethmoidal labyrinth. Ann Otol Rhinol Laryngol  1929;38:869-901.   4 Van Alyea OE. The ostium maxillare: anatomic study of its surgical accessibility. Arch  Otolaryngol 1936;24:553-569.   5 Van Alyea OE. Ethmoid labyrinth: anatomic study, with consideration of the clinical  significance of its structural characteristics. Arch Otolaryngol 1939;29:881-902.   6 Van Alyea OE. Sphenoid sinus: anatomic study, with consideration of the clinical  significance of the structural characteristics of the sphenoid sinus. Arch Otolaryngol  1941;34:225-253.   7 Van Alyea OE. Nasal Sinuses: An Anatomic and Clinical Consideration. Baltimore:  Williams & Wilkins; 1951.   8 Myerson M. The natural orifice of the maxillary sinus. I. Anatomic studies. Arch  Otolaryngol 1932;15:80-91.   9 Hajek M. Pathologie und therapie der entzundlichen erkrankungen der nebenhohlen  der nase, 5th ed. Leipzig: Deuticke; 1926.   10 Neivert H. Symposium on maxillary sinus: Surgical anatomy of the maxillary sinus.  Laryngoscope 1930;40:1-4.   11 Draf W. Endoscopy of the Paranasal Sinuses. New York: Springer-Verlag; 1983.   13 Messerklinger W. Uber die drainage der menschlichen nasennebenholen unter normalen  und pathologischen bendingungen II: die stirnhole und ihr ausfuhrungssystem.  Monatssch Ohrenheilkd 1967;101:313-326.   14 Messerklinger W. Endosckopiche diagnose und chirurgie der rezidivierenden sinusitis.  In: Krajina Z, ed. Advances in Nose and Sinus Surgery. Zagreb, Yugoslavia: Zagreb  University; 1985.   15 Naumann H. Pathologische anatomie der chronischen rhinitis und sinusitis. In: Proceed-  ings VIII International Congress of Oto-Rhinolaryngology. Amsterdam, the Netherlands:  Excerpta Medica; 1965:80.   16 Stammberger H. Endoscopic endonasal surgery—concepts in treatment of recurring  rhinosinusitis. Part I. Anatomic and pathophysiologic considerations. Otolaryngol Head  Neck Surg 1986;94:143-147.   17 Stammberger H. Endoscopic endonasal surgery—concepts in treatment of recurring  rhinosinusitis. Part II. Surgical technique. Otolaryngol Head Neck Surg 1986;94:147-156.   18 Wigand ME, Steiner W, Jaumann MP. Endonasal sinus surgery with endoscopical control:  from radical operation to rehabilitation of the mucosa. Endoscopy 1978;10:255-260.   19 Wigand ME. Transnasal ethmoidectomy under endoscopical control. Rhinology 1981;  19:7-15.   20 Wigand ME. Endoscopic Surgery of the Paranasal Sinuses and Anterior Skull Base.  New York: Thieme; 1990.   21 Draf W. [Surgical treatment of the inflammatory diseases of the paranasal sinuses.  Indication, surgical technique, risks, mismanagement and complications, revision  surgery]. Arch Otorhinolaryngol 1982;235:133-305.   22 Kennedy DW, Zinreich SJ, Rosenbaum AE, Johns ME. Functional endoscopic sinus  surgery. Theory and diagnostic evaluation. Arch Otolaryngol 1985;111:576-582.   23 Rice DH, Schaefer SD. Endoscopic Paranasal Sinus Surgery. New York: Raven Press;  1988.   24 Rice DH. Basic surgical techniques and variations of endoscopic sinus surgery. Otolaryngol  Clin North Am 1989;22:713-726.   25 Schaefer SD. Endoscopic total sphenoethmoidectomy. Otolaryngol Clin North Am  1989;22:727-732.    Schaefer SD. An anatomic approach to endoscopic intranasal ethmoidectomy. Laryn-  goscope 1998;108(11 Pt 1):1628-1634.   May M, Schaitkin B, Kay SL. Revision endoscopic sinus surgery: six friendly surgical  landmarks. Laryngoscope 1994;104(6 Pt 1):766-767.   May M, Sobol SM, Korzec K. The location of the maxillary os and its importance to  the endoscopic sinus surgeon. Laryngoscope 1990;100(10 Pt 1):1037-1042.   Parsons D, Bolger W, Boyd E. The “ridge”—a safer entry to the sphenoid sinus during  functional endoscopic sinus surgery in children. Oper Tech Otolaryngol-Head Neck  Surg 1994;5:43-44,    Bolger WE, Keyes AS, Lanza DC. Use of the superior meatus and superior turbinate in  the endoscopic approach to the sphenoid sinus. Otolaryngol Head Neck Surg  1999;120:308-313.   Hosemann W, Gross R, Gode U, et al. The anterior sphenoid wall: relative anatomy  for sphenoidotomy. Am J Rhinol 1995;9:137-144.   Stankiewicz JA. The endoscopic approach to the sphenoid sinus. Laryngoscope  1989;99:218-221.    Historically, there have been two endoscopic surgical anatomic  approaches described to address chronic inflammatory disease of  the ethmoid, maxillary, and sphenoid sinuses: the anteroposterior  (AP) approach and the posteroanterior (PA) approach.'* As will  be seen later in this dissection manual, the approach that I suggest  using is essentially a hybrid of both of these approaches. This  hybrid approach brings to light the most important concepts gained  from these two historical approaches. The goal is to help inexpe-  rienced young surgeons gain confidence in their endoscopic surgical  skills, in order to perform a safe, methodical, stepwise surgery  that is individualized to the patient’s specific pathology and  anatomic findings.    Anteroposterior exenteration of the ethmoid sinuses is the tech-  nique most widely used in the United States.'? In this approach,  the surgeon begins with an anterior ethmoidectomy by removing  the uncinate process, bullar cells, and agger nasi cells, and occasion-  ally entering the frontal recess. The surgeon then proceeds as far  posteriorly as needed to remove the diseased ethmoid cells and  polyps and to establish drainage to the dependent sinuses that  are blocked. A limited maxillary antrostomy is typically not  performed until most ethmoid cells have been addressed. If a  sphenoidotomy is indicated, a transethmoidal operation through  the common wall of the sphenoid and posterior ethmoid sinus is  performed.   Proponents of the AP approach argue that this technique enables  the surgeon to address anterior ethmoidal disease without the  need for extensive surgery.'?° Some surgeons do not share this  view, however, arguing that patients frequently have pan sinus  disease affecting not only the anterior ethmoid’s dependent sinuses  (maxillary and frontal) but also the sphenoethmoidal recess and  surrounding ostia draining the posterior ethmoids and sphenoid  sinuses.° In the AP approach, the surgeon is taught to stay “infero-  medially,” as the ethmoidectomy proceeds posteriorly, to minimize  the chances of inadvertently penetrating the orbital wall or the  skull base. Yet the problem for the inexperienced surgeon is that  the anatomy is often distorted because of pathological conditions  or prior surgery. In addition, inexperienced surgeons may face  orientation difficulties with respect to how far inferomedially they  have to go, which can cause inadvertent intracranial penetration  through the posterior cribriform plate. Furthermore, during the  course of the surgical procedure, the nasal telescope or camera    may become rotated within the nose. Unsuspecting surgeons may  think that they are heading in an inferoposterior direction when  in fact they are following a superior or lateral trajectory toward  the skull base or orbit. In the absence of other consistent anatomic  landmarks as internal reference points, surgeons may fail to see  that they are improperly oriented.   Entering the sphenoid sinus through the inferomedial portion  of the posterior wall of the ethmoid sinus, just lateral to the superior  turbinate, is advised to avoid injury to the optic nerve and the  internal carotid artery, which lie behind the lateral portion of this  common wall. However, significant problems remain with entering  the sphenoid sinus through the AP approach. First, a transethmoidal  sphenoidotomy does not offer an optimal access; the bone of the  anterior wall of the sphenoid is thicker retroethmoidally than  paramedially adjacent to the nasal septum in the area of the natural  sphenoid ostium.’ Second, because this procedure is performed  relatively close to the optic nerve and the carotid artery, specific  anatomic variations in these skull-base structures may lead to  significant complications. Third, if the ostiomeatal complex theory  also applies to the sphenoethmoidal recess and the surrounding  ostia to the posterior sinuses (posterior ostiomeatal complex),  then whichever endoscopic surgical technique is selected must  also address the natural drainage areas of these sinuses. In other  words, the natural ostium of the sphenoid needs to be enlarged  rather than a new one created through the common wall of the  sphenoid and posterior ethmoid cells. Therefore, it would make  sense to stay medial to the superior turbinate, rather than lateral  to it, to access the natural ostium of the sphenoid.    Recognizing the potential difficulties with the AP approach,  especially with more extensive disease of the paranasal sinuses,  Wigand?4* described the PA approach. In this approach, the surgeon  initially opens the sphenoid sinus, beginning with a posterior  partial resection of the middle turbinate. The posterior ethmoid  sinus is opened by limited removal of the posterior free body of  the middle turbinate. The sphenoid is entered by using a suction  tip or probe with gentle pressure 1 to 2cm above the upper edge  of the posterior nasal choanal arch. Wigand noted that his technique  poses little danger of perforating the skull base because the rigid  plate of the sphenoid planum will be encountered if the surgeon  goes too high. Nevertheless, he advised against exposing the  posterior ethmoid cells as far as the ethmoid roof at this point.    Rather, he advocated first exposing and removing the anterior  wall of the sphenoid sinus. Once the roof of the sphenoid and  lateral wall are identified (as the superior and lateral limits of  dissection, respectively), a retrograde dissection of the ethmoid  cells is performed. Wigand described performing an antrostomy  as the last step of his surgical dissection through the posterior  fontanelle since this is a consistent reference point for safely  entering the maxillary sinus.   According to Wigand, the PA approach provides clear exposure  of the surgical field, reducing the risk of serious complications  and yielding reliable results without long-term crusting. This  approach, however, is more extensive than the AP approach,  irrespective of the extent of the disease. The technique involves  routine opening of the sphenoid, frontal, and maxillary sinuses  (a pan-sinus operation). It also requires a certain degree of precision  and experience in determining the exact location of the sphenoid  sinus ostium in the sphenoethmoidal recess. With advanced disease,  the anatomy in this area may be significantly distorted and the  superior and middle turbinate may be difficult to identify. The  mean distance from the sphenoid ostium to the skull base (posterior  cribriform) is 8mm (range, 3-17 mm). Thus, the sphenoid ostium    can be very close to the posterior cribriform, creating the potential  for inadvertent intracranial penetration when attempting to enter  the sphenoid too superiorly.®    1 Messerklinger W. Endosckopiche diagnose und chirurgie der rezidivierenden sinusitis.  In: Krajina Z, ed. Advances in Nose and Sinus Surgery. Zagreb, Yugoslavia: Zagreb  University; 1985.   2 Stammberger H. Endoscopic endonasal surgery—concepts in treatment of recurring  rhinosinusitis. Part II. Surgical technique. Otolaryngol Head Neck Surg 1986;94:147-156.   3  Wigand ME, Steiner W, Jaumann MP. Endonasal sinus surgery with endoscopical control:  from radical operation to rehabilitation of the mucosa. Endoscopy 1978;10:255-260.   4 Wigand ME. Endoscopic Surgery of the Paranasal Sinuses and Anterior Skull Base. New  York: Thieme; 1990.   5 Kennedy DW, Zinreich SJ, Rosenbaum AE, Johns ME. Functional endoscopic sinus surgery.  Theory and diagnostic evaluation. Arch Otolaryngol 1985;111:576-582.   6 Casiano RR. Correlation of clinical examination with computer tomography in paranasal  sinus disease. Am J Rhinol 1997;11:193-196.   7 Hosemann W, Gross R, Gode U, et al. The anterior sphenoid wall: relative anatomy for  sphenoidotomy. Am J Rhinol 1995;9:137-144.    nificance of the structural characteristics of the sphenoid sinus. Arch Otolaryngol  1941;34:225-253.    3 The Use of Anatomic Landmarks: A Stepwise Approach to the    In 1994, May and colleagues! cited six user-friendly anatomic  landmarks that are almost always present despite previous surgery:    1. The arch (or convexity) formed by the posterior edge of the  lacrimal bone, marking the lacrimal duct at the anterior margin  of the middle meatus   2. The anterior superior attachment of the middle turbinate  (vertical lamella)   3. The middle meatal antrostomy and its bony “ridge,” along its  superior border, formed by the junction of the floor of the orbit  with the lamina papyracea and resected margin of the posterior  fontanelle    Using these landmarks, revision endoscopic sinus surgery (ESS)  for recurrent or persistent disease in the maxillary, ethmoid,  sphenoid, or frontal sinuses can be safely performed. May was  one of the first to acknowledge that in advanced sinus disease,  anatomic landmarks, such as the uncinate process, basal lamella,  and superior or middle turbinates, are not always readily identifi-  able. He was also one of the first to point out that the floor of the  orbit, as seen through an antrostomy, serves as a consistent  landmark from which other structures may be found. The bony  “ridge” along the superior border of the antrostomy corresponds  to the medial orbital floor, which facilitates identification of the  inferior lamina papyracea prior to proceeding with an ethmoid-  ectomy. As will be seen later in this manual, this ridge is also  useful in locating the posterior ethmoid and sphenoid sinuses.   Despite prior reports that showed great intersubject variability,  May et al? and Stankiewicz? suggested that it was clinically effica-  cious to use standard measurements from the columella to orient  the surgeon during ESS.”? They based this suggestion on anecdotal  experience and prior anatomic studies by others, noting that the  distance from the area of the anterior nasal spine to the sphenoid  ostium is ~60mm (range, 47-70mm).**° If 1cm is added for the  length of the columellar base, the mean distance to the sphenoid  ostium would be approximately 70mm. For this reason, May  advocated labeling instruments with colored tape to warn the  surgeon when the anterior face of the sphenoid is reached (~7 cm).   Today, many instruments come premarked in centimeters from  the tip to allow for such measurements. However, there will likely  be variability among surgeons’ measurements of these distances.    In isolation, these measurements have not been shown to be  clinically reliable.   Schaefer’ was the first to described a “hybrid or combined  technique” that blended the conservation goals of the anteropos-  terior (AP) approach with the anatomic virtues of the posteroan-  terior (PA) approach. Surgery begins with identification and  complete removal of the uncinate process. If further surgery of  the ethmoid sinus is warranted, the maxillary natural ostium is  enlarged posteriorly or inferiorly, rather than anteriorly, to avoid  injury to the lacrimal canal. Schaefer noted that this immediately  exposes the level of the orbital floor. Like May, Schaefer recognized  the importance of the medial orbital floor as a very important  landmark to facilitate identification of the inferior lamina papyracea  prior to proceeding with an ethmoidectomy. He also advocated  removal of the inferior two thirds of the ethmoid cells in an AP  direction using a 0-degree telescope.   Often this involves removal of most, if not all, of the basal lamella  of the middle turbinate to address the drainage area of the posterior  sinuses and to facilitate entry into the sphenoid sinus. If the ostium  cannot be visualized or palpated, the sphenoid is entered in the  inferomedial quadrant of the anterior wall of the sinus. This  approach ensures that the surgeon will maintain a safe distance  from the skull base. It is only after the sphenoid roof has been  identified that a superior dissection of the sphenoid face or ethmoid  cavity (if indicated) is performed, as with the PA approach.   Schaefer’s approach, like May’s, recognizes the importance of  performing an antrostomy prior to an ethmoidectomy to identify  the orbital floor and medial orbital wall. Schaefer was the first to  note the importance of performing an inferior ethmoidectomy  before proceeding posteriorly using the medial orbital floor as a  reference point. As the surgeon proceeds posteriorly, it is the orbital  wall that dictates the trajectory and not some ill-defined and  often distorted lamella or turbinate structure, as advocated by  proponents of the AP approach.   Schaefer’s study, however, did not define the vertical extent of  the initial “inferior ethmoidectomy” from the level of the medial  floor of the orbit. Mosher’ has shown that the height of the ethmoid  labyrinth ranges from 2.5 to 3cm; however, this height may vary  even more depending on whether it is measured anteriorly or  posteriorly.   Similarly, the distance of two thirds of the ethmoid cells, as  described by Schaefer, can be quite variable. The maximum vertical  distance permitted for an “inferior ethmoidectomy” as the surgeon    Fig. 3.1(a) Distances from the columella and antrostomy ridge to critical structures: 9cm to the posterior sphenoid; 7 cm to the anterior sphenoid or  posterior wall of posterior ethmoid; 5cm to the anterior wall of the posterior ethmoids. (b) Shaded area denotes the “safe zone” of inferior orbital  dissection within 1 cm of the antrostomy ridge. Arrows denote the key measurement points illustrated in Fig. 3.2b.    proceeds posteriorly before critical skull base structures are at  risk remains unclear. Similarly, the distances to the critical struc-  tures in the posterior and lateral walls of the sphenoid sinus remain  undefined.   In 2001, Casiano® confirmed May’s and Schaefer’s observations  on a series of human cadavers. In this study, two examiners,  with varying experience in endoscopic sinus surgery, performed  endoscopic and direct measurements from the columella and  medial orbital floor to critical orbital and skull-base structures.  The distances to four critical skull-base or orbital structures (the  carotid artery, optic nerve, mid-ethmoid roof, and anterior ethmoid  artery) and to the anterior and posterior walls of the sphenoid  sinus were measured (Fig. 3.1). The mean, ranges, and standard    Mean, min., max., and SD for measurements from the  columellar base (mm)    deviations for all measurements (endoscopic and direct) were  calculated. In addition, the variability in measurements between  examiners and between the endoscopic and direct measurements  was also determined. The mean and range of values for each of  the variables correlated well both between examiners and between  endoscopic and direct measurements. The columellar measure-  ments appeared to be very consistent between examiners and  between endoscopic and direct measurements (Fig. 3.2).   When the antrostomy ridge and adjacent medial orbital floor  was used, there was some slight variability between the individual  measurements of the examiners and between endoscopic and  direct measurements. However, the differences in measurements  were no more than a few millimeters and did not appear to affect    Mean, min., max., and SD measurements from the  antrostomy ridge (mm)    Fig. 3.2(a) Mean, minimum, maximum, and standard deviation (SD) for measurements from the columellar base (in millimeters). (b) Mean, minimum,  maximum, and SD for measurements from the antrostomy ridge (in millimeters). PM, posterior maxillary sinus; AS, anterior sphenoid sinus; PS,  posterior sphenoid sinus; ON, optic nerve at canalicular portion; CA, cavernous carotid artery; AA, anterior ethmoidal artery; E, ethmoid roof at the  junction of the orbital wall. Columellar measurements greater than 9cm represent “extra-sinus” extension into the orbit or skull base or posterior  sphenoid wall (black dashed line in a). Staying within 1cm of the antrostomy ridge along the inferior orbital wall keeps the surgeon away from most    the overall clinical utility of these values. Casiano concluded that  the bony ridge of the antrostomy and adjacent medial orbital  floor, when combined with the use of columellar measurements,  are easily identifiable and consistent anatomic landmarks that  provide even the most inexperienced surgeon with very reliable  information to navigate through even the most distorted paranasal  sinus cavities. For example, staying within 1 cm of the antrostomy  ridge, along the medial orbital wall and anterolateral sphenoid  sinus, keeps the surgeon well away from critical skull base struc-  tures (Figs. 3.1b and 3.2b). This is particularly important for  advanced cases with distorted anatomy of the paranasal sinuses,  due to prior surgery or significant inflammatory disease (e.g.,  polyps). This critical anatomic landmark as well as others are  reviewed throughout the course of this dissection manual, and  their practical use in endoscopic sinus surgery and in maintaining  the surgeon’s orientation within this complex anatomic area is  illustrated.    May M, Schaitkin B, Kay SL. Revision endoscopic sinus surgery: six friendly surgical  landmarks. Laryngoscope 1994;104(6 Pt 1):766-767.   May M, Sobol SM, Korzec K. The location of the maxillary os and its importance to the  endoscopic sinus surgeon. Laryngoscope 1990;100(10 Pt 1):1037-1042.   Stankiewicz JA. The endoscopic approach to the sphenoid sinus. Laryngoscope  1989;99:218-221.   Van Alyea OE. Sphenoid sinus: anatomic study, with consideration of the clinical sig-  nificance of the structural characteristics of the sphenoid sinus. Arch Otolaryngol  1941;34:225-253.   Lang J. Clinical Anatomy of the Nose, Nasal Cavity and the Paranasal Sinuses. New York:  Thieme; 1989.   Calhoun KH, Rotzler WH, Stiernberg CM. Surgical anatomy of the lateral nasal wall.  Otolaryngol Head Neck Surg 1990;102:156-160.   Schaefer SD. An anatomic approach to endoscopic intranasal ethmoidectomy. Laryngoscope  1998;108(11 Pt 1):1628-1634.   Mosher HP. The surgical anatomy of the ethmoidal labyrinth. Ann Otol Rhinol Laryngol  1929;38:869-901.   Casiano RR. A stepwise surgical technique using the medial orbital floor as the key  landmark in performing endoscopic sinus surgery. Laryngoscope 2001;111:964-974.    Several instruments are required to perform basic endoscopic  sinus dissection in the laboratory (Fig. 4.1). As one gains more  surgical experience with advanced procedures, or proceeds with  live cases, however, additional instrumentation may be needed  depending on the type of procedure or the surgeon’s personal  preferences. In addition to a 30-degree endoscope, the minimum  instrumentation required for most of the basic dissections in this  manual include the following:    3.5-mm straight non-through-cut forceps (Fig. 4.1, A)  3.5-mm straight through-cut forceps (B)    Powered instrumentation (microdebrider), with a 4-mm straight  and/or 60-degree blade, is very helpful during dissection.   For advanced procedures, a 70-degree endoscope is useful to  visualize lateral or superior recesses of the frontal, maxillary, or  sphenoid sinus. Curettes of various sizes are useful for removing  thick bone, especially around the frontal ostium or sphenoid    rostrum (Fig. 4.2). Powered instrumentation with cutting or  diamond burs may also be necessary to carefully remove bone  around critical structures, such as the lacrimal sac, skull base,  optic nerve, or carotid artery (Fig. 4.3). A 15-degree angled bur  should suffice when drilling endonasally. When drilling antero-  superiorly in the frontal sinus, a more angled bur, such as a 40-,  50-, or 60-degree angled bur, is helpful but not absolutely necessary.  To overcome the sometimes challenging reach of a straight or  15-degree drill, or curette, in the area of the frontal sinus, one  can perform an anterosuperior septectomy and place the drill  through the contralateral nostril. The same principle applies to  complicated skull base cases where extensive bone drilling may  be required. Bi-nostril, four-handed techniques, combined with  carefully placed septectomies, improve the surgical exposure and  facilitate the placement of instruments and telescopes.    A clear adhesive dressing (e.g., OpSite, Smith & Nephew, Andover,  MA) is placed over the patient’s eyes to protect them. This allows  the surgeon to visualize and palpate the eyes during the surgical  procedure, in the event of an acute orbital hematoma and rapidly  progressive proptosis. The patient’s face is draped to expose only  the forehead, eyes, nose, and upper lip. The mouth and endotracheal  tube are typically draped unless a concomitant sublabial or oral  procedure is planned.    The surgeon should be sitting or standing comfortably at the  patient’s side. A right-handed surgeon typically stands on the  right side of the patient; Fig. 4.4 demonstrates the position for a  single surgeon). If the surgeon chooses to sit, then a Mayo stand  (cushioned with a pillow) is used to rest the elbow of the arm  holding the telescope at a comfortable height over the patient’s  head. The video tower and any intraoperative imaging devices  are positioned at the head of the table, facing the surgeon. The  surgeon’s neck should be in a comfortable neutral position, without  any significant extension or flexion, to avoid long-term strain on  the surgeon’s C-spine, which can result in neck pain.   For basic sinus surgery, the patient’s head is secured on a donut  pillow and angled slightly toward the surgeon. For skull base  approaches when the patient’s head is secured with pins, it is  helpful to extend or flex the head (i.e., at the atlanto-occipital joint),    depending on the approach, in addition to angling the head toward  the surgeon. For more anterior approaches such as anterior cranial  fossa approaches, it is useful to slightly extend the head about 15  degrees, whereas for posterior fossa approaches through the clivus  and upper cervical spine, it is helpful to have the head in slight  flexion. For approaches to the pituitary and cavernous sinus, no  flexion or extension is necessary. Angling the head toward the  surgeon will aid surgeon comfort while operating. Placing the  patient in the reverse Trendelenburg position at approximately 15  degrees may decrease blood loss and improve visualization during  endoscopic sinus surgery, whether used throughout the procedure  or as a maneuver when heavy bleeding is encountered.'”   The manner in which the endoscope is grasped, or instrumenta-  tion introduced into the nose, may vary depending on the surgeon's  preference, the specific length and type of endoscope or camera,    and the specific anatomic area being addressed. Generally, surgeons  determine which manner is best suited to their hands.   A 30-degree endoscope is all that is typically necessary for most  of the dissections described in this manual. A 0-degree telescope  may also be used, but it may limit adequate visualization of the  lateral nasal structures (e.g., maxillary natural ostium, maxillary  sinus, supraorbital ethmoidal cells, etc.). The axis of the endoscope  is directed toward the occipital area of the head. The superior  border of the inferior turbinate is kept in view during the initial  part of the procedure until the medial orbital floor is identified  through the middle meatal antrostomy. This keeps the surgeon  directed toward the choanal arch and superior nasopharynx, in  the trajectory of the sphenoid natural ostium. The endoscope is  positioned at the nasoseptal angle with gentle superior retraction  of the nasal tip, and the surgical instrumentation is inserted inferior  to the endoscope (Fig. 4.5, in which the white arrow represents  the trajectory of the instrument and the endoscope toward the  nasopharynx).   A 70-degree endoscope can be used if further visualization is  required into the superior or lateral recesses of the frontal, maxil-  lary, or sphenoid sinus. The 30- or 70-degree endoscope is placed    along the floor of the vestibule looking superiorly (as when working  around the frontal ostium) or medially (as when performing a  septoplasty). In these cases, the instruments may be introduced  superior to the endoscope (Fig. 4.6, in which the white arrow  represents the trajectory of the instrument and endoscope toward  the frontal recess). Introducing angled instruments and endoscopes,  especially when dissecting the frontal sinus, can be quite chal-  lenging when initially learning this skill. It is worth the practice  in the cadaver lab setting to allow it to become second nature  before applying it in the operating room (OR).   The specific OR setup may vary based on surgical team preference.  The standard setup positions both right-handed surgeons next to  each other on the patient’s right side, sharing one video screen  (Fig. 4.7), or using two video screens (Fig. 4.8). Left-handed  co-surgeons may position themselves on the patient’s left side  (Fig. 4.9). In some advanced skull base procedures, where drilling  of bone or manipulating tissue around critical neurovascular  structures is necessary, it is helpful to have the endoscope fixed  in place with the help of a co-surgeon (Fig. 4.10), or by utilizing  a specially designed endoscope holder (Fig. 4.11), enabling the  surgeon to operate with both hands simultaneously. Longer    endoscopes may be more helpful than standard length endoscopes,  to keep the co-surgeons’ hands from getting in each other’s way,  or from hitting the endoscope lens, light cable, or camera. The  operating surgeon uses one hand to hold the power instrumentation  or a surgical instrument, and the other hand to hold a suction    cannula. The assisting surgeon holds the endoscope, anticipating  the surgical partner’s moves, with good lines of communication  throughout the procedure. The free hand may be used to hold an  additional suction or other instrument depending on the specifics  of the case. Every case is unique, and requires good preoperative  planning by the surgical team, as well as intraoperative maneuver-  ing of endoscopes and instruments through both nostrils, to  maximize the best possible visualization and introduction of  surgical instruments by the operating surgeon.    1 Gan EC, Habib AR, Rajwani A, Javer AR. Five-degree, 10-degree, and 20-degree reverse  Trendelenburg position during functional endoscopic sinus surgery: a double-blind  randomized controlled trial. Int Forum Allergy Rhinol 2014;4:61-68.   2  Hathorn IF, Habib AR, Manji J, Javer AR. Comparing the reverse Trendelenburg and  horizontal position for endoscopic sinus surgery: a randomized controlled trial. Oto-  laryngol Head Neck Surg 2013;148:308-313.    The skull base and accompanying neurovascular foramina (Fig.  5.1) may be divided into the anterior, middle, and posterior skull  base and adjacent cranial fossa. It is made up of the ethmoid,  frontal, sphenoid, temporal, and occipital bones. Endoscopic  approaches into each of these very complex anatomic areas requires    Sphenoid bone:  Lesser wing  Sphenoidal crest  Superior orbital fissure  Tuberculum sellae  Anterior clinoid  process  Optic canal  Hypophyseal fossa  Posterior clinoid  process  Dorsum sellae    a very good understanding of the critical neurovascular foramina  coursing through these bones, and how they relate to the paranasal  sinuses and orbit.   Computed tomography (CT) is recognized as the standard  preoperative imaging study of choice for the paranasal sinuses,    skull base, and orbit. It demarcates the critical bony landmarks  that help avoid orbital or intracranial complications, and provides  insight into the extent and severity of the sinonasal and skull  base disease. Having a comprehensive understanding of CT anatomy  is a critical part of the preoperative workup prior to performing  any endoscopic procedure of the paranasal sinuses, orbit, or skull  base. In select cases, magnetic resonance imaging (MRI) may also  be necessary (see Chapter 6).   Most variants of normal sinus anatomy have poor correlation  with rhinosinusitis disease but can have significant importance  for surgical planning and safety.' A complete review of the CT may  highlight anatomic risk factors for a cerebrospinal fluid (CSF) leak  such as a steep skull base, fovea ethmoidalis asymmetry, or a deep  olfactory sulcus.” Prior surgery or extensive disease can also have  caused bony dehiscences that can increase the risk of injury, for  example, dehiscent or exposed arteries such as the internal carotid  or anterior ethmoid. Extensive pneumatization can also subject  these vessels to injury, as well as other structures, such as the optic  nerve. An understanding of the relationships or proximity of critical  anatomic structures can guide safe sinonasal dissection.    8 Foramina or fissures:  ¢ Lateral (1)  - Pterygomaxillary fissure  (to infratemporal fossa)  ¢ Medial (1)  - Sphenopalatine foramen  ¢ Inferior (2)  - Greater and lesser palatine foramen  ¢ Posterior (3)  - V2 canal and foramen rotundum  - Vidian (pterygoid) canal and foramen  - Palatovaginal (pharyngeal) canal  ¢ Anterior/Superior (1)  - Inferior orbital fissure    The anterior and posterior ethmoids are divided by the basal  lamella of middle turbinate (also known as the third lamella or  ground lamella). The sphenoid and posterior ethmoid are divided  by the basal lamella of superior turbinate.    Important structures that can be protruding or  dehiscent in the sphenoid    Uncinate attaches medial Uncinate attaches lateral  Frontal drains to ethmoid infundibulum Frontal drains medial (into middle meatus)    ¢ Middle third  - Basal lamella (divide ethmoids)  - Lamina papyracea insertion  - Transitions vertical to horizontal  - In coronal plane    ¢ 3 turbinate tails   ¢ Maxillary posterior wall (M)  ¢ Ethmoid/sphenoid wall (E/S)    Sphenoid os ~ 1 cm  superior and medial  to superior turbinate    1 Shpilberg KA, Daniel SC, Doshi AH, Lawson W, Som PM. CT of anatomic variants of the  paranasal sinuses and nasal cavity: poor correlation with radiologically significant  rhinosinusitis but importance in surgical planning. AJR Am J Roentgenol 2015;  204:1255-1260.   Labruzzo SV, Aygun N, Zinreich SJ. Imaging of the paranasal sinuses: mitigation, identifica-    tion, and workup of functional endoscopic surgery complications. Otolaryngol Clin  North Am 2015;48:805-815.    Magnetic resonance imaging (MRI) is a complementary modality  for evaluating complicated rhinosinusitis, invasive sinonasal infec-  tion, and sinonasal mass lesions. It is far superior to computed  tomography (CT) because of its inherent superior soft tissue  resolution and multiplanar capabilities, which renders it the study  of choice for characterization and extent of disease processes  beyond the paranasal sinuses, such as perineural spread and  intraorbital and intracranial extension.   One of the disadvantages of MRI over CT is its inability to display  the cortical bone/air interface. Because both cortical bone and  air have signal voids, MRI is suboptimal for delineating intricate  sinonasal anatomy and the drainage pathways necessary to guide  the surgeon during functional endoscopic sinus surgery (FESS).  Chronic desiccated secretions and fungal infection may also appear  as signal voids on MRI, which easily can be misinterpreted as  normal aerated sinuses; CT, on the other hand, is a better modality  because of their hyperdense attenuation.    Imaging of the paranasal sinuses includes high-resolution (3-mm)  T1- and T2-weighted images of the orbit, skull base, and adjacent  intracranial compartment. Images should be acquired in the axial  and coronal planes, and sagittal planes can be added as necessary.    Contrast-enhanced T1-weighted images are routinely obtained in  the axial and coronal planes using fat-suppression techniques and  gadolinium chelate contrast agents to maximize tumor contrast  and depict dural invasion or perineural spread.'®   Axial flair and diffusion-weighted images of the whole brain  are also obtained. Additionally, a contrast-enhanced three-  dimensional (3D) gradient echo T1-weighted sequence through  the entire brain and skull base, reconstructed at 1-mmi slice  thickness, is done for intraoperative guidance at our institution.  A 3D constructive interference in steady state (CISS) sequence is  done if a cerebrospinal fluid (CSF) leak is suspected. Table 6.1  lists the most commonly used MRI sequences and correlated  characteristic observations.    Normal anatomy of the paranasal sinuses, the relevant exocranial  openings, and the relevant fat planes are depicted in Figs 6.1, 6.2,  6.3, 6.4, 6.5, 6.6, 6.7, 6.8.    T1-weighted images are the best sequences to depict bone marrow  invasion. Nonsuppressed spin echo T1-weighted sequences are    Used to reflect tissue cellularity and found to be useful in differentiating between benign and highly cellular tumors    such as lymphoma and in the diagnosis of infectious processes such as pyogenic sinusitis    Best display of sinonasal anatomy, delineation of fat planes surrounding the paranasal sinuses, PPF, and other skull base    Most helpful for delineating tumor boundaries  Discriminates between solid neoplasm and fluid (retained, inspissated, and postobstructive secretions)  Bony involvement of the anterior skull base, sinonasal cavity, and periorbita    Differentiates between solid tumor and mucosal inflammatory/infectious material  Dural and pial enhancement, infiltration of skull base, sinonasal cavity, periorbital    Note: T1-weighted sequence before and after contrast can be performed with fat suppression, which results in increased    sensitivity in detection of the enhancing component from surrounding fat planes.    Abbreviations: ADC, apparent diffusion coefficient; CISS, constructive interference in steady state; CSF, cerebrospinal fluid; DWI, diffusion-weighted imaging; EPI, echo planar  imaging; FFE, balanced fast field echo; FIESTA, fast imaging employing steady-state acquisition; FISP, true fast imaging with steady-state; PPF, pterygopalatine fossa.  °CISS has different names based on the manufacturer. It is called FIESTA by General Electric, FISP by Siemens, and FFE by Philips.    Fig. 6.1. (a—h) Axial T1-weighted (T1W) images (caudal to cranial). Ant., anterior; Fn., foramen; ICA, internal carotid artery; LR, lateral rectus; m.,  muscle; MR, middle rectus; NLD, nasolacrimal duct; n., nerve; ON, optic nerve; Post., posterior; PPF, pterygopalatine fossa; SOV, superior ophthalmic  vein; SR, superior rectus muscle.    CHAPTER 6 ® Magnetic Resonance Sinonasal and Skull Base Anatomy 27    Fig. 6.2. (a-g) Coronal T1W images (anterior to posterior). Fn., foramen; CN V, trigeminal nerve; ICA, internal carotid artery; n., nerve; ON, optic  nerve; PPF, pterygopalatine fossa.    ; ; : ; Maxillary sinus < Maxillary sinus  Inferior turbinate Inferior turbinate    Fig. 6.3 (a-g) Coronal T2-weighted (T2W) fat-saturated images (anterior to posterior). (d) is magnification of (c). Ant., anterior; Fn., foramen; ICA,  internal carotid artery; LL, lateral lamella; ML, medial lamella; NLD, nasolacrimal duct; n., nerve; ON, optic nerve; PPF, pterygopalatine fossa.    Fig. 6.4 (a—d) Axial T1W postcontrast fat-saturated images (inferior to superior through the central skull base). Cranial nerve (CN) VI is seen as a  filling defect surrounded by the enhancing basilar venous plexus (c). CN V, trigeminal nerve; IAC, internal auditory canal; ICA, internal carotid artery;  PPF, pterygopalatine fossa; REZ, root entry zone; TG, trigeminal ganglion.    Fig. 6.5 (a-d) Coronal T1W postcontrast fat-saturated images (anterior  to posterior). (d) is magnification of (c). Ant., anterior; Fn., foramen; ICA,  internal carotid artery; ON, optic nerve; SOF, superior orbital fissure.    Fig. 6.7 Axial constructive interference in steady state (CISS) images. (a) At the level of the internal auditory canal. (b) At the level of Meckel’s cave.  CN, cranial nerve; IAC, internal auditory canal; REZ, root entry zone; TG, trigeminal ganglion.    Fig. 6.8 Coronal T1W postcontrast image. Normal anatomy of the left  cavernous. Solid enhancing lesion (schwannoma) in the right cavernous  sinus (asterisk) obliterating the normal anatomy of the cranial nerves. CN,  cranial nerve.    useful to look for soft tissue infiltration within fat-containing areas  surrounding the sinonasal cavities, such as the orbits, exocranial  openings of neurovascular foramina, pterygopalatine fossa, pre-  maxillary soft tissues, retroantral fat, and bone marrow of the  skull base, as this can be an early sign of disease extension beyond  the confines of the sinuses.    There are anatomic variants of skull base mineralization and  sinus pneumatization that can mimic a bony lesion or aneurysm  if not recognized. The anterior clinoid and pterygoid processes  of the sphenoid and the petrous apex are the most common sites  of asymmetric pneumatization. Nonpneumatized bone contains  fatty marrow, which shows suppression of the T1 hyperintensity  on fat-suppressed sequences and can be confirmed on CT (Fig. 6.9).   Similarly, arrested pneumatization of the sphenoid sinus or  pseudolesion is a benign developmental anomaly, and presents  as a nonexpansile lesion with osteosclerotic borders, internal  calcification with fat, and does not involve the adjacent foramina.  It is usually associated with a hypoplastic sphenoid sinus. On MRI,  it follows fat signal and is high on T1-weighted images and does  not enhance (Fig. 6.10).   Pneumatization of the anterior clinoid process can mimic an  aneurysm but demonstrates the presence of air on all imaging  sequence, which can also be confirmed on CT (Fig. 6.11). Aneurysm  of the paraclinoid internal carotid artery, on the other hand, appears  as a prominent flow void on all imaging sequences, demonstrates  expansion of the anterior clinoid process, and is not pneumatized  on CT (Fig. 6.12).   Fat-saturated T1-weighted techniques with contrast are usually  included to facilitate detection and increased sensitivity for lesion  enhancement, as well as perineural spread of disease in the skull  base, orbit, and cavernous sinus, and intracranial extension of  disease (Figs. 6.13 and 6.14).”®    Fig. 6.9 Normal fatty marrow pterygoid process. (a) Axial T1W. (b) Axial  T1W fat-saturated. (c) Axial computed tomography (CT). Axial T1W image  (a) demonstrates high signal intensity of fatty marrow in the right pterygoid  process (asterisk), which saturates out on the fat suppressed image  (b) and demonstrates fatty attenuation on CT (c).    Fig. 6.10 Pseudolesion: arrested pneumatization of the sphenoid.  (a) Axial T1W image. (b) Axial T1W postcontrast fat-saturated image. (c)  Axial CT. Axial T1W (a) shows a hypoplastic left sphenoid sinus with fat  signal intensity (asterisk). Axial T1W postcontrast fat-saturated image (b)  shows suppression of the fat signal intensity with no appreciable enhance-  ment (asterisk). Axial CT (c) demonstrates a hypoplastic sphenoid sinus  with a non-expansile lucency containing fat density with interspersed  curvilinear calcifications.    Fig. 6.11 Pseudolesion: aerated anterior clinoid process. (a) Axial T1W  image. (b) Axial T2W fat-saturated image. (c) Axial CT. Axial T1W (a) and  fat-saturated T2W (b) images show a hyper-aerated anterior clinoid process  (asterisk). Axial CT (c) confirms the presence of aeration (asterisk).    Fig. 6.12 Paraclinoid internal carotid aneurysm mimicking an aerated  anterior clinoid process. (a) Axial T1W image. (b) Axial T2W fat-saturated  image. (c) Axial CT. Axial T1W (a) and T2W fat-saturated image (b) show  a prominent flow void at the level of the anterior clinoid process (arrow).  Axial CT (c) shows smooth scalloping of the anterior clinoid process  (arrowhead) by the aneurysm (asterisk) in addition to the lack of aeration  of the clinoid.    CHAPTER 6 ® Magnetic Resonance Sinonasal and Skull Base Anatomy 33    Fig. 6.13 Squamous cell cancer. Extensive perineural spread along CN V.  (a) Axial TI1W image. (b) Axial T1W postcontrast fat-saturated image.  (c) Coronal T1W. (d) Coronal T1W postcontrast fat-saturated image. (e)  Coronal T1W postcontrast fat-saturated image (e) is posterior to (d). Axial  T1W (a) shows soft tissue in the pterygopalatine fossa (PPF) (asterisk) and  pterygomaxillary fissure (PMF) (circle). Axial T1W postcontrast fat-saturated  image (b) demonstrates abnormal thickening and enhancement in the  left pterygopalatine fossa (asterisk), pterygomaxillary fissure (circle), foramen  rotundum (solid arrow), inferior orbital fissure (dashed arrow), and cavernous  sinus (arrowhead). Coronal T1W (c) and coronal T1W postcontrast fat-  saturated image (d) show an enlarged foramen rotundum (solid arrow)  and vidian canal (double arrow) with abnormal enhancement and loss of  fat planes and enhancement in the masticator space (star). Coronal T1W  postcontrast fat-saturated image (e) shows tumor in the left cavernous  sinus (arrowhead) extending into the foramen ovale (curved arrow).    Fig. 6.14 Metastatic melanoma and perineural spread along V1. (a) Axial T1W image. (b) Coronal T1W fat-saturated image. (c) Coronal T2W  fat-saturated image. Axial TI1W (a) and coronal T1W fat-saturated postcontrast (b) images demonstrate an enhancing mass along the right  supraorbital nerve (arrow). Coronal T2W fat-saturated image (c) shows abnormal high signal in the thickened nerve within the supraorbital foramen    T2-weighted imaging is the most useful sequence for delineat-  ing tumor boundaries and for distinguishing between the high  T2 signal intensity of inflamed mucosa and adjacent tumor  (Fig. 6.15).°   The pattern of contrast enhancement can also help distinguish  tumor from inflammatory disease in the sinuses because the former  usually demonstrates prominent enhancement whereas the latter  usually demonstrates thin, avid peripheral enhancement (Fig.    6.15).'° Adjacent soft tissues and muscles can also enhance due  to inflammation or denervation changes.   The various pathological processes can be characterized  based on its MRI signal characteristics, as summarized in  Table 6.2.   Inflamed mucosa is associated with increased submucosal edema  and increased secretions, both of which contain 98% water. On  T1-weighted sequences, water has a long relaxation time and is    CHAPTER 6 ™ Magnetic Resonance Sinonasal and Skull Base Anatomy 35    Fig 6.15 Sinonasal malignancy and postobstruction inflammatory changes. (a) Coronal T1W precontrast image. (b) Coronal T1W postcontrast fat-  saturated image. (c) Coronal T2W fat-saturated image. Coronal T1W precontrast (a) and coronal T1W postcontrast fat-saturated (b) images demonstrate  a heterogeneously enhancing soft tissue mass lesion (asterisk) with intermediate to low T1W and T2W signal. Coronal T2W fat-saturated image (c)  shows associated postobstruction changes in the ipsilateral maxillary and frontal sinuses as well as right greater than left ethmoid sinuses with T2W    seen as low signal intensity (“dark”), whereas on T2-weighted  sequences it is seen as high signal intensity (“bright”). Therefore,  on MRI, inflamed sinonasal mucosa is characterized by low  T1-weighted and high T2-weighted signal intensities (Fig. 6.16)."'  Inflamed mucosa may also demonstrate a polyploid configuration  (Fig. 6.17).'?    Signal intensity of sinonasal secretions on MRI is largely depen-  dent on the proportion of proteins in the secretions on both T1- and  T2-weighted images (Table 6.3; Fig. 6.18). Mucoceles may also  have variable signal intensities on MRI, depending on their protein  content, inspissation, and possible superinfection, and do not show  contrast enhancement unless infected.'*"4    ormal marrow signal suppresses on fat-saturated sequences. Hence, the signal is hyperintense (bright) on T1- and T2-weighted images and becomes hypointense (dark) on  T1- and T2-weighted fat-saturated images. This does not apply to any of the other pathological entities listed in this table.   ‘Inspissated secretions, mucocele, and allergic fungal elements can have a variable appearance depending on its protein concentration as depicted in Table 6.3.   ‘Meningocele remains CSF equivalent on every sequence including CISS and fluid-attenuated inversion recovery (FLAIR).    Table 6.3 Magnetic Resonance Appearance of Sinonasal Secretions Based on  Protein Content  Protein Content    Up to 5% Hypointense Hyperintense  5-25% Hyperintense Hyperintense  26-30% Hyperintense Hypointense    Fig. 6.17 Inflammatory polyp. (a) Axial T2W fat-saturated image.  (b) Axial T1W postcontrast image. Axial T2W fat-saturated (a) and axial T1W  Fig 6.16 Mucosal thickening in the maxillary sinuses. Coronal T2W fat- _ postcontrast (b) images show a smooth polypoid inflammatory polyp with  saturated image demonstrates abnormal mild smooth mucosal thickening = T2W hyperintensity (solid arrow), T1W hypointensity (dashed arrow), and    of the maxillary sinuses (dashed arrow). smooth convex borders with thin peripheral enhancement (arrowheads).    CHAPTER 6 ™ Magnetic Resonance Sinonasal and Skull Base Anatomy 37    Fig. 6.18 Trapped secretions. (a) Coronal T2W fat-saturated image. (b) Coronal T1W image. (c) Coronal T1 postcontrast fat-saturated image. Coronal  T2W fat-saturated (a), coronal T1W (b), and coronal T1 postcontrast fat-saturated (c) images demonstrate a low central T2 and high T1 signal intensity  suggestive of inspissated secretions (solid arrow) with smooth, peripheral mucosal enhancement (dashed arrow).    Fig. 6.19 Fungal ball, mycetoma. (a) Coronal T1W image. (b) Coronal T1W postcontrast fat-saturated image. (c) Coronal T2W fat-saturated image.  Coronal T1W (a), coronal T1 postcontrast fat-saturated (b), and coronal T2W fat-saturated (c) images demonstrate an obstructed antrum (asterisk)  with the sinus opacified with mixed signal intensity and with central areas of low T2W and T1W signal intensity (solid arrow) as well as thick, smooth,  peripheral mucosal enhancement (dashed arrow).    A fungus ball also known as mycetoma or aspergilloma typically  involves a single sinus and demonstrates low signal intensity on  T1- and T2-weighted image (Fig. 6.19).'°   Allergic fungal sinusitis is an immunologic hypersensitivity reac-  tion to fungal organisms and typically involves multiple sinuses.  The immunologic reaction leads to sinus opacification with viscous  mucin and inflammatory debris known as “allergic mucin,” which has  avery low water content. On T1-weighted images, the signal intensity  is variable. On T2-weighted images, there is marked signal loss in  the affected sinus, which can mimic an aerated sinus. The T2 signal    void can be attributed to a fungal mycetoma, inspissated secretions,  or paramagnetic metals such as iron, magnesium, and manganese  (Fig. 6.20).'*'° An associated inflammatory reaction result in T2  hyperintense and hypointense T1 signal in the adjacent mucosa  with peripheral mucosal enhancement and central nonenhance-  ment (Fig. 6.21). MR imaging in invasive fungal disease will show  intermediate to low T1 and low T2, invasive appearing and vividly  enhancing soft tissue mass that can mimic a sinus neoplasm (Fig.  6.22). Sinonasal tumors are more cellular than normal or inflamed  tissue. On T1-weighted images, the majority of neoplasms tend    CHAPTER 6 ® Magnetic Resonance Sinonasal and Skull Base Anatomy 39    Fig. 6.20 Allergic fungal sinusitis and mucocele. (a) Axial T1W image. (b) Axial T2W fat-saturated image. (c) Axial CT. Axial T1W (a) and axial T2W  fat-saturated (b) images demonstrates expansion of the ethmoid and sphenoid sinuses with low T1W (asterisk) and very low T2 (asterisk) signal intensity  suggestive of very low protein content (signal void; see Table 6.3) that can mimic an aerated sinus and could easily be overlooked if only MRI was  performed. Corresponding axial CT (c) demonstrates intrinsic high attenuation (circle). Of note, the T2W signal void can be seen in the setting of a  fungal mycetoma, inspissated secretions, or paramagnetic metals such as iron, magnesium, and manganese.    Fig. 6.21 Allergic fungal sinusitis with intracranial extension. (a) Coronal T2W fat-saturated image. (b) Coronal T2W fat-saturated image. (c) Sagittal  T1W postcontrast fat-saturated image. (d) Sagittal CT. Coronal T2W fat-saturated (a,b) and sagittal T1W postcontrast fat-saturated (c) images  demonstrate areas of low signal intensity (signal void) on T2W and T1W images, suggestive of very low protein content in the sphenoid, maxillary,  and ethmoid sinuses (asterisk). Associated inflammatory reaction will result in T2 hyperintense and T1 hypointense signal in the adjacent mucosa (short  arrow) with peripheral mucosal enhancement (long arrow) and central nonenhancement. There is epidural extension noted through the posterior  aspect of the sphenoid sinus (dashed arrow). Sagittal CT (d) demonstrates high attenuation (star) consistent with inspissated secretions and allergic  mucin in addition to epidural extension through the sphenoid sinus (dashed arrow).    CHAPTER 6 ® Magnetic Resonance Sinonasal and Skull Base Anatomy 41    Fig. 6.22 Invasive fungal sinusitis mimicking sinonasal malignancy. (a) Axial T1W image. (b) Axial T1W postcontrast fat-saturated image. (c) Coronal  T1W image. (d) Coronal T2W fat-saturated image. Axial T1W image (a) demonstrates an intermediate and low T1W signal intensity lesion in the right  maxillary antrum (asterisk), extending into the premaxillary soft tissues (two asterisks), loss of fat in the pterygopalatine fossa (three asterisks), foramen  rotundum (solid arrow), and cavernous sinus (dashed arrow). Axial T1 postcontrast fat-saturated image (b) shows corresponding enhancement in the  premaxillary soft tissues (two asterisks), foramen rotundum (solid arrow), and cavernous sinus (dashed arrow). However, there is lack of enhancement  in the pterygopalatine fossa (two asterisks) that suggests devitalized tissue (necrosis) secondary to angioinvasive fungal infection. Histological analysis  revealed mucormycosis in this immunocompromised patient. Coronal T1W image (c) shows involvement of the infraorbital foramen (double arrow).  Coronal T2W fat-saturated image (d) shows high signal (edema) in the extraocular muscles (curved arrows).    Fig. 6.23 Sinonasal lymphoma. (a) Coronal T2W fat-saturated image. (b) Axial diffusion weighted imaging (DWI). (c) Axial apparent diffusion coefficient  (ADC). Coronal T2W fat-saturated image (a) demonstrates a sinonasal mass lesion with relative low T2W signal intensity (asterisk), implying a very  cellular component. Axial DWI (b) and ADC (c) images show corresponding restricted diffusion with low ADC value (star).    to have low T1 signal intensity and low to intermediate T2 signal  intensity, and usually show solid and heterogenous enhancement.   Diffusion-weighted imaging (DWI) is another useful modality  that can help differentiate benign from malignant sinonasal tumors,  particularly highly cellular tumors such as lymphoma (Fig. 6.23).  Although malignant lesions have lower apparent diffusion coef-  ficient (ADC) values compared with benign processes (due to their    high cellularity and tightly packed cells of the former and resultant  restriction of water molecules in the intercellular space), it is not  a reliable tool because there is overlap in the ADC values of benign  and malignant processes.   The 3D T2-weighted sequences such as CISS can be useful in  evaluating a CSF-containing lesion or CSF leak (Fig. 6.24) and in  differentiating a mucocele from a meningocele (Fig. 6.25).    CHAPTER 6 ™ Magnetic Resonance Sinonasal and Skull Base Anatomy 43    Fig. 6.24 Sphenoid sinus meningocele. (a) Axial fluid-attenuated inversion recovery (FLAIR) image. (b) Axial T2W fat-saturated image. (c) Axial T1W  postcontrast fat-saturated image. (d) Coronal CT. Axial FLAIR (a), axial T2W fat-saturated (b), and axial T1W postcontrast fat-saturated (c) images  demonstrate a nonenhancing cerebrospinal fluid (CSF) equivalent lesion (asterisks) in the left lateral recess of the sphenoid sinus. Correspond coronal  CT (d) better delineates the bony defect (arrowhead) lateral to the foramen rotundum (solid arrow).    Fig. 6.25 Frontal mucocele. (a) Coronal T2W fat-saturated image. (b) Coronal T1W image. (c) Coronal CISS. (d) Sagittal CISS. Coronal T2W fat-saturated  (a) and coronal T1W (b) images demonstrate a mixed signal intensity lesion in the frontal sinus with the high T2W signal intensity (thick straight white  arrow) corresponding to a low T1W component (thick straight white arrow), thus mimicking CSF (compare to CSF signal on those sequences in the  sulci; curved arrows). Meningocele was in the differential. Coronal CISS (c) and sagittal CISS (d) sequences do not confirm the CSF signal in the  above-mentioned component (thick straight white arrow) (compare the CSF signal on CISS in the sulci; curved arrows), thus excluding the possibility  of a meningocele. A mucocele was found on endoscopy.    Fischbein NJ, Kaplan MJ. Magnetic resonance imaging of the central skull base. Top  Magn Reson Imaging 1999;10:325-346.   Tomura N, Hirano H, Sashi R, et al. Comparison of MR imaging and CT in discriminating  tumor infiltration of bone and bone marrow in the skull base. Comput Med Imaging  Graph 1998;22:41-51.   Tomura N, Hirano H, Kato K, et al. Comparison of MR imaging with CT in depiction of  tumour extension into the pterygopalatine fossa. Clin Radiol 1999;54:361-366.    Curtin HD. Detection of perineural spread: fat is a friend. AJNR Am J Neuroradiol  1998;19:1385-1386.    Williams LS. Advanced concepts in the imaging of perineural spread of tumor to the  trigeminal nerve. Top Magn Reson Imaging 1999;10:376-383.    Glenn LW. Innovations in neuroimaging of skull base pathology. Otolaryngol Clin North  Am 2005;38:613-629.    Maroldi R, Farina D, Borghesi A, Marconi A, Gatti E. Perineural tumor spread. Neuroimag-  ing Clin N Am 2008;18:413-429, xi.   Loevner LA, Sonners Al. Imaging of neoplasms of the paranasal sinuses. Neuroimaging  Clin N Am 2004;14:625-646.    Madani G, Beale TJ. Differential diagnosis in sinonasal disease. Semin Ultrasound CT  MR 2009;30:39-45.    Som PM, Dillon WP, Curtin HD, Fullerton GD, Lidov M. Hypointense paranasal sinus  foci: differential diagnosis with MR imaging and relation to CT findings. Radiology  1990;176:777-781.   Som PM, Curtin HD. Head and Neck Imaging. St. Louis: Mosby; 2003.   K6ésling S, Hintner M, Brandt S, Schulz T, Bloching M. Mucoceles of the sphenoid sinus.  Eur J Radiol 2004;51:1-5.   Joshi VM, Sansi R. Imaging in sinonasal inflammatory disease. Neuroimaging Clin N  Am 2015;25:549-568.    Betts AM, Cornelius R. Magnetic resonance imaging in sinonasal disease. Top Magn  Reson Imaging 2015;24:15-22.    CHAPTER 6 ® Magnetic Resonance Sinonasal and Skull Base Anatomy 45    Aribandi M, McCoy VA, Bazan C III. Imaging features of invasive and noninvasive fungal  sinusitis: a review. Radiographics 2007;27:1283-1296.   Mossa-Basha M, Ilica AT, Maluf F, Karakoc 0, Izbudak I, Aygiin N. The many faces of  fungal disease of the paranasal sinuses: CT and MRI findings. Diagn Interv Radiol  2013;19:195-200.   Manning SC, Merkel M, Kriesel K, Vuitch F, Marple B. Computed tomography and  magnetic resonance diagnosis of allergic fungal sinusitis. Laryngoscope 1997;107:170-176.  Seo YJ, Kim J, Kim K, Lee JG, Kim CH, Yoon JH. Radiologic characteristics of sinonasal  fungus ball: an analysis of 119 cases. Acta Radiol 2011;52:790-795.    The surgeon starts examining the nasal cavity by passing a  30-degree telescope posteriorly (looking laterally) along the junc-  tion of the inferior and middle turbinates and adjacent to the  nasal septum (Fig. 7.2). The structures at the posterior nasal choana  (i.e., the posterior nasopharyngeal wall, eustachian tube opening  and torus tubarius, posterior choanal arch, posterior septum, and  posterior ends of the middle and inferior turbinates) are routinely    identified before proceeding with endoscopic surgery of the % aN Maxillary sinus  paranasal sinuses (Fig. 7.3). Early identification of these structures   : : : Nasal septum Inferior turbinate  and telescopes. The anterior ostiomeatal complex (ethmoid bulla,  uncinate process, and surrounding recesses, and drainage outflow  tracts for the maxillary, frontal, and suprabullar ethmoid air cells)  can be seen by gentle medial displacement of the middle turbinate  toward the nasal septum (Fig. 7.4).    During live surgery, hemostasis and adequate nasal exposure  and evacuation of blood are imperative. For this reason, the nose  is topically decongested and infiltrated with vasoconstrictive agents.  Hypertrophied turbinates, and/or septal spurs or deviation obstruct-  ing the nasal airway, are addressed prior to proceeding with any  sinus work, to gain the greatest exposure possible, as well as to  improve the patient’s nasal airway. A superior septal deviation,  although not necessarily symptomatic in all cases, may preclude  adequate visualization of the ethmoid air cells, as one proceeds  posteriorly toward the sphenoid sinus. Therefore, this may have  to be corrected in the interest of patient safety.'    A separate contralateral suction may be used for the continuous  evacuation of accumulated blood and debris from the nasopharynx.  When bilateral polyp disease is present, a bilateral nasal polyp-  ectomy may be performed first, to reestablish the anteroposterior  dimensions of the nose, as well as to facilitate the placement of  contralateral nasopharyngeal suction for continuous evacuation  of blood and debris. The area of the middle turbinate tail and  adjacent sphenopalatine foramen may be injected with epinephrine  or cauterized, to control hemostasis.   Suction-irrigation is performed as necessary. Monopolar or  bipolar suction cautery is helpful if discrete bleeding vessels are    1 Rudmik L, Mace J, Ferguson BJ, Smith TL. Concurrent septoplasty during endoscopic  sinus surgery for chronic rhinosinusitis: does it confound outcomes assessment?  Laryngoscope 2011;121:2679-2683.   2 Cassano M, Longo M, Fiocca-Matthews E, Del Giudice AM. Endoscopic intraoperative  control of epistaxis in nasal surgery. Auris Nasus Larynx 2010;37:178-184.    An endoscopic inferior turbinoplasty with submucous resection  of bone may be indicated when there is poor endoscopic visualiza-  tion of and access to, the nasal cavity, or if there is symptomatic  nasal obstruction due to turbinate hypertrophy.'* Frequently,  inferior turbinate bone enlargement may contribute to the turbinate  hypertrophy, with resultant nasal obstruction, and may be resistant  to medical treatment.   As a 30-degree telescope provides visualization, a microdebrider  is used to resect a wedge of soft tissue at the attachment of the  turbinate to the lateral nasal wall. Alternatively, this incision can  be made with a sickle knife, scalpel, or a cutting forceps. Mucosal  flaps are then raised on the medial and lateral surfaces of the  inferior turbinate, and the turbinate bone is partially removed in  a piecemeal fashion as far posteriorly as necessary to achieve    adequate lateralization of the turbinate into the inferior meatus  (Figs. 8.2 and 8.3).' If present, the bone of the “scroll” area should  be addressed to enable optimal positioning of the reduced turbinate  (Fig. 8.1). To minimize the risk of secondary maxillary sinusitis,  care should be taken to avoid fracturing the inferior turbinate  lamellar attachment to the lateral nasal wall, adjacent to the  maxillary natural ostium.4   For additional airway space, the lateral mucosal flap in the  inferior meatus is trimmed as needed to remove redundant mucosa.  In the case of soft tissue hypertrophy of the inferior turbinate  tail, or a “mulberry tail,” the microdebrider can be used to reduce  the enlarged soft tissue, followed by electrocautery to obtain  hemostasis. The medial and lateral mucosal flaps of the inferior  turbinate are reposed along the entire anteroposterior extent of  the inferior turbinate. This minimizes the risk of prolonged crusting  due to exposed bone (osteitis) or de-epithelialized surfaces.’ At  the conclusion of the procedure, the inferior turbinate is lateralized  into the inferior meatus.    Submucosal resection of the inferior turbinate  (arrows denote a superiorly based mucoperiosteal  flap temporarily raised to allow bone removal)    Ozcan KM, Gedikli Y, Ozcan I, Pasaoglu L, Dere H. Microdebrider for reduction of inferior  turbinate: evaluation of effectiveness by computed tomography. J Otolaryngol Head  Neck Surg 2008;37:463-468.   Brunworth J, Holmes J, Sindwani R. Inferior turbinate hypertrophy: review and graduated  approach to surgical management. Am J Rhinol Allergy 2013;27:411-415.   Passali D, Passali FM, Damiani V, Passali GC, Bellussi L. Treatment of inferior turbinate  hypertrophy: a randomized clinical trial. Ann Otol Rhinol Laryngol 2003;112:683-688.  Berenholz L, Kessler A, Sarfati S, Eviatar E, Segal S. Chronic sinusitis: a sequela of inferior  turbinectomy. Am J Rhinol 1998;12:257-261.    m Perpendicular plate of the ethmoid bone  g Anterior nasal spine    A significant septal spur or deviation may preclude adequate  endoscopic visualization and access, or may adversely affect nasal  airway patency. In these cases, a septoplasty would be indicated.'*  The endoscopic technique as described below has multiple  advantages, including improved visualization of the posterior nasal  septum and nasal cavity, the ability to perform a localized sub-  mucoperichondrial dissection, and ease of transition into endoscopic  sinus surgery.   Using a 30-degree telescope looking slightly superomedially,  an ipsilateral L-shaped or T-shaped incision is made in the septal  mucosa. The vertical portion of this incision (A in Fig. 9.2) is  placed immediately anterior to the deviated area to facilitate  cartilage or bone removal. Care is taken to preserve an approxi-  mately 10-mm strip of the cartilagenous caudal strut to reduce  the risk of dorsal collapse. The horizontal portion of the incision  (B in Fig. 9.2) is placed perpendicular to the vertical incision at    tube orifice  Crest of the  palatine bone Crest of the maxillary bone    the junction of the floor and nasal septum or just slightly superior  to this point, depending on the location of the deviation.   The incision should be made on the ipsilateral side of the devia-  tion because this is the side where the mucosa is commonly  perforated inadvertently over a septal spur (Fig. 9.2). Through  this incision, a posterosuperiorly based mucoperichondrial flap  is elevated. In order to help prevent perforation, care must be  taken to ensure that the flap is raised in the submucoperichondrial  plane. A Cottle elevator is used to vertically incise the septal  cartilage posterior to the preserved strip of caudal strut, to identify  the contralateral mucoperichondrium and to create a submuco-  perichondrial plane, being careful not to perforate the mucoperi-  chondrium on the contralateral side. The mucoperichondrial flaps  are elevated bilaterally, away from cartilage and bone posterior  to this point (Fig. 9.3). The septal spur or deviated portion of the  nasal septum is then removed, starting with a strip of cartilage  and bone along the maxillary crest.   Frequently, it is necessary to remove a strip of the perpendicular  plate of the ethmoid bone just posterior to the coronal plane of    Vertical (A) and horizontal (B) portions of an  L-shaped septoplasty incision and creation  of a posterosuperiorly based septal flap    the rhinion to free up a caudal deflection and break the cartilage  “spring” caudal to this area. Nevertheless, caudal and dorsal struts  of septal cartilage are always preserved to avoid the risk of septal  collapse and saddle-nose deformity. Periodic transillumination  should reveal a bright light posterosuperior to the rhinion, where  it is safe to remove cartilage or bone without the risk of dorsal  collapse (Fig. 9.4a). Transillumination caudal to the rhinion implies  that the surgeon is removing cartilage too close to the dorsal strut,  with impending loss of dorsal support (Fig. 9.4b).   At the conclusion of the procedure, the mucoperichondrial flaps  are returned to their normal position. The vertical septal incision  may be sutured, although this is usually not necessary unless the  flap interferes with the introduction of the telescope or instruments,  or there is a contralateral perforation at the same level. Through  and through absorbable sutures can be used for this purpose.  Blood is allowed to drain through the horizontal incision to  minimize the risk of hematoma formation.   Gentle pressure dressings or packing are generally not required  unless the septal incisions are completely sutured, in which case  these techniques help to minimize the risk of septal hematoma  formation. Septal splints may be considered to provide stabilization  of the cartilaginous septum and minimize the risk of adhesions  to the lateral nasal wall, and have been demonstrated to improve  mucosal status in the postoperative period.*   In cases with caudal septal deviation, a traditional hemi-  transfixion incision is made, requiring the use of a headlight. A  mucoperichondrial flap is elevated on the ipsilateral side. A caudal  strut of cartilage is preserved and left attached to the mucoperi-  chondrium of the contralateral side. Posterior to the caudal strut,  the cartilage is incised, and a contralateral submucoperichondrial  plane is created as in the description of the endoscopic septoplasty  described above. The anterior nasal spine is identified, and the  deviated anterior septum is detached from the nasal spine. A  persistent caudal concavity to the ipsilateral side may also require  scoring (horizontally) with a scalpel. The endoscope may then be  inserted through the mucosal incision and the remainder of the  procedure is performed using the endoscopic technique.    Endoscopic septoplasty:  correct level of transillumination behind the nasal  bone and superior to the rhinion    Endoscopic septoplasty:  incorrect level of transillumination caudal to the  rhinion, risking dorsal collapse    1 Rudmik L, Mace J, Ferguson BJ, Smith TL. Concurrent septoplasty during endoscopic  sinus surgery for chronic rhinosinusitis: does it confound outcomes assessment?  Laryngoscope 2011;121:2679-2683.   2 Hwang PH, McLaughlin RB, Lanza DC, Kennedy DW. Endoscopic septoplasty: indications,  technique, and results. Otolaryngol Head Neck Surg 1999;120:678-682.   3 Han JK, Stringer SP, Rosenfeld RM, et al. Clinical consensus statement: septoplasty with  or without inferior turbinate reduction. Otolaryngol Head Neck Surg 2015;153:708-720.   4 Jung YG, Hong JW, Eun YG, Kim MG. Objective usefulness of thin silastic septal splints  after septal surgery. Am J Rhinol Allergy 2011;25:182-185.    Middle turbinate enlargement may be due to hypertrophy or the  presence of a concha bullosa. In such cases, a middle turbinate  reduction or turbinoplasty may be indicated to improve visualiza-  tion or access to the nasal cavity or sinuses during an endoscopic  procedure, to relieve resultant obstruction of the osteomeatal  complex in the case of recurrent acute or chronic rhinosinusitis,  and in some cases, to improve nasal airway obstruction.'” Although  the diagnosis of rhinologic headache is controversial, if headache  is suspected to be caused by contact between an enlarged middle  turbinate and the adjacent structures, turbinoplasty may be  indicated.3*   A conservative reduction of the middle turbinate head can be  performed without adversely affecting the nasal airway, olfaction,  or ostial drainage from the anterior ethmoids or frontal sinuses.*°  The procedure is performed using a Tru-Cut forceps or microde-  brider, starting anteriorly and moving posteriorly toward the tail  of the middle turbinate (Figs. 10.1 and 10.2). The posterior  attachment (tail) of the resected portion of the middle turbinate  is usually freed with a microdebrider and cauterized.    Care is taken to sharply resect the middle turbinate head while  avoiding fracturing or de-epithelializing the vertical lamella of the  turbinate adjacent to the olfactory cleft. If sharp resection is not  adequately performed, or if a microdebrider is improperly used,  the oscillations of the microdebrider may inadvertently fracture  the vertical lamella of the middle turbinate, rendering it unstable.  This can lead to lateralization of the middle turbinate, resulting  in maxillary, ethmoid, and/or frontal sinus obstruction. If this  occurs, the ethmoid cavity can be temporarily lightly packed with  resorbable biomaterials or nonabsorbable packing, to keep the  middle turbinate from lateralizing. Alternatively, an absorbable  suture may be placed between the middle turbinate and nasal  septum. The mucosal membranes on the medial aspect of the  middle turbinate as well as around its “axilla” are preserved to  avoid scarring of the olfactory cleft or frontal recess, respectively.   In the case of a concha bullosa, reduction of the lateral portion  of the middle turbinate is preferably performed using cold instru-  mentation in attempt to minimize the risk of fracture of the vertical  lamella. However, a microdebrider may also be carefully used. A  vertical incision is made through the mucosa and the thin bone  of the pneumatized middle turbinate head, dividing the medial  from the lateral bony lamella of the concha bullosa. The lateral  conchal bone can then be resected with a Tru-Cut forceps or  microdebrider, leaving the medial conchal bone and vertical lamella  intact, up against the nasal septum.    Medial edge of the basal (ground)  lamella of the middle turbinate  after head removal    Havas TE, Lowinger DS. Comparison of functional endonasal sinus surgery with and  without partial middle turbinate resection. Ann Otol Rhinol Laryngol 2000; 109:634-640.  Banfield GK, McCombe A. Partial resection of the middle turbinate at functional endoscopic  sinus surgery. J R Army Med Corps 1999;145:18-19.   Patel ZM, Kennedy DW, Setzen M, Poetker DM, DelGaudio JM. “Sinus headache”: rhinogenic  headache or migraine? An evidence-based guide to diagnosis and treatment. Int Forum  Allergy Rhinol 2013;3:221-230.    Choby GW, Hobson CE, Lee S, Wang EW. Clinical effects of middle turbinate resection  after endoscopic sinus surgery: a systematic review. Am J Rhinol Allergy 2014;28:502-507.  Giacchi RJ, Lebowitz RA, Jacobs JB. Middle turbinate resection: issues and controversies.  Am J Rhinol 2000;14:193-197.   m Posterior fontanelle area and posterior third of the inferior  turbinate    Using an angled probe, the uncinate process, hiatus semilunaris,  and infundibulum are identified. The uncinate process is gently  fractured with the angled probe and carefully removed with a  backbiting forceps to expose the lateral (orbital) wall of the ethmoid  infundibulum and the maxillary sinus natural ostium (Fig. 11.2).  As the surgeon gains more experience with the procedure, powered  instrumentation may be used for the uncinectomy, while carefully  avoiding any injury to the lamina papyracea and conserving the  mucosa on the lateral infundibular wall.   Alternatively, a sickle knife or the sharp edge of a Freer elevator  may be used to incise through the anterior attachment of the  uncinate process, just above the inferior turbinate. This is followed  by removal of the uncinate with a straight biting Blakesley forceps.  However, this technique has been discouraged for less experienced  surgeons because it may lead to inadvertent injury of the lamina  papyracea.!   The tail or posteroinferior remnant of the uncinate may occlude  the natural ostium. Thus, this remnant must be identified and  removed to clearly see the natural ostium of the maxillary sinus.  This may be performed using a side-biting or backbiting forceps,  or can be carried out with the help of a microdebrider. Care is  taken to avoid unnecessary injury of the inferior turbinate lamella  to which the uncinate process is attached inferiorly. On the other  hand, the superior-most part of the uncinate may be left intact  if exposure of the frontal recess is not indicated.” Otherwise, this  part of the uncinate can be removed with an upbiting forceps or,  for more experienced surgeons, with a microdebrider.   After an adequate uncinectomy is performed, the surgeon  should be able to clearly identify the natural ostium of the  maxillary sinus. The superior border of the natural ostium  demarcates the junction of the medial orbital floor (MOF) with  the lamina papyracea (i.e., the junction of the orbital floor with  the medial wall of the orbit) (Figs. 11.3 and 11.4). A curved  suction, with its tip directed inferolaterally away from the lamina  papyracea, can be passed through the natural ostium into the  maxillary sinus.    For limited disease of the anterior ostiomeatal complex, an  uncinectomy with exposure of the maxillary natural ostium, and  a limited antrostomy may be all that is necessary. However, if  there is significant sinus disease, then the MOF should be identified  through a wider middle meatal antrostomy prior to proceeding  with an ethmoidectomy. As the surgeon gains more experience  with the procedure, identification of the MOF may merely require  visualizing the superior margin of the maxillary sinus natural  ostium, obviating the need for unnecessary wide antrostomy.   In patients with advanced sinonasal disease (such as allergic  fungal rhinosinusitis and nasal polyps), as well as in revision  surgery, a wide antrostomy may be indicated.*° This is carried  out by removal of the posterior fontanelle. As the wide antrostomy  is created, the surgeon should be able to identify the MOF, which  corresponds to the superior horizontal bony ridge of the antrostomy.  The surgeon should be aware that the MOF rises a bit superiorly  as one proceeds posteriorly. However, the horizontal level of the  MOF always remain below the skull base, and thus helps in keeping  the surgeon oriented in a safe and correct anteroposterior trajectory    Medial (cut edge) of the middle turbinate  basal lamella (horizontal portion)    as he or she proceeds through the ethmoid air cells, toward the  sphenoid sinus (Figs. 11.5 and 11.6).°°   In the absence of any “normal” ostiomeatal complex landmarks,  or when there is difficulty identifying the natural ostium of the  maxillary sinus, the maxillary sinus can be entered through the  posterior fontanelle, superior to the posterior third of the inferior  turbinate. This approach ensures that the surgeon remains at a  safe distance below the orbital floor, because the latter rises  superiorly as one proceeds posteriorly away from the maxillary  natural ostium (Fig. 11.7). The surgeon should be also aware that  the orbit floor is higher medially than laterally.   When performing the antrostomy through the posterior fon-  tanelle area, care must be taken that the nasal as well as the  medial maxillary sinus mucosa are both penetrated. Failure to do  so may result in lateral elevation of the medial maxillary sinus  mucosa and subsequent formation of a maxillary sinus cyst, or  mucocele. A curved frontal curette with a sharp edge may be  used for this purpose. A wider antrostomy is then created by  moving anteriorly toward the maxillary natural ostium in a    Superior inclination of the orbital floor as one  proceeds toward the sphenoid ostium   floor fontanelle area  staying a greater  distance from  the orbital floor    Correct AP trajectory  (staying at the level of  the orbital floor)   retrograde fashion. The site of the natural ostium needs to be    A wide antrostomy is created by removing most of the posterior  fontanelle. During posterior enlargement of the antrostomy through  the fontanelle area, it is important not to take down the posterior  vertical ridge of the antrostomy too flush with the coronal plane  of the posterior wall of the maxillary sinus, to avoid injuring the  greater palatine nerve, which descends in its canal within this  ridge (vertical plate of the palatine bone), at the junction of the  medial and posterior walls of the maxillary sinus.    Retrograde enlargement of the maxillary antrostomy, starting  in the posterior fontanelle area, may be minimally carried out by  anteriorly following the MOF, along the horizontal antrostomy  ridge, to a point just behind the convexity of the nasolacrimal  duct. At this point, the MOF, being lower anteriorly, appears to  be approximating the lamellar attachment of the inferior turbinate  to the lateral nasal wall.   The MOF must always be kept in view, and be constantly referred  to, throughout the endoscopic surgery. Failure to visualize the  superior margin of the antrostomy (i.e., the MOF) may cause the  surgeon to unknowingly proceed in a more superior direction  toward the skull base (Fig. 11.8). The camera alignment on the  monitor screen must also be periodically checked to ensure that  the camera has not been inadvertently rotated. The endonasal  anatomy should be aligned so that the upper border of the monitor  screen corresponds to the superior part of the anatomy (Fig. 11.9).  The opening of the antrostomy should always face medially in  the sagittal plane (parallel to the nasal septum), with the superior  horizontal antrostomy ridge projecting in an anteroposterior  direction toward the orbital apex.   The surgeon should be able to identify the posterior wall of the  maxillary sinus and the posterior vertical bony ridge of the  antrostomy. The posterior wall of the maxillary sinus, as seen  through the antrostomy, demarcates the approximate level of the  coronal plane of the anterior wall of the sphenoid sinus (or the  posterior wall of the posterior ethmoid) approximately 7 cm from  the columella, adjacent to the nasal septum posteriorly (Fig. 11.9).   Whenever indicated, the surgeon can pass angled scopes and  instruments through the middle meatal antrostomy to visualize,  and gain access to, the inferior, lateral and anterior walls and  recesses of the maxillary sinus as required.    1 Singhania AA, Bansal C, Chauhan N, Soni S. A comparative study of two different  uncinectomy techniques: swing-door and classical. Iran J Otorhinolaryngol 2012;24:  63-67.   2 Byun JY, Lee JY. Usefulness of partial uncinectomy in patients with localized maxillary  sinus pathology. Am J Otolaryngol 2014;35:594-597.   3 Lee JM, Chiu AG. Role of maximal endoscopic sinus surgery techniques in chronic  rhinosinusitis. Otolaryngol Clin North Am 2010;43:579-589, ix.   4 Schaefer SD. An anatomic approach to endoscopic intranasal ethmoidectomy. Laryngoscope  1998;108(11 Pt 1):1628-1634.   5 May M, Schaitkin B, Kay SL. Revision endoscopic sinus surgery: six friendly surgical  landmarks. Laryngoscope 1994;104(6 Pt 1):766-767.   6 Casiano RR. A stepwise surgical technique using the medial orbital floor as the key  landmark in performing endoscopic sinus surgery. Laryngoscope 2001;111:964-974.   7 Harvey RJ, Shelton W, Timperley D, et al. Using fixed anatomical landmarks in endoscopic  skull base surgery. Am J Rhinol Allergy 2010;24:301-305.   8 Wuttiwongsanon C, Chaowanapanja P, Harvey RJ, et al. The orbital floor is a  surgical landmark for the Asian anterior skull base. Am J Rhinol Allergy 2015;29:  e216-e219.    g Horizontal (Superior) antrostomy ridge  @ Medial orbital floor (MOF)  mg Lamina papyracea (Medial orbital wall)    The anterior ethmoid air cells are located medial to the horizontal  antrostomy ridge and medial to the lamina papyracea. The ethmoid  bulla is the inferior-most anterior ethmoid air cell, adjacent and  superomedial to this ridge (Fig. 12.1). The ethmoid bulla is first  entered inferomedially away from both the skull base and the  lamina papyracea. This is followed by removal of the anterior and  inferior walls of the ethmoid bulla. The medial wall of the bulla  is the lamina papyracea and the adjacent part of horizontal  antrostomy ridge and the MOF. The posterior wall of the bulla  is formed by the coronally oriented basal lamella of the middle  turbinate and may be separated from it by a retrobullar recess.  The superior wall of the ethmoid bulla can extend up to the skull  base, or may be separated from it by one or more suprabullar  cells.! If a microdebrider is used for the ethmoidectomy, care is  taken to keep the microdebrider opening pointed perpendicular  or away from the lamina papyracea, until the latter is clearly  identified.   In advanced disease or distorted cavities, the surgeon first  performs an inferior ethmoidectomy to identify early the inferior  portion of the lamina papyracea and its junction with the MOF?    At this point, the surgeon must begin to regularly palpate the eye  prior to removing any additional ethmoidal cells. By looking for  movement in the orbital wall, bony dehiscences and periorbita  exposure may be identified, and the lateral limit of dissection is  determined. The key to a safe ethmoidectomy is early identification  of the lamina papyracea.   The surgeon should be aware that the lamina papyracea location  is variable in relation to the sagittal plane of the lower margin of  the middle meatal antrostomy, where the inferior turbinate inserts  into the lateral nasal wall (Herzallah classification, Fig. 12.2).° In  type I, which accounts for two thirds of the cases, the lamina  papyracea is located within 2mm on either side of this sagittal  plane; in type Il, the lamina is positioned more than 2mm medial  to this plane and thus is more prone to inadvertent penetration  during anterior ethmoid dissection; and in type III, the lamina  papyracea is more than 2mm lateral to this sagittal plane (e.g.,  due to expansion by allergic fungal mucin). In the latter type, the  surgeon needs to perform a somewhat more lateral dissection to  ensure clearance of ethmoid air cells over the lamina papyracea.  However, many of these cases are accompanied by bony erosion  or dehiscence, with periorbital exposure and a higher risk of injury.*   A good exercise, in the cadaver lab, is to fracture or remove a  small piece of bone from the lamina papyracea to illustrate the  movement of the periorbita while palpating the eye (Fig. 12.3).  This step is further reviewed in Chapter 32.    The lamina papyracea, once identified, represents the lateral  limits of one’s dissection. The tip of the forceps, or opening of the  microdebrider cannula, should always be pointed away from the  orbit to avoid inadvertent orbital penetration. Once the lamina  papyracea is clearly seen circumferentially around the tip of the  instrument, the opening may be rotated toward the orbit to remove  residual septations, while constantly keeping the tip of the instru-  ment under vision.   The surgeon should initially remain within a safe distance of  approximately 10mm above the level of the horizontal antrostomy  ridge (Fig. 12.4). This corresponds to the approximate size of a    large upbiting forceps. Superior dissection of the anterior ethmoid  air cells is further discussed in Chapter 15.    1 Cashman EC, Macmahon PJ, Smyth D. Computed tomography scans of paranasal sinuses  before functional endoscopic sinus surgery. World J Radiol 2011;3:199-204.   2 Schaefer SD. An anatomic approach to endoscopic intranasal ethmoidectomy. Laryngoscope  1998;108(11 Pt 1):1628-1634.   3 May M, Schaitkin B, Kay SL. Revision endoscopic sinus surgery: six friendly surgical  landmarks. Laryngoscope 1994;104(6 Pt 1):766-767.   4 Casiano RR. A stepwise surgical technique using the medial orbital floor as the key  landmark in performing endoscopic sinus surgery. Laryngoscope 2001;111:964-974.   5 Herzallah IR, Marglani OA, Shaikh AM. Variations of lamina papyracea position from  the endoscopic view: a retrospective computed tomography analysis. Int Forum Allergy  Rhinol 2015;5:263-270.    columella Horizontal line denoting level of the medial  orbital floor and horizontal antrostomy ridge    m Horizontal line from the posterior medial orbital floor (MOF)  to the nasal septum  m Ethmoid roof (fovea ethmoidalis)    The posterior ethmoid air cells may be entered safely through the  basal or ground lamella of the middle turbinate (Fig. 13.2).    } Posterior  Endoscopically, the area of safe entry through the basal lamella ethmoids  is at the middle third of an imaginary horizontal line drawn at ;  the level of the posterior MOF to the nasal septum (Fig. 13.3). By ety    using this landmark, the surgeon consistently enters the inferior-  most posterior ethmoid air cells adjacent to the transitional ridge  of the middle meatal antrostomy (the junction between the  horizontal and vertical antrostomy ridges).! The floor of the  inferior-most posterior ethmoid cell floor can be easily identified  at or slightly inferior to the level of the posterior MOF and medial  to the transitional ridge of the antrostomy (Fig. 13.4). Upon entering  the posterior ethmoids, the surgeon should first dissect the inferior  posterior ethmoid air cells just posteromedial to the transitional  ridge of the maxillary antrostomy, and along the inferior portion  of the medial orbital wall, toward the anterior sphenoid wall. This Horizontal portion of basal or ground  is carried out prior to dissection of the more superior posterior lamella of the middle turbinate  ethmoid air cells. Fig. 13.1    Vertical portion of the  basal (ground) lamella  separating the suprabullar  cells from the superior  posterior ethmoid cells   turbinate inferior posterior  ethmoidal cells  through the middle  turbinate basal lamella  at the orbital floor level  and 5 cm from the  columnella   of entry into  the sphenoid  sinus at 7 cm  from the  columnella    By following the lateral (ethmoid) surface of the middle turbinate  anteroposteriorly, the surgeon can reach the superior turbinate  and the sphenoethmoidal recess, after removing a portion of the  basal lamella. The space between the middle and superior turbinates  (superior meatus) can now be seen from the posterior ethmoid  cavity, and is the same recess that one can see from the nasal  cavity between the superior and middle turbinates as seen from  the septal side. This space is the common outflow tract for the  posterior ethmoid cells (Fig. 13.5).   For teaching purposes, particularly in the microsurgical lab,  the space between the middle and superior turbinates (superior  meatus) can be easily confirmed by passing a probe or a dissector  in the nasal cavity between the nasal septum and the medial  surface of the middle turbinate until the tip of the dissector reaches  the meatus, which is a recess or space between the middle and  superior turbinates that forms the drainage outflow tract to the  posterior ethmoid air cells. One can track this outflow proximal to  the ethmoid cavity (Fig. 13.5). It should be noted that the superior    Vertical (superior)  portion of basal  (ground) lamella  of the middle  turbinate    Safe zone of entry  into the inferior posterior  ethmoid cell at 5 cm from  the columnella posterior  ethmoid floor seen at or slightly  below the medial orbital floor level    Horizontal (inferior)  portion of basal  (ground) lamella of  the middle turbinate    Transantral view of completed middle meatal  antrostomy looking medially (left side)    insertion of the antrostomy oftheantrostomy b  Posterior ethmoid  seen through  Superior superior meatus  turbinate >  Septum her  (rostrum area) funp nate  basal  lamella a  Vertical portion of Medial orbital  middle turbinate : wall: anterior  basal lamella } VA ethmoid cavity  f Transitional  : ridge of the  Superior antrostomy  turbinate  Posterior  orbital  Superior floor  meatus  Posterior wall:  Cut end of the maxillary sinus  basal lamella of the  middle turbinate  Posterior ethmoid and basal Medial orbital wall:  lamella of the superior turbinate inferior posterior  (anterior wall of sphenoid sinus) ethmoid cavity b    turbinate might be challenging to identify in some revision or  extensive polyp cases. In these cases, the posterior MOF is the  principal landmark used in identifying the level of initial entry  into the sphenoid sinus ostium area, adjacent to the posterior  nasal septum. Nevertheless, identification of the superior turbinate  facilitates identification of the sphenoid ostium in an uncomplicated  case,*>> as is typically performed during a transnasal pituitary  adenoma removal. This is discussed further in subsequent chapters.   The surgeon should also dissect the posterior ethmoid air cells  that extend inferolaterally along the slope of the lamina papyracea  into the retromaxillary area. This ensures clearance of disease  from this frequently missed location, helps correct identification  of the lamina papyracea posteriorly, and also provides better access  to the lateral part of the sphenoid sinus.® This retromaxillary  posterior ethmoid air cell was also referred to as the Herzallah  cell (Fig. 13.6), to be differentiated from the Haller cell which is  located more anteriorly as an infraorbital extension of the anterior  ethmoid air cells along the roof of the maxillary sinus. Once the  lateral (orbital) and the medial (turbinate) walls of the posterior  ethmoids have been identified, the surgeon may proceed with  further dissection of the superior cells of the posterior and anterior  ethmoid cavity, including the suprabullar area, thus completing  the total ethmoidectomy. In advanced disease, where a sphenoid  sinusotomy may already be planned, it is safer to postpone further    superior ethmoid dissection until a sphenoidotomy is performed,  and the sphenoid roof and lateral wall are identified. This enables  safer identification of the posterior ethmoid roof and the postero-  medial orbital wall, by following the sphenoid roof (planum) and  the lateral sphenoid wall, respectively. This is carried out in a  retrograde (posteroanterior) direction as described in the Wigand  approach in Chapter 2, and as will be discussed in more detail in  Chapter 15. Such an approach is especially important for revision  cases with distorted anatomy.    1 Casiano RR. A stepwise surgical technique using the medial orbital floor as the  key landmark in performing endoscopic sinus surgery. Laryngoscope 2001;111:  964-974.   2 Gupta T, Aggarwal A, Sahni D. Anatomical landmarks for locating the sphenoid ostium  during endoscopic endonasal approach: a cadaveric study. Surg Radiol Anat 2013;35:  137-142.   3  Eweiss AZ, Ibrahim AA, Khalil HS. The safe gate to the posterior paranasal sinuses:  reassessing the role of the superior turbinate. Eur Arch Otorhinolaryngol 2012;269:  1451-1456.   4 Kim HU, Kim SS, Kang SS, Chung IH, Lee JG, Yoon JH. Surgical anatomy of the natural  ostium of the sphenoid sinus. Laryngoscope 2001;111:1599-1602.   5 Orlandi RR, Lanza DC, Bolger WE, Clerico DM, Kennedy DW. The forgotten turbinate:  the role of the superior turbinate in endoscopic sinus surgery. Am J Rhinol 1999;13:  251-259.    posterior ethmoid air cells: novel description and surgical implications. Otolaryngol  Head Neck Surg 2016;155:340-346    m Superior turbinate tail and basal lamella and adjacent nasal  septum, ~7cm from the columella   m Horizontal line from the posterior MOF to the posterior nasal  septum    Once the superior turbinate is identified, the sphenoid ostium  can be located superomedial to the tail of the superior turbinate  and adjacent to the nasal septum (Fig. 14.2). The ostium lies  approximately 1.5 to 2cm above the arch of the posterior choana  and 7cm from the nasolabial angle of the columella.'” The area  of the sphenoid natural ostium in the anterior wall of the sinus  usually lies at the middle third of the sphenoid sinus’s vertical  height. For this reason, the sphenoid sinus floor, which lies sig-  nificantly inferior to the ostium, is not readily visible upon the  initial opening. Variable degrees of sphenoid sinus pneumatization  may exist, sometimes extending into the pterygoid process and  the greater wing of the sphenoid bone, to create a prominent  lateral sphenoid recess (Fig. 14.3).    Base  of the  pterygoid  bone  Lateral  pterygoid  plate  Vidian Sphenoid Pharyngealor Medial  foramen rostrum palatovaginal pterygoid  canal (artery) plate  Fig. 14.1  : Superior  Sphenoid turbinate  ostium (tail)  Middle  turbinate    A direct transnasal sphenoid sinusotomy may be performed via  the sphenoethmoidal recess, medial to the middle turbinate,  without performing an ethmoidectomy or antrostomy (Fig. 14.4).  The superior turbinate is exposed endoscopically by reducing the  middle turbinate head, if enlarged (as previously described).  Otherwise, the middle turbinate may be lateralized with a periosteal  elevator. As discussed previously, the sphenoid is initially identified  adjacent to the nasal septum, and superomedial to the tail of the    Correct trajectory into the sphenoid sinus  adjacent to the nasal septum, at the level  of the sphenoid sinus natural ostium    Transethmoidal trajectory into the  sphenoid sinus, risking inadvertent  penetration into the carotid artery    superior turbinate, with a small straight ball probe or periosteal  elevator. With gentle two-finger pressure and walking superiorly  between the nasal septum and the superior turbinate tail, the  ostium area is entered approximately 1cm superomedial to the  superior turbinate tail.’   Entering the sphenoid medially, through the area of its natural  ostium, keeps the surgeon away from the critical structures, and  obviates the possibility of inadvertent injury to the sphenoid  internal carotid artery (ICA) located more laterally (Fig. 14.5). The  latter may occur when a blind transethmoidal entry into the  sphenoid sinus, lateral to the tail of the superior turbinate, is  performed. Entering the sphenoid medially also permits enlarge-  ment of the normal sphenoid ostium, thus restoring the normal    mucociliary flow of the sphenoid sinus. It also minimizes the risk  of creating a separate drainage area through the back wall of the  posterior ethmoid sinus.   In a well-pneumatized sphenoid, its posterior wall measures  approximately 9cm from the base of the columella. The posterior  wall of the sphenoid (clivus) is palpated to confirm entry into the  sphenoid, before proceeding to open up the face of the sphenoid.   The sphenoid ostium is enlarged inferomedially, and then laterally  by resecting the posterior (inferior) third of the superior turbinate  and its basal lamella (which forms part of the common wall  between the posterior ethmoid cells and the sphenoid sinus).  Lateral enlargement of the sphenoid ostium should be kept initially  inferior to the MOF level, resecting this posterior (inferior) portion  of the superior turbinate and adjacent basal lamella. A Kerrison  rongeur, mushroom punch, or powered instrumentation, may be  used to carefully remove this wall only after confirming an air-  containing space behind it. Blind removal, without confirming an    Suprabullar ethmoidal cells  Vertical (superior) portion  of basal (ground) lamella  of the middle turbinate    Safe zone  of entry into  the sphenoid  sinus at 7 cm  from the    air-containing space, can risk inadvertent injury to the ICA. The  upper two thirds of the superior turbinate vertical lamella, adjacent  to the cribriform plate, are preserved to avoid olfactory epithelial  damage and permanent hyposmia or anosmia.?* Olfactory anatomy  is discussed in Chapter 17.   When significant anatomic distortion exists in the area of the  sphenoethmoidal recess, the superior turbinate may not be clearly  visible. In these situations, the MOF is used to determine the  approach into the sphenoid sinus (Fig. 14.6). The sphenoid sinus  is entered and identified medially adjacent to the nasal septum,  approximately 7cm from the base of the columella, at the level  of the posterior MOF. When the posterior MOF is used as a reference  point, the sphenoid sinus will be entered consistently in its middle  third, adjacent to the nasal septum, at the level of the sphenoid  natural ostium (red arrow in Fig. 14.6b).’ Once the common wall  between the sphenoid and posterior ethmoid sinuses is removed,  one can appreciate that most of the sphenoid sinus cavity lies    below the level of the MOF, and conversely, most of the posterior  ethmoid cells lie above the MOF (Fig. 14.7).   Surgeons may also use the natural curvature of the maxillary  middle meatal antrostomy to direct them toward the sphenoid  sinus in an inferomedial direction as they proceed posteriorly  (Fig. 14.8). If the maxillary natural ostium (or anterior antrostomy  ridge) is used as a reference point, then the sphenoid will be  entered slightly more inferiorly, where thicker bone may be  encountered, necessitating a bone curette or cutting bur to facilitate  removal.    Inferomedial  trajectory as one  proceeds toward  the sphenoid sinus  1 cm superior and  parallel to the  antrostomy ridge    1 Gupta T, Aggarwal A, Sahni D. Anatomical landmarks for locating the sphenoid ostium  during endoscopic endonasal approach: a cadaveric study. Surg Radiol Anat 2013;  35:137-142.   2 Casiano RR. A stepwise surgical technique using the medial orbital floor as the key  landmark in performing endoscopic sinus surgery. Laryngoscope 2001;111:964-974.   3 Say P, Leopold D, Cochran G, Smith L, Greiner T. Resection of the inferior superior  turbinate: does it affect olfactory ability or contain olfactory neuronal tissue? Am J  Rhinol 2004;18:157-160.   4 kim KS, Choi YS, Kim HJ, Yoon JH. The risk of olfactory disturbance from conchal plate  injury during ethmoidectomy. Am J Rhinol 2003;17:307-310.    A superior ethmoid dissection is carefully performed in a pos-  teroanterior and superoinferior direction. This is particularly  effective, and safer, for cases with distorted anatomy (i.e., revision  cases, significant polyps, osteoneogenesis, or bone erosion). Initially,  the surgeon restricts the dissection to an area adjacent to the  orbital wall and lateral ethmoid roof where the bone is thickest  (Fig. 15.1). Additional passes along the medial ethmoid roof are  then performed to open up more medially located cells, once the  roof of the ethmoid is identified laterally.   A small ball probe is used to carefully fracture individual eth-  moidal septations away from the orbit and skull base, and picked  up with a forceps or suction tip. If the septations are thick due  to osteoneogenesis, a Kerrison rongeur may be used. A microde-  brider can be carefully used to shave loose mucosal edges overlying    The fovea ethmoidalis or roof of the ethmoid air cells  slopes inferomedially toward the skull base attachment  of the middle and superior turbinate vertical lamellae.  Its bone is thicker adjacent to the orbit.    these septations. However, the tip opening of the microdebrider  should initially be kept facing away from the orbit and skull base,  until these structures are clearly visualized circumferentially around  the tip. Never blindly enter or palpate an unknown cavity, or  fracture skull base septations with a microdebrider.   The surgeon should observe that the roof of the anterior ethmoid  slopes medially by as much as 45 degrees. Bone tends to be thicker  in areas where there is bony septation perpendicularly attached to  a bony wall. For example, in the case of the ethmoid roof, the bone  is thicker laterally close to the orbit and thinner medially, adjacent  to the middle turbinate vertical lamella insertion into the skull base,  lateral to the cribriform plate. The degree of thinning at the level of  the olfactory fossa (the length of the thin lateral lamella that joins  the fovea ethmoidalis to the cribriform plate) has been classified by  Keros, if only to bring awareness to the surgeon as to the variability  of bony thinning in this area, where the surgeon has to exhibit the  highest degree of caution, so as to minimize inadvertent intracranial  penetration.'? Keros classified the olfactory fossa depth as follows:  type 1, olfactory fossa 1 to 3mm deep; type II, olfactory fossa 4 to  7mm deep; type III, olfactory fossa 8 to 16mm deep. In type Ill  olfactory fossae, the surgical risk of intracranial entry during endo-  scopic sinonasal surgery increases if one is not careful (Fig. 15.2).    Measurement points for the  olfactory fossa depth under  the Keros classification    As surgeons proceed with the retrograde dissection along the  skull base, they should keep in mind that the anterior ethmoid  artery may be hanging in a bony mesentery below the skull base,  approximately 5 to 10mm behind the frontal recess, in approxi-  mately one third of cases. Such a low position of the artery is  particularly found in cases with significant supraorbital ethmoidal  pneumatization (Fig. 15.3).4 To minimize the risk of arterial  retraction and orbital hematoma, dissection in this area should  initially start medially (in contrast to what was previously discussed  for ethmoid roof dissection). If there is inadvertent laceration of  the artery medially, then there is less risk of retraction, and the  artery can be easier to cauterize.   Note that the anterior ethmoid artery is situated approximately  1cm posterior to the posterior wall of the frontal infundibulum  and courses in an anteromedial direction over the anterior  fovea ethmoidalis in the roof of the superior-most suprabullar  ethmoidal cell. This will be discussed in more detail in a subsequent  chapter.    Whenever possible, the mucosa along the orbital wall and  ethmoid roof is left undisturbed to avoid granulations, osteitis,  prolonged healing, osteoneogenesis, and fibrosis. Only the mucosa  overlying the septations is removed. This can be facilitated by the  use of cutting forceps or powered instrumentation. However, this  may not always be possible, or advisable, particularly in revision  cases with severe destructive nasal polyps, “condemned mucosa,”  osteoneogenesis, and skull base or orbital bone erosion.    1 Erdogan S, Keskin IG, Topdag M, Ozturk M, Sari F, Mutlu F. Ethmoid roof radiology;  analysis of lateral lamella of cribriform plate. Otolaryngol Pol 2015;69:53-57.   2 Ramakrishnan VR, Suh JD, Kennedy DW. Ethmoid skull-base height: a clinically relevant  method of evaluation. Int Forum Allergy Rhinol 2011;1:396-400.   3 Keros P. Uber die praktische Bedeutung der Niveauunter-schiede der Lamina cribrosa  des Ethmoids. Laryngol Rhinol Otol 1965;41:808-813.   4 Jang DW, Lachanas VA, White LC, Kountakis SE. Supraorbital ethmoid cell: a consistent  landmark for endoscopic identification of the anterior ethmoidal artery. Otolaryngol  Head Neck Surg 2014;151:1073-1077.   w Vertical line from the maxillary natural ostium area, posterior  and parallel to the nasolacrimal duct and sac convexity    The frontal recess is bordered anteriorly by the posteromedial  wall of the agger nasi or frontal infundibular cells, posteriorly by  the anteromedial face of the superior-most suprabullar air cells,  laterally by the upper part of the lamina papyracea, and medially  by the vertical lamella of the middle turbinate (Fig. 16.1). The  frontal sinus infundibulum (lower funnel-shaped part of the frontal  sinus) and the frontal ostium are found more anterolateral to the  frontal recess, so that the infundibulum lies superior to the agger  nasi or the superior-most frontal infundibular cell. In other words,  the frontal recess lies between two columns of air cells: an anterior  column composed of the uncinate process, agger nasi, and/or  frontal infundibular cells, and a posterior column composed  of the bulla and suprabullar ethmoid air cells (Fig. 16.1b and    Fig. 16.2). However, the majority of the frontal infundibulum  actually lies in the plane of the uncinate process, agger nasi, and  frontal infundibular cells (anterior column shaded in red in Fig.  16.2b). The frontal infundibulum, frontal ostium, and frontal recess  together make up the frontal sinus outflow tract.'   Anatomic variants along the frontal sinus outflow tract may  become diseased and contribute to the obstructive problem.”?  Frontal cells were classified into four types (frequently called frontal  recess cells, frontal infundibular cells, or Kuhn cells): type I, one  cell above the agger nasi cell; type II, two or more cells above the  agger nasi cell, but below the level of the frontal infundibulum;  type III, at least one cell extending into the frontal sinus; type IV,  independent cell not in contiguity with the other cells and within  the frontal sinus (Fig. 16.3). In the recent international frontal  sinus anatomy classification,’ type I and II cells are referrer to as  “supra agger cells”, while type III is called “supra agger frontal  cell”. On the other hand, the posterior column of cells in relation  to the frontal recess includes: supra bulla cell (cell above the bulla  ethmoidalis that does not enter the frontal sinus); supra bulla  frontal cell (cell that originates in the supra-bulla region and  pneumatizes into the posterior region of the frontal sinus);  supraorbital ethmoid cell (an anterior ethmoid cell that pneumatizes    Frontal sinus infundibulum  Posterior Anterior Superior-most (arrow denotes outflow tract  ethmoid artery ethmoid artery suprabullar cell through frontal recess)   Column of cells (agger and frontal infundibular)  b at the coronal plane of the uncinate process    around, anterior to, or posterior to the anterior ethmoidal artery  over the roof of the orbit). Lastly, one more cell in relation to the  frontal recess is the frontal septal cell that can push the drainage  pathway laterally.   Additionally, the degree of pneumatization varies among patients  as well as and from one side to the other. Aplastic or hypoplastic  frontal sinus cavities may be present. The frontal sinus also  undergoes progressive degrees of pneumatization from birth to  adulthood (Fig. 16.4).   The coronal plane of the frontal sinus infundibulum (Fig. 16.5)  is identified by drawing a line superiorly from the anterior border  of the antrostomy (i.e., maxillary natural ostium area or uncinate  process, anterior to the face of the ethmoid bulla) to a point 5 to  10mm behind the anterior attachment, or “axilla,” of the middle  turbinate (green dashed arrow in Fig. 16.5a). As noted previously,  this corresponds to the column of cells in the plane of the uncinate,  agger nasi, and frontal infundibular cells. If one takes a more  posterior course, at the level of the ethmoid bulla and suprabullar    cells, one may be directed too far posteriorly toward the back wall  of the frontal infundibulum (red dashed arrow in Fig. 16.5a). This  may result in an inadvertent penetration of the skull base at this  level. Endoscopically, the correct point of entry into the frontal  recess and infundibulum with a small ball probe will be in a  superolateral direction, adjacent to the middle turbinate vertical  lamella, and slightly posterior to the coronal plane of the superior  attachment of the uncinate process, but anterior to the coronal  plane of the anterior wall of the ethmoid bulla (Fig. 16.6). The  tip of the probe should be directed slightly laterally toward the  orbital roof to avoid inadvertent skull base penetration through  the lateral lamella of the cribriform plate. A two-finger (i.e., gentle)  technique should be used to probe the frontal recess and infun-  dibulum, with minimal or no pressure exerted. Probing of the  frontal sinus should never be lateral, or adjacent to the medial  orbital wall, and in a medial direction (Fig. 16.7). This can result  in advertent penetration through the lateral lamella of the crib-  riform plate or medial fovea ethmoidalis.    Middle turbinate Frontal sinus .  vertical lamella infundibulum Suprabullar cell Frontal sinus    Frontal anterior  ronal attachment  sinus  recess Frontal sinus  recess  Superior-most  a suprabullar cell b  Fig. 16.8a, b  Middle turbinate Frontal sinus  vertical lamella infundibulum Suprabullar cell Medial wall type |  Frontal frontal cell    The anterior ethmoid artery (see Chapter 15) is located at an  average of 20mm (range, 17 to 25 mm) from the anterior attach-  ment of the middle turbinate, or 10mm behind the posterior  border of the frontal sinus infundibulum.’ The septations that  comprise the roof of the suprabullar cells, and the agger nasi or  frontal cells, are gently displaced anteroinferiorly with an angled  probe to avoid inadvertent penetration into the anterior cranial  fossa at the level of the anterior ethmoid artery.   A Draf type I frontal sinusotomy is performed when the cells  around the frontal recess are cleared and the frontal sinus ostium  is identified. It entails leaving the roof of the superior-most  suprabullar and agger nasi (or frontal infundibular) cells intact  (Fig. 16.8). A Draf type Ila frontal sinusotomy entails removing  the roof of these cells to provide clear exposure and transillumina-  tion of the internal frontal sinus cavity (Fig. 16.9). The frontal  sinus opening may be completely obscured by the roof of either  of these cells, so that penetrating the roof is necessary to enter  the frontal sinus (“uncapping the egg”).° A Draf Ila may also involve  further widening of the frontal sinus outflow tract by curetting  the thick bone that forms the mucosally covered bony anterior  boundary of the frontal sinus opening at the frontonasal suture  area, or the so-called frontal beak.’   An upbiting or giraffe forceps is used to carefully collect the  bony fragments of the cells around the frontal sinus outflow tract.  As with the ethmoid, maxillary, and sphenoid sinuses, an attempt  is made to preserve as much of the frontal recess and frontal  infundibulum mucosa circumferentially as possible, to facilitate  healing and to diminish the risk of fibrosis, osteoneogenesis, and  subsequent ostial stenosis or complete closure. Tru-cut forceps  or powered instrumentation with angled cannulas can be used  effectively for this purpose.   Palpation of the posterior wall of the frontal sinus is the key  for confirming the correct identification of the frontal sinus, and  maintaining one’s orientation. Palpation of the posterior frontal  infundibulum wall, with a small angled ball probe, identifies the  coronal plane behind which the anterior skull base (fovea ethmo-  idalis and cribriform plate) is located. Additionally, the medial  (intersinus septum) and lateral (orbital) walls of the frontal  infundibulum should be palpated. Note that the medial wall of    the frontal infundibular opening is made up of the anterior 25%  of the middle turbinate vertical lamella. This is further discussed  in Chapter 23.   Transillumination with a thin fiberoptic light cable or merely  an angled telescope facilitates identification and confirmation of  the frontal sinus. When the frontal sinus is correctly identified,  the telescope’s light transilluminates the frontal area. In contrast,  a supraorbital extension of an ethmoid cell transilluminates in  the medial canthal area.   In the presence of osteoneogenesis or fibrosis, more advanced  extended endoscopic frontal sinusotomy procedures may be  required. A Draf IIb or Draf III may be safely performed as long  as the surgeon maintains the correct orientation anterior to the  coronal plane of the posterior infundibular wall and adjacent  anterior edge of the cribriform plate and olfactory fibers. This is  further discussed in Chapter 23.   For selected indications, one can dilate the frontal recess and  infundibulum with the use of balloon “sinuplasty” instrumentation.  This tends to preserve the frontal infundibular mucosa, and  displaces the medial ethmoidal septations inferolaterally, where  they can be carefully removed with a microdebrider or forceps  in a nontraumatic and mucosa-sparing manner, or just left alone,  as in an in-office balloon sinuplasty as a stand-alone procedure.    1 McLaughlin RB Jr, Rehl RM, Lanza DC. Clinically relevant frontal sinus anatomy and  physiology. Otolaryngol Clin North Am 2001;34:1-22.   2  Langille M, Walters E, Dziegielewski PT, Kotylak T, Wright ED. Frontal sinus cells:  identification, prevalence, and association with frontal sinus mucosal thickening. Am  J Rhinol Allergy 2012;26:e107-e110.   3 Bent JP, Cuilty-Siller C, Kuhn FA. The frontal cell as a cause of frontal sinus obstruction.  Am J Rhinol 1994;8:185-191.   4 Wormald PJ, Hoseman W, Callejas C, Weber RK, Kennedy DW, Citardi MJ, Senior BA,  Smith TL, Hwang PH, Orlandi RR, Kaschke O, Siow JK, Szczygielski K, Goessler U,  Khan M, Bernal-Sprekelsen M, Kuehnel T, Psaltis A. The International Frontal Sinus  Anatomy Classification (IFAC) and Classification of the Extent of Endoscopic Frontal  Sinus Surgery (EFSS). Int Forum Allergy Rhinol. 2016;6:677-696.   5 Lee WC, Ming Ku PK, van Hasselt CA. New guidelines for endoscopic localization of the  anterior ethmoidal artery: a cadaveric study. Laryngoscope 2000;110:1173-1178.   6 Stammberger H. “Uncapping the Egg”: The Endoscopic Approach to Frontal Recess and  Sinuses. Tuttlingen (Germany): Karl Storz; 2004:15-17.   7 Hosemann W, Gross R, Goede U, Kuehnel T. Clinical anatomy of the nasal process of  the frontal bone (spina nasalis interna). Otolaryngol Head Neck Surg 2001;125:60-65.    Section Ill Advanced Endoscopic Sinonasal,  Orbital, and Skull Base Surgical Anatomy  and Techniques    The olfactory area is a region of the superomedial nasal cavity  that is lined by olfactory neuroepithelium, containing the cell  bodies of olfactory receptor neurons (Fig. 17.1). Axons from these  neurons form fiber bundles that traverse the cribriform plate of  the ethmoid bone, to connect with the olfactory bulbs of the  brain.'? Although many routine nasal and sinus procedures do  not involve dissection in this region, rhinologic surgeons must be  familiar with olfactory anatomy, to avoid injury to the skull base,  and for cases in which dissection in this area is necessary. Clinical  situations that require dissection in the olfactory region may  include (1) olfactory mucosal biopsy for diagnostic or research  purposes, (2) partial superior turbinate resection to facilitate safe  identification of the sphenoid natural ostium during sphenoidotomy  or transsphenoidal procedures, (3) removal of polyps arising within  the olfactory cleft, (4) dissection to permit repair of ethmoid roof    meningocele or repair of cerebrospinal fluid (CSF) leak, and (5)  anterior skull base resection for the management of tumors such  as esthesioneuroblastoma. Sphenoidotomy, CSF leak repair, and  skull base resection are covered in detail elsewhere in this manual.  Here we focus on anatomy, landmarks, and dissection at the  olfactory cleft.   When surgically approaching the olfactory cleft, it is important  to review the computed tomography (CT) imaging to determine  the configuration of the skull base (Fig. 17.2). As discussed in  Chapter 15, the Keros classification describes the height of the  olfactory fossa, which informs the surgeon how much lateral  cribriform lamella exists within the surgical field and how much  is vulnerable to iatrogenic injury. Asymmetry between the left  and right fossa is not uncommon. Using the 30-degree endoscope,  the olfactory cleft can be visualized between the nasal septum  and the middle turbinate. If there is a septal deviation or spur, it  may be necessary to first perform a septoplasty. If there is a large  or diseased middle turbinate, or a middle turbinate concha bullosa  deformity, it may be helpful to resect a portion of the middle  turbinate, without destabilizing it. Suction cautery for hemostasis    Schematic organization of the peripheral olfactory anatomy. The olfactory epithelium lines portions of the superior turbinates and cor-    responding septum, and is the site at which inspired odors bind receptors on primary olfactory sensory neurons (OSNs). OSNs are short-lived and are  replaced continually from stem cells (SC) in the basal layers of the epithelium. Sustentacular and microvillar cells (Sus) are glia-like supporting cells;  also depicted are Bowman’s glands, which produce mucus. Axons from the OSNs join to form nerve fibers, which project through the cribriform plate  to synapse in the glomerular layer of the olfactory bulbs. The mitral and tufted neurons of the bulb send fibers to higher centers via the olfactory    Fig. 17.2 The anatomy of the olfactory cleft. (a) Coronal CT slice demonstrates the cribriform plate region. The red marking outlines the area lined  by olfactory mucosa, along the nasal septum superiorly and along the medial face of the vertical lamellae of the superior turbinates. Arrows mark the  vertical lamella of the cribriform plates. (b) The same region is depicted schematically. Note that the olfactory bulbs sit in a fossa intracranially, with  a variable vertical height, which can be assessed by reviewing the CT preoperatively (Keros classification).    following middle turbinate resection is recommended, as obscured  visualization can be dangerous when instrumenting near the skull  base. The superior turbinate should be seen next, when advancing  the endoscope more posteriorly and staying close to the septum.   In cases where an olfactory mucosa biopsy is desired, this may  be performed in the office setting or as part of an operating room  procedure. In the office setting, the nose is decongested with  oxymetazoline and then a small pledget soaked in lidocaine and  oxymetazoline is placed gently between the middle turbinate and  septum for anesthesia. A small amount of lidocaine 1% with  epinephrine 1:100,000 can also be infiltrated into the septal mucosa    in this region. Using a sickle knife, the mucosa can be incised for  about 1 cm along the nasal septum posterosuperiorly, opposite  the vertical lamella of the superior turbinate. A small posterior  based flap may be created and then removed using small cups or  non-through-cutting forceps. Hemostasis is obtained using topical  packing temporarily. Only one side should be biopsied.   In the operating room, obtaining olfactory tissue is usually done  by taking superior turbinate samples. Studies “mapping” the  presence and location of olfactory epithelium in humans have  determined that intervening patches of respiratory mucosa become  more numerous with age, resulting in decreased olfactory area.*    Fig. 17.3. (a) Endoscopic view removing polyps from olfactory cleft using a microdebrider. Note that polypoid disease may be resected down to  healthy-appearing tissue or periosteum starting in the septal angle and working posteriorly with an angled microdebrider blade along the cribriform  plate. The remnant of the middle and superior turbinate vertical lamellae is preserved. (b) Schematic drawing depicting the result following polyp    Generally the inferior one-third of the superior turbinate is non-  olfactory. The vertical lamella of the superior or supreme (if present)  turbinates are usually olfactory-lined. A portion of the superior  turbinate may be resected safely by using a small straight through-  cutting forceps or turbinate scissors to incise across the vertical  lamella in an anterior to posterior cut, parallel to the skull base,  a few millimeters superior to the sphenoid ostium. Recall that  the sphenoid ostium is 1.5 to 2 cm above the choanal arch, and  usually sits at about the middle third of the sinus’s vertical height,  so this can be used to estimate the location of the skull base. Next,  a non-through-cutting forceps may be used to gently grasp the  inferior portion of the turbinate and separate remaining attach-  ments for removal en bloc. The initial sharp cut prevents transmis-  sion of force to the thin skull base attachments when grasping  the turbinate. In contrast, if one were to simply pull the superior  turbinate bluntly, there is a risk of disrupting the skull base and  causing iatrogenic CSF leak.   Another clinical situation in which dissection within the olfactory  cleft may be necessary is the removal of polyps. Some patients  with chronic rhinosinusitis with nasal polyps do have polypoid  disease within the olfactory cleft. We have found that careful    removal of polyps from this region appears to result in improved  postoperative olfactory function.’ For this procedure, the olfactory  cleft is identified and approached as described above. Partial middle  turbinate resection, removal of septal spurs, and identification of  the sphenoid ostium and skull base are performed. Using a  microdebrider, polyps medial to the middle and superior turbinate  vertical lamellae are removed gently under direct visualization,  taking care to avoid pressure superiorly that could cause a skull  base injury (Fig. 17.3). Polypoid disease may be removed down  to underlying healthy tissue or periosteum.    1 Goldstein BJ, Lane AP. Future directions in chemosensory research. Otolaryngol Clin  North Am 2004;37:1281-1293.   2 Holbrook EH, Leopold DA. An updated review of clinical olfaction. Curr Opin Otolaryngol  Head Neck Surg 2006;14:23-28.   3 Keros P. [On the practical value of differences in the level of the lamina cribrosa of the  ethmoid]. Z Laryngol Rhinol Otol 1962;41:809-813.   4 Holbrook EH, Wu E, Curry WT, Lin DT, Schwob JE. Immunohistochemical characterization  of human olfactory tissue. Laryngoscope 2011;121:1687-1701.   5 Kuperan AB, Lieberman SM, Jourdy DN, Al-Bar MH, Goldstein BJ, Casiano RR. The effect  of endoscopic olfactory cleft polyp removal on olfaction. Am J Rhinol Allergy 2015;  29:309-313.   m Anterior third of the inferior turbinate lamellar insertion into  the lateral wall of the nose    In select cases, an endoscopic dacryocystorhinostomy (DCR)  may be indicated when epiphora is due to nasolacrimal duct  obstruction.'* The nasolacrimal sac is found anterior to the most  anterior attachment of the middle turbinate in the lateral nasal wall.>°  A line drawn anteriorly from the anterior attachment of the middle  turbinate bisects approximately the inferior third of the lacrimal  sac (Fig. 18.1). The nasolacrimal duct courses slightly diagonal and  parallel to the uncinated process in a posteroinferior direction toward  the inferior meatus. The nasolacrimal duct may be divided into two  parts: (1) a bony (or intraosseous) nasolacrimal duct (12 mm); and  (2) a membranous nasolacrimal duct (5 mm). The intraosseous  portion has a bony wall circumferentially and is typically identified  as a prominent convexity in the lateral wall of the nose running  adjacent to the anterior middle meatal margin (Fig. 18.2). The bony  wall of the intraosseous portion may be very thin or completely  dehiscent posteriorly, adjacent to the uncinate process or maxillary  natural ostium. Superiorly, the lacrimal sac receives the opening of    the common canaliculus, the common outflow tract into the nose  from the superior and inferior canaliculi (Fig. 18.3). Rarely, is this  portion of the lateral nasal wall involved in cases of nasal polyposis,  and therefore it can be used as a useful landmark to identify the  area of the agger nasi and uncinate process, posterior to it.    Lacrimal  sac area  Lacrimal  duct area  Nasolacrimal sac we Valve of    The membranous nasolacrimal duct is located in the inferior  meatus and consists of a membranous medial wall and a bony  lateral wall. The membranous medial wall collapses into the lumen  and functions as a one-way valve (Hasner’s valve) to minimize  retrograde flow of secretions or air into the nasolacrimal duct   turbinate vertical lamella  insertion into the medial  wall of the maxilla    and sac. Hasner’s valve may be seen traversing the anterior third  of inferior meatal wall. With a small probe, a mucosal canal or  trench can be followed superiorly toward the apex of the inferior  meatus, along its lateral wall, to identify Hasner’s valve and the  lacrimal ostium (Fig. 18.4). Occasionally, Hasner’s valve is absent.  In these cases, a patulous opening looking into the bony nasolac-  rimal duct may be seen in the superior recess of the inferior meatus  adjacent to the inferior turbinate lamellar insertion into the lateral  nasal wall (Fig. 18.5).   In endoscopic DCR, the bone on the medial side of the lacrimal  sac (formed by the thick frontal process of the maxilla anteriorly  and the thin lacrimal bone posteriorly) is removed using a drill  and/or Kerrison rongeur. The lacrimal sac is then opened while  a probe is passed through the lower or upper canaliculus to tent  the medial wall of the sac. The common canaliculus is identified  and a stent can be left in place, particularly if there is stenosis of,  or granulation tissue around, the common canaliculus.    1 Grob SR, Campbell A, Lefebvre DR, Yoon MK. External versus endoscopic endonasal  dacryocystorhinostomy. Int Ophthalmol Clin 2015;55:51-62.   2 Leong SC, Macewen CJ, White PS. A systematic review of outcomes after dacryocysto-  rhinostomy in adults. Am J Rhinol Allergy 2010;24:81-90.   3. Knisely A, Harvey R, Sacks R. Long-term outcomes in endoscopic dacryocystorhinostomy.  Curr Opin Otolaryngol Head Neck Surg 2015;23:53-58.   4 Huang J, Malek J, Chin D, et al. Systematic review and meta-analysis on outcomes for  endoscopic versus external dacryocystorhinostomy. Orbit 2014;33:81-90.   5 Wormald PJ, Kew J, Van Hasselt A. Intranasal anatomy of the nasolacrimal sac in endoscopic  dacryocystorhinostomy. Otolaryngol Head Neck Surg 2000;123:307-310.   6 Yung MW, Logan BM. The anatomy of the lacrimal bone at the lateral wall of the nose:  its significance to the lacrimal surgeon. Clin Otolaryngol Allied Sci 1999;24:262-265.    Orbital decompression may be indicated for a patient with an  orbital subperiosteal abscess, orbital abscess, periorbital or orbital  hematoma, or severe Graves’ ophthalmopathy with exposure  keratitis and possible visual loss.'"* When a subperiosteal abscess  is present, only the lamina papyracea needs partial or complete  removal to ensure adequate drainage of the abscess loculations  into the nasal cavity. This may require exposing the periorbita  over the superomedial or inferomedial orbital walls to allow  adequate drainage of all abscess septations (Fig. 19.1). The peri-  orbita is left intact without any incisions (Fig. 19.2).   For patients with Graves’ ophthalmopathy, the lamina papyracea  and medial orbital floor are removed medial to the infraorbital nerve  through a wide antrostomy, preserving a bony strut (corresponding    to the horizontal ridge of the maxillary antrostomy). The lamina  papyracea is removed posterior to the level of nasolacrimal con-  vexity and inferior to the border of the fovea ethmoidalis (skull  base), taking care not to injure the anterior or posterior ethmoid  arteries. In a standard medial orbital decompression, the posterior  lamina papyracea is removed 2 to 5mm anterior to the optic strut,  although if incorporating an optic nerve decompression, or desiring  maximum orbital decompression, a more posterior dissection is  warranted. Postoperative diplopia is a potential risk, but may be    minimized by preserving the horizontal ridge of the antrostomy  and placing the periorbital incisions parallel to the superior and  inferior borders of the medial rectus muscle, adjacent to the margins  of the superior oblique and inferior rectus muscles, respectively,  where an intraorbital fat “corridor” exists (Fig. 19.3). It is through  these two fat corridors that the experienced endoscopic sinus  surgeon may also endoscopically approach and remove intraconal  neoplasms of the orbit.   The periorbita is incised with a sickle knife from posterior to  anterior to enable herniation of orbital fat into the ethmoid and  occasionally the maxillary sinus cavities (Fig. 19.4). Gentle palpation  of the orbit externally enables prolapse of orbital fat into the  ethmoid sinus cavity and helps visualize if there are any residual  tethering periorbital fascial bands. Multiple passes with the sickle  knife or blunt ball-tip probe may be necessary to ensure lysis of  all the periorbital fascial bands and ensure maximum decompres-  sion. Care should be taken to preserve at least a 10-mm-wide    sling of periorbita overlying the medial rectus muscle to minimize  the risk of postoperative diplopia. The general rule of thumb is  approximately 3 to 4mm of decompression per complete wall  decompressed. However, only the medial aspect of the medial  orbital floor is decompressed endoscopically. Endoscopic medial  and inferior orbital decompression enables approximately 4 to  5mm of proptosis reduction. Further reduction in proptosis can  be achieved with complete decompression of the orbital floor  medial and lateral to the infraorbital nerve. This can increase  the medial/inferior decompression up to 8mm of reduction.  However, the latter may require a combined endoscopic and  external transorbital approach using a transconjunctival incision  (discussed later in Chapter 36). Care is taken not to occlude the  maxillary, frontal, or sphenoid sinus ostia with orbital fat, which  can result in secondary ostial obstruction and rhinosinusitis.’* In  these situations an extended middle meatal antrostomy or an  extended sphenoid/frontal sinusotomy may be prudent.    Page EL, Wiatrak BJ. Endoscopic vs external drainage of orbital subperiosteal abscess.  Arch Otolaryngol Head Neck Surg 1996;122:737-740.   Deutsch E, Eilon A, Hevron IJ, Hurvitz H, Blinder G. Functional endoscopic sinus surgery  of orbital subperiosteal abscess in children. Int J Pediatr Otorhinolaryngol 1996;34:181-190.  Ulualp SO, Massaro BM, Toohill RJ. Course of proptosis in patients with Graves’ disease  after endoscopic orbital decompression. Laryngoscope 1999;109:1217-1222.  Shepard KG, Levin PS, Terris DJ. Balanced orbital decompression for Graves’ ophthal-  mopathy. Laryngoscope 1998;108(11 Pt 1):1648-1653.    Lund VJ, Larkin G, Fells P, Adams G. Orbital decompression for thyroid eye disease: a  comparison of external and endoscopic techniques. J Laryngol Otol 1997;111:1051-1055.  Kennedy DW, Goodstein ML, Miller NR, Zinreich SJ. Endoscopic transnasal orbital  decompression. Arch Otolaryngol Head Neck Surg 1990;116:275-282.   Lee WC. Recurrent frontal sinusitis complicating orbital decompression in Graves’ disease.  J Laryngol Otol 1996;110:670-672.    Bough ID Jr, Huang JJ, Pribitkin EA. Orbital decompression for Graves’ disease complicated  by sinusitis. Ann Otol Rhinol Laryngol 1994;103:988-990.    In patients with worsening visual acuity due to multiple pathologi-  cal processes such as traumatic neuropathy, recalcitrant pseudo-  tumor cerebri, Graves’ disease, or neoplastic compression, an optic  nerve decompression may be indicated.'*   The coronal plane of the orbital apex may be found by following  a vertical line, parallel and at the coronal plane of the superior  vertical ridge of the antrostomy, and adjacent to the posterior  wall of the maxillary sinus, toward the junction of the posterior  ethmoid sinus roof with the superomedial orbital wall (Fig. 20.1).  The orbital apex is located approximately 8 cm from the columella.  The canalicular portion of the optic nerve is identified as it takes  an abrupt turn medially at this point, coursing toward the optic  chiasm.   The thicker bone of the optic canal can be removed to achieve  a 270-degree decompression by thinning the bone with a fine  diamond bur and removing the medial wall, floor, and roof of the  optic canal in this area, and carefully removing thinned bone with  a Kerrison rongeur away from the optic nerve.? Superolateral    Optic  nerve  Posterior  ethmoid  Cavernous  internal  carotid Maxillary  sinus  Sphenoid Vertical line at the coronal plane  sinus of the posterior maxillary sinus  wall delineates the approximate  level of the orbital apex  Fig. 20.1    decompression of the optic canal is technically challenging with  increased risk of cerebrospinal fluid (CSF) leak and injury to the  optic nerve. Therefore, the decompression of the superolateral  aspect should be performed using a 2-mm drill and diamond bur  under copious irrigation, followed by a 2-mm Kerrison rongeur  placed between the anterior cranial fossa dura and the optic canal  to dissect the thin bone and unroof the optic canal. The lateral  aspect of the optic strut forming the canal floor as well as the  base of anterior clinoid is extremely difficult to remove safely via  an endonasal approach and can put the ophthalmic artery at risk.>®   In the cadaver laboratory, optic nerve decompression can be  carefully performed utilizing a fine diamond drill, Kerrison rongeur,  and small angled curette and angled endoscopes. The length of  the canalicular portion is approximately 8 to 12mm. The intra-  canalicular dura and falciform ligament can be opened endoscopi-  cally medial to lateral exposing the intracanalicular segments of  the optic nerve. The optic nerve sheath is continuous with the  dura mater in this area (Fig. 20.2). Incision of this thick sheath  reveals the optic nerve. The space around the nerve is continuous  with the subdural space and results in a CSF leak if left open to  the nasal cavity. Therefore, if the optic nerve sheath is opened,  one must be prepared to close the CSF leak (Fig. 20.3). Care must  be taken to avoid injury to the ophthalmic and carotid arteries  while performing the lateral incision toward the distal dural ring.    Planum of the optic nerve  sphenoidale Orbital apex  (8 cm from the    Kountakis SE, Maillard AA, El-Harazi SM, Longhini L, Urso RG. Endoscopic optic nerve  decompression for traumatic blindness. Otolaryngol Head Neck Surg 2000;123(1 Pt 1):  34-37.    Luxenberger W, Stammberger H, Jebeles JA, Walch C. Endoscopic optic nerve decompres-  sion: the Graz experience. Laryngoscope 1998;108:873-882.    Yildirim AE, Karaoglu D, Divanlioglu D, et al. Endoscopic endonasal optic nerve decompres-  sion in a patient with pseudotumor cerebri. J Craniofac Surg 2015;26:240-242.    Graham SM, Carter KD. Combined endoscopic and subciliary orbital decompression for  thyroid-related compressive optic neuropathy. Rhinology 1997;35:103-107.    Abhinav K, Acosta Y, Wang WH, et al. Endoscopic endonasal approach to the optic canal:  anatomic considerations and surgical relevance. Neurosurgery 2015;11(Suppl 3):431-445,  discussion 445-446.    Liu JK, Christiano LD, Patel SK, Tubbs RS, Eloy JA. Surgical nuances for removal of  tuberculum sellae meningiomas with optic canal involvement using the endoscopic  endonasal extended transsphenoidal transplanum transtuberculum approach. Neurosurg  Focus 2011;30:E2.   @ Cribriform plate and olfactory cleft medial to the middle and  superior turbinates vertical lamellae    Endoscopic ligation or cauterization of the anterior ethmoid artery  has been advocated in select cases with anterior epistaxis.'? The  anterior and posterior ethmoid arteries are branches of the  ophthalmic artery, which arises from the internal carotid artery    and enters the orbit via the optic foramen, medial to the optic  nerve (see Chapter 32). The ophthalmic artery then runs on the  medial wall of the orbit beneath the lower border of the superior  oblique muscle. The artery gives off both the anterior and posterior  ethmoid arteries, which can be seen penetrating the periorbita  into their respective bony canals, coursing through the roof of the  ethmoid sinus (Fig. 21.1).? Occasionally, the anterior ethmoid  artery courses within a mucosal fold up to several millimeters  below the level of the bony ethmoid roof. This is usually associated  with the presence of well-pneumatized ethmoid cells.* The posterior    ethmoid artery is usually protected by a bony canal. Additionally,  branching of these arteries may occur within the ethmoid roof,  giving off an occasional middle ethmoid artery. The ethmoid arteries  then enter the cranial cavity medially, anterior and posterior to  the cribriform plate area. Both arteries give off meningeal branches  to the dura as they enter intracranially. Additional branches can  be seen from the anterior ethmoid artery to the septal angle and  nasal bones/nasion area.   Several cadaveric studies have demonstrated the variability of  the location of the anterior ethmoid artery within the nose. The  distance from the nasal sill to the anterior ethmoid artery is  approximately 6 to 7cm, and the distance to the posterior ethmoid  artery is approximately 7 to 8cm.>”’ The artery could be identified  endoscopically within the posterior wall of the most superior  suprabullar ethmoidal cell and approximately 11mm posterior to  the common wall between the posterior wall of the frontal  infundibulum and this superior-most suprabullar cell.4® The anterior  ethmoid artery foramen is approximately 24mm from the anterior  lacrimal crest. The distance between the anterior and posterior  ethmoid arteries is approximately 12mm, and between the  posterior ethmoid artery and optic nerve approximately 6mm.   Preoperatively, the anterior ethmoid artery should be identified  on the computed tomography (CT) scan (see Chapter 5). It can be  seen as it emerges between the superior oblique and medial rectus    muscle creating an indentation in the medial orbital wall. It should  be determined if the artery runs in a mesentery below the skull  base, as this may place it at a greater risk of injury and of lateral  retraction into the orbit during surgery, if it is cut flush with the  orbital wall. If this is anticipated, it is best to cauterize the artery  prior to transecting it. This should be performed medially (away  from the orbital wall), so as to avoid inadvertent retraction of the  artery into the orbit, with resultant orbital hematoma.    1 Woolford TJ, Jones NS. Endoscopic ligation of anterior ethmoidal artery in treatment  of epistaxis. J Laryngol Otol 2000;114:858-860.   2 Metternich FU, Brusis T. [Ethmoid sinus operation for therapy of recurrence severe  epistaxis]. Laryngorhinootologie 1998;77:582-586.   3 Lee WC, Ming Ku PK, van Hasselt CA. New guidelines for endoscopic localization of the  anterior ethmoidal artery: a cadaveric study. Laryngoscope 2000;110:1173-1178.   4 Simmen D, Raghavan U, Briner HR, et al. The surgeon’s view of the anterior ethmoid  artery. Clin Otolaryngol 2006;31:187-191.   5 Aziz ZS, Zaya NE, Bass RM. Anatomic measurements of the anterior and posterior ethmoid  arteries in cadaveric heads using endoscopic sinus instrumentation. Ear Nose Throat J  2014;93:E11-E15.   6 Zong Y, Li X, Jiang Y, Xu J, Li J. Transnasal approach to the anterior skull base: an  endoscopic anatomic study. J Craniofac Surg 2014;25:1041-1043.   7 Moon HJ, Kim HU, Lee JG, Chung IH, Yoon JH. Surgical anatomy of the anterior ethmoidal  canal in ethmoid roof. Laryngoscope 2001;111:900-904.   8 Jang DW, Lachanas VA, White LC, Kountakis SE. Supraorbital ethmoid cell: a consistent  landmark for endoscopic identification of the anterior ethmoidal artery. Otolaryngol  Head Neck Surg 2014;151:1073-1077.   gw Inferior turbinate lamellar attachment to the lateral nasal wall  @ Medial orbital wall and medial orbital floor (MOF)    Extended maxillary sinusotomies may be indicated in select cases  with recalcitrant maxillary mucosal disease (iatrogenic, infectious,  systemic) and/or mucociliary dysfunction.' Other indications  include the following:   Resistant infections or osteitis with or without irreversible  mucosal disease and microabscesses    Extended maxillary approaches offer the advantage of a wide  postoperative access that can deliver the benefit of local application  of medications, nasal saline irrigations, and follow-up inspection  of the cavity. The variations for extended maxillary sinusotomies  include the following:    This chapters illustrates the principles behind each surgical  technique, highlighting the main differences among them  (Table 22.1).    Most patients requiring an extended maxillary sinusotomy typically  have failed a prior middle meatal antrostomy.' Therefore, the main  goal is to remove the remaining remnant of the medial maxillary  sinus wall, all the way inferiorly as close as possible to the level of  the nasal floor (Fig. 22.1). Utilizing a 30-degree endoscope, a middle  meatal antrostomy is revised, as described in previous chapters,  ensuring the incorporation of the natural ostium. The bony attach-  ment of the inferior turbinate to the lateral nasal wall is detached,  and the inferior meatus is connected with the middle meatus (Fig.  22.2). The medial orbital wall and floor should be identified. The  inferior turbinate is temporarily fractured and displaced superomedi-  ally, and is reduced anteriorly (as discussed in Chapter 8) to view  the lateral wall of the inferior meatus. Hasnet’s valve is then identified.  Working above and below the inferior turbinate, a common inferior/  middle meatal antrostomy is created, inferior and posterior to Hasner’s  valve (Fig. 22.3). This can be performed using a curette, a Tru-Cut  forceps, a microdebrider, or a backbiting forceps. All bony edges can  then be trimmed down using a diamond drill or microdebrider. The  inferior turbinate remains attached anteriorly and posteriorly, like  a hammock. The nasolacrimal duct remains intact (Fig. 22.4).    Using a combination of 30- and 70-degree endoscopes, all foreign  material, debris, irreversibly damaged mucosal membranes/polyps,  and secretions are removed. Removal of mucosal elements induces  maxillary cavity contracture and osteoneogenesis. However, at  times this is preferable to persistent crusting and infection due  to mucosal disease. This procedure provides adequate access to  the inferior and lateral (zygomatic) recesses of the maxillary sinus  while preserving the nasolacrimal duct and a functional inferior  turbinate.    The modified extended maxillary antrostomy, also known as the  mega-antrostomy, is similar to the extended maxillary sinusotomy  discussed above, except that the inferior turbinate is resected in  its posterior half to two thirds (shaded area in Fig. 22.5). Like the  extended version discussed previously, it is considered in patients  with recalcitrant maxillary sinusitis that is refractory to medical  therapy and a well-created middle meatal antrostomy. Both the  extended maxillary sinusotomy and the modified extended maxil-  lary antrostomy offer an endoscopic advantage over the historically  performed, more radical, Caldwell-Luc procedure, being that they  can be performed entirely endoscopically, including mucosal  removal if necessary.??   Classically described, this extended maxillary mega-antrostomy  is a mucosal-sparing procedure that avoids nasolacrimal duct  injury. However, as with the extended sinusotomy, it does not  preclude one from utilizing this wide cavity to remove tissue or  debris. It permits maxillary drainage by gravity, which is helpful  in cases with impaired mucociliary transport (e.g., cystic fibrosis,  primary or secondary ciliary dyskinesia). In addition, it offers a  wide cavity for postoperative access for irrigations and debridement.  However, unlike the extended maxillary sinusotomy discussed  previously, most of the inferior turbinate is sacrificed, accept for  a small remnant anteriorly and at the tail, which may not be  functionally significant.    Transected lacrimal  duct and orifice  Medial orbital wall:  inferior posterior  ethmoid sinus    A more radical endoscopic medial maxillectomy may be indicated  for patients with a variety of benign and malignant nasal and  paranasal sinus neoplasms. Perhaps the most common indication,  however, is for the resection of inverted papillomas.*'° The resec-  tion begins with a complete inferior turbinectomy. Any remaining  medial maxillary wall, including the nasolacrimal duct, is then  resected (Fig. 22.6). The margins of resection for the medial  maxillectomy are as follows: (1) the floor of the nose inferiorly,  (2) the posterior wall of the maxillary sinus posteriorly (excluding  the greater palatine nerve), (3) the floor of the orbit superiorly,  and (4) the anterior maxillary wall anteriorly.   Resection of the osseous and membranous nasolacrimal duct  is necessary to visualize the anterior maxillary sinus wall as far    superiorly and anteriorly as possible. The procedure then proceeds  with an anterior ethmoidectomy, posterior ethmoidectomy, and  wide sphenoidotomy with complete removal of the mucous  membranes if they are involved by neoplasm. In the most classic  descriptions of a medial maxillectomy, the lamina papyracea and  adjacent MOF are carefully removed from the anterior and posterior  ethmoid cavity with a periosteal elevator. The thickest bone is  encountered anteriorly at the nasolacrimal duct, inferiorly along  the horizontal ridge of the antrostomy, posteriorly at the orbital  apex, and superiorly at the junction of the ethmoid roof and orbital  wall. Therefore, it may be necessary to thin these areas of thick  bone with a diamond bur prior to removal with a periosteal elevator.  A dacryocystorhinostomy, or at least a vertical marsupialization  of the nasolacrimal duct remnant, is sometimes performed at the  end of the procedure to minimize the risk of nasolacrimal duct  stenosis or closure.    1 Rodriguez MJ, Sargi Z, Casiano RR. Extended maxillary sinusotomy in isolated refractory  maxillary sinus disease. Otolaryngol Head Neck Surg 2007;137:508-510.   2 Costa ML, Psaltis AJ, Nayak JV, Hwang PH. Long-term outcomes of endoscopic maxillary  mega-antrostomy for refractory chronic maxillary sinusitis. Int Forum Allergy Rhinol  2015;5:60-65.   3 Wang EW, Gullung JL, Schlosser RJ. Modified endoscopic medial maxillectomy for  recalcitrant chronic maxillary sinusitis. Int Forum Allergy Rhinol 2011;1:493-497.   4 Sarber KM, O’Connor PD, Doellman MS, et al. Surgical relationship of the nasolacrimal  system to the maxillary line: performing safe mega antrostomy. Allergy Rhinol  (Providence) 2015;6:158-161.   5 Lund VJ. Optimum management of inverted papilloma. J Laryngol Otol 2000;114:194-197.   6 Sukenik MA, Casiano R. Endoscopic medial maxillectomy for inverted papillomas of  the paranasal sinuses: value of the intraoperative endoscopic examination. Laryngoscope  2000;110:39-42.   7 Chee LW, Sethi DS. The endoscopic management of sinonasal inverted papillomas.  Clin Otolaryngol Allied Sci 1999;24:61-66.   8 Tufano RP, Thaler ER, Lanza DC, Goldberg AN, Kennedy DW. Endoscopic management  of sinonasal inverted papilloma. Am J Rhinol 1999;13:423-426.   9 Kamel RH. Transnasal endoscopic medial maxillectomy in inverted papilloma. Laryn-  goscope 1995;105(8 Pt 1):847-853.   10 Stankiewicz JA, Girgis SJ. Endoscopic surgical treatment of nasal and paranasal sinus  inverted papilloma. Otolaryngol Head Neck Surg 1993;109:988-995.    An endoscopic extended frontal sinusotomy procedure (Draf type IIb  or III) may be indicated in select cases with chronic frontal rhinosi-  nusitis refractory to medical and more traditional endoscopic surgical  management (Fig. 23.1).'° After identifying the superior aspect of  the lamina papyracea and anterior ethmoid roof, the approximate  level of the coronal plane of the posterior frontal sinus infundibular  wall is determined. The latter is a critical landmark for perform-  ing extended frontal sinusotomies. Extended frontal sinusotomies  may be accomplished either directly through the medial frontal  infundibulum area (supraturbinal) corresponding to the anterior    Frontal intersinus septum Left  (circle denotes structures removed frontal  during a Draf III frontal sinusotomy) sinus    attachment of the middle turbinate vertical lamella (anterior one  fourth), or through a more midline approach (transeptal), in cases  with more osteoneogenic changes; (A and B on Fig. 23.2).   For a Draf type IIb frontal sinusotomy, the anterior one fourth  of the middle turbinate vertical lamella is removed, starting at its  anterior insertion, and heading superiorly in the direction of the  posterior wall of the frontal sinus infundibulum or superior aspect  of the nasoseptal angle (Fig. 23.3). This orients the surgeon away  from the skull base and anterior cribriform plate. The bony medial  margin of the frontal infundibular opening is also the superior  point of insertion of this portion of the middle turbinate vertical  lamella represented by the green shaded area in Fig. 23.3. and is  illustrated endoscopically in Fig. 23.4. This bony insertion making  up the medial infundibular border, is removed with curettes or  powered instruments, to identify the junction of the perpendicular  plate with the frontal intersinus septum several millimeters medial  to this insertion (Fig. 23.5). The mucosa on the posterior wall of    Frontal intersinus septum  (circle denotes what is removed  during a Draf III frontal sinusotomy)    CHAPTER 23 ® Extended Frontal Sinusotomy and the Modified Lothrop Procedure 93    Supraturbinal (A) and transseptal (B)  cell approaches at the coronal plane of  the anterior middle turbinate attachment    Area of resection of middle turbinate  for a Draf IIb or III frontal sinusotomy    the frontal infundibular area is preserved whenever possible. In  many cases, however, this is not possible because of the significant  amount of fibrosis or osteoneogenesis in the area. A Draf type III  frontal sinusotomy (modified Lothrop procedure), or frontal sinus  drill out, is indicated in the latter cases.   If one has to access the frontal through a midline approach, the  anterior olfactory fili are identified first, medial to the middle  turbinate vertical lamella, and posterior to the coronal plane of  the posterior wall of the frontal infundibulum (red dashed line in  Fig. 23.6a). Only the anterior one fourth of the middle turbinate  vertical lamella makes up the medial margin of the frontal infun-  dibulum. Therefore, the remaining portion of the middle turbinate    vertical lamella lies lateral to the cribriform plate and is in continu-  ity with the lateral lamella of the cribriform plate and medial  fovea ethmoidalis. Although intraoperative navigation is useful in  identifying the correct trajectory when a transnasal midline frontal  sinus approach is used, an important exercise is to elevate a  posteriorly based flap starting in the much wider septal angle  area anterior to the cribriform plate, at the coronal plane just  anterior to the anterior attachment of the middle turbinate. The  narrow V-shaped groove of the anterior cribriform plate and first  olfactory fili is identified (Fig. 23.6), along with the posterior  frontal infundibular wall, as the posterior limits of bony removal.°  A 30-, 45-, or 70-degree endoscope looking superiorly is used.  However, once the anterosuperior septectomy is performed, even  a O-degree endoscope and straight instruments may be used  without difficulty to access the common frontal cavity.   An anterosuperior septectomy is performed, anterior to the level  of the anterior cribriform plate, with cutting forceps or powered  instrumentation, corresponding to the coronal plane of the posterior  wall of the frontal sinus infundibulum as seen through a trans-  ethmoid frontal sinusotomy on one side or through a transseptal  frontal sinusotomy in the midline. The anterosuperior septectomy  facilitates exposure and introduction of instrumentation from both  sides of the nose (Fig. 23.7). Posterior to this plane, the potential  is increased for inadvertent intracranial penetration, or injury to  the cribriform plate and olfactory nerve fibers. The coronal plane  of posterior wall of the frontal sinus infundibulum and bur are  always kept visualized at all times, as one proceeds across the  midline to the opposite side, or superiorly through the frontal  sinus along the intersinus septum, so as not to create an inadvertent  injury to the skull base with concomitant cerebrospinal fluid (CSF)  leak. The perpendicular plate may be resected all the way to the  nasal bones anteriorly. The dense bone at the nasofrontal (“beak”)  area, corresponding the nasion in the midline, is removed with a  cervical spine bone curette, cutting forceps, or angled cutting burs  gradually enlarging the common frontal ostium and providing    increased access to the superior and anterior aspects of the frontal  sinus. Additional enlargement laterally toward the orbit (supra-  canthal dermis area) is also performed to enlarge the lateral  dimensions of the opening, providing greater access to the  supraorbital recesses of the frontal sinus as seen from the contra-  lateral side.   Drilling the supracanthal bone of the orbit is generally performed  by visualizing with an endoscope and introducing the drill through  the contralateral nostril. Intermittent palpation of the nasion  dermis, as well as supracanthal dermis, is necessary to determine  the anterior and lateral limits of burring, respectively. On select  cases, with significant osteoneogenesis, this is done proactively  with the intent of identifying the lateral and anterior limits of  dissection, and ensuring that a maximum common frontal opening    is achieved.’ Generally, no adverse cosmetic effects are seen with  limited exposure of the nasion or supracanthal dermis. Mild  bleeding may be cauterized with monopolar suction cautery.  Occasionally, one or more frontal intersinus cells may have to be  completely removed to effectively enlarge the common frontal  ostium and provide an adequate outflow track.   The final common extended frontal sinusotomy opening is a  horseshoe-shaped opening (Fig. 23.8), measuring approximately  8 to 10mm anteroposteriorly (at the level of the nasofrontal bone,  or “beak” area), and 20 to 26mm laterally from orbital wall to  orbital wall (between medial orbital walls, as measured through  the coronal plane of the common frontal opening).? The posterior,  lateral, and anterior walls of the common frontal ostium are made  up of the posterior wall of the frontal sinus, supracanthal lateral    CHAPTER 23 @ Extended Frontal Sinusotomy and the Modified Lothrop Procedure 95    Coronal plane at  the level of the  posterior frontal  sinus wall, but  anterior to the  cribriform plates    nasal dermis, and anterior wall of the frontal sinus at the nasion  (nasofrontal “beak”) area, respectively. The final ostium should  enable compete transillumination and visualization of the full  extent of the frontal sinus, including its lateral (supraorbital)  recesses when inspected from the contralateral nasal cavity  (Fig. 23.9). If closer examination of the frontal sinus is warranted,  a flexible fiberoptic nasopharyngoscope may be inserted through  the common frontal ostium. Fig. 23.10 illustrates the relative  trajectory into the frontal sinus when a more midline (supraturbinal/  transseptal) approach is used, versus a more posterolateral approach  through the frontal infundibulum. The green circle demarcates  the entry area into the frontal for a more midline approach. It is  much more anterior relative to the frontal infundibular trajectory  demarcated by the red circle posterolaterally.    1 Ulualp SO, Carlson TK, Toohill RJ. Osteoplastic flap versus modified endoscopic Lothrop  procedure in patients with frontal sinus disease. Am J Rhinol 2000;14:21-26.   2 Kikawada T, Fujigaki M, Kikura M, Matsumoto M, Kikawada K. Extended endoscopic  frontal sinus surgery to interrupted nasofrontal communication caused by scarring of  the anterior ethmoid: long-term results. Arch Otolaryngol Head Neck Surg 1999;125:92-96.   3 Casiano RR, Livingston JA. Endoscopic Lothrop procedure: the University of Miami  experience. Am J Rhinol 1998;12:335-339.   4 Gross CW, Zachmann GC, Becker DG, et al. Follow-up of University of Virginia experience  with the modified Lothrop procedure. Am J Rhinol 1997;11:49-54.   5 McLaughlin RB, Hwang PH, Lanza DC. Endoscopic trans-septal frontal sinusotomy: the  rationale and results of an alternative technique. Am J Rhinol 1999;13:279-287.   6 Eloy JA, Vazquez A, Liu JK, Baredes S. Endoscopic Approaches to the Frontal Sinus:  Modifications of the Existing Techniques and Proposed Classification. Otolaryngol Clin  North Am 2016;49:1007-1018.   7 Chin D, Snidvongs K, Kalish L, Sacks R, Harvey RJ. The outside-in approach to the modified  endoscopic Lothrop procedure. Laryngoscope 2012;122:1661-1669.    m@ Sphenoid rostrum  m= Vomerorostral suture line  m@ Sphenoid intersinus septum    Endoscopic ipsilateral surgery of the sphenoid sinus, as described  previously, is the first line of surgical treatment for sphenoid sinus  disease, as it is with any of the other sinuses. However, in some  circumstances the need arises for more extensive surgery. The  extended approach is usually reserved for cases where disease  persists, despite conventional endoscopic surgery. As with the  frontal and maxillary sinuses, the reasons for failure of the primary  sphenoid sinusotomy procedure may be due to scarring or osteo-  neogenesis, causing narrowing or obstruction of the opening. The  extended approach may also be indicated for wide exposure or  removal of neoplasms or mucoceles.'?   The concept of an extended sphenoid sinusotomy procedure is  similar to the widely used endoscopic endonasal transsphenoidal  surgery of the pituitary, but it is used here with the goal of com-  municating both sphenoid sinuses into a common drainage pathway,  to minimize the chances of restenosis, and to improve access for  postoperative examinations, debridements, or administration of  topical medications.’ This is similar in concept to a frontal sinus  Draf III (Lothrop) procedure or maxillary mega-antrostomy. This  procedure can also be used to gain access to an osteoneogenic  sphenoid sinus from the contralateral (uninvolved or normal) side.   The procedure starts by identifying and opening one sphenoid  sinus (Fig. 24.1). Typically the sinus that is opened first is the one  that is easier to access. The sphenoid is opened in the usual manner  as described elsewhere in this dissection manual. The mucosa  overlying the sphenoid rostrum is then removed or reflected  anteriorly, exposing the vomerorostral suture line. The suture is  disrupted with a Cottle elevator, and access to the contralateral  side is achieved at a level corresponding to the sphenoid natural  ostium (Figs. 24.2 and 24.3). The contralateral septal mucosa is  elevated laterally, should a septal flap be anticipated in the future  (see Chapter 33). Once both sphenoid ostia are identified, the  rostrum and intersinus septum are removed to create a common  sphenoid cavity (Fig. 24.4). With thinner bone, this can easily be  performed using standard medium- to large-sized noncutting  forceps. However, for thicker bone, a bur may be necessary, or  one risks damage to the forceps. The common sphenoid cavity  may be enlarged by removing the remaining anterior wall of the    sphenoid sinuses superiorly to the level of the roof of the sphenoid  (planum sphenoidale), and inferiorly with the floor of the sphenoid  sinus (basisphenoid). More laterally, its common wall with the  posterior ethmoid cells is removed until the sphenoid cavity is  contiguous with the medial orbital wall (orbital apex at this level).    The carotid artery, optic nerve, and lateral opticocarotid recess  are identified as early in this process as possible if visible in the  superolateral wall of the sphenoid sinus bilaterally, or through  intraoperative navigation. Care must be taken when removing the  sphenoid intersinus septum posteriorly in the common sphenoid  cavity, as its insertion may be on the parasellar or paraclival carotid  artery, and its removal may result in an inadvertent injury to the  carotid artery. This is most common when the intersinus septum  is asymmetrically directed laterally on the posterior wall of the  sphenoid sinus, as is typically the case with a dominant sphenoid  on one side, and a hypoplastic sphenoid on the other. It is best  to thin this bone down with a diamond bur, and then remove it    carefully with neurosurgical Kerrison bone rongeurs. Care should  also be taken not to injure the sphenopalatine artery while  incorporating the posterior ethmoid cavity into the common  sphenoid cavity, or when drilling the inferolateral bony face of  the sphenoid sinus.    1 Kennedy DW. Prognostic factors, outcomes and staging in ethmoid sinus surgery.  Laryngoscope 1992; 102(12 Pt 2, Suppl 57):1-18.   2 Musy PY, Kountakis SE. Anatomic findings in patients undergoing revision endoscopic  sinus surgery. Am J Otolaryngol 2004;25:418-422.   mw Base of the pterygoid process and adjacent greater wing of the  sphenoid bone    Identification of the sphenopalatine foramen and pterygopalatine  fossa may be indicated in cases in which posterior epistaxis requires  endoscopic cauterization or ligation of the sphenopalatine or  internal maxillary vessels.'? Exposure and control of these vessels  may also be necessary during an endoscopic resection of a juvenile  angiofibroma or other neoplasms involving the pterygopalatine  fossa.*-’   The sphenopalatine foramen is circular or oval, and is usually  found in the posterior part of the superior meatus, a few millimeters  above the tail of the middle turbinate (Fig. 25.1). The foramen is  formed when the sphenopalatine notch is closed superiorly against  the lower surface of the body of the sphenoid bone (Fig. 25.2).  The notch itself is formed anteriorly by the orbital process of the  palatine bone, inferiorly by the upper edge of the vertical plate  of the palatine bone, and posteriorly by the sphenoid process of  the same bone. A small bony ridge, the crista ethmoidalis, usually  points to the sphenopalatine foramen, with the latter lying either  completely or partially posterosuperior to this bony “pointer” (class  I and II, respectively). Occasionally, the sphenopalatine foramen  consists of two separate openings, a larger superior opening and  a small inferior one (class III).°   The internal maxillary artery branches to form the sphenopala-  tine artery. The branching pattern of the sphenopalatine artery  varies. In most cases it divides into two branches, but occasionally  it may have three or more branches (Fig. 25.3).°"!! It ultimately  forms two terminal branches. These branches are the posterolateral  nasal artery, usually emerging at the anteroinferior compartment  of the sphenopalatine foramen, and the posterior nasal septal  artery, which courses medially toward the posterior nasal septum,  just inferior to the ostium of the sphenoid sinus and the tail of  the superior turbinate.   The posterolateral nasal artery (PLNA) provides most of the  blood supply to the lateral nasal wall, including the blood supply    to the inferior and middle turbinates. As the PLNA branches from  the sphenopalatine artery, it descends in an inferior vertical course  over the perpendicular process of the ascending plate of the palatine  bone. It gives a substantial branch to the middle turbinate while  the main trunk, known as the inferior turbinate artery, continues  to descend caudally and slightly anteriorly to enter the inferior  turbinate 1 to 1.5cm from its posterior end. Here it divides into  two branches. The first branch runs along the superior aspect of  the inferior turbinate, and the second runs in the midportion of  the inferior turbinate in a more medial position.'*"? The posteriorly  pedicled inferior turbinate flap utilized for skull base repair is  based on the inferior turbinate artery.!-"4   Occasionally, the PLNA gives a branch to the superior turbinate,  whereas in most cases the blood supply of the superior turbinate  comes from the posterior nasal septal artery."   The septal branch divides into at least two branches as it passes  along the face of the sphenoid sinus (Fig. 25.4). This artery and  its branches form the blood supply for the vascularized posteriorly    CHAPTER 25 ® Sphenopalatine Foramen, Pterygopalatine Fossa, and Vidian Canal 99    based septal flap used in skull base reconstruction. When raising  a septal flap, care must be taken not to injure these arteries, as  this will compromise the blood supply of the flap. The superior  incision of the septal flap should be made at the same axial  plane of the lower edge of the sphenoid ostium, as the superior  branch of the septal artery runs in close proximity to the inferior  aspect of the sphenoid ostium, and may be subject to injury. The  other area were the artery may be at risk is at the junction of the  nasal septum with the arch of the posterior choana. If the inferior  incision of the septal flap is placed too high on the posterior border  of the nasal septum, the main blood supply to the flap may be  compromised as well.'° If the most superior branch of the septal  artery is transected in the course of a sphenoid sinusotomy, it  should be cauterized.   The vidian nerve carries parasympathetic fibers to the nose and  paranasal sinuses. Although it is controversial, and not widely  performed, a vidian neurectomy was originally described in the  1960s as a surgical means to treat intractable vasomotor rhinitis  (watery rhinorrhea component).'” The unsatisfactory long-term    outcomes and the complications related to the procedure led to  the procedure being largely abandoned.'® With better understanding  of the anatomy and improved visualization using the nasal endo-  scope, there has been some renewed interest in complete or partial  endoscopic vidian neurectomy as a potential solution to medically  refractory vasomotor rhinitis.'”7!   The vidian nerve is also an important landmark that helps  determine the location of the petrous portion of the internal carotid  artery, and it has been used during skull base surgery. The vidian  nerve enters its bony canal inferolateral to the second genu of  the internal carotid artery within the thick foramen lacerum  fibrocartilaginous tissue.?*-*° It is found coursing along the floor  of the lateral sphenoid sinus in a posterior to anterior direction.  This bony canal may be dehiscent. The easiest way to visualize  the nerve is to expose the sphenopalatine foramen first. A wide  sphenoid sinusotomy is then performed to determine the level  of the sphenoid floor. The vidian foramen may be found along the    inferior bony face of the sphenoid sinus (basisphenoid) immediately  posterior and perpendicular to the sphenopalatine foramen (Fig.  25.5). A smaller foramen and canal holding the pharyngeal or  palatovaginal artery may also be tracked just inferomedial to the  vidian foramen, and sometimes may be confused with it. The  latter artery usually arises from the sphenopalatine artery within  the pterygopalatine fossa and immediately takes a course toward  its bony canal running parallel and posterior to the upper division  of the septal branch of the sphenopalatine artery, inferior to the  sphenoid ostium.   Access to the pterygopalatine fossa is needed when dealing  with tumors arising in this space, or to access the lateral recess  of the sphenoid sinus and other structures posterolateral to this  area. With advancement in surgical techniques, the transpterygoid  approach has become an important method to access the para-  median skull base, including the foramen lacerum, petrous internal  carotid artery, Meckel’s cave, cavernous sinus, lateral nasopharynx,  and infratemporal fossa.**?° This is discussed in more detail  elsewhere in this dissection manual.   The pterygopalatine fossa is located between the pterygoid  process posteriorly, the posterior wall of the maxillary sinus  anteriorly, and the palatine bone medially. It communicates with  the infratemporal fossa via the pterygomaxillary fissure laterally.  It contains the internal maxillary artery and its terminal branches  anteriorly, and the pterygopalatine ganglion and second division  of the trigeminal nerve (V2) posteriorly close to the base of the  pterygoid process.”* The vertical plate of the palatine bone and  posterior maxillary sinus bony wall are removed to expose these  pterygopalatine fossa structures (Fig. 25.6). At a minimum, a wide  middle meatal antrostomy should be created prior to removal of  the posterior maxillary wall. At times, an extended maxillary  sinusotomy or medial maxillectomy may be necessary to gain  maximum exposure.”° The contents of the fossa are exposed by  removing the thin posterior wall of the maxillary sinus with a    Kerrison bone rongeur, and carefully removing the periosteum.  Pterygopalatine space fat can be carefully teased away or cauterized,  and the vascular and neural structures can be identified.   The internal maxillary artery and its branches, the sympathetic  and parasympathetic nerve plexus, veins, and buccal fat can be  seen within the pterygopalatine fossa (Fig. 25.7). In an anterior  to posterior direction, one can identify veins, followed by arteries,  and then neural structures adjacent to the base of the pterygoid  process (a helpful mnemonic is “VAN”). Superiorly, the infraorbital  nerve may be seen coursing toward the foramen rotundum,  superolateral to the vidian foramen, within the lateral base of the  pterygoid process.?’    Arteries to  the deep  portion of the  temporalis  muscle  Lateral  pterygoid  muscle    CHAPTER 25 ® Sphenopalatine Foramen, Pterygopalatine Fossa, and Vidian Canal 101    Budrovich R, Saetti R. Microscopic and endoscopic ligature of the sphenopalatine artery.  Laryngoscope 1992;102(12 Pt 1):1391-1394.   Sharp HR, Rowe-Jones JM, Biring GS, Mackay IS. Endoscopic ligation or diathermy of  the sphenopalatine artery in persistent epistaxis. J Laryngol Otol 1997;111:1047-1050.  Srinivasan V, Sherman IW, O’Sullivan G. Surgical management of intractable epistaxis:  audit of results. J Laryngol Otol 2000;114:697-700.   Carrau RL, Snyderman CH, Kassam AB, Jungreis CA. Endoscopic and endoscopic-assisted  surgery for juvenile angiofibroma. Laryngoscope 2001;111:483-487.   Tseng HZ, Chao WY. Transnasal endoscopic approach for juvenile nasopharyngeal  angiofibroma. Am J Otolaryngol 1997;18:151-154.   Fagan JJ, Snyderman CH, Carrau RL, Janecka IP. Nasopharyngeal angiofibromas: selecting  a surgical approach. Head Neck 1997;19:391-399.   Ungkanont K, Byers RM, Weber RS, Callender DL, Wolf PF, Goepfert H. Juvenile  nasopharyngeal angiofibroma: an update of therapeutic management. Head Neck  1996;18:60-66.    Wareing MJ, Padgham ND. Osteologic classification of the sphenopalatine foramen.  Laryngoscope 1998;108(1 Pt 1):125-127.   Simmen DB, Raghavan U, Briner HR, Manestar M, Groscurth P, Jones NS. The anatomy  of the sphenopalatine artery for the endoscopic sinus surgeon. Am J Rhinol 2006;20:  502-505.   Fortes FS, Sennes LU, Carrau RL, et al. Endoscopic anatomy of the pterygopalatine  fossa and the transpterygoid approach: development of a surgical instruction model.  Laryngoscope 2008;118:44-49.   McClurg SW, Carrau R. Endoscopic management of posterior epistaxis: a review. Acta  Otorhinolaryngol Ital 2014;34:1-8.   Padgham N, Vaughan-Jones R. Cadaver studies of the anatomy of arterial supply to  the inferior turbinates. J] R Soc Med 1991;84:728-730.   Fortes FS, Carrau RL, Snyderman CH, et al. The posterior pedicle inferior turbinate  flap: a new vascularized flap for skull base reconstruction. Laryngoscope 2007;117:  1329-1332.    Choby GW, Pinheiro-Neto CD, de Almeida JR, et al. Extended inferior turbinate flap  for endoscopic reconstruction of skull base defects. J Neurol Surg B Skull Base  2014;75:225-230.   Lee HY, Kim HU, Kim SS, et al. Surgical anatomy of the sphenopalatine artery in lateral  nasal wall. Laryngoscope 2002;112:1813-1818.   Zhang X, Wang EW, Wei H, et al. Anatomy of the posterior septal artery with surgical  implications on the vascularized pedicled nasoseptal flap. Head Neck 2015;37:1470-1476.  Golding-Wood PH. Observations on petrosal and vidian neurectomy in chronic vasomotor  rhinitis. J Laryngol Otol 1961;75:232-247.   Zhang H, Micomonaco DC, Dziegielewski PT, Sowerby LJ, Weis E, Wright ED. Endoscopic  vidian neurectomy: a prospective case series. Int Forum Allergy Rhinol 2015;5:423-430.    Robinson SR, Wormald PJ. Endoscopic vidian neurectomy. Am J Rhinol 2006;20:197-202.  Lee JC, Kao CH, Hsu CH, Lin YS. Endoscopic transsphenoidal vidian neurectomy. Eur  Arch Otorhinolaryngol 2011;268:851-856.   Liu J, Pinheiro-Neto CD, Fernandez-Miranda JC, et al. Eustachian tube and internal  carotid artery in skull base surgery: an anatomical study. Laryngoscope 2014;124:  2655-2664.   Wormald PJ. Endoscopic Sinus Surgery Anatomy, Three-Dimensional Reconstruction,  and Surgical Technique. New York: Thieme; 2013.   Kassam AB, Vescan AD, Carrau RL, et al. Expanded endonasal approach: vidian canal  as a landmark to the petrous internal carotid artery. J Neurosurg 2008;108:177-183.  de Lara D, Ditzel Filho LF, Prevedello DM, et al. Endonasal endoscopic approaches to  the paramedian skull base. World Neurosurg 2014;82(6, Suppl):S121-S129.  Rivera-Serrano CM, Terre-Falcon R, Fernandez-Miranda J, et al. Endoscopic endonasal  dissection of the pterygopalatine fossa, infratemporal fossa, and post-styloid compart-  ment. Anatomical relationships and importance of eustachian tube in the endoscopic  skull base surgery. Laryngoscope 2010;120(Suppl 4):S244.   Kasemsiri P, Solares CA, Carrau RL, et al. Endoscopic endonasal transpterygoid approaches:  anatomical landmarks for planning the surgical corridor. Laryngoscope 2013;123:811-815.  Herzallah IR, Elsheikh EM, Casiano RR. Endoscopic endonasal study of the maxillary  nerve: a new orientation. Am J Rhinol 2007;21:637-643.    m Pterygoid process of the sphenoid bone  w Lateral pterygoid muscles  mw Meckel’s cave    Understanding the endoscopic anatomy and approaches to the  infratemporal fossa is especially important for select cases requiring  tumor resection and biopsy.'? As with many other approaches,  wide exposure and good visualization is the key. Depending  on the lateral extent of the neoplasm, an endoscopic medial  maxillectomy alone may provide adequate lateral exposure.  However, sometimes it has to be combined with more limited  external approaches.?* An adequate endoscopic medial maxil-  lectomy should extend superiorly to the level of the orbital floor,  posteriorly to the vertical ridge of the antrostomy, inferiorly to  the floor of the nasal cavity, and anteriorly to the level of the  anterior maxillary sinus wall. The palatine bone and greater palatine  nerve are preserved unless they are involved with tumor or in  cases where resection is necessary for adequate exposure. The  lacrimal duct (including Hasner’s valve) may be spared, if it is not  involved with disease. However, most of the time the lacrimal  duct has to be resected to better visualize and access the antero-  medial wall of the maxillary sinus just lateral to the lacrimal duct.   If further exposure is needed, an endoscopic modified Denker  procedure can be performed by removing a portion of the pyriform  aperture with a Kerrison bone rongeur or drill. Additionally, the  anterior wall of the maxillary sinus, inferior to the infraorbital  foramen, can be removed through an endoscopic Denker or sublabial  anterior maxillotomy (Caldwell-Luc) approach. Instruments may  be advanced laterally through the anterior maxillary cavity, while  visualizing with the endoscope medially, or conversely, visualizing  endoscopically through the anterior maxillary defect and introduc-  ing instruments medially through the nostril. Others have advocated  the addition of temporary overlapping septal incisions and flaps  through a bi-nostril approach to gain further access to this area.*-’   To access the infratemporal fossa, the base of the pterygoid  process needs to be identified, by laterally or medially reflecting,  or even completely resecting, the neurovascular structures of the  pterygopalatine fossa including the greater palatine nerve. The goal  is to expose the base of the pterygoid process, foramen rotundum,  and vidian foramen, as discussed previously.'° Dissection of the    pterygopalatine fossa from medial to lateral begins by identifying  the sphenopalatine foramen, which is located in the palatine bone  anterior to the pterygoid bone. Further dissection proceeds by  removing the posterior wall of the maxillary sinus laterally and  the palatine bone medially. The internal maxillary artery and its  branches are located anterior to the nerves and can be identified  by following the sphenopalatine artery. Identification of the Vz  nerve can be achieved by following the infraorbital nerve located  on the roof of the maxillary sinus, posteriorly to the foramen  rotundum. Identification of the vidian nerve can be achieved by  identification of the vidian canal, which is located on the lateral  floor of the sphenoid sinus (Fig. 26.1). Further dissection and  elevation of the lateral pterygoid muscle off the lateral base of  the pterygoid bone exposes the infratemporal fossa. The lateral  margin of the foramen ovale (V3 branch of the trigeminal) and  the foramen spinosum (middle meningeal artery) just posterior  to it may be seen in this area (Fig. 26.2). Removal of the base of  the pterygoid bone with a bur exposes the anterior border of the  foramen ovale even further (Fig. 26.3).   The posterior margin of a nonpneumatized base of the pterygoid  bone becomes the anterior margin of the foramen ovale. Incising    CHAPTER 26 ® Transpterygoid Approaches to the Infratemporal Fossa and Meckel’s Cave 103    the dura at the base of the pterygoid process (once the bone is  removed down to dura), just anterior to the V3 and the foramen  ovale, exposes Meckel’s cave, and the trigeminal ganglion intracrani-  ally, within the middle cranial fossa. In a well-pneumatized  sphenoid with a prominent lateral sphenoid recess, the base of  the pterygoid bone is pneumatized lateral to the intrasphenoidal  course of V2 and the vidian nerve canals. The lateral sphenoid  recess corresponds to this pneumatized base of the pterygoid  process. Therefore, to access the foramen ovale and Meckel’s cave,  one must remove the anterior and posterior walls of the lateral  sphenoid sinus recess, corresponding to pneumatized base of the  pterygoid bone (Figs. 26.4 and 26.5).    1. Falcon RT, Rivera-Serrano CM, Miranda JF, et al. Endoscopic endonasal dissection of the  infratemporal fossa: anatomic relationships and importance of eustachian tube in the  endoscopic skull base surgery. Laryngoscope 2011;121:31-41.    2  Kassam AB, Gardner P, Snyderman C, Mintz A, Carrau R. Expanded endonasal approach:  fully endoscopic, completely transnasal approach to the middle third of the clivus,  petrous bone, middle cranial fossa, and infratemporal fossa. Neurosurg Focus 2005;  19:E6.    3 Prosser JD, Figueroa R, Carrau RI, Ong YK, Solares CA. Quantitative analysis of endoscopic  endonasal approaches to the infratemporal fossa. Laryngoscope 2011;121:1601-1605.    4 Hardillo JAU, Vander Velden L-A, Knegt PP. Denker operation is an effective surgical  approach in managing juvenile nasopharyngeal angiofibroma. Ann Otol Rhinol Laryngol  2004;113:946-950.    5 Eloy JA, Murray KP, Friedel ME, Tessema B, Liu JK. Graduated endoscopic multiangle  approach for access to the infratemporal fossa: a cadaveric study with clinical correlates.  Otolaryngol Head Neck Surg 2012;147:369-378.    6 Murray KP, Friedel ME, Liu JK, Tessema B, Eloy JA. A graduated endoscopic multi-angle  approach for access to the infratemporal fossa: a cadaveric study. Laryngoscope  2011;121(Suppl $4):S237.    7 Liu JK, Husain Q, Kanumuri V, Khan MN, Mendelson ZS, Eloy JA. Endoscopic graduated  multiangle, multicorridor resection of juvenile nasopharyngeal angiofibroma: an  individualized, tailored, multicorridor skull base approach. J Neurosurg 2016;124:  1328-1338   8 Hosseini SM, Razfar A, Carrau RL, et al. Endonasal transpterygoid approach to the  infratemporal fossa: correlation of endoscopic and multiplanar CT anatomy. Head Neck  2012;34:313-320.   9 Rivera-Serrano CM, Terre-Falcon R, Fernandez-Miranda J, et al. Endoscopic endonasal  dissection of the pterygopalatine fossa, infratemporal fossa, and post-styloid compartment.  Anatomical relationships and importance of eustachian tube in the endoscopic skull  base surgery. Laryngoscope 2010;120(Suppl 4):S244.    The paired sphenoid sinuses represent a gateway to the sella turcica  and surrounding skull base. Perhaps the most common indication  for endoscopic transsphenoidal surgery is the resection of a  pituitary adenoma, a technique that has been reported extensively  in the world literature.'~’ In these cases, bilateral sphenoid sinus-  otomies are necessary to gain full sellar exposure, as well as the  ability to freely maneuver surgical instruments. In addition, an  extended sphenoid sinusotomy may be necessary to improve access  to a lateral sphenoid recess behind the medial pterygomaxillary  fossa; to improve visualization while repairing a cerebrospinal  fluid (CSF) leak; for exposure and removal of a meningoencepha-  locele; or for access into a contralateral diseased and osteoneogenic  sphenoid sinus when the ipsilateral outflow tract is too fibrotic  or bony.®?   An extended sphenoid sinusotomy begins by identifying the  sphenoid sinus ostium, as described previously in Chapter 14.  The ostium is then widened to its superior, medial, lateral, and  inferior limits using a Kerrison rongeur or high-speed drill. In  most cases, accessing the sella turcica and surrounding regions  requires a bilateral extended sphenoid sinusotomy. This approach  entails a posterior septectomy, resection of the sphenoid rostrum  to which it attaches, and removal of the intersinus septum. The  rostrum and intersinus septum may be resected with a rongeur  or with a high-speed drill; in either case, care is taken to avoid  fracturing or inadvertently pulling the intersinus septum to prevent  tearing the carotid artery, to which the septum can occasionally  attach. Additional exposure and freedom of movement can be  achieved with bilateral posterior ethmoidectomies.   In a well-pneumatized sphenoid sinus, the sella turcica (pituitary  fossa) is often seen as a convexity in the posterosuperior region  of the common sphenoid cavity (Fig. 27.1).'*"4 However, until  more experience is gained, the surgeon may need to localize  the pituitary fossa with intraoperative fluoroscopy or, more  commonly, a stereotactic navigation system prior to bone    removal. In addition to the sella turcica, several other landmarks  may be identified, including the tuberculum sellae and planum  sphenoidale (anterosuperiorly); the clival recess (inferiorly); the  carotid and optic protuberances (paired structures); and the  opticocarotid recesses (the space between the latter two structures)  (Fig. 27.2).   Two major transsphenoidal approaches are possible at this point:  the endoscopic endonasal transsellar approach, which provides  direct access to the pituitary fossa and is appropriate for most  pituitary lesions, and the endoscopic endonasal transplanum  transtuberculum approach (which provides access to the suprasellar  cistern for the management of craniopharyngiomas, retrochiasmatic  lesions, and pituitary lesions with suprasellar extension).!>-'”   In the transsellar approach, once the sella is localized, the bone  is thinned with a cutting or diamond bur, or gently removed with  an osteotome. A Kerrison rongeur is used to gently remove the  remaining bone and expose the dura of the sella turcica. The dura  is then incised, exposing the pituitary gland or neoplasm within  the sella turcica (Fig. 27.3).   In the transplanum transtuberculum, the planum sphenoidale  (or sphenoid roof) is resected using a combination of high-speed  drilling and rongeur, exposing the dura mater beyond it (Fig. 27.4).  Care must be taken to coagulate the superior intercavernous sinus    Optic nerve convexities  coursing toward chiasm,  anterior to sella turcica,  and superior to planum  sphenoidale    just posterior to the tuberculum sellae before incising the dura.  This route will lead to the superior aspect of the sella and suprasel-  lar cistern. The dura, which lies anterior and superior to the sella  turcica, is incised; the diaphragma sellae is reflected inferiorly,  exposing the suprasellar structures. Key suprasellar structures  include the optic chiasm, hypophyseal arteries, and the pituitary  stalk coursing posterior to the optic chiasm to enter the sell turcica  through the diaphragm sellae.    CHAPTER 27 ® Approach to the Sella Turcica and Suprasellar Region 105    1. Koren I, Hadar T, Rappaport ZH, Yaniv E. Endoscopic transnasal transsphenoidal  microsurgery versus the sublabial approach for the treatment of pituitary tumors:  endonasal complications. Laryngoscope 1999;109:1838-1840.   2  Nasseri SS, McCaffrey TV, Kasperbauer JL, Atkinson JL. A combined, minimally invasive  transnasal approach to the sella turcica. Am J Rhinol 1998;12:409-416.   3 Aust MR, McCaffrey TV, Atkinson J. Transnasal endoscopic approach to the sella turcica.  Am J Rhinol 1998;12:283-287.   4 Carrau RL, Jho HD, Ko Y. Transnasal-transsphenoidal endoscopic surgery of the pituitary  gland. Laryngoscope 1996;106:914-918.   5 Sethi DS, Pillay PK. Endoscopic management of lesions of the sella turcica. J Laryngol  Otol 1995;109:956-962.   6 Gandhi CD, Christiano LD, Eloy JA, Prestigiacomo CJ, Post KD. The historical evolution  of transsphenoidal surgery: facilitation by technological advances. Neurosurg Focus  2009;27:E8.   7 Patel SK, Husain Q, Eloy JA, Couldwell WT, Liu JK. Norman Dott, Gerard Guiot, and  Jules Hardy: key players in the resurrection and preservation of transsphenoidal surgery.  Neurosurg Focus 2012;33:E6.   8 Zweig JL, Carrau RL, Celin SE, et al. Endoscopic repair of cerebrospinal fluid leaks to  the sinonasal tract: predictors of success. Otolaryngol Head Neck Surg 2000;123:195-201.   9 Hegazy HM, Carrau RL, Snyderman CH, Kassam A, Zweig J. Transnasal endoscopic  repair of cerebrospinal fluid rhinorrhea: a meta-analysis. Laryngoscope 2000;110:  1166-1172.   10 Casiano RR, Jassir D. Endoscopic cerebrospinal fluid rhinorrhea repair: is a lumbar  drain necessary? Otolaryngol Head Neck Surg 1999;121:745-750.   11 Eloy JA, Kuperan AB, Choudhry OJ, Harirchian S, Liu JK. Efficacy of the pedicled nasoseptal  flap without cerebrospinal fluid (CSF) diversion for repair of skull base defects: incidence  of postoperative CSF leaks. Int Forum Allergy Rhinol 2012;2:397-401.   12 Schmidt RF, Choudhry OJ, Raviv J, et al. Surgical nuances for the endoscopic endonasal  transpterygoid approach to lateral sphenoid sinus encephaloceles. Neurosurg Focus  2012;32:E5.   13 Sethi DS, Stanley RE, Pillay PK. Endoscopic anatomy of the sphenoid sinus and sella  turcica. J Laryngol Otol 1995;109:951-955.   14 Tomovic S, Esmaeili A, Chan NJ, et al. High-resolution computed tomography analysis  of variations of the sphenoid sinus. J Neurol Surg B Skull Base 2013;74:82-90.   15 Liu JK, Christiano LD, Patel SK, Tubbs RS, Eloy JA. Surgical nuances for removal of  tuberculum sellae meningiomas with optic canal involvement using the endoscopic  endonasal extended transsphenoidal transplanum transtuberculum approach. Neurosurg  Focus 2011;30:E2.   16 Liu JK, Eloy JA. Endoscopic endonasal transplanum transtuberculum approach for  resection of retrochiasmatic craniopharyngioma. J Neurosurg 2012;32(Suppl):E2.   17 Liu JK, Christiano LD, Patel SK, Eloy JA. Surgical nuances for removal of retrochiasmatic  craniopharyngioma via the endoscopic endonasal extended transsphenoidal transplanum  transtuberculum approach. Neurosurg Focus 2011;30:E14.    28 Lateral Sphenoid Sinus Wall, Internal Carotid Artery, and  Adjacent Neurovascular Structures    m Vidian canal, petrous apex, foramen lacerum, medial cavernous  sinus dural sheath, opticocarotid recess, anterior clinoid process    A complete understanding of the structures in the lateral sphenoid  sinus wall, including the course of the internal carotid artery (ICA),  is crucial to minimize complications during endoscopic access to  the petrous apex, the retroclival region, and the cavernous sinus  (Fig. 28.1). Many classification systems for the course of the ICA  have been described.'* However, understanding the anatomy and  relevant surgical landmarks from an endoscopic perspective is  paramount for the endoscopic skull base surgeon, and they have  been well described in the literature.>*  The ICA may be divided into six segments (Fig. 28.2)°:    1. Parapharyngeal ICA: from the common carotid bifurcation to  the ICA foramen. This segment courses immediately posterior  to the lateral-most extent of the cartilaginous eustachian tube.   2. Petrous ICA: from the carotid canal to the posterolateral aspect  of the foramen lacerum. This segment can be safely identified  by drilling medial to lateral along the inferior edge of the  vidian canal.   3. Paraclival ICA: from the posterolateral aspect of the foramen  lacerum to the superomedial aspect of the petrous apex. This  segment has extracavernous and intracavernous components.   4. Parasellar ICA: from the superomedial aspect of the petrous  apex to the proximal dural ring. This is the only segment  of the ICA that is completely located inside the cavernous  sinus.   5. Paraclinoid ICA: from the proximal dural ring to the distal  dural ring. Drilling the bone off of the medial opticocarotid  recess enables identification of this segment.   6. Intradural ICA: from the distal dural ring to the ICA  bifurcation.    The parasellar and paraclinoid segments of the ICA, form  a C-shaped curve, with its convexity directed anteriorly. The  inferior horizontal segment of this curve starts as the parasellar  ICA and bends anteriorly at a variable angle to run horizontally  forward and slightly upward. The ICA then bends superiorly as the    anterior vertical limb of the “C” and then bends posteriorly again,  exiting the cavernous sinus and forming the superior horizontal  segment that runs medial to the anterior clinoid process as the  paraclinoid segment before entering the subarachnoid space  intracranially.   The distance between the two ICAs is narrowest at the level  of the paraclinoid ICA, and special care must be taken during  procedures in this region. Furthermore, in patients with well-  pneumatized sphenoid sinuses, the ICAs may project far into the  lumen of the sphenoid sinuses, and special care must be taken to  avoid inadvertent vascular injury by entering too far laterally  through the posterior wall of the posterior ethmoid sinuses. For  this reason, the sphenoid sinus is generally entered medially  adjacent to the septum, as previously described. A more compre-  hensive description of this anatomy and classification system is  detailed by Labib et al° and Herzallah and Casiano.°   With a diamond bur, the bone over the ICA and lateral wall of  the sphenoid can be thinned and carefully removed with a Kerrison  bone rongeur. This exposes the various segments of the ICA, as  well as the medial dural sheath that encases it and makes up the  medial wall of the cavernous sinus. Note that the paraclinoid carotid  artery may not be encased by this medial dural sheath, and therefore    CHAPTER 28 & Lateral Sphenoid Sinus Wall, Internal Carotid Artery, and Adjacent Neurovascular Structures 107    Pneumatized  posterior wall of  the lateral recess  of the sphenoid  sinus    may be prone to inadvertent injury. The lateral sphenoid wall  bone becomes thicker as one proceeds inferiorly toward the vidian  nerve and floor of the nose. Removal of the medial dural sheath  superior to the V2 canal reveals cranial nerves III, IV, VI, and V,  coursing toward the superior orbital fissure within the cavernous  sinus (Fig. 28.3). The V2 nerve lies outside of the cavernous sinus.  It courses inferior to the cavernous sinus in an anterior direction  toward the foramen rotundum, which can be found at the antero-  lateral base of the pterygoid process. The V3 nerve lies inferolateral  to the V, canal behind the bony wall of a well-pneumatized    sphenoid sinus lateral recess. In the absence of a lateral recess, it  lies posterior to the base of the pterygoid process. The anterior  margin of the foramen ovale and V; is the posterior base of the  pterygoid process.    1 Bouthillier A, van Loveren HR, Keller JT. Segments of the internal carotid artery: a new  classification. Neurosurgery 1996;38:425-432, discussion 432-433.   2  Gibo H, Lenkey C, Rhoton AL Jr. Microsurgical anatomy of the supraclinoid portion of  the internal carotid artery. J Neurosurg 1981;55:560-574.   3 Rhoton AL Jr. The supratentorial arteries. Neurosurgery 2002; 51(4, Suppl):S53-S120.   4 Rhoton AL Jr. The cavernous sinus, the cavernous venous plexus, and the carotid collar.  Neurosurgery 2002; 51(4, Suppl):S375-S410.   5 Labib MA, Prevedello DM, Carrau R, et al. A road map to the internal carotid artery in  expanded endoscopic endonasal approaches to the ventral cranial base. Neurosurgery  2014;10(Suppl 3):448-471, discussion 471.   6 Herzallah IR, Casiano RR. Endoscopic endonasal study of the internal carotid artery  course and variations. Am J Rhinol 2007;21:262-270.    The modern era anterior skull base can be traced back to the work  by Cushing (transcranial removal of an orbital tumor) in the early  20th century, and later to Ketcham’s report on the first anterior  craniofacial resection in 1963.' Additional craniofacial approaches,  originally described to manage trauma, were also adapted as  anterior approaches to the skull base in the 1980s by surgeons  like Joram Raveh.’ The first series of exclusively endoscopic surgery  for esthesioneuroblastoma was first reported by Casiano in 2001.  The steps described by this report, to endoscopically resect the  anterior skull base, have not significantly changed since then.  However, the reconstruction technique of anterior skull base defects  has evolved, as multiple techniques utilizing free grafts or pedicled  flaps have been described with equally effective results.*°   Endoscopic anterior skull base surgery has several applications,  including resection of benign nonneoplastic conditions (e.g.,  meningoencephaloceles), benign neoplasms, or carefully selected  malignant neoplasms. Meningiomas, low-grade malignancies  (hemangiopericytomas), and olfactory neuroblastomas are typical  examples of conditions in which a formal endoscopic anterior  skull base (or hemi-anterior skull base) resection is indicated.  High-grade malignancies with limited skull base involvement are  also being effectively managed endoscopically. That being said,  cases must be carefully selected for endoscopic approaches, and  the option for a combined open craniofacial approach should be  presented to all patients, in the event the tumor is still surgically  resectable, but clearance of oncological margins is not possible  through an endoscopic approach alone, due to the lack of adequate  exposure. A variety of external incisions for external approaches  to the skull base or paranasal sinuses are discussed elsewhere in  this book.   Endoscopic anterior skull base resection requires a skill set that  is a step beyond the more advanced endoscopic sinus surgical  techniques, and requires that the surgeon become familiar with  extended sinusotomies (sphenoid, frontal, and maxillary) before  proceeding with skull base surgery. The first part of the surgery  could be safely completed with a setup similar to advanced    endoscopic sinus surgery. Microdebriders are often useful for  debulking of tumor, whereas straight and angles cutting and  diamond burs facilitate removal of skull base bone, prior to dural  resection. Endoscopic bipolar cautery forceps is important to  control intracranial bleeding and should be available and ready  to use prior to making the skull base cuts. Hemostatic agents used  for neurosurgery, in addition to neurosurgical suction tips and  pledgets, should also be readily available for intracranial dissection.  Grafts (autografts, allografts, etc.) and nasal packing material should  also be available for repair of the skull base defect. Depending on  the case, additional sites should be prepped for harvesting of grafts  or flaps.   Endoscopic anterior skull base resection could be done entirely  with a two-handed technique (single surgeon holding the endo-  scope and camera with one hand and operating with the other  hand). However, cuts on the skull base and dura, as well as intra-  cranial dissection, are best done with a three- or four-handed  technique, where one surgeon is holding the endoscope and another  is performing a two-handed dissection, with the option of a fourth  hand providing additional retraction, suction, or assistance. Both  surgeons may stand side by side, to the right of the patient (for  right-handed surgeons). This allows the surgeon holding the  telescope to have better control and more efficient visualization,  as well as a more natural access to assist if a fourth hand is needed.  It is also possible for otolaryngologist and neurosurgeon to stand  facing each other on both sides of the patient’s head, depending  on the preference of the skull base team and the intraoperative  equipment set up. Visualization is the key for endoscopic skull  base surgery, and both operating surgeons should feel comfortable  and oriented with the image on the monitor to maximize success  and minimize risks. The use of a 30- or 45-degree endoscope  provides good exposure and minimal distortion, although some  portions of surgery may be done safely with a 0-degree endoscope,  and others may require a 70-degree endoscope. Regular length  endoscopic sinus surgery endoscopes could be used for the entire  endoscopic anterior skull base resection, as long as both surgeons  can position their hands without significantly interfering with  the other surgeon’s movements. Longer endoscopes and reverse  light cable endoscopes are available that allow the surgeon holding  the telescope to position his/her hands away from the surgeon  who is performing the surgical resection.   The use of surgical navigation is optional, depending on the  experience of the surgical team. It is usually most helpful for large    tumors of the anterior skull base extending posteriorly to the carotid  artery. However, for tumors confined to the anterior skull base,  and particularly for small tumors, use of intraoperative navigation  may complicate the setup and is not very useful. Therefore, it is  not routinely used for anterior skull base resection.   The procedure is best described as having three somewhat  distinct steps: step 1, anterior skull base surgical exposure and  clearance of intranasal margins; step 2, anterior skull base resection  and clearance of intracranial margins; and step 3, skull base  reconstruction (see Chapter 34). There may be situations where  only the first step (exposure and clearance of intranasal margins)  is performed, leaving the other two steps for a later date (a staged  procedure).    Step 1: Anterior Skull Base Surgical  Exposure and Clearance of  Intranasal Margins    Surgical exposure refers to the steps preceding the first dural cuts  (Fig. 29.1). The first step is central debulking of the space-occupying  portion of the tumor, for exposure of the nasal landmarks or  determination of the tumor epicenter or site of origin. This enables  the surgeon to customize the degree of nasal resection based on  tumor extent, as visualized endoscopically, and confirmed with  frozen sections. The first goal should be establishing the patency  of the nasal airway between the nasal vestibule and the posterior  choana on both sides, to have adequate space to start the dissection,  as well as to expose the area of the sphenopalatine arteries for  submucosal injection of lidocaine with epinephrine, or cauteriza-  tion, to control bleeding. Following this, bilateral maxillary  antrostomies should be performed to identify the orbital floors.  It should be kept in mind that both middle turbinates are resected  with an anterior skull base resection. However, an effort is made  to save the inferior turbinates if uninvolved microscopically with    tumor. More often than not though, a medial maxillectomy may  be more oncologically advisable on the ipsilateral side of the tumor.  This may involve removal of the lamina papyracea and bone over  the lacrimal apparatus on the lateral anterior nasal cavity. Frozen  section margins are taken from the lateral nasal wall as well as  lacrimal apparatus, if indicated.   The lamina papyracea is removed on the ipsilateral side if tumor  appears to extend into the lateral ethmoid sinus. The periorbita  may be biopsied (for a staged procedure such as orbital exentera-  tion), or completely resected and immediately reconstructed with  allograft at the time of the definitive skull base reconstruction. A  bilateral ethmoidectomy is performed, with complete mucosal  stripping of the medial orbital walls as well as fovea ethmoidales.  Tissue is sent from the anterior versus posterior ethmoid sinuses,  as well as all other sinuses, for permanent histological analysis  and accurate tumor (versus inflammatory) mapping.   An extended sphenoid sinusotomy, exposing the planum  sphenoidale, optic canal, and parasellar carotid arteries, is per-  formed. Mucosal frozen section margins are taken from the superior  nasopharyngeal mucosa bilaterally, as well as the sphenopalatine  area if the tumor extends laterally to this area. The basisphenoid  is burred down to normal-appearing bone, if there appears to be  close approximation of tumor to the bone in this area, or if there  are positive margins around the sphenoid rostrum. Once the radical  sphenoethmoidectomy and maxillary antrostomies (and/or medial  maxillectomy) are completed, the nasal septum is inspected, and  if adequate uninvolved mucosa is noted on either side of the nasal  septum, a posterior nasoseptal flap could be harvested. The superior  margins of the flap should be cleared by frozen section, however.   The nasoseptal flap is tucked in the ipsilateral maxillary sinus  or nasopharynx. It is usually uncommon to have both sides of the  nasal septum uninvolved with disease, but should this present  itself, bilateral nasoseptal flaps may be raised. Otherwise, a superior  septectomy is performed with backbiting or Tru-Cut forceps, and  septal margins cleared inferiorly and anteriorly, bilaterally (Fig.  29.2). To complete the skull base exposure, an extended frontal  sinusotomy (Lothrop procedure) should be performed. This    identifies the posterior table of the frontal sinus bilaterally, and,  with a cutting bur, the bone underneath the nasion and the adjacent  nasal bone are partially removed, to ensure adequate clearance  of bony margins at this level. Once the skull base is exposed, and  all intranasal margins are cleared, the anterior and posterior  ethmoid arteries are coagulated along their respective canals  bilaterally with monopolar or bipolar cautery. However, this latter  step may be avoided if one is considering staging the skull base  portion. Otherwise a cerebrospinal fluid (CSF) leak is possible,  and may have to be repaired.    Step 2: Anterior Skull Base Resection and  Clearance of Intracranial Margins    The actual anterior skull base resection can be roughly divided  into six bony cuts: two in the coronal plane (i.e., posterior  common frontal sinus table and planum sphenoidale), two in  the sagittal plane (i.e., fovea ethmoidalis bilaterally), and two in  the axial plane (i.e., septectomy and crista galli) (Fig. 29.3). If a  three-handed technique is used (preferred for this portion of the  dissection), one hand is retracting the specimen into the nasal  cavity while the other hand makes the superior cut with Tru-Cut  forceps or with skull base scissors. The first cut is the inferior cut  through the nasal septum, as already discussed for the superior  septectomy. The inferior cut extends from the common frontal  sinusotomy cavity (Lothrop procedure) to the common sphenoid  sinusotomy cavity. The degree of septectomy depends on the  extent of tumor involvement and one’s ability to clear that septal  margins.   The superior resected end of the perpendicular plate is removed  along with the crista galli in the midline with a diamond bur,  exposing the falx cerebri bilaterally. This is generally done prior  to performing the coronal and lateral bony cuts. The lateral bony  cuts are then performed with 3- to 4-mm diamond burs to thin  the vertical lamella of the cribriform plate and the fovea ethmoidalis  until dura is visualized. Irrigation is used to prevent excessive    heating of the bone and to enable clearance of bone dust. The  entire thickness of bone could be removed with the drill, although  more commonly final bone removal is performed with angled  Kerrison rongeurs.   A wide enough bony defect should be created to enable instru-  ments (scissors or very small Tru-Cut forceps) to make the sub-  sequent dural cuts and to obtain dural frozen sections. The two  coronal bony cuts involve the anterior sphenoid planum and  posterior wall of the common frontal sinus. The thickness of the  sphenoid planum and posterior frontal sinus could be significant,  and extensive drilling may be required at this level. Once all the  anterior skull base bone is removed, there will be a “floating” or  “pulsating” anterior skull base. It is not uncommon at this stage  of the dissection to have a CSF leak through small dural tears. An  upbiting small Tru-Cut forceps may be used to perform the dural  cuts and simultaneously to collect dural samples to be used as  frozen section margins. Alternatively, up-biting endoscopic skull  base microscissors could be used, and a strip of dura could be  separately harvested, for margins.   Next, the axial cuts through the falx cerebri are performed  bilaterally, enabling one to reflect the final anterior skull base  specimen, consisting of the olfactory bulbs and adjacent anterior  skull base dura, inferiorly into the nose. The resection is completed  by making the posterior dural cuts. The posterior dural cuts over  the planum sphenoidale expose the olfactory nerves, whereas  lateral cuts expose the inferior aspect of the frontal lobes. Any  bleeding dural or parenchymal vessels are cauterized with bipolar  cautery. The olfactory nerves can be transected at this point, and  margins sent for frozen section. Small subdural vessels are com-  monly encountered at this level (between the crista galli and the  falx cerebri) and can be controlled with bipolar cautery. The  specimen is either delivered through the nasal vestibule, or pushed  into the nasopharynx and delivered transorally, depending on its  size. The final bilateral anterior skull base (ASB) defect after a  completed ASB resection is depicted in Fig. 29.4. For select  neoplasms, a hemi-ASB resection may be indicated in an attempt   wall Falx cerebri  Cut edge and cut edge  of ethmoid of crista galli  roof and    to salvage one intact olfactory apparatus on the contralateral side.  The technique is similar to the bilateral ASB resection discussed  above. However, the contralateral sinuses, the mucoperiosteum  of the nasal septum, and the contralateral falx cerebri over the  contralateral olfactory bulb are preserved (Fig. 29.5). The crista  galli may also be carefully drilled with a diamond bur and removed.  However, care must be taken that the contralateral olfactory bulb  is not traumatized with the drilling.    Many anterior skull base reconstruction techniques have been  described in the literature for repair of anterior skull base defects,    including single layer or multiple layer reconstruction techniques.  Skull base reconstruction techniques are discussed in Chapter 34.  However, single-layer, intermediate-thickness, acellular dermal  allograft has proven to be as reliable as other reported multilayer  techniques. One drawback is prolonged crusting, in that the grafted  area needs to be periodically debrided for over 6 months, depending  on the status of the surrounding mucosa, as well as the presence  of postoperative radiation. When spared by the disease, a posterior  nasoseptal flap decreases the amount of crusting and expedites  healing at the anterior skull base, when used to cover the acel-  lular dermal allograft. However, the flap must not be relied upon  alone to achieve an effective watertight closure. It is merely for  mucosal coverage over the central portions of the grafted defect.  No matter what technique is utilized, the goals of reconstruc-  tion are to provide a durable airtight and watertight separation  between the nasal cavity and the anterior cranial fossa, as well as  to eliminate dead space and to prevent postoperative hematoma  or seroma formation, which could lead to infection (meningitis  or abscess).   Following surgery, patients are monitored in the intensive care  unit setting overnight for mental status and neurologic monitoring.  Standard CSF leak precautions are used, including strict bed rest  for the first night, head of bed elevated, stool softeners, Foley  catheter, and codeine for cough. Routine use of a lumbar drain is  not advised, as this is more likely to cause intracranial hypotension  and pneumocephalus. Patients ambulate progressively and are  instructed to abstain from strenuous physical activities for 4 weeks  after surgery. Perioperative antibiotics are administered the day  of surgery (ceftriaxone and vancomycin) and postoperative antibiot-  ics are used while the patient’s nose remains packed (amoxicillin,  first-generation cephalosporin or clindamycin). Standard postopera-  tive venous thromboembolic prophylaxis is used. Packing is  removed 7 days after surgery. Postoperative imaging studies  (magnetic resonance imaging) are obtained prior to discharge as  a baseline for comparison with subsequent studies.   Overall, the postoperative course is less morbid than with open  anterior skull base approaches. Pain is usually mild to moderate  and well controlled with acetaminophen. Severe headaches,  especially if associated with altered mental status or focal neurologic  deficit, should trigger imaging studies to rule out bleeding, tension  pneumocephalus, or abscess, as well as CSF sampling for meningitis.  CSF leak occurs in less than 5% of the patients, but could be a  challenging complication, especially in extensive cases. It is first  managed conservatively with a lumbar drain in the absence of  worsening pneumocephalus. Revision surgery is needed when  the lumbar drain is either not tolerated or not successful (after 3  to 5 days). The techniques used for salvage surgery, depending  on the extent of the leak, include an additional alloplastic graft  patch, an abdominal fat graft, an inferior turbinate pedicled flap,  and a pericranial flap. Patients are seen at regular monthly intervals,  after packing removal, for nasal endoscopy and debridement. Loose  crusts and secretions are removed and patients are instructed to  use Saline nasal rinses to help with healing. Culture-directed topical  antibiotics may be necessary. Debridement under a general  anesthetic may be necessary after a few months to reestablish  any common frontal or sphenoid patency, or for removal of  granulations and extruded graft material, to speed up the healing  process.    1 Ketcham AS, Wilkins RH, Vanburen JM, Smith RR. A combined intracranial facial approach  to the paranasal sinuses. Am J Surg 1963;106:698-703.    2  RavehJ, Vuillemin T. Advantages of an additional subcranial approach in the correction  of craniofacial deformities. J Craniomaxillofac Surg 1988;16:350-358.    3  Casiano RR, Numa WA, Falquez AM. Endoscopic resection of esthesioneuroblastoma.  Am J Rhinol 2001;15:271-279.    4 Germani RM, Vivero R, Herzallah IR, Casiano RR. Endoscopic reconstruction of large  anterior skull base defects using acellular dermal allograft. Am J Rhinol 2007;21:615-618.    5 Zanation AM, Thorp BD, Parmar P, Harvey RJ. Reconstructive options for endoscopic  skull base surgery. Otolaryngol Clin North Am 2011;44:1201-1222.    6 Clavenna MJ, Turner JH, Chandra RK. Pedicled flaps in endoscopic skull base reconstruction:  review of current techniques. Curr Opin Otolaryngol Head Neck Surg 2015;23:71-77.    Borg A, Kirkman MA, Choi D. Endoscopic endonasal anterior skull base surgery: a systematic  review of complications over the past 65 years. World Neurosurg 2016;95:383-391.    Casiano RR. Endonasal resection of the anterior cranial base. In: Ferris R, Myers EN, eds.  Masters Techniques in Otolaryngology—Head and Neck Surgery. Philadelphia: Lippincott  Williams & Wilkins; 2013.   Eloy JE, Tessema B. Casiano RR. Endoscopic approaches to the anterior cranial fossa. In:  Hwang PH, Kennedy DW, eds. Rhinology: Diseases of the Nose, Sinuses, and Skull Base.  New York: Thieme Medical Publishers. 2012;605-614.   Harvey RJ, Winder M, Parmar P, Lund V. Endoscopic skull base surgery for sinonasal  malignancy. Otolaryngol Clin North Am 2011;44:1081-1140.   Lieberman S, Casiano RR, Endoscopic surgery on EsthesioNeuroBlastoma. In: Bcker S,  Castelnuovo P, eds. Atlas of Surgery on the Nose, Paranasal Sinuses, and the Skull Base.  SCR Publishers; 2015.   Rawal RB, Gore MR, Harvey RJ, Zanation AM. Evidence-based practice: endoscopic  skull base resection for malignancy. Otolaryngol Clin North Am 2012;45:1127-1142.   Zhang M, Singh H, Almodovar-Mercado GJ, Anand VK, Schwartz TH. Required Reading:    The most impactful articles in endoscopic endonasal skull base surgery. World Neurosurg  2016;92:499-512.e2.    30 Approaches to the Clivus, Petrous Apex, Craniocervical  Junction, and Odontoid Decompression   Cranial nerves (CNs) III, IV, V, VI, VII, IX, X, XI, and XII    Endoscopic approaches to the clivus, petrous apex, and upper  cervical spine have gained traction over the last decade as more  surgeons appreciate the need for less morbid access to pathology  within these central structures. The entire length of the clivus  can be accessed endoscopically, from the dorsum sellae down to  the foramen magnum. Chordomas, the most commonly encountered  lesions of the clivus, demonstrate variable endoscopic accessibility  depending on lateral extension. Although gross total resection of  a chordoma is ideal, in many cases residual tumor is addressed  with radiotherapy. Proton beam therapy has proven more reliable  than traditional radiotherapy, but is not widely available at present.!  Other lesions of the clivus include chondromas, chondrosarcomas,  and clival extension of cholesterol granulomas arising from the  petrous apex.’   Petrous apex lesions were traditionally accessed through a narrow  lateral approach that placed the labyrinth and facial nerve at risk.  However, endoscopic transsphenoidal access has been shown to  be a safe and reliable alternative with less morbidity. Cholesterol  granulomas are the most common petrous apex pathology encoun-  tered, and they require the creation of an endoscopic drainage  pathway that is capable of remaining patent to prevent ongoing  expansion and bony destruction of the petrous apex and adjacent  clivus.** Cholesteatomas and schwannomas are less common lesions  of the petrous apex. As lateral access is limited with endoscopic  approaches to the petrous apex, many solid tumors involving  this area require a lateral approach or a combination of staged  endoscopic and lateral approaches for complete resection.   Endoscopic approaches to the upper cervical spine enable  decompression of the cervicomedullary junction and removal of  pathology such as arthritic deposits, congenital malformations,  and osteomyelitis.*'! These endoscopic approaches are often    performed in conjunction with an open cervical spinal fusion  procedure through a posterior incision to ensure stability of the  craniocervical junction postoperatively.   The clivus, Latin for “slope,” is best visualized in a sagittal view  of the cranial base extending from the posterior aspect of the  dorsum sellae down to the foramen magnum intracranially, and  from the posterior wall of the sphenoid sinus down to the posterior  nasopharynx, approximately level with the superior aspect of the  eustachian tubes (Fig. 30.1). The lateral extent of clival resection  is generally limited by the paraclival portion of the internal carotid  arteries and the hypoglossal canals more inferiorly. The clivus  separates the nasopharynx from the posterior cranial fossa. The  posterior portion of the sphenoid bone (basisphenoid) and  the basilar portion of the occipital bone (basiocciput) compose  the clivus. It is divided into three levels for classification purposes:  upper, middle, and lower thirds (Fig. 30.2). On endoscopic view,  the upper third corresponds with the level of the dorsum sellae  and cannot be visualized without transposition of the pituitary  gland; the middle third extends from the floor of the sella to the  floor of the sphenoid sinus; the lower third extends from the floor  of the sphenoid sinus to the foramen magnum. The upper and  middle thirds of the clivus form a concave surface intracranially  that cradles the pons. The clival periosteum is densely adherent  to the dura adjacent to the pons and medulla, and the basilar  venous plexus flows between layers of this dura with connections    to the inferior petrosal sinuses laterally, the cavernous sinuses  superiorly, and the marginal sinus and epidural venous plexus  inferiorly (Fig. 30.3). Just deep to the clivus and underlying  dura, the basilar artery traverses superiorly and often deviates  from the midline, giving off multiple branches including the  anteroinferior cerebellar arteries, superior cerebellar arteries, and  posterior cerebral arteries, which contribute to the circle of Willis  (Fig. 30.4).   A posterior septectomy is required for endoscopic exposure  during clival resection, and it can be tailored to the size necessary  for the exposure needed. Resection of large clival neoplasms often  requires a large posterior septectomy extending from the floor of  the nasal cavity up to the skull base (Fig. 30.5a). For cervical spine  and foramen magnum decompression, the septectomy can be  limited to an inferoposterior septectomy below the level of the  sphenoid rostrum and sphenoid sinus, (Fig. 30.5b). Nasoseptal  flaps should be harvested prior to the septectomy to prevent    artery CN VII Cavernous Ophthalmic  Mamillary body CN VIII sinus nerve (CN V1)  Posterior cerebral CN IX Internal carotid /— Maxillary  artery CNX artery nerve (CN V2)  Mandibular  Superior cerebellar Nawal vi) nerve (CN V3)  artery CN XII cana  Trigeminal  Anterior inferior CN XI Facial — nerve (CN V)  cerebellar artery nerve (CN VII)  Posterior inferior  cerebellar artery See eA Da ee ae Glussopnaingedl Vestibulocochlear  nerve agus nerve (CN VIII  Anterior spinal Bas vertebral nerve nerve Nerve (CN IX)   artery ry (CN Xl) (CN X)    CHAPTER 30 ® Approaches to the Clivus, Petrous Apex, Craniocervical Junction, and Odontoid Decompression 115    compromise of the vascular pedicle, and draped into the ipsilateral  maxillary sinus until utilized for closure at the conclusion of the  procedure.   The extent of surgical exposure is determined by the extent of  clival pathology. Lesions involving the upper and middle thirds  of the clivus require bilateral total ethmoidectomies, creation of  acommon sphenoid cavity with removal of the sphenoid rostrum  and intersinus septations, and often removal of the sphenoid sinus  floor between the vidian canals using a high-speed cutting or  diamond bur. The middle and inferior turbinates can be partially  resected or out-fractured to facilitate bi-nostril access for the  endoscope and instrumentation. Lesions with lateral extension  may require maxillary antrostomies and transpterygoid access  via drilling of the base of the pterygoid process superiorly for  access into the middle cranial fossa/infratemporal fossa, or drilling  of the medial and lateral pterygoid plates inferiorly for access into  the lateral nasopharynx/parapharyngeal space. Disease directly  posterior and lateral to the internal carotid arteries necessitates  careful exposure of the vessels from the superior extent of the  pathology down to the vertical paraclival segments. Intraoperative  navigation is imperative when surgical access involves risk of  injuring these vessels.   Exposure of the inferior third of the clivus requires removal of  a portion of the posterior nasopharyngeal mucosa, which can be  pedicled inferiorly. The underlying fascia, superior pharyngeal  constrictor musculature, and paraspinal musculature (including  the longus colli and splenius capitis medially) are removed to  expose the lower clivus and floor of the sphenoid (basisphenoid).  Removal of tissue and bone in this area is limited laterally by the  superior eustachian tubes, second genu of the carotid artery, and  a thick layer of foramen lacerum fibrocartilaginous tissue separating  the two. Once adequate exposure of the clivus has been achieved  for a given pathology, removal of bone proceeds with a cutting  or diamond bur from a medial to lateral direction, with the  paraclival carotid arteries and eustachian tubes serving as the  lateral limits of dissection in most cases. Bleeding can be substantial  from the venous plexus within the cancellous bone of the clivus    and basisphenoid, as well as the basilar venous plexus just deep  to the clivus (Fig. 30.6), and may require a two-surgeon, four-hand  technique that enables simultaneous drilling and suctioning to  improve visualization as well as temporary packing of the clival  defect with hemostatic agents to prevent excessive blood loss.  Particular care should be taken to avoid injury to the abducens  nerve, which can be found adjacent and posteromedial to the  paraclival carotid midway up the vertical height of the middle  third of the clivus. A portion of the abducens nerve is also contained  within the two dural sheaths of the basilar venous plexus just  inferomedial to the entrance of Dorello’s canal (Fig. 30.6), which  is located lateral to the parasellar carotid artery.'? Opening the  inner layer of the clival or upper C-spine dura to visualize the  posterior cranial fossa reveals the vertebral arteries, basilar artery  with its branches, pons, and brainstem (Fig. 30.7).    Slightly superior to the eustachian tube and torus tubarius, as  one is drilling away the basisphenoid bone laterally, lies the thick  fibrocartilaginous tissue that makes up the foramen lacerum and  the adjacent anterior (second) genu of the intrapetrous carotid  artery. The hypoglossal canal, occipital condyle, and jugular foramen  can be reached with further removal of basisphenoid bone  inferolaterally. Table 30.1 lists important intracranial landmarks  by corresponding level of clival approach.   Endoscopic access to the petrous apex is obtained by drilling  with a high-speed diamond bur inferior and medial to the anterior  genu of the intrapetrous carotid artery (where the vertical paraclival  segment turns 45 degrees posterolateral and becomes the petrous  portion of the carotid artery at the second genu). In patients with  poorly pneumatized sphenoid sinuses, the vidian canal can be  used to guide the dissection to the second genu. However, with    Table 30.1 Intracranial Landmarks of the Upper, Middle, and Lower Clivus    Upper clivus Interpeduncular cistern  Posterior cerebral artery  Superior cerebellar artery  Cranial nerve III    intraoperative navigation this is rarely necessary. Management of  a cholesterol granuloma then proceeds with marsupialization of  the cyst, removal of septations and cyst contents, and placement  of a stent that maintains patency until postoperative healing and  remucosalization is complete over a period of 6 to 12 months.  Cholesterol granulomas (Fig. 30.8, small arrows) that extend medial  to the paraclival internal carotid artery are readily addressed  through the medial transsphenoidal endoscopic approach (Fig.  30.8, large arrow). Cholesterol granulomas that do not extend  adequately medial to the paraclival carotid may require exposure  of the vessel and lateralization of the vertical segment for several  millimeters of additional access. An infrapetrous approach has  been described that enables endoscopic access to far lateral lesions  within the petrous apex. In this approach, a 1-cm portion of the  cartilaginous eustachian tube is removed, pterygopalatine contents  are displaced laterally as the vidian nerve is sacrificed, and the  pterygoid base and superior aspect of the pterygoid plates are  drilled for transpterygoid access between the horizontal petrous    CHAPTER 30 ® Approaches to the Clivus, Petrous Apex, Craniocervical Junction, and Odontoid Decompression 117    arte  o Arch of the  Posterior =| | ~ atlas (C1)  atlantoaxial "hh i \ \ \ Odontoid  ligament c Hf a : process  between wy 4 .\ 4  C1 and C2 Atlantoaxial  ligaments  Transverse ligament Body of the  axis (C2)  Posterior Anterior  longitudinal longitudinal  ligament Intervertebral ligament  fibrocartilage  Fig. 30.9    carotid and the eustachian tube remnant medial to the mandibular  division of the trigeminal nerve."   When odontoid decompression is performed endoscopically, a  nasoseptal flap is harvested prior to performing a posteroinferior  septectomy. The posterior nasopharyngeal soft tissues are removed  or displaced inferiorly, as discussed above, until the lower clivus  and the anterior arch of C1 are encountered (Fig. 30.9).°''! The  soft palate may be retracted anteriorly with a small rubber catheter  placed through the nostril and back out of the oral cavity to improve  visualization, particularly with pathology that extends at or below  C2.’® Simultaneous transoral instrumentation and transnasal  endoscopy, or vice versa, may also be necessary in select cases.  Drilling proceeds with cutting or diamond burs to remove the  anterior arch of C1, and the underlying ligaments are removed to  expose the odontoid process (Fig. 30.10). The center of the odontoid  is hollowed with a diamond bur to a thin shell. The remaining  thin shell of fragmented bone is gently removed from the underlying  alar and cruciate ligaments. Care should be taken not to transect  the odontoid prior to hollowing its core, as this creates a floating  odontoid with the potential for neural injury at the foramen  magnum due to vibrations caused by further drilling. Removal of  a rheumatoid pannus or any other pathology at the craniocervical  junction is then completed, and pulsatile dura should be visualized  following a complete decompression. If the underlying dura remains  intact and no leakage of cerebrospinal fluid (CSF) is noted, then  reconstruction using nonvascularized or vascularized grafts should  be adequate for appropriate healing. If the dura is violated, a  high-flow CSF leak is encountered and typically requires multi-  layered reconstruction. Staged posterior cervical fusion is carried  out by the neurosurgical team as soon as possible following  endoscopic cervical spine decompression in the setting of cranio-  cervical instability.    1 Endoscopic resection of clival and posterior cranial fossa tumors. In: Wormald P-J, ed.  Endoscopic Sinus Surgery. Stuttgart: Georg Thieme Verlag; 2013.   2 Turner JH, Fernandez FI, Tsao GJ, Hwang PH, Nayak JV. The clivus. In: Palmer JN, Chiu  AG, eds. Atlas of Endoscopic Sinus and Skull Base Surgery. Philadelphia: Elsevier;  2013:303-315.   3 McLaughlin N, Kelly DF, Prevedello DM, Shahlaie K, Carrau RL, Kassam AB. Endoscopic  endonasal management of recurrent petrous apex cholesterol granuloma. J Neurol  Surg B Skull Base 2012;73:190-196.   4 Paluzzi A, Gardner P, Fernandez-Miranda JC, et al. Endoscopic endonasal approach to  cholesterol granulomas of the petrous apex: a series of 17 patients: clinical article.  J Neurosurg 2012;116:792-798.   5 Feng K, Qiuhang Z, Wei Z, et al. Anatomy of the petrous apex as related to the endoscopic  endonasal approach. J Clin Neurosci 2012;19:1695-1698.   6 Burns TC, Mindea SA, Pendharkar AV, Lapustea NB, Irime I, Nayak JV. Endoscopic  transnasal approach for urgent decompression of the craniocervical junction in acute  skull base osteomyelitis. J Neurol Surg Rep 2015;76:e37-e42.   7 Deopujari CE, Karmarkar VS, Shah NJ. Endoscopic approaches to the craniovertebral  junction and odontoid process. World Neurosurg 2014;82(6, Suppl):S49-S53.   8 Liu JK, Patel J, Goldstein IM, Eloy JA. Endoscopic endonasal transclival transodontoid  approach for ventral decompression of the craniovertebral junction: operative technique  and nuances. Neurosurg Focus 2015;38:E17.   9 Eloy JA, Vazquez A, Mady L], Patel CR, Goldstein IM, Liu JK. Mucosal-sparing posterior  septectomy for endoscopic endonasal approach to the craniocervical junction. Am J  Otolaryngol 2015;36:342-346.   10 Fang CH, Friedman R, Schild SD, et al. Purely endoscopic endonasal surgery of the  craniovertebral junction: a systematic review. Int Forum Allergy Rhinol 2015;5:754-760.   11 Eloy JA, Vazquez A, Marchiano E, Baredes S, Liu JK. Variations of mucosal-sparing  septectomy for endonasal approach to the craniocervical junction. Laryngoscope  2016;126:2220-2225.   12 Reddy RK, Reddy RK, Jyung RW, Eloy JA, Liu JK. Gruber, Gradenigo, Dorello, and Vail:  key personalities in the historical evolution and modern-day understanding of Dorello’s  canal. J Neurosurg 2016;124:224-233.   13 Zanation AM, Snyderman CH, Carrau RL, Gardner PA, Prevedello DM, Kassam AB.  Endoscopic endonasal surgery for petrous apex lesions. Laryngoscope 2009;119:19-25.   Medial pterygoid plate and muscle  Lateral pterygoid plate and muscle  Tensor veli palatini    Surgical approaches to the nasopharynx and parapharyngeal spaces  can present a challenge due to the complex anatomy in this region.  For malignant tumors in this anatomic area, primary radiation or  chemoradiation has been the standard of care, due to the challenge  of gaining surgical access, as well as the radiosensitive nature of  many of these tumors.'* Tumors requiring surgical approaches  have classically been approached externally, which can carry  significant morbidity. However, with improved endoscopic  techniques, resection of selected nasopharyngeal malignancies  has become an increasingly viable option. Additionally, endoscopic  approaches to select parapharyngeal lesions and neoplasms can  provide enhanced access and excellent visualization of an otherwise  difficult to reach superomedial parapharyngeal space.*® Primary  lesions that may be addressed by these techniques are primary  nasopharyngeal carcinomas and adenocarcinomas, recurrent  nasopharyngeal carcinomas, nasopharyngeal and parapharyngeal  minor salivary gland lesions, and schwannomas of the superomedial  parapharyngeal space, among others.   The nasopharynx is open to the nasal passages anteriorly beyond  the plane of the posterior choana (Fig. 31.1). The posterior edge  of the vomer is in the midline and demarcates the anterior border  of the nasopharynx. The inferior aspect is open to the oropharynx,  but is otherwise bordered by the soft palate and its intrinsic  musculature. The lateral walls of the nasopharynx are made up  by the pharyngobasilar fascia and the superior pharyngeal constric-  tors posteriorly, and the eustachian tube and medial pterygoid  plate anteriorly. The cartilaginous segment of the eustachian tube  protrudes from the lateral pharyngeal wall as the torus tubarius.  The fossa of Rosenmiiller is located posterosuperior to the torus  and is an important site for identification of occult malignancy.  The posterior wall and roof of the nasopharynx is predominantly  occupied by the adenoids or pharyngeal tonsil. Deep to this,  posteriorly, lies the pharyngeal raphe, where the superior pha-  ryngeal constrictors merge, followed by the buccopharyngeal fascia,  alar fascia, and the prevertebral fascia. The basisphenoid and    basiocciput provide the osseous posterior boundary of the naso-  pharynx superiorly, whereas the anterior arch of C1 is encountered  at the inferior aspect of the posterior nasopharynx. This is located  at the level of the soft palate and inferior eustachian tube opening.  At the lateral superior border lies the foramen lacerum, which  consists of fibrocartilaginous tissue, separating the second genu  of the internal carotid artery from the superior borders of the  cartilaginous eustachian tube and nasopharyngeal space.”"!°  The parapharyngeal space is often described as an inverted  pyramid. Its base is the lateral skull base, comprising portions of  sphenoid and temporal bones. The posterior skull base border  lies between the jugular foramen and the root of the styloid process  posteriorly. The lateral skull base border lies between the styloid  process and the lateral pterygoid plate along the sphenoid wing.  The anterior skull base border lies between the pterygoid plates  and the foramen lacerum along the basisphenoid. The medial  skull base boundary is along the petrous temporal bone from the  foramen lacerum to the jugular foramen. The apex of the pyramid  is at the greater cornu of the hyoid bone. The medial border of  the space is the pharyngeal wall. The lateral border generally  follows along the plane of the ramus of the mandible, potentially    Hypoglossal Longus  nerve capitus .  Accessory muscle Rectus  nerve capitis Occipital  Glossopharyngeal anterior bone  nerve muscle  Fig. 31.1    CHAPTER 31 ® Approach to the Nasopharynx and Parapharyngeal Space 119    Hypoglossal Longus |  nerve capitus .  Accessory muscle pecs  nerve capitis Occipital  Glossopharyngeal anterior 4,  one  nerve muscle  Fig. 31.2    including a segment of the deep lobe of the parotid and the medial  pterygoid superiorly, and the posterior digastric muscle inferiorly.  The posterior border follows along the carotid sheath and lies  adjacent to the paravertebral muscles. Anteriorly, the space is  defined by the plane of the pterygomandibular raphe. The space  is further subdivided into the pre-styloid and post-styloid spaces  based on the plane of the tensor veli palatini’s fascial attachment  to the styloid process. Generally, the major neurovascular structures  in the parapharyngeal space are found in the post-styloid compart-  ment, including the carotid artery, jugular vein, cervical sympathetic  chain, cranial nerves IX to XII, and cervical contributions to the  ansa cervicalis. Notable contributions to the pre-styloid compart-  ment include V3 and the deep lobe of the parotid gland.”   Endoscopic resection of nasopharyngeal lesions requires adequate  access to all affected areas of the nasopharynx (Fig. 31.2). As such,  careful review of the imaging preoperatively is critical in planning  the surgical access. The extent of resection needs to be individual-  ized for every patient, depending on the initial radiographic extent  of disease, as well as intraoperative endoscopic and histopathologi-  cal findings. Maneuvers to improve endoscopic access include  performing a posterior septectomy, sphenoethmoidectomy, partial  turbinate reduction, medial maxillectomy, and inferior transptery-  goid approaches through the medial or lateral pterygoid plates.  Based on the extent of disease, completing all of these techniques  may not be necessary."!   The procedure starts with adequate nasal decongestion with a  topical vasoconstrictor. Submucosal injection with 1% lidocaine  with epinephrine may also be used in the area of the sphenopalatine  artery and along the posterior septum to address intraoperative  bleeding. If planning a pedicled nasoseptal flap for reconstruction  of the ultimate nasopharyngeal and skull base defect, the flap  should be elevated at the beginning of the procedure to maximize  available mucosa for coverage. More likely than not, a contralateral  nasoseptal flap is needed in most cases involving a unilateral  nasopharyngectomy, because the ipsilateral branches of the internal  maxillary artery are typically sacrificed during the exposure.    Smaller neoplasms limited to the central nasopharynx can be  endoscopically resected circumferentially down to soft tissue  and bone, with clear margins. However, neoplasms located more  laterally in the nasopharynx, including those neoplasms involving  the torus tubarius and cartilaginous eustachian tube and sur-  rounding paraspinal musculature, require access to the medial  parapharyngeal space and resection of the cartilaginous eustachian  tube, for adequate clearance of the lateral margins of resection.  This procedure represents the maximum extent of endoscopic,  and perhaps oncological, resection. Further lateral extension of  neoplasm likely will need more extensive external exposure, with  or without endoscopic visualization, to control and resect the  parapharyngeal carotid artery.   The procedure begins with a complete sphenoethmoidectomy,  medial maxillectomy, and posterior septectomy. A common  sphenoid sinus cavity (extended sphenoid sinusotomy) is created  from the ipsilateral side by removing the rostrum. The floor of  the sphenoid is resected with cutting burs until the soft tissue of  the superior nasopharynx (pharyngobasilar fascia, superior constric-  tor muscles, and midline raphe) is identified and margins are  cleared. Reduction of the bone of the posterior wall of the maxillary  sinus is then performed with a high-speed bur or Kerrison bone  rongeurs.   The vertical plate of the palatine bone is removed, exposing the  greater palatine nerve, medial pterygoid muscle, and medial and  lateral pterygoid plates (Figs. 31.3, 31.4, 31.5). The lateral pterygoid  plate is initially preserved, demarcating the sagittal plane of the  bony-cartilaginous junction of the eustachian tube in the superior  parapharyngeal space posteriorly, and medial to the parapharyngeal  carotid artery (Fig. 31.2). The medial pterygoid muscle is resected,  exposing the tensor palatine muscle coursing along the anterior  wall of the cartilaginous eustachian tube (Fig. 31.6). The carti-  laginous eustachian tube runs anterior and medial to the cervical  segment of the internal carotid as it runs through the parapha-  ryngeal space. Careful attention is necessary if dissecting lateral  to the sagittal plane of the lateral pterygoid plate when resecting    the cartilaginous eustachian tube (at the bony-cartilaginous  junction), as injury to the parapharyngeal carotid artery or V3;  branch of the trigeminal nerve may occur.*'?   A vertical incision is made medial to the tumor in the posterior  nasopharynx, deep into the pharyngobasilar fascia and superior  constrictor muscles, and margins are cleared (Fig. 31.2). A plane  of dissection continues within the deeper aspects of the superior  constrictor muscles (medially) and paraspinal muscles (laterally),  as the tumor is gradually elevated with the medial cartilaginous  eustachian tube anterolaterally. Margins can again be sampled at  this level corresponding to the posterior margins of the tumor.  Additional muscle can be resected if there is microscopic evidence  of tumor. Immediately superior and slightly posterior to the  cartilaginous eustachian tube lies a thick sheet of fibrocartilaginous  tissue that can measure up to 1cm in thickness. This makes up  the soft tissue of the foramen lacerum, and separates the torus  tubarius from the second genu of the internal carotid artery. Small  Tru-Cut forceps are general used to cut through this tissue, thereby    detaching and rotating the eustachian tube inferoanteriorly. Tissue  may be sampled in this area to clear this margin as well. Finally,  the bony-cartilaginous eustachian tube can be transected anterior  and medial to the bony petrous portion of the carotid, and medial  and posterior to the V3.°'? Further drilling of the bone encircling  the lateral petrous portion of the carotid artery and soft tissue  dissection in the parapharyngeal space exposes the entire extent  of the parapharyngeal carotid artery, which may be tortuous and  variable and in this location (Fig. 31.7).    1 Chen MK, Lai JC, Chang CC, Liu MT. Minimally invasive endoscopic nasopharyngectomy  in the treatment of recurrent T1-2a nasopharyngeal carcinoma. Laryngoscope 2007;  117:894-896.   2 Castelnuovo P, Dallan I, Bignami M, et al. Nasopharyngeal endoscopic resection in the  management of selected malignancies: ten-year experience. Rhinology 2010;48:84-89.    CHAPTER 31 ® Approach to the Nasopharynx and Parapharyngeal Space 121    Van Rompaey J, Suruliraj A, Carrau R, Panizza B, Solares CA. Access to the parapharyngeal  space: an anatomical study comparing the endoscopic and open approaches. Laryn-  goscope 2013;123:2378-2382.   To EW, Lai EC, Cheng JH, Pang PC, Williams MD, Teo PM. Nasopharyngectomy for  recurrent nasopharyngeal carcinoma: a review of 31 patients and prognostic factors.  Laryngoscope 2002;112:1877-1882.   Battaglia P, Turri-Zanoni M, Dallan I, et al. Endoscopic endonasal transpterygoid  transmaxillary approach to the infratemporal and upper parapharyngeal tumors.  Otolaryngol Head Neck Surg 2014;150:696-702.   Youssef A, Carrau RL, Tantawy A, et al. Endoscopic versus open approach to the  infratemporal fossa: a cadaver study. J Neurol Surg B Skull Base 2015;76:358-364.  Eisele DW, Richmon JD. Contemporary evaluation and management of parapharyngeal  space neoplasms. J Laryngol Otol 2013;127:550-555.    Martins C, Rhoton AL. Anatomy of the cranial base. In: Hanna EY, DeMonte F, eds.  Comprehensive Management of Skull Base Tumors. New York: Informa Healthcare;  2008:3-42.   Castelnuovo P, Dallan I, Tschabitscher M. Surgical Anatomy of the Internal Carotid  Artery: An Atlas for Skull Base Surgeons. New York: Springer; 2013.   Myers EN, Johnson JT. Management of Tumors of the Parapharyngeal Space Operative  Otolaryngology Head and Neck Surgery. Philadelphia: Saunders; 2008:657-670.  Schmidt RF, Choudhry OJ, Raviv J, et al. Surgical nuances for the endoscopic endonasal  transpterygoid approach to lateral sphenoid sinus encephaloceles. Neurosurg Focus  2012;32:E5.   Fortes FS, Pinheiro-Neto CD, Carrau RL, Brito RV, Prevedello DM, Sennes LU. Endonasal  endoscopic exposure of the internal carotid artery: an anatomical study. Laryngoscope  2012;122:445-451.    m Orbital apex, annulus of Zinn, and optic canal  gm Medial, inferior, and lateral rectus muscles   m Superior oblique and inferior oblique muscles  g Orbital portion of the optic nerve    Knowledge of intraorbital anatomy is critical for endoscopic  resection of orbital neoplasms and lesions.'"° Many key anatomic  landmarks of orbital anatomy relevant to endoscopic surgery can  be seen on preoperative computed tomography (CT) imaging,  specifically the inferior rectus and medial rectus muscles, along  the floor and medial wall of the orbit, respectively (Fig. 32.1).  Understanding the anatomy of the medial orbit is particularly  important for the endoscopic surgeon because these struc-  tures frequently serve as anatomic reference points for many  procedures.”®    Endoscopic removal of the thin bony medial wall of the orbit  (lamina papyracea), as performed in a medial orbital decompression,  reveals the periorbita. Deep to the periorbita is the orbital fat.  Removal of the orbital fat reveals the medial rectus muscle. The  medial aspect of the inferior rectus muscle may be seen running  adjacent to the horizontal ridge of the antrostomy (Fig. 32.2).  Further removal of fat between these two muscles, and reflection    Anterior ethmoid  artery (branch of the  ophthalmic artery)  Superior  oblique  muscle  Medial    of the medial rectus superiorly, exposes the course of the intra-  orbital optic nerve and the posterior aspect of the globe (Fig.  32.3). The ophthalmic artery, which arises from the internal carotid  artery inferomedial to the optic nerve (cranial nerve [CN] II), can  be visualized and followed anterior to its insertion onto the optic    Supraorbital nerve  Superior oblique Superior rectus muscle  muscle Frontal nerve  Lacrimal gland  Trochlear nerve  (CN IV)   nerve (CNIII) nerve (CNIV) nerve (CN VI)  Dorsal nasal Superior rectus  artery muscle (cut)    2nd genu of the the lateral recess  internal carotid artery of the sphenoid  sinus    nerve to become the central retinal artery. The annulus of Zinn,  representing the thick fibrotic insertion point for all the extraocular  muscles, can be identified after removing bone at the orbital apex.   Superiorly, with removal of the roof of the optic canal (lesser  wing of the sphenoid), one can visualize the canalicular portion  of the optic nerve. In addition, the anterior and posterior ethmoid  arteries (branches of the ophthalmic artery) can be visualized  (Fig. 32.4) along the superomedial aspect of the orbit, usually at  the frontoethmoidal suture line (although the position varies).  Endoscopically, the intraorbital portions of the anterior and  posterior ethmoid arteries, which branch from the ophthalmic  artery, may be identified coursing toward their respective canals  in the ethmoid roof (Fig. 32.4b).   The orbit can be dissected posteriorly to the interface with the  cavernous sinus. With the removal of the superior orbital roof,  the entire course of the optic nerve and its relationship to the  carotid artery, the trigeminal nerve (CN V), abducens nerve (CN  VI), oculomotor nerve (CN III), and the trochlear nerve (CN IV)  may be seen (Fig. 32.4b). Intranasally, when the medial orbital  wall, sella, and sphenoid bone are removed, one is able to visualize  a different view of this relationship (Fig. 32.5).    1 Dutton JJ, Waldrop TG. Atlas of Clinical and Surgical Orbital Anatomy (Expert Consult  Title), 2nd ed. New York: Elsevier Health Sciences; 2011.   2 Guthoff R, Katowitz JA. Oculoplastics and Orbit (Essentials in Ophthalmology). Berlin:  Springer; 2007.   3. Tse D. Color Atlas of Oculoplastic Surgery. Philadelphia: Lippincott Williams & Wilkins;  2011.   4 Signorelli F, Anile C, Rigante M, Paludetti G, Pompucci A, Mangiola A. Endoscopic treatment  of orbital tumors. World J Clin Cases 2015;3:270-274.   5 Abuzayed B, Tanriover N, Gazioglu N, Eraslan BS, Akar Z. Endoscopic endonasal approach  to the orbital apex and medial orbital wall: anatomic study and clinical applications.  J Craniofac Surg 2009;20:1594-1600.   6 Castelnuovo P, Turri-Zanoni M, Battaglia P, Locatelli D, Dallan I. Endoscopic endonasal  management of orbital pathologies. Neurosurg Clin N Am 2015;26:463-472.   7 Morales-Avalos R, Santos-Martinez AG, Avalos-Fernandez CG, et al. Clinical and surgical  implications regarding morphometric variations of the medial wall of the orbit in relation  to age and gender. Eur Arch Otorhinolaryngol 2016;273:2785-2793.   8 Takahashi Y, Miyazaki H, Ichinose A, Nakano T, Asamoto K, Kakizaki H. Anatomy of  deep lateral and medial orbital walls: implications in orbital decompression surgery.  Orbit 2013;32:409-412.    Vascular pedicled flaps have been adopted for the reconstruction  of skull base defects following endoscopic skull base surgery,  with reliable outcomes. Pedicled vascularized flaps offer an  advantage in reconstruction because they conform to irregular  surfaces, they are easier to mobilize, and they promote quicker  healing. The nasoseptal flap represents the workhorse for skull  base reconstruction, especially high-flow cerebrospinal fluid (CSF)  leaks, achieving a decrease in the rate of leaks to less than 5%.'°  It is also preferred in patients for whom postoperative radiotherapy  is anticipated.'®   The nasoseptal flap is a versatile flap with a large arc of rotation  and large surface area. It can be used for reconstruction of midline  sagittal defects of the anterior, middle, or posterior cranial fossa."  It is pedicled on the posterior nasoseptal artery, which is a branch  of the posterior nasal artery arising from the sphenopalatine artery,  a terminal branch of the internal maxillary artery. Knowledge of  its anatomic course is crucial prior to harvesting a nasoseptal flap.  The posterior nasoseptal artery travels just inferior to the sphenoid  sinus ostium. It typically branches into two or three branches  before entering the mucoperiosteum of the posterior nasal septum  (Fig. 33.1). Therefore, particular attention is drawn to protect this  artery during an ipsilateral sphenoidotomy, in order to avoid  compromise of the vascular pedicle.'*   The nasoseptal flap can be raised at anytime during surgery as  long as the pedicle is maintained and protected, particularly during  a sphenoidotomy and posterior septectomy. If a high-flow CSF  leak is anticipated, it can be harvested at the beginning of surgery  and tucked into the nasopharynx or into a previously created  ipsilateral maxillary antrostomy.® It can also be harvested prior  to tumor resection. If it is not deemed necessary at the end of the  procedure, it can always be returned to its original position and  reharvested in the future, if necessary.°    Initially, the nose is decongested with oxymetazoline-soaked  pledgets for approximately 10 minutes. With a 30-degree endo-  scope, the surgeon assesses if the septal mucosa is involved in a  neoplastic process, as this would contraindicate the use of a  nasoseptal flap and would lead to tumor seeding. If septal spurs  and deviations are present, the contralateral side is preferable to  avoid technical difficulties, as inadvertent mucosal perforations  or tears occur more often on the side of the septal spur. Prior  septoplasty may increase the difficulty associated with flap harvest  and compromise its viability. The flap size can be adjusted to  accommodate the size of the defect intended for repair within  limitations.”   With a No. 15 blade or cautery, an incision is performed in a  posterior to anterior fashion at the junction of the nasal septum  and nasal floor, along the maxillary crest (Fig. 33.2). However,  this incision can be extended laterally to include most of the nasal  floor mucosa, depending on the size of the defect. The incision is  then continued posteriorly along the posterior free edge of the  nasal septum, along the medial edge of the posterior choana, in  an orientation toward the torus of the eustachian tube. (The orienta-  tion of the pedicle should always be kept in mind to avoid its  transection, with subsequent flap vascular compromise.) A parallel  incision is then carried out along the superior edge of the choana,    just inferior to the sphenoid ostium. This should include the  posterior septal branch and all its branches. This incision is  continued superiorly, medial to the vertical lamella of the superior  and middle turbinates. Care is taken to maintain an orientation  1cm below the insertion of the septum to the skull base, to avoid  injury to the olfactory epithelium and alter olfactory function.  The incisions are then brought anteriorly, resulting in two parallel  incisions along the septum (superior and inferior) that meet at  the caudal septum, through a vertical incision. The latter incision  determines the length of the flap needed, and it can be extended  as far anteriorly as the mucocutaneous junction. The width of the  flap is greatest at its midportion.   A Cottle elevator is used to elevate the nasoseptal flap in an  anterior to posterior direction toward the posterior choana. Angled  microscissors can be used to further facilitate elevation of the flap  along the previously placed incisions. In addition, non-cutting  forceps can be used to gently pull the flap down from a superior  to inferior and anterior to posterior direction, thereby tearing the  flap along its superior border in a controlled fashion toward its  pedicle posteriorly. It is important to avoid avulsing the pedicle,  which runs from the arch of the posterior choana to the just below  the sphenoid ostium. Also, mucosal perforations should be avoided  during dissection, although the flap is still usable if this occurs.   Once raised, the flap is then moved away from the surgical field  and the defect is prepped for repair. The entire recipient site is  demucosalized, and any septations removed to provide a flat surface  for the flap. The orientation of the flap should be examined prior  to rotating it to ensure that the mucosal surface faces the intranasal  space and that the mucoperichondrial and mucoperiosteal surface  faces the defect. In some cases, it is better to excise the rostrum,  and lower the bony face of the common sphenoid cavity to the  level of the floor of the sphenoid sinus with a bur, to avoid bony  projections that can compress the vascular pedicle and limit rotation  of the flap.   Nasal crusting is expected for approximately 6 weeks postop-  eratively. This can partly be attributed to exposed septal cartilage,  which mucosalizes over that period of time. This can be addressed  with frequent debridements and nasal saline irrigations until  adequate remucosalization occurs. An alternative would be to    rotate a contralateral anteriorly based septal mucoperiosteal flap,  after posterior bony septectomy, to cover the exposed bone or  cartilage. However, this would eliminate the use of a contralateral  posteriorly based flap in the future.    The posterior pedicled inferior turbinate flap presents an option  for the reconstruction of skull base defects of moderate size. This  flap provides a reliable vascular pedicle with a good arc of rotation.  Its surface area is not as large as that of the nasoseptal flap, but  it still represents a viable option in reconstruction of more limited  skull base defects, particularly in revision cases, where a previous  septectomy or compromise of the nasoseptal flap pedicle may  have occurred. It should also be considered when tumors involve  the septum.'*   The posterior pedicled inferior turbinate flap is based on the  inferior turbinate artery, a branch of the nasolateral artery. The  latter supplies most of the lateral nasal wall and arises from  the sphenopalatine artery. The nasolateral artery travels in an  anteroinferior course over the perpendicular plate of the vertical  process of the palatine bone. It then branches into the inferior  turbinate artery and enters the inferior turbinate superior to its  lateral attachment.'° The inferior turbinate artery further divides  into two branches—one along the upper portion of the inferior  turbinate (superolateral), and the other along its midportion  anteriorly close to bone (inferomedial) (Fig. 33.3).'° Another vascular  pedicle that contributes to the blood supply of the inferior turbinate  is the angular artery, a branch of the facial artery.'”   In the past, the posterior pedicled inferior turbinate flap was  used for the reconstruction of oroantral fistulas and closure  of nasal septal perforations.'® Based on the location and length  of its pedicle, the posterior pedicled inferior turbinate flap is  useful for smaller defects involving the clivus and sella.'° It has a  limited ability to reach the anterior skull base, but can be used    in combination with other reconstructive modalities as an adjunct  for reconstructing anterior skull base defects. In addition, bilateral  flaps can be harvested to increase the reconstructive surface area.  As with the nasoseptal flap, tumor involvement will preclude the  use of an inferior turbinate flap, as well as prior inferior partial  or complete turbinectomy, or an atrophic turbinate. This can reduce  the mucosal surface area available for reconstruction.   After decongesting the nose, the inferior turbinate is infiltrated  submucosally with a solution of 1% lidocaine and 1:100,000  epinephrine into its junction with the lateral nasal wall, tail, and  anterior attachment. The inferior turbinate can then be gently  medialized and in-fractured to expose its lateral surface. It is best  to initially identify the sphenopalatine artery at its foramen and  follow it as it branches into the nasolateral artery in order to  identify the vascular pedicle. The size of the flap to be harvested  can be designed according to the size of the defect. It is advisable  to harvest the entire inferior turbinate to ensure more adequate  surface area coverage.   The incisions are made using a blade or cautery. Two parallel  incisions are made along the sagittal plane of the inferior turbinate  (Fig. 33.4). Superiorly the incision begins anterior to the spheno-  palatine foramen and continues anteriorly on the lateral nasal  wall over the attachment of the inferior turbinate. Inferiorly the  incision begins posteroinferior to the sphenopalatine foramen,  then descends to the nasal floor, anterior to the eustachian tube,  and then is brought anteriorly along the caudal margin of the  inferior turbinate. These incisions are then connected with a vertical  incision placed over the head of the inferior turbinate, at its anterior  attachment. The flap is then elevated, using a Cottle elevator, in  a mucoperiosteal plane.   Elevation starts anteriorly. An attempt is made to leave the  turbinate bone in place if feasible, and then dissected off once the  flap is elevated. Dissection of an inferior turbinate flap can be  more challenging than a nasoseptal flap. It is crucial, during eleva-  tion, to avoid injury or avulsion of the vascular pedicle as it enters  at the superior aspect of its posterolateral attachment. Care should  also be taken to avoid injury to Hasner’s valve in the inferior  meatus. If this happens, or is necessary for creation of a wider  flap, then vertical marsupialization of the lacrimal duct proximal  to Hasner’s valve may minimize the risk of postoperative duct  stenosis and epiphora.    Ifa larger flap is needed, the inferior incision can also be extended  to include the lateral mucoperiosteum of the inferior meatus and  lateral nasal wall over the lacrimal apparatus, just posterior to  the mucocutaneous junction (Fig. 33.5). These extensions of the  inferior turbinate flap offer a greater surface area than the inferior  turbinate flap alone, and hence can cover larger defects. However,  it is quite difficult to elevate carefully without creating mucosal  tears and perforations. It is based on the facial and anterior ethmoid  arteries. Its pitfalls include disruption of the nasolacrimal duct,  and mucoperiosteal elevation is tedious.”°   Once harvested, the flap is unrolled by carefully removing all  bony elements. This assists in unrolling the flap. It is crucial during  this step to avoid placing any traction on the vascular pedicle.  One technical complexity is the difficulty with unrolling the flap  due to its nature to retain its original convexity. It can then be  tucked into the nasopharynx and protected with overlying pledgets  until the defect is ready for repair. During repair, the flap needs  to be in its normal rotation, unfolded, with the mucosal surface  facing the intranasal space and the mucoperiosteal surface facing  the defect. The posterior pedicled inferior turbinate flap is associ-  ated with minimal postoperative complications and morbidity.  Nasal crusting is encountered, which resolves once remucosalization  occurs within 6 weeks.    1 Hadad G, Bassagasteguy L, Carrau RL, et al. A novel reconstructive technique after  endoscopic expanded endonasal approaches: vascular pedicle nasoseptal flap. Laryn-  goscope 2006;116:1882-1886.   2 Kassam AB, Thomas A, Carrau RL, et al. Endoscopic reconstruction of the cranial base  using a pedicled nasoseptal flap. Neurosurgery 2008;63(1, Supp! 1):0ONS44-ONS52,  discussion ONS52-ONS53.   3  Zanation AM, Carrau RL, Snyderman CH, et al. Nasoseptal flap reconstruction of high  flow intraoperative cerebral spinal fluid leaks during endoscopic skull base surgery.  Am J Rhinol Allergy 2009;23:518-521.   4 Liu JK, Schmidt RF, Choudhry OJ, Shukla PA, Eloy JA. Surgical nuances for nasoseptal  flap reconstruction of cranial base defects with high-flow cerebrospinal fluid leaks  after endoscopic skull base surgery. Neurosurg Focus 2012;32:E7.   5 Eloy JA, Shukla PA, Choudhry OJ, Singh R, Liu JK. Challenges and surgical nuances in  reconstruction of large planum sphenoidale tuberculum sellae defects after endo-  scopic endonasal resection of parasellar skull base tumors. Laryngoscope 2013;123:  1353-1360.   6 Eloy JA, Patel AA, Shukla PA, Choudhry OJ, Liu JK. Early harvesting of the vascularized  pedicled nasoseptal flap during endoscopic skull base surgery. Am J Otolaryngol  2013;34:188-194.   7 Eloy JA, Choudhry OJ, Shukla PA, Kuperan AB, Friedel ME, Liu JK. Nasoseptal flap  repair after endoscopic transsellar versus expanded endonasal approaches: is there  an increased risk of postoperative cerebrospinal fluid leak? Laryngoscope 2012;122:  1219-1225.    Eloy JA, Patel SK, Shukla PA, Smith ML, Choudhry OJ, Liu JK. Triple-layer reconstruction  technique for large cribriform defects after endoscopic endonasal resection of anterior  skull base tumors. Int Forum Allergy Rhinol 2013;3:204-211.    Eloy JA, Choudhry OJ, Friedel ME, Kuperan AB, Liu JK. Endoscopic nasoseptal flap repair  of skull base defects: is addition of a dural sealant necessary? Otolaryngol Head Neck  Surg 2012;147:161-166.    Bhatki AM, Pant H, Snyderman CH, et al. Reconstruction of the cranial base after  endonasal skull base surgery: Local tissue flaps. Oper Tech Otolaryngol—Head Neck  Surg 2010;21:74-82.    Tang IP, Carrau RL, Otto BA, et al. Technical nuances of commonly used vascularised  flaps for skull base reconstruction. J Laryngol Otol 2015;129:752-761.    Vazquez A, Liu JK, Eloy JA. Endoscopic endonasal surgery of the sphenoid sinus: extended  approaches. Oper Tech Otolaryngol—Head Neck Surg 2014;25:174-179.    Anstead ASJ, Liu J. Cerebral spinal fluid leak repair. Oper Tech Otolaryngol—Head Neck  Surg 2014;25:187-193.    Fortes FS, Carrau RL, Snyderman CH, et al. The posterior pedicle inferior turbinate  flap: a new vascularized flap for skull base reconstruction. Laryngoscope 2007;117:  1329-1332.   Padgham N, Vaughan-Jones R. Cadaver studies of the anatomy of arterial supply to  the inferior turbinates. J] R Soc Med 1991;84:728-730.   Hadar T, Ophir D, Yaniv E, Berger G. Inferior turbinate arterial supply: histologic analysis  and clinical implications. J] Otolaryngol 2005;34:46-50.   Neligan PC, Mulholland §, Irish J, et al. Flap selection in cranial base reconstruction.  Plast Reconstr Surg 1996;98:1159-1166, discussion 1167-1168.   Yip J, Macdonald KI, Lee J, et al. The inferior turbinate flap in skull base reconstruction.  J Otolaryngol Head Neck Surg 2013;42:6.   Harvey RJ, Sheahan PO, Schlosser RJ. Inferior turbinate pedicle flap for endoscopic  skull base defect repair. Am J Rhinol Allergy 2009;23:522-526.   Patel MR, Taylor RJ, Hackman TG, et al. Beyond the nasoseptal flap: outcomes and  pearls with secondary flaps in endoscopic endonasal skull base reconstruction.  Laryngoscope 2014;124:846-852.    There are many types of skull base defects of varying location  and size. In all cases, skull base reconstruction has three goals:    The type of reconstruction chosen depends on the size of the  defect, the degree of cerebrospinal fluid (CSF) leak (high or low  flow), and the extent of involvement of the surrounding native  tissues. There are many methods of repair, using a variety of inlay  and onlay techniques, with nonvascularized or vascularized tissues.  For any repair associated with a CSF leak, we utilize a nonvascular-  ized layer of rehydrated acellular dermal graft (Alloderm; LifeCell  Corp., Branchburg, NJ) as a first layer, with or without a second  vascularized flap layer.'    Reconstruction is performed utilizing acellular dermal graft of  approximately 1-mm thickness (medium thickness). The size of  the graft is determined by measuring the anterior skull base defect  from orbit to orbit (laterally) and from the posterior table of the  common frontal sinus to the resected edge of the sphenoid planum  (anteroposteriorly). Then, 2cm is added onto the distance on each  of the four sides; for example, a 4cm by 3cm defect would require  an 8cm by 7cm graft. The intrasinus and orbital bony edges around  the defect are circumferentially de-mucosalized (if not already  performed), creating a surface for graft fusion. The sized acellular  dermal graft is positioned centrally over the defect so that it  will span the anterior skull base defect circumferentially like a  “hammock.” The peripheral edge of the graft is tucked intracranially  circumferentially over the orbits, over the bony edge of planum  sphenoidale, and behind the posterior table of the common frontal  sinus (Fig. 34.1). The surgeon must always visualize the free graft  edge circumferentially while the inlay “intercranial pockets” are  created. The free edges of the graft are folded intranasally to lie  over the de-mucosalized bony surface of the intrasphenoidal roof,  superomedial orbital wall, and posterior common frontal sinus  cavity. Cylindrical wedges of dry Surgicel (Surgicel; Ethicon Inc.,  Somerville, NJ) wrapped around Gelfoam (Gelfoam; Division of    Pfizer Inc., New York, NY) are placed circumferentially into the  intracranial pockets over the orbits, planum sphenoidale, and  posterior table of the common frontal sinus. These wedges hold  the inlay edges of the graft firmly against the intracranial bone  circumferentially at all times. The “onlay” portion of the reconstruc-  tion remains affixed to the intranasal bone, irrespective of any  movement of the more central “hammock” portion of the skull  base graft, and ensures a watertight closure (Fig. 34.2).   Reconstruction of a hemi-anterior skull base defect is similar  to the bilateral reconstruction except that the medial aspect of  the graft rests on the contralateral dura of the falx cerebri/olfactory  bulb and upper septal mucoperichondrium (Fig. 34.3).   When possible, a second vasculaized layer with a nasoseptal  flap is added to achieve a more rapid remucosalization of the  grafted skull base. The vascularized layer reduces the time needed    for secondary healing, granulation formation, and crusting, which  may last up to 6 months. However, a flap is not absolutely necessary  for a functional watertight repair.   The full surface area of the repair is carefully overlaid with  hydrated compressed Gelfoam. In the case of a bilateral anterior  skull base resection and reconstruction, the repair is supported  with at least one polyvinyl alcohol compressed nasal packing  (Merocel; Medtronic Xomed, Jacksonville, FL) positioned between  the common frontal and common sphenoid sinuses. In a hemi-  anterior skull base repair, the Merocel is placed from the ipsilateral  sphenoid sinus to the frontal infundibulum area. The nonabsorbable  packing is removed approximately 1 week after surgery in an  outpatient setting. Oral antibiotics are discontinued when the  packing is removed. A lumbar drain is not routinely used.    The principles of reconstruction for defects with a CSF leak in this  region are very similar to those of anterior skull base reconstruction,  but there are several key clinical pearls that help create a durable  and effective reconstruction. Reconstruction is performed with a  1-mm-thick acellular dermal graft, but the graft is sized to be  two times the size of the bony defect. The bony defect edges are  de-mucosalized within the sphenoid sinus. Acellular dermal graft  is positioned and centered over the defect. The graft is tucked  into the defect to create an inlay graft lining a portion of the  sellar or suprasellar (intracranial) area previously occupied by  tumor. The free edge of the graft is seen intranasally at all times  within the sphenoid sinus, and upon tucking the graft into the  defect, the edges temporarily curl into the sphenoid cavity like  a flower. The central (intrasellar) part of the graft is held in position  using small cylindrical pieces of absorbable Gelfoam wrapped in  Surgicel, creating a “plug” that serves to push and affix the inlay  portion of the graft into the sellar or suprasellar defect (Fig. 34.4).  The free intrasinus ends or curls of acellular dermal graft are then  unfurled over the edges of bone circumferentially within the  sphenoid sinus, and held in place with hydrated compressed  Gelfoam (Fig. 34.5). This maneuver seals off the CSF leak and fills    much of the dead space (if present). Care is taken not to overpack  intracranially around the optic chiasm and optic nerves, especially  in suprasellar defects. Once the “plug” is placed, the intranasal  edges of the graft are gently arranged to minimize overlap on  itself and to ensure contact with the exposed intrasinus bone  circumferentially. Usually this acellular dermal matrix repair is  sufficient on its own. However, if the defect is particularly large    and/or there is a high flow CSF leak, then a second layer utilizing  a vascularized flap may be warranted. The repair is supported  with a Merocel nasal tampon positioned between the repair and  the posterior septectomy (Fig. 34.6). The nonabsorbable packing  is removed approximately 1 week after surgery in the outpatient  clinic. Antibiotics are discontinued when the packing is removed.  A lumbar drain is not routinely used.    A second layer can help to support a repair and also can speed  up the mucosalization of the defect. Multiple studies have shown  that pedicled vascularized flaps can be particularly beneficial in  speeding up the healing process and aid in sealing the repair.”  Our group uses these as a second layer in the event of a large  defect, in patients who are expected to heal poorly, in a high-flow  CSF leaks, or in cases where there is a leak after initial repair. The  technique for harvesting common vascularized flaps is covered  elsewhere in this book (Chapter 33).    A free mucosal graft is applied as a second layer over the graft  repair. These free mucosal grafts are easily accessible from the  septum, middle turbinate, inferior turbinate, lateral nasal wall,  and nasal floor. They are easy to maneuver, can be raised quickly  within the nasal cavity, and tend to have a high rate of success.*°  As a general rule, the surgeon should plan to have 50% of the    graft’s surface area directly approximated to vascularized bone  or cartilage where it can receive nutrients. Thus, a mucosal graft  is harvested of the size to cover twice the entire surface area of  the acellular dermal graft repair. It is placed in saline. The acellular  dermal graft reconstruction is performed as described above, but  a slightly larger area of bone is circumferentially de-mucosalized  to provide surface area for free mucosal graft adherence. Once  the initial reconstruction is complete, the free mucosal graft is  positioned over the primary reconstruction. Any folds are removed,  and the graft is smoothed against the acellular dermal graft  reconstruction, ensuring that no blood or debris are between the  mucosa and the acellular dermal graft. As noted previously, at  least 50% of the free mucosal graft edges are in contact with exposed  bone circumferentially. The full surface area of the mucosal graft  is carefully overlaid with hydrated compressed Gelfoam, which  also serves to compress the mucosal graft against underlying  acellular dermal graft and bone. The repair is supported with a  Merocel nasal tampon.    The most commonly used pedicled flap for anterior skull base  reconstruction is the nasoseptal flap.*? Unilateral or bilateral  nasoseptal flaps can be utilized to provide coverage over the central  portion of the acellular dermal graft repair. Additionally, other  pedicled flaps, such as inferior or middle turbinate flaps and lateral  nasal wall flaps, are useful if the nasoseptal flap is not available.  The flaps do not provide for a watertight closure, but do allow for  quicker remucosalization and less prolonged crusting. The technique  of raising many of these flaps is discussed elsewhere in this book  (Chapter 33). Although these flaps do have their own blood supply,  it is still essential to ensure that the flaps contact de-epithelialized  bone in order to firmly adhere to the skull base. The flap pedicle  is laid out without kinking, twisting, or tension to ensure adequate  blood flow. The flap should contact bone along the length of the  flap and the pedicle. As with free mucosal grafts, folds at the edges  should be smoothed out, ensuring good contact and maximizing    tissue adherence. The flap is carefully covered with hydrated  compressed Gelfoam and supported with a Merocel nasal tampon  for a week.    Although pedicled intranasal flaps are more convenient (when  available), there are extranasal options for repair, such as peri-  cranium flaps based off the supratrochlear and supraorbital arteries,  temporoparietal fascia flaps based off the superficial temporal  artery, and palatal flaps based off the descending palatine vessels.’-'°  The pericranial flap is discussed in Chapter 35. However, if inter-  ested, the reader is encouraged to review the suggested references  below for further surgical details regarding these flaps.    1 Germani RM, Vivero R, Herzallah IR, Casiano RR. Endoscopic reconstruction of  large anterior skull base defects using acellular dermal allograft. Am J Rhinol 2007;21:  615-618.   2 Liu JK, Schmidt RF, Choudhry OJ, Shukla PA, Eloy JA. Surgical nuances for nasoseptal  flap reconstruction of cranial base defects with high-flow cerebrospinal fluid leaks  after endoscopic skull base surgery. Neurosurg Focus 2012;32:E7.   3 Thorp BD, Sreenath SB, Ebert CS, Zanation AM. Endoscopic skull base reconstruction:  a review and clinical case series of 152 vascularized flaps used for surgical skull base  defects in the setting of intraoperative cerebrospinal fluid leak. Neurosurg Focus  2014;37:E4.    4 Clavenna MJ, Turner JH, Chandra RK. Pedicled flaps in endoscopic skull base reconstruc-  tion: review of current techniques. Curr Opin Otolaryngol Head Neck Surg 2015;23:  71-77.   5 Ting JY, Metson R. Free graft techniques in skull base reconstruction. Adv Otorhinolaryngol  2013;74:33-41.   6 Kimple AJ, Leight WD, Wheless SA, Zanation AM. Reducing nasal morbidity after skull  base reconstruction with the nasoseptal flap: free middle turbinate mucosal grafts.  Laryngoscope 2012;122:1920-1924.   7 Oliver CL, Hackman TG, Carrau RL, et al. Palatal flap modifications allow pedicled  reconstruction of the skull base. Laryngoscope 2008;118:2102-2106.   8 Safavi-Abbasi S, Komune N, Archer JB, et al. Surgical anatomy and utility of pedicled  vascularized tissue flaps for multilayered repair of skull base defects. J Neurosurg  2016;125:419-430.   9 Kim GG, Hang AX, Mitchell CA, Zanation AM. Pedicled extranasal flaps in skull base  reconstruction. Adv Otorhinolaryngol 2013;74:71-80.   10 Patel MR, Taylor RJ, Hackman TG, et al. Beyond the nasoseptal flap: outcomes and  pearls with secondary flaps in endoscopic endonasal skull base reconstruction.  Laryngoscope 2014;124:846-852.    35 Common Adjunctive External Skin Incisions for Approaches  to the Frontal and Maxillary Sinuses    Supraorbital foramen  Superomedial rim of the orbit  Anterior lacrimal crest  Gingiva-mucosal junction  Infraorbital foramen/nerve  Pyriform aperture    Even when used in a more limited fashion in combination with  an endoscopic transnasal approaches, there is still a place for  external incisions and approaches to the paranasal sinuses,  particularly when it comes to the frontal and maxillary sinuses.  External incisions and approaches are most commonly utilized  today for hard to access tumors or trauma involving these sinus  cavities.'? It can also be used for complex inflammatory disease,  particularly in an acutely infected setting, or when other approaches  have failed. Often it is utilized to assist with an endoscopic approach  to access pathology (for instrumentation access or improved  visualization), or when an endoscopic approach has failed. The  sinus can be accessed in many different ways externally, and this  should be tailored to the pathology, the location of the disease,  as well as patient characteristics, such as the need for cosmesis.   A small external incision can be used at the superomedial rim  of the orbit, such as with a Lynch incision, to control the ethmoidal  arteries. Various brow-type incisions can also be used for an  endoscopic-assisted approach for flushing the sinus, for accessing  a type IV frontal sinus cell, or for a tumor that is not totally or  easily accessed from below alone.   For more extensive external access, a full brow incision, a mid-  forehead crease incision, or the more traditional bicoronal flap  can be utilized. This typically is done if an osteoplastic flap or  frontal sinus cranialization, with/without frontal obliteration, is  necessary. In the vast majority of these cases, the bicoronal incision  is used to prevent the risk of troublesome paresthesias of the  forehead due to injury or division of the supraorbital nerve.    The procedure starts with an incision above the hairline extending  from just anterior and superior to the ears (A in Fig. 35.1). When  necessary, this incision can be extended down to the tragus. A    pericranial flap can be elevated as part of this approach, by dividing  down to the bone, as this will be pedicled inferiorly on at least  one supraorbital vascular pedicle. Dissection of the pericranial  flap is carried out between the pericranium and the soft tissue  layer, dissecting the loose areolar tissue to generate the flap (Fig.  35.2). Alternatively, leaving the pericranium on the flap, the dis-  section is carried down on the bone using a periosteal elevator  (1B and 2B in Fig. 35.1). The dissection is carried down to the  supraorbital rim; the surgeon should be careful to preserve the  supraorbital foramen and neurovascular pedicled encountered at  the orbital rim. The supraorbital foramen, and thus the sensory  nerve of the same name associated with it, is found approximately  2 to 3cm off the midline at the superior orbital rim and can be  easily palpated as a bony notch. Dividing this nerve leaves the  patient with permanent paresthesia of the ipsilateral forehead. It  is often useful to keep the periosteum attached inferiorly in order  to hinge the bone flap (in the case of an osteoplastic flap) for  easier reconstruction.   The sinus can be mapped out using different methods. Tradition-  ally, this was done using a 6-foot Caldwell view radiograph. Today,  this is typically done utilizing navigation technology. If this is not  available, pilot holes with a small drill bit can be done inferiorly,  starting on the superior orbital rim medially, to introduce an  endoscope and map out the sinus through transillumination (C  in Fig. 35.1). The risks of not mapping out the sinus are a cavity  that is too small, making removal of mucosa challenging, or risking  entry into the anterior cranial fossa due to poor visualization,  with resultant cerebrospinal fluid leak.   Once several pilot holes are created with a small bur, a sagittal  saw can be used in a beveled fashion to connect the pilot holes  (D in Fig. 35.1). The saw should bevel the cuts inward to enable  the bone flap to sit flat without falling into the cavity. It is helpful  to plan for reconstruction prior to finishing the bone cuts by  utilizing screws and plates and predrilling these holes for later  use. If this step is not done at this point, the plating will have to  be done directly on the bone flap, making this more challenging  and time consuming. The bone flap can then be removed. Often  a knife is needed to make the final cuts through the sinus mucosa,  and the flap can be removed utilizing an elevator. Alternatively,  the anterior table of the frontal sinus may be removed as a free  bone graft and set aside for later plating at the conclusion of the  procedure (E in Fig. 35.1).   After the flap is removed, the pathology can be accessed and  addressed, and the flap replaced. If cranializing or obliterating the    CHAPTER 35 ™® Common Adjunctive External Skin Incisions for Approaches to the Frontal and Maxillary Sinuses 133    sinus, the mucosa must be removed completely, as well as the  intersinus septum, drilling the remaining mucosa from both the  sinus as well as the bone flap. Otherwise, the patient is placed at  risk for future mucocele formation or recurrent obstructive sinus  disease. This can be quite challenging in very pneumatized frontal  sinuses with supraorbital extensions extending posteriorly. The  nasofrontal outflow tract must be obliterated as well in these  instances, using muscle, cartilage, or other material. The wound  can then be closed in layers.    This is often utilized in males, particularly those with male-pattern  baldness, as the forehead crease may be more appealing cosmeti-  cally. The procedure is carried out in a similar manner to a bicoronal    approach, although the incision follows the line of the crease and  does not typically require extension to the upper ear (A in  Fig. 35.1).   The forehead incision may be more limited in select cases, when  used in combination with an endoscopic approach (as with a  modified Lothrop procedure). When a more limited forehead crease  incision is performed, the anterior table is partially removed  ipsilaterally. A small defect the size of a quarter, or smaller, is  created in order to introduce an endoscope or instruments or drill  burs, while simultaneously working back and forth between the  external and transnasal endoscopic approach (Figs. 35.3, 35.4,  35.5). A typical example would be a unilateral osteoma, or other  benign neoplasm, extending supraorbitally, where a complete  bilateral osteoplastic flap or anterior table removal is not necessary  to achieve complete removal. The defect can be covered with a  small piece of titanium mesh and screwed in place. The mucosa  of the sinus can also be drilled away and the cavity can also be  obliterated through an endoscopic approach.   If a large pericranial flap is still needed, or where greater exposure  is needed bilaterally, the forehead incision should be carried down  to the pericranium (not to bone), and then dissection should be  carried upward to the hairline, creating the pericranial cut at this  more superior level to preserve length of the flap. If a pericranial  flap is not needed, the forehead incision can just be carried down  to bone. The remainder of the procedure follows the steps in the  bicoronal approach.    This is currently used to access the anterior and posterior ethmoid  arteries, if unable to be controlled endoscopically. It can also be  used to drain an acute infection and access the anterior ethmoid    Opening superior anterior table of frontal sinus simultaneously  visualizing through an intranasal endoscope (Draf II or III)    sinus, medial orbit, as well as the frontal sinus through a  trephine.   A small curvilinear incision is made from the upper medial  orbital rim extending on the nasal side wall (Fig. 35.6). One’s  thumb can be used as an approximate outline for the incision.  The thumb is placed on the globe with the tip touching the    undersurface of the upper medial supraorbital rim, and marked  with a marking pen. After dividing the soft tissue, elevation is  carried down under the periosteum until the lacrimal crest is  found. Hemostasis is controlled with monopolar or bipolar cautery.  Care should be taken to avoid the trochlea as well as the medial  canthal ligament. To identify the arteries, dissection is carried  approximately 24mm from the anterior lacrimal crest to the  anterior ethmoid artery, found at the anterior aspect of the  ethmoid-frontal suture line. Dissecting approximately another  12mm posteriorly enables identification of the posterior ethmoid  artery. The optic nerve is only about another 6mm posterior to  this artery; thus, care needs to be taken in the dissection and  avoidance of monopolar cautery beyond this point. To enter the  ethmoid sinus, a small drill or Kerrison bone rongeur can be used  just posterior to the lacrimal crest. For a trephine, the drill should  be placed just under the superior orbital rim, aiming toward the  midline and upward. A catheter can be left for irrigation, or instal-  lation of medication, into the frontal sinus. The wound can be  closed in layers around it.    CHAPTER 35 ™® Common Adjunctive External Skin Incisions for Approaches to the Frontal and Maxillary Sinuses 135    The vast majority of maxillary sinus surgery is now done endoscopi-  cally. There are some instances where this needs to be combined  with an open approach to either access the anterior wall of the  sinus, such as for removal of a dentigerous cyst extending into  the sinus, or to assist in access to the pterygopalatine or infra-  temporal fossa. Traditional incisions into the maxillary sinus include  the Caldwell-Luc incision, as well as the Weber-Ferguson incision  for more aggressive tumors. In addition, a midfacial degloving or  modified Denker incision might be used for more posterior lesions  that extend or originate in the pterygopalatine/infratemporal fossa,  such as a juvenile nasopharyngeal angiofibroma. These can be  combined with an endoscopic approach as well.    The Caldwell-Luc approach starts with a sublabial incision. The  incision should be made just below the gingiva-mucosal junction.  It is important that adequate tissue is left for suturing later. Typically  this incision extends from the frenulum to just above the canine  tooth, although it can be extended in either direction if necessary.  This may have to be modified in the edentulous patient. Division  is carried down to the periosteum, and a periosteal elevator should  be used to elevate superiorly, utilizing lip retraction for visualization  (Fig. 35.7). Care should be used to identify the infraorbital foramen,  and thus the infraorbital nerve, in the canine fossa. An osteotome,  high-speed drill, or Kerrison bone rongeur can then be used to    open the maxillary sinus through its anterior wall, but inferior  to the infraorbital nerve. It is usually not necessary to remove a  bone flap. Back-elevating the remaining gingiva enables closure  that is often done using running sutures to avoid an oral-antral  fistula through the upper gingiva-buccal sulcus.    When further lateral access is needed, the Caldwell-Luc or endo-  scopic approach can be combined with other approaches to avoid  external incisions. Utilizing techniques such as a midfacial degloving  can be helpful, thus utilizing the nostril either ipsilaterally or  contralaterally. To accomplish this, the gingival incision can be  extended bilaterally across the midline by transecting the frenulum.  Vestibular nasal incisions can be carried out for access by making  a circumferential incision inside each nostril. A complete transfixion  incision is made to separate the nasal tissues. Care should be  taken to avoid injury to the cartilages of the nose. Dissection can  then be used up through the pyriform aperture (A in Fig. 35.8).  For further access, a medial maxillectomy can be carried out,  providing extensive access to the lateral recesses of the maxillary  sinus). Closure is carried out similar to that for the Caldwell-Luc  approach, with an additional need to close the vestibular incisions  without tension to avoid vestibular stenosis. If a medial maxil-  lectomy is performed, the membranous nasolacrimal duct should  be resected flush with the level of the orbital floor. Although  epiphora is rare with resection, the remaining portions of the  duct may be vertically marsupialized to minimize the chance of  restenosis.    The Denker approach consists of removing a portion or all of the  pyriform aperture bone and adjacent medial maxilla as well as  the anterior maxillary wall (as with a Caldwell-Luc procedure).  Many times, this can be done entirely endoscopically. However,  this can all be achieved through a Caldwell-Luc approach as well  (B in Fig. 35.8). If done transnasally, the bone edge of the pyriform  aperture is identified by palpation just anterior to the anterior  attachment of the inferior turbinate. A vertical incision using a  blade is performed over the edge of the bony piriform aperture,  anterior to the head of the inferior turbinate. Once the pyriform  aperture is exposed, the blunt dissection proceeds in a subperiosteal  plane, elevating the subdermal soft tissues of the cheek, using a  Cottle or Freer periosteal elevator, to expose the bony anterior  maxillary wall. A Kerrison bone rongeur is used to remove a  segment of the pyriform aperture bone and as much of the anterior    maxillary wall as necessary to achieve the desired amount of  visualization, or introduction of instruments, to access the lateral  recesses of the maxillary sinus or the infratemporal fossa. Endo-  scopes can be introduced laterally through the anterior maxillary  sinus, whereas instrumentations are inserted medially through  the nostril, or vice versa. Excessive removal of pyriform bone, may  result in lateral retraction and depression of the alar soft tissues.  A small plate or mesh can be inserted at the conclusion of the  procedure if this is the case.    1 Thumfart WF, Platzer W, Gunkel AR, Maurer H, Brenner E. Nose, paranasal sinuses,  midface, orbit, and pituitary. In: Surgical Approaches in Otorhinolaryngology. New  York: Thieme Stuttgart; 1999:155-246.   2 Myers EN. Operative Otolaryngology Head and Neck Surgery. Section 1: Nasal Cavity,  Nasopharynx, and Sinuses. Philadelphia: WB Saunders; 1997:2-171.    36 External Approach to the Superior, Lateral, and Inferior  Orbital Walls and Adjacent Paranasal Sinuses    There are numerous external surgical approaches to access the  orbit and surrounding orbital walls with adjacent sinuses and  skull base. Deciding on the best approach depends on the loca-  tion of the lesion and the surgical objective (excisional versus  incisional biopsy). Most lesions of the orbit can be accessed  through an anterior orbitotomy. Excision of large tumors of the  lacrimal gland and deep posterolateral lesions requires a lateral  orbitotomy or craniotomy. Lesions outside the confines of the  orbit can also be managed through a combined approach utiliz-  ing the incision and transorbital approach that provides the best  exposure.   Fig. 36.1 reviews the periorbital neurovascular pedicles that  the surgeon must be attentive to in order to minimize bleed-  ing or postoperative anesthesia due to injury to the terminal  branches of V; or V2. Fig. 36.2 illustrates a sagittal view through  the midline orbit. External transorbital approaches through the  upper or lower eyelid need to avoid injury to critical periorbital  structures, such as the superior or inferior tarsus and the levator  palpebrae and orbicularis oculi muscles. The orbital septum is  a good reference point when identifying the appropriate sub-  periosteal plane as one progresses toward the bony floor or roof  of the orbit.    The superior eyelid crease incision’ provides direct access to the  anterior, superomedial, and superolateral orbit. This is the most  common approach in oculofacial surgery. It has the advantages  of being quick and direct, and affords excellent postoperative  cosmesis. Anatomically, the eyelid crease is defined by fibrous  attachments from the levator aponeurosis to the overlying skin  and orbicularis muscle.   The crease is marked from the punctum to the lateral canthus  (Fig. 36.3). The length of the incision may be truncated as necessary;  that is, a superomedial lid crease incision provides excellent access  to the superomedial orbit, whereas a lateral lid crease incision  can provide access to the lacrimal gland and fossa. After incising  the eyelid crease, dissection proceeds in the post-orbicularis oculi  fascial plane (black arrow in Fig. 36.4). The orbital septum is  identified as a thin white fibrous tissue immediately posterior to  the orbicularis muscle. Dissection can be carried to the superior  orbital rim if a subperiosteal approach is desired (Fig. 36.5). Care  is taken to avoid damage to the contents of the supraorbital notch  located along the medial third of the orbit. Otherwise, the septum  is buttonholed with Westcott scissors to enable prolapse of the  preaponeurotic fat pads. The fat pads are dissected from the  underlying levator aponeurosis. At this point, anterior neoplasms  in the area of the lacrimal sac fossa, roof, and superomedial orbit  can be readily accessed for excision or biopsy. Careful hemostasis  is of critical importance when posterior to the orbital septum, as  uncontrolled bleeding may lead to a potentially sight-threatening  orbital compartment syndrome. A similar approach can be used  on the lower lid using a subciliary incision to access anterior inferior  lesions.    Access to the lower eyelid and inferomedial and lateral orbit may  be achieved with a transconjunctival approach through the lower  eyelid forniceal conjunctiva.” The transconjunctival method affords  excellent cosmesis as well as quick and direct access to the  extraconal and intraconal spaces outside Tenon’s capsule. Alter-  natively, the subperiosteal space can be readily entered at the  inferior orbital rim.    Insertion of Supraorbital  levator palpebrae artery Supratrochlear  superioris muscle and nerve artery and nerve    Lateral hi  palpebral igament  ligament  Maxilla  (frontal  process)  Nasal  Orbital septum  septum V/  Inferior  F turbinate  Inferior  tarsus  Zygomatic Infraorbital  bone artery  and vein  Fig. 36.1  Frontal Superior conjunctival  sinus fornix Levator  palpebrae  ‘ superioris  Orbital muscle  septum  Orbicularis  oculi  muscle 5 :  (palpebral a  portion) tarsa  (Miller’s)  Superior muscle  tarsus  Cornea  Lens  Inferior  tarsus  Orbicularis  oculi  muscle  (palpebral  portion)  Orbital  septum  Inferior conjunctival Maxillary  fornix sinus  Fig. 36.2    The eyelid is everted and the fornix is exposed using a 4-0 silk  traction suture placed at the eyelid margin. A horizontal incision  is then made at least 4mm below the inferior tarsal margin through  the conjunctiva and lower eyelid retractors (Fig. 36.6). The dis-  section may then be carried inferiorly in the preseptal (black arrow  in Fig. 36.7) or retroseptal plane (red arrow in Fig 36.7); the inferior    CHAPTER 36 ® External Approach to the Superior, Lateral, and Inferior Orbital Walls and Adjacent Paranasal Sinuses 139    rim periosteum may be easily accessed from either path. The  conjunctiva and the lower lid retractors are secured and retracted  superiorly over the globe. The septum is fully exposed. The  subperiosteal space is entered by incising the arcus marginalis at  the inferior orbital rim and reflecting it superiorly. Surgical access  may be augmented with a lateral canthotomy (A in Fig. 36.8) and  inferior cantholysis (B in Fig. 36.8), creating a “swinging eyelid”  with enhanced lateral exposure. In some instances it may be  necessary to extend the incision medially posterior to the caruncle.  In these cases the inferior oblique must be identified and handled  with care. It can be disinserted from its origin at the posterior  lacrimal crest and reinserted upon completion of tumor resection  or it can be retracted with a muscle hook in order to provide  wider access to the inferomedial space.    The transcaruncular approach is useful for accessing the medial  orbit and bony wall.? This can be performed in isolation or in  conjunction with an endoscopic approach for large medial tumors  requiring extensive dissection.   Dissection begins by grasping the caruncle and incising it verti-  cally in line with the medial extensions of the upper and lower  conjunctival fornices (Fig. 36.9). The incision is then extended  several millimeters superiorly and inferiorly, taking care to stay    in the fornix so as to avoid injuring the canaliculi. Blunt dissection  is then carried posterior to the posterior lacrimal crest in order  to avoid injuring the lacrimal drainage system. The extraconal  fat may be entered directly at this point, or a subperiosteal dis-  section can be carried out to access the lamina papyracea and  facilitate posterior visualization that is often obscured by orbital  fat. The anterior and posterior ethmoidal neurovascular bundles  are identified near the frontoethmoidal suture line and spared.  This approach may be joined with an inferior transconjunctival  approach by disinserting the inferior oblique muscle as previously  mentioned.    Biopsy of intraconal lesions can be difficult because of the rectus  muscles. This approach disinserts the medial rectus muscle for  easy access to the medial intraconal space.*° Note, the lateral rectus  can be removed as well if the lesion is along the lateral intraconal  space.   A 180-degree nasal conjunctival peritomy is performed (Fig.  36.10). Tenon’s capsule is identified and dissected off the globe  along with the conjunctiva. The inter-rectus spaces are bluntly  dissected to the level of the posterior globe. The medial rectus is  isolated and secured using a double whipstitch before being  disinserted from the sclera. The medial orbit is exposed with  malleable retractors and the fat retracted using neurosurgical  cottonoids. The optic nerve is nearby and should not be manipulated  to avoid inducing traumatic optic neuropathy. Upon excision of  the lesion, the medial rectus is secured to the globe and the  conjunctiva is closed.    The lateral orbitotomy with or without bone removal is useful to  gain access to posterolateral orbital masses.*’ A Stallard-Wright    Fig. 36.11 Red line: lateral upper lid crease incision; blue line: modified  Stallard incision.    extended brow incision or a lateral lid crease incision can be used  to expose the lateral orbital wall (Fig. 36.11). The periosteum of  the lateral orbital rim is incised from the maxillozygomatic suture  line inferiorly to just above the frontozygomatic suture superiorly.  As the periosteum is reflected from the lateral wall of the orbit,  the zygomaticotemporal and facial neurovascular bundles are  encountered and preserved, if possible. Bone along the lateral  orbit can be removed (inferiorly above the zygomatic arch and  superiorly above the frontozygomatic suture line) to excise large  lesions. Drill holes are placed straddling the planned superior and  inferior bone cuts for future reapproximation. The globe is protected  as the bone is removed using a high-frequency oscillating bone  saw. Access to the orbit is then achieved by incising the periorbita  posterior to the arcus marginalis. The bone is then replaced upon  excision of the tumor.    1 Pelton RW. The anterior eyelid crease approach to the orbit. Curr Opin Ophthalmol  2009;20:401-405.   2 Davies BW, Hink EM, Durairaj VD. Transconjunctival inferior orbitotomy: indications,  surgical technique, and complications. Craniomaxillofac Trauma Reconstr 2014;7:169-174.   3 Shorr N, Baylis HI, Goldberg RA, Perry JD. Transcaruncular approach to the medial orbit  and orbital apex. Ophthalmology 2000;107:1459-1463.   4 Tanenbaum M. Anterior orbitotomies. In: Tse DT, ed. Color Atlas of Oculoplastic Surgery.  Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2011.   5 Galbraith JE, Sullivan JH. Decompression of the perioptic meninges for relief of papilledema.  Am J Ophthalmol 1973;76:687-692.   6 Nerad JA. Surgical approaches to the orbit: approach to deep lateral lesions: the lateral  orbitotomy. In: Nerad JA, ed. Techniques in Ophthalmic Plastic Surgery: A Personal  Tutorial. Philadelphia: Saunders Elsevier; 2010.   7 Kr6nlein RU. Zur pathologie und operativen behandlung der dermoidcysten der orbita.  Beitr Z Klin Chir 1889;4:149-163.    Endoscopic sinus surgery (ESS) was initially adapted for use in  the pediatric patient population in the 1980s, following early  successes in adult patients. Since that time, technology and  knowledge has advanced such that endoscopic approaches for  both common and uncommon pediatric sinonasal conditions have  become the standard of care. There are still, however, both technical  and anatomic challenges in performing ESS, particularly in small  children who are still growing and developing.    Although technical considerations are important in children in  whom ESS is considered, proper patient selection is critical.  Understanding the underlying disease process also helps the  surgeon better understand the indications for surgery. In adults,  chronic rhinosinusitis (CRS) is further classified as with or without  nasal polyps. Pediatric chronic rhinosinusitis (PCRS) is often  theorized to arise from frequent and recurrent viral upper respira-  tory infections (URIs). Histological studies have identified lym-  phocytes as a more common cell type on tissue specimens from  pediatric ESS patients, whereas eosinophils are more prominent  in adult ESS specimens.' Knowing this information, as well as the  understanding that preschool age children can normally suffer  from 6 to 10 viral URIs each year, is important to distinguish  pathological sinus disease in children compared with a normal  annual rate of respiratory infections.   Some authors have categorized ESS indications in children as  absolute or relative.” Absolute indications include invasive fungal  sinusitis, allergic fungal sinusitis, mucocele/mucopyocele formation,  intraorbital or intracranial complications of acute rhinosinusitis,  complete nasal obstruction with polyps, recalcitrant dacryocystitis,  and some neoplasms and congenital lesions. Relative indications  for pediatric ESS evoke much more controversy, and include those  patients who have failed “adequate medical therapy.” The definition  of maximal medical therapy can vary from one clinician to another,  but should include at a minimum nasal saline rinses, nasal steroid  sprays, and oral antibiotics (21+ days). For the most severely affected  patients, systemic risk factors for CRS should be evaluated, and  might include a sweat chloride test, ciliary biopsies, immunode-  ficiency workup, formal allergy testing, and possibly even workup  for gastroesophageal reflux in select patients. The timing of these  diagnostic interventions is highly variable, and may occur before,  after, or concomitant with surgical interventions for pediatric CRS.    An additional significant pathophysiological difference between  adult and pediatric CRS patients involves the role of the pharyngeal  tonsils, more commonly referred to as the adenoids. These tissues  situated in the posterior and superior nasopharynx are immunologi-  cally active in young children, and do not undergo anatomic  and functional involution until the teenage years. Studies have  identified the adenoids as the source of the common bacteria  identified in children with CRS,’ and those patients with more  sinonasal symptoms are more likely to have a higher concentration  of bacteria within the adenoid tissue.* Removal of the adenoid  tissue has also resulted in improved mucociliary clearance in  children.’ As a result of their role as a bacterial reservoir, a majority  of otolaryngologists consider adenoidectomy the first-line surgical  treatment for pediatric CRS, prior to considering ESS, resulting in  improvement rates postoperatively ranging from 60 to 100%.°’  Some authors have advocated performing adenoidectomy in  conjunction with other surgical procedures, such as balloon  sinuplasty and even ESS.®    In all patients, paranasal sinus development can vary widely based  on age, chronicity of sinus disease, and other anatomic abnormali-  ties. A careful and diligent review of recent computed tomography  (CT) scans is particularly important for surgical planning in children  for whom ESS is being considered. As a general rule, CT imaging  should be obtained only in cases of recalcitrant rhinosinusitis  when an usual course is suspected, intraorbital or intracranial  complications are suspected, or when surgical intervention is  planned (Fig. 37.1). In essence, CT scans should not be used to  make the diagnosis of rhinosinusitis in children, but instead are  used for surgical planning.   Once obtained, however, CT scans should be reviewed to  determine the presence of each paranasal sinus, as well as the  degree of development and aeration (Fig. 37.2). In addition to  common radiographic changes indicative of inflammation such  as opacification, mucosal wall thickening, and bony remodeling  changes, it is critically important to note the degree of development  in each paranasal sinus. A history of recent upper respiratory  symptoms or cough should alert the clinician, as there is a high  incidence of sinus imaging abnormalities in these patients.?""!   The maxillary and ethmoid sinuses are present at birth, and by  early childhood the sphenoid and frontal sinuses begin to develop  as evaginations off of the ethmoids. The frontal sinuses can have    the most variable course of development and are often the last  to reach full adult size. It is critical to determine the presence or  absence and the degree of aeration of a particular sinus in a young  child in order to avoid attempting entry into a sinus that does not  exist or is extremely underdeveloped. The degree of sinus develop-  ment is also important to consider when endoscopic skull base  surgery is contemplated in younger children.   Anatomic variants should also be sought during the routine CT  scan review. These include concha bullosa, Haller cells, septal    deviations, inferior turbinate hypertrophy, and Onodi cells (Fig.  37.3). The presence of anatomic variants, however, does not seem  to correlate with a higher incidence of ipsilateral sinusitis in  children.'* Although the etiology of pediatric rhinosinusitis is less  often due to anatomic abnormalities, their presence is still impor-  tant for preoperative planning and intraoperative recognition.    Once the decision has been made to proceed with ESS in children,  much of the surgical dissection technique and strategy is similar  to that in adults, albeit in a more conservative manner. Some early  concerns about ESS in children centered on its effects on facial  growth. However, later studies have failed to show any noticeable  long-term effects.'*"4 Nonetheless, past enthusiasm for the pro-  cedure has been tempered in recent years by a more conservative  approach to surgery.   Because of the smaller size of intranasal cavities and structures,  specialized pediatric ESS equipment is helpful, including the use  of 2.7-mm diameter rigid endoscopes in O-, 30-, and 70-degree  configurations. Many sinus instruments are now available in  pediatric sizes, and in the smallest patients otologic instruments  can sometimes be used as a substitute. At a minimum, having  pediatric-sized straight and up-biting through and non-through  cutting forceps enables the surgeon to tackle most pediatric ESS  dissections. A backbiter is also essential, as there is no suitable  alternative when this instrument is needed.   Mucosal decongestion is also critically important because of  the narrowed surgical field. Meticulous decongestion can be  accomplished by first using topical oxymetazoline squirted into  the nose soon after intubation. As the patient is being prepared  further and prior to draping, one or two cottonoid pledgets soaked  in oxymetazoline can be placed using the assistance of a headlight  or overhead light along the floor of the nose, to help with inferior  turbinate decongestion. Once the patient has been properly prepped    and draped, rigid endoscopic assistance can be used to specifically  apply oxymetazoline-soaked cottonoid pledgets in the middle  meatus, sphenoethmoidal recess, medial to the middle turbinate  (MT), and along the floor of the nasal cavity adjacent to the inferior  turbinate. These endoscopically placed pledgets should stay in for  a minimum of 5 minutes. A surgeon who is patient will be rewarded  with a more wide open surgical field following meticulous efforts  at mucosal decongestion, especially in younger patients.   Following adequate decongestion, further adjuvant efforts at  hemostasis can include injection of key anatomic points with 1%  lidocaine with 1:100,000 parts of epinephrine. The total quantity  of lidocaine with epinephrine should not exceed 7 mg/kg of body  weight, so the cumulative amount injected should be monitored  and communicated with the anesthesia provider to ensure that  an accidental overdose does not occur. Intranasal injection of the  uncinate process, ethmoid bulla, and the sphenopalatine foramen  region, coupled with transoral injection of the greater palatine  foramen can provide additional hemostasis. Following injection,  the mucosal points of injection are packed again with oxymetazoline-  soaked pledgets for several minutes to tamponade any mucosal  oozing, prior to beginning the ESS procedure.    As in adults, initial identification of intranasal structures such  as the inferior turbinate, nasal floor, nasal septum, and posterior  choana is critical to provide the surgeon with anatomic orientation.  The choice of rigid endoscope is surgeon dependent, but either a  O- or 30-degree endoscope is adequate for these early steps. If  obstructing nasal polyps are present and prohibit identification  of these basic anatomic structures, then initial polyp removal can  be performed using a microdebrider until the anterior-to-posterior  dimensions of the nasal cavity can be clearly seen, much as is  done in adults.   Once the surgeon is properly oriented, endoscopic dissection  can progress in a systematic fashion, as in adult patients, and  discussed earlier in the basic dissection section of this manual.  Because of the mucosal nature of pediatric CRS, following creation  of the maxillary antrostomy often the only additional dissection  necessary is to open the anterior ethmoids. Again, careful review  of the preoperative CT imaging is critical to ensure that an adequately  pneumatized and developed ethmoid bulla is present prior to  attempted surgical entry. After opening of the bulla, further dis-  section is guided by the degree of ethmoid mucosal inflammation  and obstructive disease.    A special mention should be made about the treatment of the  MT in pediatric ESS. Although much controversy exists in the  adult rhinology field about sacrifice versus preservation of the  MT, the conservative nature of dissection in pediatric ESS generally  dictates the preservation of the MT if at all possible. If the MT is  diseased and nonfunctional, pathologically enlarged such as ina  large concha bullosa, or has been destabilized sufficiently by  removal of at least two of its three anchoring points, then the MT  may be sacrificed carefully. If the MT is preserved, the patient is  at higher risk of synechia formation due to the tight anatomic  confines of a surgically opened ethmoid cavity. In addition,  postoperative debridement may be limited depending on the age  and cooperation level of pediatric patients. Thus, a number of  adjunctive measures have been employed in pediatric ESS patients  to stent the MT in place and prevent lateralization. Stenting  materials include a rubber glove finger cot, rolled-up Gelfilm  stent, or newer options such as the steroid- impregnated drug-  eluding stents. The optimal choice of stenting material ultimately  comes down to a number of patient factors, as well as surgeon  experience.    Even as the techniques of ESS and its indications were refined in  children, the enthusiasm for performing concomitant septoplasty  in children has remained low, based primarily on earlier animal  studies on rabbits as well as canine pups.'*° Further investigation  using animal models seemed to indicate that preservation of the  mucoperichondrium of the nasal septum was the key step to  preventing midface growth abnormalities.'” Over time, a body of  evidence has accumulated that shows limited and conservative  pediatric septoplasty is safe, and this is succinctly summarized  by Lawrence.'® Although there is no widely accepted minimum  age for which septoplasty is considered absolutely safe, waiting  until facial growth is nearly complete at approximately 14 to 15  years of age is prudent for those patients with only mild nasal  obstruction. For more severe nasal obstruction from a deviated  septum, other authors have advocated using an external rhinoplasty  approach in patients as young as 5 to 6 years of age.'® In the end,  the potential risks of disturbing midfacial growth patterns from  an overly aggressive mucoperichondrial resection must be balanced  against the long-terms effects of severe nasal obstruction and  chronic open-mouth breathing on facial growth and dentition. If  pediatric septoplasty is performed, it should be reserved for the  most severely obstructed patients, and a conservative resection  of any obstructing septal bone or cartilage coupled with mucop-  erichondrial preservation seems to be the key to a long-term  successful outcome.    Concomitant inferior turbinate hypertrophy may also be present,  and further contribute to nasal obstruction, particularly at the  site of the internal nasal valve (Fig. 37.3a). A variety of methods  for treatment of inferior turbinate hypertrophy exist if medical  therapy with nasal steroid sprays fails. The range of surgical options  include the more aggressive partial turbinectomy or submucous    resection of conchal bone versus less invasive options such as  radiofrequency ablation for volume reduction of the turbinates.  Because of theoretical concerns about disruption of facial growth,  many pediatric sinus surgeons opt for the less invasive radiofre-  quency ablation, and they may also outfracture the conchal bone  in order to address both the soft tissue and bony components of  the inferior turbinate.    Surgical management of choanal atresia has evolved from primarily  an open procedure performed in a transpalatal fashion to one in  which the surgeon can repair the obstruction completely from a  transnasal, endoscopic approach. Historically, transnasal approaches  involved a “puncture, dilate, and stent” technique, with postopera-  tive stents being left in place for anywhere from a few weeks to  a few months. The improved visualization achieved with endoscopic  techniques facilitates a more precise surgical technique. In children  with choanal atresia, preoperative CT imaging is essential, and  attention should be paid to findings particular to these lesions,  including the thickness of the atretic plate, the thickness of the  vomer, and medial impingement on the posterior nasal cavity  from the medial pterygoid plates (Fig. 37.4). With those findings  in mind, the overall surgical strategy is to create a common posterior  neo-choana instead of two separate unilateral openings. This is  accomplished by cautious removal of the posterior septum until  the dissection is in a coronal plane more anterior than the atretic  plate, as well as possible removal of bone from the lateral choanal    wall/medial pterygoid plate anterior to the eustachian tube.  Circumferential removal of tissue in such a fashion may predispose  the patient to restenosis, and thus many surgeons use postoperative  stents to counteract the formation of cicatricial scar tissue.  Endotracheal tubes of an appropriate size, and trimmed to a length  in which they will fit in the superior oropharynx, are most com-  monly used for stenting. However, intranasal stents can be associ-  ated with increased scar tissue formation, columella pressure  necrosis, cartilage destruction, and airway obstruction with stent  occlusion.!° Because of these associated risks, some surgeons opt  to perform choanal atresia resection without postoperative stenting.  When the surgeon chooses not to stent, intranasal mucoperiosteal  flaps may be fashioned from the mucosa overlying the atretic  plate and posterior septum, and used to reline the neo-choana,  following the removal of the posterior bony septum and bony  atretic plate.*? Large randomized studies looking at the success  of postoperative stenting versus no stenting are lacking,”! so the  ultimate choice of postoperative care is based on the surgeon’s  experience.    Continued improvements in endoscopic techniques and equipment  have enabled expansion of ESS beyond the traditional confines  of the nasal and sinus cavities. As these techniques gained favor  in adult patients with skull base pathology, the inevitable adoption  of these same procedures in children with comparable pathology  has occurred. But given the unique developmental aspects of the  pediatric sinonasal structures, adoption of endoscopic skull base  surgery in children has proceeded cautiously.   The feasibility of adapting to the pediatric population the same  techniques for skull base dissection and reconstruction used in  adults has been explored, primarily using radiographic studies.  Key anatomic landmarks such as pyriform aperture width and  sphenoid pneumatization do not seem to be a limitation for  endoscopic dissection, except in the youngest of patients. Clival  intercarotid distances appear stable with age, and should not limit  dissection in any age, but a careful review of preoperative imaging  is always a necessity.”* The pattern of sphenoid pneumatization  occurs in a temporal posterior direction, and reaches nearly adult  volume by 14 to 16 years of age.” It is also critical to note that  skull base pathology may have altered the development and  pneumatization of the paranasal sinuses, yet another reason to  perform a critical review of preoperative imaging (Table 37.1).”    Table 37.1Anatomic Checklist for Reviewing Preoperative Imaging in Pediatric  Patients Undergoing Endoscopic Skull Base Surgery 
atlas-of-operative-oral-and-maxillofacial-surgery-c.-j.-haggerty-r.-m.-laughlin-eds.-z-library Endoscopic Sinonasal Dissection Guide. Including Orbit and Skull Base (Casiano) 2 ed (2017)_djvu.txt