Hemoptysis

Hemoptysis. In a study of 70 patients undergoing bronchial artery embolization for massive hemoptysis, causative radiologic abnormalities were seen in 86% of the chest radiographs [39]. This was similar to an earlier study showing 82% of chest radiographs could detect the side and predict the cause of bleeding [40]. However, in a comparable study of 80 patients with massive hemoptysis, chest radiographs demonstrated the cause of bleeding in only 35% of cases, most of whom had tuberculosis or malignancy [28]. Although radiography can be useful in directing treatment to the correct site of bleeding, a study of 20 patients undergoing BAE for massive hemoptysis showed that radiography localized the site of hemoptysis in only 35% of patients [41]. Similar findings were reported in a larger study of 348 patients, which included both massive and moderate recurrent hemoptysis patients [17]. Chest radiographs were performed in all patients and were abnormal in 313 patients (90%). However, these radiographs were suggestive of the etiology of hemoptysis in only 90 patients (26%).


Hemoptysis

Hemoptysis. These findings indicate that additional imaging in conjunction with chest radiograph is warranted in massive hemoptysis.


Hemoptysis

Hemoptysis. Hemoptysis 44]. However, these prior variables excluded a significant portion of patients with nonmassive hemoptysis. In addition, imaging recommendations did not significantly differ between the two prior nonmassive hemoptysis variables. For these reasons, these risk factors have been removed, and there is a single nonmassive variable.


Hemoptysis

Hemoptysis. Additional recent studies reporting BAE as a viable therapeutic option for nonmassive hemoptysis includes Dave et al [46], who reported BAE outcomes on 58 patients. In this study, 17% of the population presented with nonmassive hemoptysis, and the top two causes of hemoptysis were bronchiectasis and malignancy. The success rates proved to be similar between patients presenting with nonmassive versus massive hemoptysis. This study asserted that nonmassive hemoptysis might be the harbinger of future episodes of massive hemoptysis, especially in patients with underlying lung disease. These results justify BAE as a treatment of nonmassive hemoptysis. Woo et al [18] reported BAE outcomes on 406 patients, 30% of whom presented with nonmassive hemoptysis. This study also demonstrated similar success rates between patients with nonmassive versus massive hemoptysis. Shin et al [19] reported BAE outcomes on 163 patients, including 41% presenting with nonmassive hemoptysis; outcomes were not stratified by hemoptysis severity. Bhalla et al [15] reported similar post-BAE outcomes between patients presenting with nonmassive versus massive hemoptysis. Ishikawa et al [47] published the largest study on outcomes for nonmassive hemoptysis. Elective BAE was performed on 489 noncancer patients from Japan with varying degrees of nonemergent hemoptysis. They reported immediate bleeding cessation in 93% of patients, with 87% and 58% of patients remaining free of hemoptysis at 1 and 3 years, respectively. The most common causes of hemoptysis in this study were bronchiectasis (34%) and nontuberculous mycobacterium (24%).


Hemoptysis

Hemoptysis. Cryptogenic nonmassive hemoptysis has demonstrated a very high immediate and long-term success rate following BAE. In a retrospective study [48] reviewing 319 patients, 35 patients were identified as having cryptogenic hemoptysis, 23 of whom reported nonmassive hemoptysis. Thirty-three of the 35 patients with cryptogenic hemoptysis were successfully treated with BAE, and 97% of these patients remained free of hemoptysis at 20 months. The authors reported that there was no correlation between severity of hemoptysis and the diameter of the embolized bronchial artery. These results were not compared to the patients with a known cause of hemoptysis.


Hemoptysis

Hemoptysis. CT Chest with IV Contrast As with massive hemoptysis, CT with IV contrast is the primary modality to determine hemoptysis etiology. Thirumaran et al [44], in an early study establishing CT as a diagnostic tool for nonmassive hemoptysis, retrospectively studied 270 patients with hemoptysis and a normal chest radiograph, with 94% reporting mild hemoptysis, and commonly with repeated episodes. Although the most common cause of hemoptysis was acute bronchitis (63%), the second most common cause was a respiratory tract neoplasm, the majority of which was a lung primary malignancy (n = 22/270). Lee et al [49] reported performing CT examinations on all 221 patients evaluated for hemoptysis, 48% with nonmassive hemoptysis and 52% with massive hemoptysis. Interestingly, both cohorts had similar etiologies, with bronchiectasis followed by active tuberculosis as the leading causes for hemoptysis, and CT proved to be the superior diagnostic imaging modality over bronchoscopy and arteriography for identifying the cause of hemoptysis.


Hemoptysis

Hemoptysis. CT with IV contrast is now the established imaging modality to determine the etiology of nonmassive hemoptysis, and therefore, there are no recent publications comparing its efficacy to other imaging modalities.


Hemoptysis

Hemoptysis. CT Chest without IV Contrast As discussed in Variant 1, CT chest without IV contrast is only warranted in the diagnosis of hemoptysis in patients with poor renal function or life-threatening contrast allergy. The limited number of studies reviewing the utility of


Hemoptysis

Hemoptysis. Hemoptysis CT chest without IV contrast for the evaluation of hemoptysis did not differentiate between massive versus nonmassive quantities of hemoptysis.


Hemoptysis

Hemoptysis. CT Chest without and with IV Contrast Although very early publications studying the utility of CT in patients presenting with nonmassive hemoptysis performed chest protocols including acquisitions both without IV contrast followed by acquisitions with IV contrast, there are no data to support that there is any added value of CT chest without IV contrast prior to the administration of IV contrast in the diagnosis of nonmassive hemoptysis or in the preprocedural planning of BAE.


Hemoptysis

Hemoptysis. CTA Chest There are no recent studies comparing the benefits of a routine chest CT with IV contrast to CTA in patients with nonmassive hemoptysis. As previously discussed, preprocedural CTA or routine CT with IV contrast has become the standard of care for arterial planning of BAE. In a recent study reporting the outcomes of BAE in patients with primarily nonmassive hemoptysis, all 489 noncancer patients underwent a CTA prior to embolization [47]. The authors noted that conventional aortography previously used to detect origins of the bleeding bronchial arteries was effectively replaced by arterial mapping information provided by CTA.


Hemoptysis

Hemoptysis. Radiography Chest Chest radiographs continue to be a reasonable initial imaging choice in patients with nonmassive hemoptysis, especially when used to confirm a clinical diagnosis for benign disease such as acute bronchitis or pneumonia. There are no recent studies comparing the utility of chest radiographs with other imaging modalities.


Hemoptysis

Hemoptysis. Variant 3: Recurrent hemoptysis. Initial imaging. Recurrent hemoptysis is a new variant for this update. It is defined as repeated episodes of hemoptysis following initial treatment with either medical therapy or BAE. Typically, the etiology of recurrent hemoptysis is known and usually not life threatening, although there is a wide range of hemoptysis severity. Recent literature shows a trend of more commonly treating patients with nonmassive recurrent hemoptysis with interventional or surgical procedures rather than conservative therapies compared with patients with an initial presentation of nonmassive hemoptysis. Therefore, imaging recommendations differ between patients initially presenting with nonmassive hemoptysis and patients presenting with recurrent nonmassive hemoptysis.


Hemoptysis

Hemoptysis

Hemoptysis. Hemoptysis


Hemoptysis

Hemoptysis. outcomes were due to sequelae from BAE or sequelae from recurrent hemoptysis. Of the handful of studies documenting lack of clinically significant change following BAE, Tom et al [4] specifically studied long-term clinical parameters of patients prior to and following BAE. Of the 69 patients with hemoptysis initially treated with BAE, 17 patients had at least 5 years of clinical data before and 5 years of clinical data after the initial BAE. The authors identified that pulmonary function parameters declined at the same rate prior to the initial BAE as they had following BAE.


Hemoptysis

Hemoptysis. CT Chest with IV Contrast Patients with recurrent hemoptysis typically have a known cause. Bronchiectasis due to repeated or indolent infection is the most common cause for recurrent hemoptysis in most large studies. In patients with cystic fibrosis, for example, recurrent hemoptysis may be an indicator of acute infection [60], and CT may not be indicated. There are limited data evaluating the utility of CT chest with IV contrast in the setting of a known cause of hemoptysis.


Hemoptysis

Hemoptysis. CT Chest without IV Contrast There is no relevant literature supporting the use of CT chest without IV contrast in the assessment of recurrent hemoptysis.


Hemoptysis

Hemoptysis. CT Chest without and with IV Contrast There is no relevant literature supporting the use of CT chest without IV contrast prior to a CT performed with IV contrast in patients with recurrent hemoptysis.


Hemoptysis

Hemoptysis. CTA Chest There are no recent data comparing the diagnostic advantages between routine CT with IV contrast with CTA in patients with recurrent hemoptysis. However, a recent publication studied the potential benefit of CTA for preprocedural planning for BAE in patients with recurrent hemoptysis. Zhao et al [61] reported retrospective data on 15 patients who had developed recurrent hemoptysis out of the 135 patients treated with BAE over a 2-year interval. BAE resulted in recurrent hemoptysis within 24 hours in 65% of the arteries initially embolized, arteries that were selected based on their abnormal appearance at conventional arteriography. CTA chest studies performed after the initial embolization in these patients successfully identified 16 additional suspected bleeding arteries, which subsequently were embolized and resulted in complete hemoptysis cessation. This article suggests that CTA provides improved sensitivity in the identification of arteries causing hemoptysis over conventional arteriography in patients with recurrent hemoptysis.


Hemoptysis

Hemoptysis. Radiography Chest There is no relevant literature supporting the use of chest radiographs in patients with recurrent hemoptysis. However, chest radiography remains clinically relevant in potentially detecting an acute, commonly infectious cause that can be treated by noninvasive therapies.


Hemoptysis

Hemoptysis. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch.acr.org/list. The appendix includes the strength of evidence assessment and rating round tabulations for each recommendation.


Hemoptysis

Hemoptysis. For additional information on the Appropriateness Criteria methodology and other supporting documents go to www.acr.org/ac.


Workup of Noncerebral Systemic Arterial Embolic Source. Introduction/Background Noncerebral systemic arterial embolism is an important cause of patient morbidity and mortality [1]. Arterial emboli can originate from a variety of cardiac and noncardiac sources. Cardiac sources include thrombus within the left atrium and left ventricle, valvular disease such as endocarditis, and cardiac neoplasms. Noncardiac sources of arterial embolism include thrombus and atherosclerosis within the aorta and peripheral arteries.


Workup of Noncerebral Systemic Arterial Embolic Source. Intracardiac thrombus has been thoroughly described in the cardiology and neurology literature with several factors that predispose its formation and the potential for arterial embolization. For example, atrial fibrillation has been shown to be a significant risk factor for atrial thrombogenesis [2,3]. Complex left atrial appendage morphology also confers increased likelihood of thrombus development [4]. Myocardial infarction often results in focal hypokinesis or akinesis of the left ventricular myocardium, which predisposes to thrombus formation [5,6]. Aortic and mitral valve endocarditis as well as valvular neoplasms are other potential sources for arterial embolism detectable with imaging [7,8]. Aortic thrombi tend to be associated with aortic pathology including dissection, aneurysm, or ulcerative lesions [9,10]. Thrombus formation can also occur in the aorta secondary to hypercoagulable states such as malignancy, trauma, postoperative states, hormonal therapy, and inherited hypercoagulable disorders [1,11,12].


Workup of Noncerebral Systemic Arterial Embolic Source. When a cardiac or noncardiac embolic source dislodges, the resulting embolus can occlude a variety of peripheral and visceral arteries causing ischemia [1,9,11,12]. Characteristic locations for noncerebral arterial occlusion include the upper extremities, abdominal viscera, and lower extremities [1,9,11]. Ischemia in these regions can progress to tissue infarction resulting in limb amputation, bowel resection, or nephrectomy. Determining the source of arterial embolism is essential in order to direct treatment decisions. Treatment options vary and include anti-coagulation, endovascular or surgical embolectomy, and peripheral arterial angioplasty with or without stenting to maintain long- term vascular patency [1,9,11-14].


Workup of Noncerebral Systemic Arterial Embolic Source. The variants in this document assume that the diagnosis of an arterial occlusion has already been established by other means. For example, in the setting of an acute onset cold painful leg, the use of lower extremity arteriography, CT angiography (CTA), or MR angiography (MRA) could be employed to demonstrate arterial occlusion. This document specifically pertains to the workup of a suspected embolic etiology of the already known arterial occlusion.


Workup of Noncerebral Systemic Arterial Embolic Source. aResearch Author, University of Texas Southwestern Medical Center, Dallas, Texas. bUT Southwestern Medical Center, Dallas, Texas. cNaval Medical Center Portsmouth, Portsmouth, Virginia. dPanel Chair, Emory Healthcare, Atlanta, Georgia. ePanel Chair, Duke University Medical Center, Durham, North Carolina. fPanel Vice-Chair, University of Michigan, Ann Arbor, Michigan. gPanel Vice-Chair, Massachusetts General Hospital, Boston, Massachusetts. hUniversity of Michigan, Ann Arbor, Michigan. iAllegheny Health Network, Pittsburgh, Pennsylvania. jUniversity of North Carolina School of Medicine, Chapel Hill, North Carolina. kSentara Norfolk General Hospital/Eastern Virginia Medical School, Norfolk, Virginia; American College of Emergency Physicians. lVA Palo Alto Health Care System, Palo Alto, California and Stanford University, Stanford, California. mThe University of Texas MD Anderson Cancer Center, Houston, Texas; Commission on Nuclear Medicine and Molecular Imaging. nDuke University Medical Center, Durham, North Carolina, Primary care physician. oMayo Clinic, Rochester, Minnesota; Society of Cardiovascular Computed Tomography. pSpecialty Chair, UT Southwestern Medical Center, Dallas, Texas. qSpecialty Chair, Emory University Hospital, Atlanta, Georgia.


Workup of Noncerebral Systemic Arterial Embolic Source. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization.


Workup of Noncerebral Systemic Arterial Embolic Source. Reprint requests to: publications@acr.org


Workup of Noncerebral Systemic Arterial Embolic Source. All elements are essential: 1) timing, 2) reconstructions/reformats, and 3) 3-D renderings. Standard CTs with contrast also include timing issues and reconstructions/reformats. Only in CTA, however, is 3-D rendering a required element. This corresponds to the definitions that the CMS has applied to the Current Procedural Terminology codes.


Workup of Noncerebral Systemic Arterial Embolic Source. OR Discussion of Procedures by Variant Variant 1: Known upper extremity arterial occlusion. Suspected embolic etiology. Next imaging study to determine source. The variant assumes that an upper extremity arterial occlusion has already been established. Typically, this diagnosis is made by CTA, arteriography, or MRA, although the clinical examination or another imaging study could also be used.


Workup of Noncerebral Systemic Arterial Embolic Source. Aortography Chest Conventional catheter aortography has largely been replaced by noninvasive imaging modalities such as CTA and MRA given their high sensitivity/specificity for detecting aortic pathologies such as mural thrombus [16,17]. Aortography is typically used as an alternative diagnostic strategy following initial noninvasive imaging and when therapeutic interventions are being considered [11,17].


Workup of Noncerebral Systemic Arterial Embolic Source. CT Heart Function and Morphology With IV Contrast The primary role of cardiac CT in the initial evaluation of upper extremity arterial embolic occlusion is in the workup of cardiac thrombus as a source. Multiple studies have established high rates of atrial thrombus detection by cardiac CT compared to transesophageal echocardiography (TEE) [18-27]. Meta-analyses have found sensitivities of 96% to 99% and specificities of 92% to 94% for detection of left atrial or left atrial appendage thrombus with cardiac CT compared to a TEE reference standard [28-30]. When compared with intraoperative findings, cardiac CT was 100% sensitive and 85% specific for finding left atrial thrombus [31]. Complex left atrial appendage morphologies which predispose to thrombus formation can also be characterized by cardiac CT [32-34]. Additionally, cardiac CT can differentiate left ventricular thrombus from the myocardial wall with 1 study demonstrating a sensitivity, specificity, and positive and negative predictive values of 94%, 97%, 94%, and 97%, respectively [35]. Studies have also demonstrated cardiac CT to have comparable accuracy to TEE for identification of vegetations in the setting of infective endocarditis, another potential source of arterial embolism [36-38]. Cardiac CT can identify cardiac neoplasms, both benign and malignant, which have the potential to shed and embolize to distal arterial beds [39,40].


Workup of Noncerebral Systemic Arterial Embolic Source. CTA Chest With IV Contrast Multidetector chest CTA with intravenous (IV) contrast can be used to evaluate for at-risk atherosclerotic plaque or the presence of thrombus in the thoracic aorta. CTA is useful in the assessment of the size, extent, and location of an embolic source in the aorta, which can aid in management decisions [13,41]. A number of small studies have used chest CTA to detect aortic mural thrombus that was suspected of embolization [1,12-14,42]. Specific data on the sensitivity and specificity of this imaging modality are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRA Chest Without IV Contrast Chest MRA without IV contrast is an imaging study, which can detect the presence of thrombus in the thoracic aorta. One small study found this examination to have a higher detection rate for aortic thrombus when compared with contrast-enhanced MRA, although the difference was not statistically significant [44]. In another study, sensitivity, specificity, and diagnostic accuracy of unenhanced steady-state free precession MRA were 100% for the detection of thoracic aorta pathology compared to a contrast-enhanced MRA reference standard; however, this analysis only included 1 case of mural thrombus [43]. Data comparing MRA of the chest to other imaging modalities are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRI Heart Function and Morphology Without and With IV Contrast Cardiac MR is a noninvasive imaging study that can detect intracardiac thrombus as well as valvular and neoplastic pathologies. A meta-analysis of 7 studies showed that delayed contrast-enhanced cardiac MR had a pooled sensitivity of 100% and a specificity of 99% for detecting left atrial and left atrial appendage thrombus in patients with atrial fibrillation [45]. In another meta-analysis, there was no significant difference in sensitivity and specificity between cardiac CT and cardiac MR in the detection of left atrial appendage thrombus [29]. Contrast-enhanced cardiac MR had a sensitivity of 88% and a specificity of 99% compared to surgical or pathological confirmation of left ventricular thrombus [46]. Cardiac MR is also an accurate imaging modality for the evaluation of valvular disease, including aortic and mitral valve vegetations, which can dislodge and result in arterial embolism [37,47]. Additionally, cardiac MR offers detailed soft tissue characterization for the analysis of benign and malignant intracardiac neoplasms [39,48].


Workup of Noncerebral Systemic Arterial Embolic Source. MRI Heart Function and Morphology Without IV Contrast Cardiac MR without contrast provides a detailed anatomic evaluation of the heart chambers. In the workup of embolic sources, the primary role of cardiac MR is in the identification of intracardiac thrombus. A meta-analysis of 7 studies showed that cine cardiac MR had a pooled sensitivity of 91% and a specificity of 93% for detecting left atrial and left atrial appendage thrombus in patients with atrial fibrillation [45]. Furthermore, cine cardiac MR had an 82% sensitivity and a 100% specificity in detecting left ventricle thrombus in postmyocardial infarction patients compared with a standard delayed enhancement cardiac MR [49]. Cardiac MR without contrast is also capable of identifying valvular pathology and cardiac neoplasms, although data on its applicability in the setting of systemic arterial embolism are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. US Duplex Doppler Abdomen There is no relevant literature to support the use of Doppler ultrasound (US) of the abdomen as an initial imaging modality in the evaluation of the source of known embolic upper extremity arterial occlusion.


Workup of Noncerebral Systemic Arterial Embolic Source. US Echocardiography Transesophageal TEE is an invasive diagnostic study with the ability to detect cardiac pathology predisposed to embolism. TEE has a sensitivity of 93% to 100% and a specificity of 95% to 99% for detecting left atrial appendage thrombus when compared to intraoperative findings [31,50,51]. Furthermore, TEE can evaluate left ventricular systolic dysfunction, spontaneous echo contrast, slow left atrial appendage peak flow velocities, and complex left atrial appendage morphologies, which are all associated with left atrial thrombus and thromboembolic risk [2,4]. In addition, TEE can detect left ventricular thrombus with 1 study reporting a 40% sensitivity and a 96% specificity for the modality compared to findings at surgery or pathology [46]. Proximal aortic thrombus can also be assessed using TEE, although evaluation is limited by blind spots (distal ascending aorta and proximal aortic arch) owing to air in the trachea [10,13]. Detection of valvular disease and intracardiac neoplasms can also be accomplished with TEE.


Workup of Noncerebral Systemic Arterial Embolic Source. US Echocardiography Transthoracic Resting Transthoracic echocardiography (TTE) is a noninvasive imaging modality capable of detecting cardiac pathology susceptible to embolism. TTE is inferior to TEE in the assessment of left atrial appendage thrombus because the


Workup of Noncerebral Systemic Arterial Embolic Source. 5 Workup of Noncerebral Systemic Arterial Embolic Source transducer is distant from the left atrium when placed on the chest [52]. In 1 study, a cardiac embolic source was detected by TEE in about 40% of patients with normal TTE [53]. In another study, a cardiac embolic source was identified by TTE in 15% of the study group compared with 57% by TEE [54]. Sensitivity and specificity were 23% and 96%, respectively, for the detection of left ventricular thrombus compared to findings at surgery or pathology [46]. In the detection of left ventricle thrombus, contrast-enhanced TTE had a 64% sensitivity and a 99% specificity compared to a delayed enhancement cardiac MR standard [49]. TTE can also be applied for the diagnosis of valvular disease and cardiac neoplasms. There is no evidence to support the use of TTE in the evaluation of aortic thrombus.


Workup of Noncerebral Systemic Arterial Embolic Source. Aortography Chest and Abdomen Conventional catheter aortography has largely been replaced by noninvasive imaging modalities such as CTA and MRA given their high sensitivity/specificity for detecting aortic pathologies such as mural thrombus [16,17]. Aortography is typically used as an alternative diagnostic strategy following initial noninvasive imaging and when therapeutic interventions are being considered [11,17].


Workup of Noncerebral Systemic Arterial Embolic Source. CT Heart Function and Morphology With IV Contrast The primary role of cardiac CT in the initial evaluation of mesenteric or renal arterial embolic occlusion is in the workup of cardiac thrombus as a source. Multiple studies have established high rates of atrial thrombus detection by cardiac CT compared to TEE [18-27]. Meta-analyses have found sensitivities of 96% to 99% and specificities of 92% to 94% for detection of left atrial or left atrial appendage thrombus with cardiac CT compared to a TEE reference standard [28-30]. When compared to intraoperative findings, cardiac CT was 100% sensitive and 85% specific for finding left atrial thrombus [31]. Complex left atrial appendage morphologies that predispose to thrombus formation can also be characterized by cardiac CT [32-34]. Additionally, cardiac CT can differentiate left ventricular thrombus from the myocardial wall, with 1 study demonstrating a sensitivity, specificity, and positive and negative predictive values of 94%, 97%, 94%, and 97%, respectively [35]. Studies have also demonstrated cardiac CT to have comparable accuracy to TEE for identification of vegetations in the setting of infective endocarditis, another potential source of arterial embolism [36-38]. Cardiac CT can identify cardiac neoplasms, both benign and malignant, which have the potential to shed and embolize to distal arterial beds [39,40].


Workup of Noncerebral Systemic Arterial Embolic Source. CTA Chest With IV Contrast In some conditions or clinical scenarios, there may be a high suspicion that the embolic source is in the thoracic aorta, and a CTA limited to the chest may be diagnostic. As such, multidetector chest CTA with IV contrast can be used to evaluate for at-risk atherosclerotic plaque or the presence of thrombus in the thoracic aorta. CTA is useful in the assessment of the size, extent, and location of an embolic source in the aorta, which can aid in management decisions [13,41]. A number of small studies have used chest CTA to detect aortic mural thrombus that was suspected of embolization [1,12-14,42]. Specific data on the sensitivity and specificity of this imaging modality are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. CTA Chest and Abdomen With IV Contrast Multidetector CTA with IV contrast can be used to evaluate for the presence of at-risk atherosclerotic plaque or thrombus in the aorta in its entirety. CTA is useful in the assessment of the size, extent, and location of an embolic source in the aorta, which can aid in management decisions [13,41]. Aortic intraluminal thrombus is oftentimes associated with aneurysm, particularly in the abdomen, which is readily detected by CTA [56,57]. A number of small studies have used CTA to detect aortic mural thrombus that was suspected of embolization [1,12-14,42]. Specific data on the sensitivity and specificity of this imaging modality are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRA Chest Without and With IV Contrast In some conditions or clinical scenarios, there may be a high suspicion that the embolic source is in the thoracic aorta and an MRA limited to the chest may be diagnostic. In 1 study, detection of thoracic aorta pathology by contrast-enhanced chest MRA was equivalent in sensitivity, specificity, and diagnostic accuracy compared to noncontrast MRA, although only a single case of thrombus was included in the analysis [43]. On the other hand, in


Workup of Noncerebral Systemic Arterial Embolic Source. 6 Workup of Noncerebral Systemic Arterial Embolic Source


Workup of Noncerebral Systemic Arterial Embolic Source. a small analysis which included 9 patients with aortic thrombus, contrast-enhanced MRA had a lower thrombus detection rate compared to a noncontrast examination, although this finding was not statistically significant [44]. Data comparing MRA of the chest to other imaging modalities are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRA Chest Without IV Contrast In some conditions or clinical scenarios, there may be a high suspicion that the embolic source is in the thoracic aorta and an MRA limited to the chest may be diagnostic. One small study found this examination to have a higher detection rate for aortic thrombus when compared with contrast-enhanced MRA, although the difference was not statistically significant [44]. In another study, sensitivity, specificity, and diagnostic accuracy of unenhanced steady- state free precession MRA were 100% for the detection of thoracic aorta pathology compared to a contrast-enhanced MRA reference standard; however, this analysis only included 1 case of mural thrombus [43]. Data comparing MRA of the chest to other imaging modalities is lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRA Chest and Abdomen Without and With IV Contrast MRA of the chest and abdomen without and with IV contrast can be used to evaluate for presence of an embolic source in the aorta in its entirety. In 1 study, detection of thoracic aorta pathology by contrast-enhanced chest MRA was equivalent in sensitivity, specificity, and diagnostic accuracy compared to noncontrast MRA, although only a single case of thrombus was included in the analysis [43]. On the other hand, in a small analysis which included 9 patients with aortic thrombus, contrast-enhanced MRA had a lower thrombus detection rate compared to a noncontrast examination, although this finding was not statistically significant [44]. Contrast-enhanced MRA of the abdomen has been used for intraluminal thrombus detection in the setting of aneurysms, although comparative data are insufficient [56-58]. Data comparing MRA of the chest and abdomen to other imaging modalities are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRA Chest and Abdomen Without IV Contrast Chest and abdomen MRA without IV contrast can be used to evaluate for the presence of an embolic source in the aorta in its entirety. One small study found this examination to have a higher detection rate for aortic thrombus when compared with contrast-enhanced MRA, although the difference was not statistically significant [44]. In another study, sensitivity, specificity, and diagnostic accuracy of unenhanced steady-state free precession MRA were 100% for the detection of thoracic aorta pathology compared to a contrast-enhanced MRA reference standard; however, this analysis only included 1 case of mural thrombus [43]. Noncontrast MRA has been used for the detection of abdominal aortic intraluminal thrombus, although there are insufficient data comparing it to contrast- enhanced MRA [56-58]. Data comparing MRA of the chest and abdomen to other imaging modalities are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRI Heart Function and Morphology Without and With IV Contrast Cardiac MR is a noninvasive imaging study that can reliably detect intracardiac thrombus as well as valvular and neoplastic pathologies. A meta-analysis of 7 studies showed that delayed contrast-enhanced cardiac MR had a pooled sensitivity of 100% and a specificity of 99% for detecting left atrial and left atrial appendage thrombus in patients with atrial fibrillation [45]. In another meta-analysis, there was no significant difference in sensitivity and specificity between cardiac CT and cardiac MR in the detection of left atrial appendage thrombus [29]. Contrast- enhanced cardiac MR had a sensitivity of 88% and a specificity of 99% compared to surgical or pathological confirmation of left ventricular thrombus [46]. Cardiac MR is also an accurate imaging modality for the evaluation of valvular disease, including aortic and mitral valve vegetations, which can dislodge and result in arterial embolism [37,47]. Additionally, cardiac MR offers detailed soft tissue characterization for the analysis of benign and malignant intracardiac neoplasms [39,48].


Workup of Noncerebral Systemic Arterial Embolic Source. MRI Heart Function and Morphology Without IV Contrast Cardiac MR without contrast provides a detailed anatomic evaluation of the heart chambers. In the workup of embolic sources, the primary role of cardiac MR is in the identification of intracardiac thrombus. A meta-analysis of 7 studies showed that cine cardiac MR had a pooled sensitivity of 91% and a specificity of 93% for detecting left atrial and left atrial appendage thrombus in patients with atrial fibrillation [45]. Furthermore, cine cardiac MR had an 82% sensitivity and 100% specificity in detecting left ventricle thrombus in postmyocardial infarction patients compared to a standard delayed enhancement cardiac MR [49]. Cardiac MR without contrast is also capable of identifying valvular pathology and cardiac neoplasms, although data on its applicability in the setting of systemic arterial embolism are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. US Duplex Doppler Abdomen There is no relevant literature to support the use of Doppler US of the abdomen as an initial imaging modality in the evaluation of the source of known embolic mesenteric/renal arterial occlusion. However, some imaging


Workup of Noncerebral Systemic Arterial Embolic Source. 7 Workup of Noncerebral Systemic Arterial Embolic Source protocols may include limited views of the abdominal aorta that may detect intraluminal aortic thrombus or significant atherosclerotic disease [56].


Workup of Noncerebral Systemic Arterial Embolic Source. US Echocardiography Transesophageal TEE is an invasive diagnostic study with the ability to detect cardiac pathology predisposed to embolism. TEE has a sensitivity of 93% to 100% and a specificity of 95% to 99% for detecting left atrial appendage thrombus when compared to intraoperative findings [31,50,51]. Furthermore, TEE can evaluate left ventricular systolic dysfunction, spontaneous echo contrast, slow left atrial appendage peak flow velocities, and complex left atrial appendage morphologies, which are all associated with left atrial thrombus and thromboembolic risk [2,4]. In addition, TEE can detect left ventricular thrombus, with 1 study reporting a 40% sensitivity and a 96% specificity for the modality compared to findings at surgery or pathology [46]. Proximal aortic thrombus can also be assessed using TEE, although evaluation is limited by blind spots (distal ascending aorta and proximal aortic arch) owing to air in the trachea [10,13]. Detection of valvular disease and intracardiac neoplasms can also be accomplished with TEE.


Workup of Noncerebral Systemic Arterial Embolic Source. US Echocardiography Transthoracic Resting TTE is a noninvasive imaging modality capable of detecting cardiac pathology susceptible to embolism. TTE is inferior to TEE in the assessment of left atrial appendage thrombus because the transducer is distant from the left atrium when placed on the chest [52]. In 1 study, a cardiac embolic source was detected by TEE in about 40% of patients with normal TTE [53]. In another study, a cardiac embolic source was identified by TTE in 15% of the study group compared with 57% by TEE [54]. Sensitivity and specificity were 23% and 96%, respectively, for the detection of left ventricular thrombus compared to findings at surgery or pathology [46]. In the detection of left ventricle thrombus, contrast-enhanced TTE had a 64% sensitivity and 99% specificity compared to a delayed enhancement cardiac MR standard [49]. TTE can also be applied for the diagnosis of valvular disease and cardiac neoplasms. There is no evidence to support the use of TTE in the evaluation of aortic thrombus.


Workup of Noncerebral Systemic Arterial Embolic Source. Aortography Chest, Abdomen, and Pelvis Conventional catheter aortography has largely been replaced by noninvasive imaging modalities such as CTA and MRA given their high sensitivity/specificity for detecting aortic pathologies such as mural thrombus [16,17]. Aortography is typically used as an alternative diagnostic strategy following initial noninvasive imaging and when therapeutic interventions are being considered [11,17].


Workup of Noncerebral Systemic Arterial Embolic Source. CT Heart Function and Morphology With IV Contrast The primary role of cardiac CT in the initial evaluation of lower extremity arterial embolic occlusion is in the workup of cardiac thrombus as a source. Multiple studies have established high rates of atrial thrombus detection by cardiac CT compared to TEE [18-27]. Meta-analyses have found sensitivities of 96% to 99% and specificities of 92% to 94% for detection of left atrial or left atrial appendage thrombus with cardiac CT compared to a TEE reference standard [28-30]. When compared to intraoperative findings, cardiac CT was 100% sensitive and 85% specific for finding left atrial thrombus [31]. Complex left atrial appendage morphologies, which predispose to thrombus formation, can also be characterized by cardiac CT [32-34]. Additionally, cardiac CT can differentiate left ventricular thrombus from the myocardial wall with 1 study demonstrating a sensitivity, specificity, and positive and negative predictive values of 94%, 97%, 94%, and 97%, respectively [35]. Studies have also demonstrated cardiac CT to have comparable accuracy to TEE for identification of vegetations in the setting of infective endocarditis, another potential source of arterial embolism [36-38]. Cardiac CT can identify cardiac neoplasms, both benign and malignant, which have the potential to shed and embolize to distal arterial beds [39,40].


Workup of Noncerebral Systemic Arterial Embolic Source. CTA Chest With IV Contrast In some conditions or clinical scenarios, there may be a high suspicion that the embolic source is in the thoracic aorta and a CTA limited to the chest may be diagnostic. As such, multidetector chest CTA with IV contrast can be used to evaluate for at-risk atherosclerotic plaque or the presence of thrombus in the thoracic aorta. CTA is useful in the assessment of the size, extent, and location of an embolic source in the aorta, which can aid in management decisions [13,41]. A number of small studies have used chest CTA to detect aortic mural thrombus that was


Workup of Noncerebral Systemic Arterial Embolic Source. CTA Chest, Abdomen, and Pelvis With IV Contrast Multidetector CTA with IV contrast can be used to evaluate for the presence of at-risk atherosclerotic plaque or thrombus in the aorta in its entirety. CTA is useful in the assessment of the size, extent, and location of an embolic source in the aorta, which can aid in management decisions [13,41]. Aortic intraluminal thrombus is oftentimes associated with aneurysm, particularly in the abdomen, which is readily detected by CTA [56,57]. A number of small studies have used CTA to detect aortic mural thrombus that was suspected of embolization [1,12-14,42]. Specific data on the sensitivity and specificity of this imaging modality are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRA Chest Without and With IV Contrast In some conditions or clinical scenarios, there may be a high suspicion that the embolic source is in the thoracic aorta and an MRA limited to the chest may be diagnostic. In 1 study, detection of thoracic aorta pathology by contrast-enhanced chest MRA was equivalent in sensitivity, specificity, and diagnostic accuracy compared to noncontrast MRA, although only a single case of thrombus was included in the analysis [43]. On the other hand, in a small analysis which included 9 patients with aortic thrombus, contrast-enhanced MRA had a lower thrombus detection rate compared to a noncontrast examination, although this finding was not statistically significant [44]. Data comparing MRA of the chest to other imaging modalities are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRA Chest, Abdomen, and Pelvis Without and With IV Contrast MRA of the chest, abdomen, and pelvis without and with IV contrast can be used to evaluate for the presence of an embolic source in the aorta in its entirety. In 1 study, detection of thoracic aorta pathology by contrast-enhanced chest MRA was equivalent in sensitivity, specificity, and diagnostic accuracy compared to noncontrast MRA, although only a single case of thrombus was included in the analysis [43]. On the other hand, in a small analysis which included 9 patients with aortic thrombus, contrast-enhanced MRA had a lower thrombus detection rate compared to a noncontrast examination, although this finding was not statistically significant [44]. Contrast- enhanced MRA of the abdomen has been used for intraluminal thrombus detection in the setting of aneurysms, although comparative data is insufficient [56-58]. Data comparing MRA of the chest, abdomen, and pelvis to other imaging modalities is lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRA Chest, Abdomen, and Pelvis Without IV Contrast Chest, abdomen, and pelvis MRA without IV contrast can be used to evaluate for the presence of an embolic source in the aorta in its entirety. One small study found this examination to have a higher detection rate for aortic thrombus when compared with contrast-enhanced MRA, although the difference was not statistically significant [44]. In another study, sensitivity, specificity, and diagnostic accuracy of unenhanced steady-state free precession MRA were 100% for the detection of thoracic aorta pathology compared to a contrast-enhanced MRA reference standard, however this analysis only included 1 case of mural thrombus [43]. Noncontrast MRA has been used for the detection of abdominal aortic intraluminal thrombus, although there is insufficient data comparing it to contrast- enhanced MRA [56-58]. Data comparing MRA of the chest, abdomen, and pelvis to other imaging modalities is lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRI Heart Function and Morphology Without and With IV Contrast Cardiac MR is a noninvasive imaging study that can reliably detect intracardiac thrombus as well as valvular and neoplastic pathologies. A meta-analysis of 7 studies showed that delayed contrast-enhanced cardiac MR had a pooled sensitivity of 100% and a specificity of 99% for detecting left atrial and left atrial appendage thrombus in patients with atrial fibrillation [45]. In another meta-analysis, there was no significant difference in sensitivity and specificity between cardiac CT and cardiac MR in the detection of left atrial appendage thrombus [29]. Contrast- enhanced cardiac MR had a sensitivity of 88% and a specificity of 99% compared to surgical or pathological


Workup of Noncerebral Systemic Arterial Embolic Source. 9 Workup of Noncerebral Systemic Arterial Embolic Source


Workup of Noncerebral Systemic Arterial Embolic Source. confirmation of left ventricular thrombus [46]. Cardiac MR is also an accurate imaging modality for the evaluation of valvular disease, including aortic and mitral valve vegetations, which can dislodge and result in arterial embolism [37,47]. Additionally, cardiac MR offers detailed soft tissue characterization for the analysis of benign and malignant intracardiac neoplasms [39,48].


Workup of Noncerebral Systemic Arterial Embolic Source. MRI Heart Function and Morphology Without IV Contrast Cardiac MR without contrast provides a detailed anatomic evaluation of the heart chambers. In the workup of embolic sources, the primary role of cardiac MR is in the identification of intracardiac thrombus. A meta-analysis of 7 studies showed that cine cardiac MR had a pooled sensitivity of 91% and a specificity of 93% for detecting left atrial and left atrial appendage thrombus in patients with atrial fibrillation [45]. Furthermore, cine cardiac MR had an 82% sensitivity and a 100% specificity in detecting left ventricle thrombus in postmyocardial infarction patients compared with a standard delayed enhancement cardiac MR [49]. Cardiac MR without contrast is also capable of identifying valvular pathology and cardiac neoplasms, although data on its applicability in the setting of systemic arterial embolism are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. US Duplex Doppler Abdomen There is no relevant literature to support the use of Doppler US of the abdomen as an initial imaging modality in the evaluation of the source of known embolic lower extremity arterial occlusion. However, some imaging protocols may include limited views of the abdominal aorta, which may detect intraluminal aortic thrombus or significant atherosclerotic disease [56].


Workup of Noncerebral Systemic Arterial Embolic Source. US Echocardiography Transthoracic Resting TTE is a noninvasive imaging modality capable of detecting cardiac pathology susceptible to embolism. TTE is inferior to TEE in the assessment of left atrial appendage thrombus because the transducer is distant from the left atrium when placed on the chest [52]. In 1 study, a cardiac embolic source was detected by TEE in about 40% of patients with normal TTE [53]. In another study, a cardiac embolic source was identified by TTE in 15% of the study group compared with 57% by TEE [54]. Sensitivity and specificity were 23% and 96%, respectively, for the detection of left ventricular thrombus compared to findings at surgery or pathology [46]. In the detection of left ventricle thrombus, contrast-enhanced TTE had a 64% sensitivity and a 99% specificity compared to a delayed enhancement cardiac MR standard [49]. TTE can also be applied for the diagnosis of valvular disease and cardiac neoplasms. There is no evidence to support the use of TTE in the evaluation of aortic thrombus.


Workup of Noncerebral Systemic Arterial Embolic Source. Variant 4: Known multiorgan system arterial occlusions. Suspected embolic etiology. Next imaging study to determine source. The variant assumes that multiorgan arterial occlusions have already been established. Typically, these diagnoses are made by CTA, arteriography, or MRA, although the clinical examination or another imaging study could also be used.


Workup of Noncerebral Systemic Arterial Embolic Source. CT Heart Function and Morphology With IV Contrast The primary role of cardiac CT in the initial evaluation of multiorgan system arterial embolic occlusion is in the workup of cardiac thrombus as a source. Multiple studies have established high rates of atrial thrombus detection by cardiac CT compared to TEE [18-27]. Meta-analyses have found sensitivities of 96% to 99% and specificities of 92% to 94% for detection of left atrial or left atrial appendage thrombus with cardiac CT compared to a TEE reference standard [28-30]. When compared with intraoperative findings, cardiac CT was 100% sensitive and 85% specific for finding left atrial thrombus [31]. Complex left atrial appendage morphologies, which predispose to thrombus formation, can also be characterized by cardiac CT [32-34]. Additionally, cardiac CT can differentiate left ventricular thrombus from the myocardial wall, with 1 study demonstrating a sensitivity, specificity, and


Workup of Noncerebral Systemic Arterial Embolic Source. 10 Workup of Noncerebral Systemic Arterial Embolic Source positive and negative predictive values of 94%, 97%, 94%, and 97%, respectively [35]. Studies have also demonstrated cardiac CT to have comparable accuracy to TEE for identification of vegetations in the setting of infective endocarditis, another potential source of arterial embolism [36-38]. Cardiac CT can identify cardiac neoplasms, both benign and malignant, which have the potential to shed and embolize to distal arterial beds [39,40].


Workup of Noncerebral Systemic Arterial Embolic Source. CTA Chest With IV Contrast In some conditions or clinical scenarios, there may be a high suspicion that the embolic source is in the thoracic aorta, and a CTA limited to the chest may be diagnostic. As such, multidetector chest CTA with IV contrast can be used to evaluate for at-risk atherosclerotic plaque or the presence of thrombus in the thoracic aorta. CTA is useful in the assessment of the size, extent, and location of an embolic source in the aorta, which can aid in management decisions [13,41]. A number of small studies have used chest CTA to detect aortic mural thrombus that was suspected of embolization [1,12-14,42]. Specific data on the sensitivity and specificity of this imaging modality are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. CTA Chest, Abdomen, and Pelvis With IV contrast Multidetector CTA with IV contrast can be used to evaluate for the presence of at-risk atherosclerotic plaque or thrombus in the aorta in its entirety. CTA is useful in the assessment of the size, extent, and location of an embolic source in the aorta, which can aid in management decisions [13,41]. Aortic intraluminal thrombus is oftentimes associated with aneurysm, particularly in the abdomen, which is readily detected by CTA [56,57]. A number of small studies have used CTA to detect aortic mural thrombus that was suspected of embolization [1,12-14,42]. Specific data on the sensitivity and specificity of this imaging modality are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRA Chest Without IV Contrast In some conditions or clinical scenarios, there may be a high suspicion that the embolic source is in the thoracic aorta and an MRA limited to the chest may be diagnostic. One small study found this examination to have a higher detection rate for aortic thrombus when compared with contrast-enhanced MRA, although the difference was not statistically significant [44]. In another study, sensitivity, specificity, and diagnostic accuracy of unenhanced steady- state free precession MRA were 100% for the detection of thoracic aorta pathology compared to a contrast-enhanced MRA reference standard; however, this analysis only included 1 case of mural thrombus [43]. Data comparing MRA of the chest to other imaging modalities is lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRA Chest, Abdomen, and Pelvis Without IV Contrast Chest, abdomen, and pelvis MRA without IV contrast can be used to evaluate for the presence of an embolic source in the aorta in its entirety. One small study found this examination to have a higher detection rate for aortic thrombus when compared with contrast-enhanced MRA, although the difference was not statistically significant [44]. In another study, sensitivity, specificity, and diagnostic accuracy of unenhanced steady-state free precession MRA were 100% for the detection of thoracic aorta pathology compared to a contrast-enhanced MRA reference standard, however this analysis only included 1 case of mural thrombus [43]. Noncontrast MRA has been used for the


Workup of Noncerebral Systemic Arterial Embolic Source. 11 Workup of Noncerebral Systemic Arterial Embolic Source


Workup of Noncerebral Systemic Arterial Embolic Source. detection of abdominal aortic intraluminal thrombus, although there is insufficient data comparing it to contrast- enhanced MRA [56-58]. Data comparing MRA of the chest, abdomen, and pelvis to other imaging modalities is lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. MRI Heart Function and Morphology Without and With IV Contrast Cardiac MR is a noninvasive imaging study that can reliably detect intracardiac thrombus as well as valvular and neoplastic pathologies. A meta-analysis of 7 studies showed that delayed contrast-enhanced cardiac MR had a pooled sensitivity of 100% and a specificity of 99% for detecting left atrial and left atrial appendage thrombus in patients with atrial fibrillation [45]. In another meta-analysis, there was no significant difference in sensitivity and specificity between cardiac CT and cardiac MR in the detection of left atrial appendage thrombus [29]. Contrast- enhanced cardiac MR had a sensitivity of 88% and a specificity of 99% compared to surgical or pathological confirmation of left ventricular thrombus [46]. Cardiac MR is also an accurate imaging modality for the evaluation of valvular disease, including aortic and mitral valve vegetations, which can dislodge and result in arterial embolism [37,47]. Additionally, cardiac MR offers detailed soft tissue characterization for the analysis of benign and malignant intracardiac neoplasms [39,48].


Workup of Noncerebral Systemic Arterial Embolic Source. MRI Heart Function and Morphology Without IV Contrast Cardiac MR without contrast provides a detailed anatomic evaluation of the heart chambers. In the workup of embolic sources, the primary role of cardiac MR is in the identification of intracardiac thrombus. A meta-analysis of 7 studies showed that cine cardiac MR had a pooled sensitivity of 91% and a specificity of 93% for detecting left atrial and left atrial appendage thrombus in patients with atrial fibrillation [45]. Furthermore, cine cardiac MR had an 82% sensitivity and a 100% specificity in detecting left ventricle thrombus in postmyocardial infarction patients compared with a standard delayed enhancement cardiac MR [49]. Cardiac MR without contrast is also capable of identifying valvular pathology and cardiac neoplasms, although data on its applicability in the setting of systemic arterial thromboembolism are lacking.


Workup of Noncerebral Systemic Arterial Embolic Source. US Duplex Doppler Abdomen There is no relevant literature to support the use of Doppler US of the abdomen as an initial imaging modality in the evaluation of the source of known embolic multiorgan arterial occlusion. However, some imaging protocols may include limited views of the abdominal aorta, which may detect intraluminal aortic thrombus or significant atherosclerotic disease [56].


Workup of Noncerebral Systemic Arterial Embolic Source. US Echocardiography Transesophageal TEE is an invasive diagnostic study with the ability to detect cardiac pathology predisposed to embolism. TEE has a sensitivity of 93% to 100% and a specificity of 95% to 99% for detecting left atrial appendage thrombus when compared with intraoperative findings [31,50,51]. Furthermore, TEE can evaluate left ventricular systolic dysfunction, spontaneous echo contrast, slow left atrial appendage peak flow velocities, and complex left atrial appendage morphologies, which are all associated with left atrial thrombus and thromboembolic risk [2,4]. In addition, TEE can detect left ventricular thrombus with 1 study reporting a 40% sensitivity and a 96% specificity for the modality compared to findings at surgery or pathology [46]. Proximal aortic thrombus can also be assessed using TEE, although evaluation is limited by blind spots (distal ascending aorta and proximal aortic arch) owing to air in the trachea [10,13]. Detection of valvular disease and intracardiac neoplasms can also be accomplished with TEE.


Workup of Noncerebral Systemic Arterial Embolic Source. Supporting Documents The evidence table, literature search, and appendix for this topic are available at https://acsearch.acr.org/list. The appendix includes the strength of evidence assessment and the final rating round tabulations for each recommendation.


Workup of Noncerebral Systemic Arterial Embolic Source. For additional information on the Appropriateness Criteria methodology and other supporting documents go to www.acr.org/ac.


Cranial Neuropathy

Cranial Neuropathy. Introduction/Background The human body has 12 paired cranial nerves (CNs) that provide specialized sensory and motor innervation to the head and neck region. As a group, the CNs have both sensory and motor components similar to those of the spinal nerves. Individually the CNs may be purely sensory, purely motor, or a mixture of both sensory and motor. Functions of the CNs may be divided into three sensory and three motor categories. The sensory group includes visceral sensory, which supplies sensory input from the internal organs; general sensory, which supplies tactile, pain, temperature, and other sensations; and special sensory, which includes the special senses of smell, vision, taste, hearing, and balance. Of the three motor functions, somatic motor nerves innervate muscles that develop from the body somites; branchial motor nerves innervate muscles derived from the branchial arches; and visceral motor nerves innervate the viscera, glands, and smooth muscle [1-4].


Cranial Neuropathy

Cranial Neuropathy. The CNs emerge in an orderly fashion from the rostral portion of the embryologically developing neural tube, which develops to form the brain. Anatomically, the 12 pairs of CNs are designated by numbers I-XII. The CNs include the olfactory (CN I), optic (CN II), oculomotor (CN III), trochlear (CN IV), trigeminal (CN V), abducens (CN VI), facial (CN VII), vestibulocochlear (CN VIII), glossopharyngeal (CN IX), vagus (CN X), spinal accessory (CN XI), and hypoglossal (CN XII) nerves. The olfactory (CN I) and optic (CN II) nerves are actually tracts formed from the telencephalon and diencephalon, respectively, and are not considered true nerves [4,5]. The CN nuclei arise in the brainstem, largely topologically arranged between the midbrain and the rostral cervical spine (CN XI). Current knowledge of CN anatomy has been improved by modern microsurgical techniques and endoscopic dissections, allowing visualization of the CN brainstem exit zones [3,4,6-13]. Various nomenclatures for the segments of the CNs are described in the anatomical, surgical, and radiological literature [5,14,15].


Cranial Neuropathy

Cranial Neuropathy. In approaching cranial neuropathy, several concepts should be emphasized: 1. Cranial neuropathy can result from pathology affecting the nerve fibers at any point from the CN nucleus to the end organ supplied by the nerve. Pathologic processes affecting the brain, CN nuclei, or nerve fiber tracts supplying CNs are often associated with multiple neurologic symptoms. The CNs may take long, circuitous routes to their end organs. A detailed knowledge of CN anatomy coupled with a careful neurologic examination is essential for proper clinical localization of potential lesions and for the selection of appropriate imaging protocols.


Cranial Neuropathy

Cranial Neuropathy. aMayo Clinic Arizona, Phoenix, Arizona. bPanel Chair, University of Iowa Hospitals and Clinics, Iowa City, Iowa. cPanel Vice-Chair, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts. dFroedtert Memorial Lutheran Hospital Medical College of Wisconsin, Milwaukee, Wisconsin. eStritch School of Medicine Loyola University Chicago, Maywood, Illinois. fMontefiore Medical Center, Bronx, New York. gNorthwestern University Feinberg School of Medicine, Chicago, Illinois; American Academy of Otolaryngology-Head and Neck Surgery. hRush University Medical Center, Chicago, Illinois; Neurosurgery expert. iHouston Methodist Hospital, Houston, Texas. jUniversity of Texas Health Science Center, Houston, Texas. kThe University of Texas MD Anderson Cancer Center, Houston, Texas. lNew York University Langone Medical Center, New York, New York. mMayo Clinic, Rochester, Minnesota. nMetroHealth Medical Center, Cleveland, Ohio. oUniversity of North Carolina School of Medicine, Chapel Hill, North Carolina; American Academy of Neurology. pNorthwestern University Feinberg School of Medicine, Chicago, Illinois; Neurosurgery expert. qGeorge Washington University Hospital, Washington, District of Columbia. rUniversity of Iowa Hospital, Iowa City, Iowa, Primary care physician. sUniversity of Colorado Denver, Denver, Colorado. tSpecialty Chair, Atlanta VA Health Care System and Emory University, Atlanta, Georgia.


Cranial Neuropathy

Cranial Neuropathy. The American College of Radiology seeks and encourages collaboration with other organizations on the development of the ACR Appropriateness Criteria through representation of such organizations on expert panels. Participation on the expert panel does not necessarily imply endorsement of the final document by individual contributors or their respective organization.


Cranial Neuropathy

Cranial Neuropathy. Reprint requests to: publications@acr.org


Cranial Neuropathy

Cranial Neuropathy. Cranial Neuropathy Special Imaging Considerations MRI is the standard modality for imaging the CNs. Imaging with 3.0T is preferred over 1.5T imaging because of superior signal-to-noise ratios, gradient strength, and spatial resolution, although diagnostic information can be obtained with 1.5T imaging when 3.0T imaging is not available or precluded [5]. A phased-array head coil suffices for most examinations; specialized surface coils may supplement examinations of peripherally located nerves [5,19,20].


Cranial Neuropathy

Cranial Neuropathy. Fundamental techniques include thin-cut T1-weighted, T2-weighted, and contrast-enhanced T1-weighted sequences. The unenhanced T1-weighted sequence remains an excellent baseline technique for anatomic evaluation because of the natural contrast provided by fat in the neck and skull base. Diffusion-weighted imaging (DWI) is useful to assess for acute infarctions, cellular tumors, or specific lesions that may affect CN function, such as epidermoids or cholesteatomas. Thin section nonecho planar DWI with decreased susceptibility artifact compared with echo planar DWI allows for increased sensitivity in detection of small cholesteatomas. The use of intravenous (IV) contrast is imperative for the evaluation of cranial neuropathy with MRI. Neck CT also requires the use of IV contrast when evaluating for lesions in the neck causing cranial neuropathy.


Cranial Neuropathy

Cranial Neuropathy. Thin-section imaging with high-spatial resolution is required to directly image the CNs or their course. Slice thickness should be calculated for optimal spatial resolution without introducing partial-volume effect. The primary plane of imaging varies with the CN of interest and should include orthogonal views. The CN nuclei and fascicular nerve segments (brainstem segments) are not well seen on MRI, but their location can be deduced by recognizing surrounding anatomy and are best imaged with various T2-weighted, multi-echo, and fluid-attenuated inversion- recovery (FLAIR) sequences [15]. Three-dimensional isotropic heavily T2-weighted sequences with low CSF artifact provide submillimeter high-spatial and contrast resolution to image the cisternal and dural cave segments of the CNs and can be reformatted into multiple planes [5,21-23].


Cranial Neuropathy

Cranial Neuropathy. Intradural and foraminal CN segments, surrounded by a vascular plexus, are best imaged with contrast-enhanced 2- D or 3-D T1-weighted images, contrast-enhanced MR angiography (MRA) or contrast-enhanced modified balanced steady-state free precession (SSFP) sequences in which the nerves appear dark while surrounded by the vascular plexus [5,15,23,24]. The peripheral or extraforaminal segments of the CNs begin as they exit the skull base where they are initially surrounded by fat and are well imaged with high-resolution axial and coronal T1-weighted and T2-weighted sequences and with SSFP sequences as they course within the face and neck [5,15]. Contrast-enhanced fat-suppressed T1-weighted techniques may emphasize abnormal nerves or lesions but can mask subtle pathology if the fat-suppression is nonuniform. Because CN examinations tend to be lengthy, strategies such as parallel imaging may improve patient compliance and image quality [15].


Cranial Neuropathy

Cranial Neuropathy. DWI and fiber tract imaging techniques have shown some improvement in visualization of CN fascicles and fiber tracts but are without sufficient reliability for routine clinical use [5,25,26].


Cranial Neuropathy

Cranial Neuropathy. In the setting of cranial neuropathy, thin-cut high-resolution CT can be complementary to MRI in characterizing the osseous integrity of the skull base and skull base foramina.


Cranial Neuropathy

Cranial Neuropathy. Knowledge of CN anatomy coupled with a careful neurologic examination can aid in tailoring imaging protocols, particularly if a central or peripheral CN palsy can be distinguished clinically. If the probable location of the causative lesion cannot be deduced clinically, imaging of the entire course of the relevant CN may be required because cranial neuropathy can result from pathology affecting the nerve fibers at any point along the course of the nerve and might require multiple imaging modalities. For example, complete evaluation of CN VII includes imaging of the parotid gland and face, because causative lesions can be intraparotid or cutaneous. Head and neck imaging is required to completely image the courses of CN IX, CN XI, and CN XII, which extend into the neck to innervate


Cranial Neuropathy

Cranial Neuropathy

Cranial Neuropathy. Cranial Neuropathy


Cranial Neuropathy

Cranial Neuropathy. end organs. Evaluation of the head, neck, and upper chest is necessary for complete evaluation of the CN X to include the recurrent laryngeal nerve. This can be accomplished by extending the neck scan into the mid thorax (aortic pulmonary window) or by adding a dedicated chest CT. Patients presenting with otalgia may require evaluation of CN V, VII, IX, and X and upper cervical nerves C2 and C3 because any of these nerves may be the source for the otalgia [27].


Cranial Neuropathy

Cranial Neuropathy. Most patients with olfactory symptoms do not require imaging, unless history or physical examination warrants it [29]. Causative factors for olfactory impairment can be categorized into three main groups, including conduction loss from sinonasal passage obstruction, sensorineural loss from olfactory neuroepithelial damage, and dysfunction from central nervous system disorders [30,31]. Trauma, aging, upper respiratory infections, and inflammatory sinonasal disorders most commonly affect the sense of smell [30-32]. Tumors affecting the cribriform plate such as squamous cell carcinomas, meningiomas, and esthesioneuroblastoma or olfactory neuroblastomas; inflammatory lesions such as sarcoidosis and granulomatosis with polyangiitis; and congenital conditions such as cephaloceles and Kallmann syndrome can also result in impaired olfaction [32-34]. Olfactory dysfunction is also associated with neurodegenerative, cognitive, and mood disorders including Alzheimer disease, Parkinson disease, and depression [30,35-38].


Cranial Neuropathy

Cranial Neuropathy. CT Head There is no relevant literature to support the use of CT head in the evaluation of the olfactory nerve.


Cranial Neuropathy

Cranial Neuropathy. CT Maxillofacial CT of the paranasal sinuses and face is useful to evaluate fractures, paranasal sinus inflammatory disease, and bony anatomy that impact olfaction [29,39-41]. CT can be used to characterize sinonasal inflammatory disease. Rhinosinusitis with nasal polyposis severity, as characterized by CT, correlates with worse olfaction [31]. Although the anatomic subunits of the olfactory pathway except for the olfactory bulbs cannot be directly visualized by CT, imaging protocols should cover the major anatomic divisions of the olfactory nerve and pathway, including the olfactory epithelium, which is located in the upper nasal cavity; the olfactory neurons and bulbs, located in the cribriform plate and inferior frontal lobes; and the olfactory pathways, which travel in portions of the temporal and


Cranial Neuropathy

Cranial Neuropathy. frontal lobes [4]. No IV contrast is necessary for osseous evaluation including posttrauma and for uncomplicated inflammatory sinonasal disease. Contrast-enhanced CT is useful to evaluate granulomatous and neoplastic disease. There is no relevant literature to support the use of combined pre- and postcontrast imaging.


Cranial Neuropathy

Cranial Neuropathy. CTA Head There is no relevant literature to support the use of CT angiography (CTA) head in the evaluation of the olfactory nerve.


Cranial Neuropathy

Cranial Neuropathy. FDG-PET/CT Efforts using functional MRI, single-photon emission CT, and fluorine-18-2-fluoro-2-deoxy-D-glucose (FDG)-PET in studying olfactory dysfunction and the role of olfaction in neurodegenerative disorders remain largely investigative and are not generally used in routine evaluations [42-48].


Cranial Neuropathy

Cranial Neuropathy. MRA Head There is no relevant literature to support the use of MRA head in the evaluation of the olfactory nerve.


Cranial Neuropathy

Cranial Neuropathy. MRI Head MRI is the mainstay for directly imaging the olfactory apparatus and is best assessed with MRI orbits, face, and neck MRI rather than MRI head, allowing for assessment of the sinonasal components of the olfactory apparatus while simultaneously evaluating the relevant brain structures that can affect olfaction.


Cranial Neuropathy

Cranial Neuropathy. US Neck There is no relevant literature to support the use of ultrasound (US) neck in the evaluation of the olfactory nerve.


Cranial Neuropathy

Cranial Neuropathy. Variant 2: Unilateral isolated weakness of the mastication muscles, paralysis of the mastication muscles, sensory abnormalities of the face and head, facial numbness, or trigeminal neuralgia (trigeminal nerve, CN V). Initial imaging. The trigeminal nerve (CN V) is the largest CN, providing general sensation to the face, part of the scalp, the nasal cavity, oral cavity, and teeth. It also provides branchial motor innervation to the muscles of mastication. The 4 central trigeminal nerve nuclei are located within the brainstem and include the mesencephalic nucleus, the principal sensory nucleus, the motor nucleus, and the spinal trigeminal tract and nucleus. The spinal trigeminal tract and nucleus extend from the midpons caudally into the upper cervical cord at the C2-C4 levels. The trigeminal nerve is divided into 3 main divisions, known as the ophthalmic (V1), maxillary (V2), and mandibular (V3) branches [3]. Symptoms of trigeminal neuropathy or neuropathic pain syndromes vary with the involved segment and division and may or may not include other sensory deficits (such as facial numbness) or motor deficits (such as weakness with mastication). In patients with clinical features of trigeminal neuropathy, initial imaging is performed along the entire course of the trigeminal nerve to evaluate for a causative lesion [57].


Cranial Neuropathy

Cranial Neuropathy. The trigeminal nerve can be affected by processes anywhere along its course from the brainstem to its peripheral branches; consequently, imaging should cover the entire course of the nerve. Brainstem lesions can affect the trigeminal nerve but rarely lead to isolated trigeminal neuropathy because of the close proximity of neural structures within the brainstem. In particular, multiple sclerosis can result in trigeminal neuralgia, necessitating imaging of the brainstem to look for demyelinating disease [58-61]. Other brainstem lesions that can affect the trigeminal nerve include infarction, hemorrhage, vascular lesions (such as compressing vascular loops, aneurysms, and


Cranial Neuropathy

Cranial Neuropathy. vertebrobasilar dolichoectasia), inflammatory and infectious conditions (such as meningitis, encephalitis, sarcoidosis, and demyelinating disease), and tumors (such as gliomas, lymphomas, and metastases) [59]. Tumors, vascular lesions, and inflammatory processes may also affect the cisternal, dural cave, cavernous, foraminal, and extracranial branches of the nerve as they traverse the Meckel cave, the pterygopalatine fossa, the orbit, the skull base, and the masticator space [59,62,63]. Perineural spread of tumor, discussed in Variant 10, can affect the trigeminal nerve anywhere along its course.


Cranial Neuropathy

Cranial Neuropathy. CT Head CT is a complementary study for evaluating the osseous integrity of the skull base and neural foramina. However, standard coverage with a CT Head is insufficient to evaluate the full extent of the trigeminal nerve divisions in the face. There is no relevant literature to support the use of combined pre- and postcontrast imaging.


Cranial Neuropathy

Cranial Neuropathy. CT Maxillofacial Maxillofacial CT is a complementary study for evaluating the osseous integrity of the skull base and neural foramina, which can be accomplished without IV contrast. CT may be helpful for visualizing perineural fat planes, which can be distorted or obliterated in patients with lesions affecting the trigeminal nerve, although MRI offers improved detection of perineural tumor spread (discussed in Variant 10) compared with CT, which has a sensitivity and specificity of 88% and 89%, respectively [64-66]. CT with IV contrast offers the benefits of vascular and mucosal enhancement and may highlight enhancing lesions. There is no relevant literature to support the use of combined pre- and postcontrast imaging.


Cranial Neuropathy

Cranial Neuropathy. Thin section contrast-enhanced navigation protocol CT is useful for noninvasive treatment planning in patients with known trigeminal neuralgia [67].


Cranial Neuropathy

Cranial Neuropathy. CTA Head There is no relevant literature to support the use of CTA head in the initial evaluation of trigeminal neuropathy.


Cranial Neuropathy

Cranial Neuropathy. In patients with clinical features of trigeminal neuralgia, high-resolution combined MRI, MRA, and CTA may be used to assess for vascular loops compressing the fifth nerve. Anatomic and dedicated vascular imaging play a complementary role. Structural MRI evaluation of the nerve and its relationship to vasculature is more commonly reported in the literature, likely related to the improved soft tissue contrast of MRI compared with CT [23,68-76]. CTA has been used to characterize the relationship of arterial vasculature relative to the fifth nerve in patients with a clinical diagnosis of trigeminal neuralgia but is less commonly used than MRI and MRA because it does not provide simultaneous high-resolution imaging of the trigeminal nerve provided by MRI [77].


Cranial Neuropathy

Cranial Neuropathy. MRA Head There is no relevant literature to support the use of MRA head in the initial evaluation of trigeminal neuropathy. In patients with clinical features of trigeminal neuralgia, MRA is commonly used as a complementary study to high- resolution MRI in assessing for vascular compression of the CN V with sensitivities of combined MRI with MRA ranging from 97% to 100%, specificities reported as 100%, and good to strong agreement found compared with surgical findings [69,71-73,76]. One group reported a lower sensitivity (50% at 3T and 33% at 1.5T) of combined high-resolution MRI with MRA for detection of neurovascular compression of CN V by smaller vessels such as the anterior inferior cerebellar artery [71].


Cranial Neuropathy

Cranial Neuropathy

Cranial Neuropathy. Cranial Neuropathy


Cranial Neuropathy

Cranial Neuropathy. In patients with clinical features of trigeminal neuralgia, 3-D heavily T2-weighted MRI sequences, MRA, and a combination of these techniques are commonly used noninvasive methods for characterizing the anatomy of vascular loops potentially compressing the fifth nerve and correlate well with surgical findings [23,68-76]. Congruence rates of imaging and intraoperative findings for neurovascular contact range from 83% to 100% [68- 70,72,75,78]. Both false-positive and false-negative imaging studies occur when assessing for neurovascular contact in the setting of trigeminal neuralgia; consequently, MRI is supportive rather than diagnostic in selecting candidates for microvascular decompression and should be interpreted in the context of the site of symptoms [69,73-75,78]. Imaging evidence of vascular trigeminal nerve root compression, the degree of compression, location of contact, and nerve volume may have prognostic value [73,77,79-81]. Trigeminal nerve size measurements have been reported as smaller on the symptomatic side in trigeminal neuralgia as measured from thin-cut MRI [82-84]. Preoperative imaging is useful for surgical planning [85].


Cranial Neuropathy

Cranial Neuropathy. Advanced MRI techniques including diffusion tensor imaging (DTI), functional MRI, and voxel-based morphometry are being used to research the pathophysiology of trigeminal neuralgia. DTI metrics suggest microstructural tissue changes in symptomatic nerves in the setting of trigeminal neuralgia compared with asymptomatic nerves and may be useful for making treatment decisions [68,86-93]. Advanced MRI techniques have also detected structural alterations in gray matter and white matter in patients with trigeminal neuralgia [94-97].


Cranial Neuropathy

Cranial Neuropathy. MR neurography is an emerging technique that may be useful in characterizing the etiology of peripheral trigeminal neuropathy [98].


Cranial Neuropathy

Cranial Neuropathy. In patients with clinical features of trigeminal neuralgia, 3-D heavily T2-weighted MRI sequences, MRA, and a combination of these techniques are commonly used noninvasive methods for characterizing the anatomy of vascular loops potentially compressing the cisternal segment of the fifth nerve and correlate well with surgical findings [23,68-76]. Congruence rates of imaging and intraoperative findings for neurovascular contact range from 83% to 100% [68-70,72,75,78]. Both false-positive and false-negative imaging studies occur when assessing for neurovascular contact in the setting of trigeminal neuralgia; consequently, MRI is supportive rather than diagnostic in selecting candidates for microvascular decompression and should be interpreted in the context of the site of symptoms [69,73-75,78]. Imaging evidence of vascular trigeminal nerve root compression, the degree of compression, location of contact, and nerve volume may have prognostic value [73,77,79-81]. Trigeminal nerve size measurements have been reported as smaller on the symptomatic side in trigeminal neuralgia as measured from thin-cut MRI [82-84]. Preoperative imaging is useful for surgical planning [85].


Cranial Neuropathy

Cranial Neuropathy. Advanced MRI techniques including DTI, functional MRI, and voxel-based morphometry are being used to research the pathophysiology of trigeminal neuralgia. DTI metrics suggest microstructural tissue changes in symptomatic nerves in the setting of trigeminal neuralgia compared with asymptomatic nerves and may be useful for making treatment decisions [68,86-93]. Advanced MRI techniques have also detected structural alterations in gray matter and white matter in patients with trigeminal neuralgia [94-97].


Cranial Neuropathy


Cranial Neuropathy

Cranial Neuropathy. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of FDG-PET/CT skull base to mid-thigh in the evaluation of isolated trigeminal mononeuropathy or isolated unilateral trigeminal neuralgia.


Cranial Neuropathy

Cranial Neuropathy. US Neck There is no relevant literature to support the use of US neck in the evaluation of isolated trigeminal mononeuropathy or isolated unilateral trigeminal neuralgia.


Cranial Neuropathy

Cranial Neuropathy. Variant 3: Unilateral isolated weakness of the facial expression, paralysis of the facial expression, hemifacial spasm, or Bell palsy (facial nerve, CN VII). Initial imaging. The facial nerve (CN VII) is one of the most complex CNs and contains branchial motor (innervation to the muscles of facial expression), visceral motor (parasympathetic innervation to most of the glands of the head), general sensory (surface innervations to a small portion of the external ear and tympanic membrane), and special sensory (taste to the anterior two-thirds of the tongue) functions [2,99]. From its nucleus in the pons, the intraparenchymal fascicular or attached segment courses superiorly along the surface of the pons after which it turns anteriorly exiting the brainstem at the pontomedullary sulcus, which is referred to as the root exit point. Its parenchymal fascicular or attached segment courses superiorly along the surface of the pons after which it turns anteriorly, detaching from the pons at the root detachment point [5,100,101]. It then traverses the cerebellopontine angle in its cisternal segment, enters the internal auditory canal within its meatal segment, and courses through the temporal bone (which includes the labyrinthine, tympanic, mastoid segments, and geniculate ganglion). The facial nerve exits the temporal bone at the stylomastoid foramen, and the extracranial segment courses through the parotid gland.


Cranial Neuropathy

Cranial Neuropathy. Peripheral, nuclear, or infranuclear facial nerve paralysis presents as ipsilateral facial paralysis with involvement of the forehead (which is usually spared with a supranuclear facial nerve palsy) and can result from pathology affecting the facial nerve nucleus or any portion of the facial nerve after exiting the brainstem within its intracranial and extracranial segments. Within the pons, the facial nuclei can be affected by intra-axial conditions such as infarction, vascular malformations, tumors, and multiple sclerosis. Brainstem lesions are often accompanied by additional neurologic symptoms that can help localize the lesion clinically [102,103]. Rarely brainstem or cortical infarct can result in an isolated facial nerve palsy [102,103]. As the facial nerve exits the brainstem and courses within the cerebellopontine angle, the internal auditory canal, and through the temporal bone, it may be affected by facial and vestibular schwannomas, meningiomas, vascular lesions, inflammation, cholesteatomas, paragangliomas, epidermoid cysts, trauma, and intrinsic bone tumors. The extracranial facial nerve may be affected by inflammation, parotid tumors, conditions of the neighboring anatomic spaces, and skull base pathology including carcinomas, sarcomas, trauma, and inflammatory disease [99,102]. Perineural spread of a tumor can result in facial nerve palsy and is discussed in Variant 10 [104].


Cranial Neuropathy

Cranial Neuropathy. Facial nerve palsy can present with facial droop, pain around the jaw or ear, hyperacusis, tinnitus, reduced taste, and decreased lacrimation or salivation. Facial paralysis in the form of Bell palsy is the most common cause of acute peripheral facial nerve palsy, attributed to inflammation of the facial nerve, which may be idiopathic or due to herpes simplex virus. Most patients experience complete recovery of function by 6 months, which can be hastened with steroids [102]. In general, Bell palsy patients need not be imaged unless the symptoms are atypical, recurrent, or persist for 2 to 4 months [102].


Cranial Neuropathy

Cranial Neuropathy. Unilateral hyperactivity of the facial nerve can occur, resulting in the spasm of the facial musculature referred to as hemifacial spasm. Hemifacial spasm is most commonly the result of vascular compression of the facial nerve, usually within the centrally (oligodendrocyte) myelinated portion of the nerve [100].


Cranial Neuropathy

Cranial Neuropathy. CT Head There is no relevant literature to support the use of routine CT head alone in the evaluation of unilateral isolated facial nerve palsy.


Cranial Neuropathy

Cranial Neuropathy. CT Temporal Bone High-resolution thin-cut temporal bone CT provides complementary useful information to MRI by characterizing the osseous integrity of the temporal bone through which the facial nerve courses. CT imaging excels at osseous imaging and characterizes well temporal bone fractures, presurgical osseous anatomy, bony facial nerve canal involvement with inflammatory middle ear disease, facial canal foraminal expansion, patterns of bone erosion, and intrinsic bone tumor matrices [2,99,105-108]. High-resolution temporal bone CT with thin sections should be obtained to evaluate the course of CN VII. Contrast may be useful in the setting of infection or when a tumor is suspected. There is no relevant literature to support the use of combined pre- and postcontrast imaging.


Cranial Neuropathy

Cranial Neuropathy. High-resolution noncontrast CT of the temporal bone is useful to characterize temporal bone fractures including fractures through the facial nerve canal, but sensitivity for nondisplaced fracture has been shown to vary with fracture location and is lowest in the mastoid segment [105,108].


Cranial Neuropathy

Cranial Neuropathy. CT Maxillofacial Temporal bone CT (complementary to MRI in patients with facial nerve palsy) is the preferred CT study and typically provides better spatial resolution than maxillofacial CT when assessing the fine detailed anatomy of the temporal bone and bony facial nerve canal. Maxillofacial CT provides better spatial resolution than head CT and, depending on institutional protocols, may provide sufficient spatial resolution to be complementary to MRI to characterize the osseous integrity of the temporal bone and assess the extracranial course of the facial nerve although the nerve itself is not directly imaged with CT [2,99,105-108]. Contrast may be useful when infection or a tumor is suspected. There is no relevant literature to support the use of combined pre- and postcontrast imaging.


Cranial Neuropathy

Cranial Neuropathy. CTA Head There is no relevant literature to support the use of CTA head as an isolated study in the initial evaluation of acute unilateral facial nerve palsy. Rarely brainstem or cortical infarct can result in isolated facial nerve palsy, and if clinically suspected, CTA may be complementary to MRI in this clinical scenario [102,103] to characterize the vasculature.


Cranial Neuropathy

Cranial Neuropathy. CTA is uncommonly reported as a complementary study to thin-cut high-resolution MRI for characterizing the anatomy of vascular loops potentially compressing the centrally myelinated portion of the facial nerve [109].


Cranial Neuropathy

Cranial Neuropathy. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use of FDG-PET/CT skull base to mid-thigh in the evaluation of isolated unilateral facial nerve palsy or hemifacial spasm.


Cranial Neuropathy

Cranial Neuropathy. MRA Head There is no relevant literature to support the use of MRA alone in the initial evaluation of acute unilateral facial nerve palsy. Rarely brainstem or cortical infarct can result in isolated facial nerve palsy, and if clinically suspected, MRA may be complementary to MRI in this clinical scenario [102,103] to characterize the vasculature.


Cranial Neuropathy

Cranial Neuropathy. MRA may be useful in the assessment of hemifacial spasm. In patients with clinical features of hemifacial spasm, MRA can be complementary to 3-D heavily T2-weighted MRI sequences for characterizing the anatomy of vascular loops potentially compressing the centrally myelinated portion of the facial nerve with sensitivity and accuracy reported as >95% and a good correlation with surgical findings [76,109,110].


Cranial Neuropathy

Cranial Neuropathy. Volumetric and 3T imaging have been reported to provide improved visualization of the facial nerve and its surrounding perineural vascular plexus [7,19,111,113].


Cranial Neuropathy

Cranial Neuropathy. In general, Bell palsy patients need not be imaged unless the symptoms are atypical, recurrent, or persist for 2 to 4 months [102]. When imaging is considered, MRI is the method of choice. Variable abnormal enhancement patterns may be seen in the canalicular, labyrinthine, geniculate, tympanic, and mastoid portions of the nerve [106,117-122]. There is a lack of consensus regarding the prognostic value of MRI in Bell palsy [118-121], and MRI is most useful for excluding other causes of facial nerve palsy.


Cranial Neuropathy

Cranial Neuropathy. High-resolution thin-cut contrast-enhanced MRI is an especially useful method to evaluate for perineural spread of a tumor, which can affect CN VII and is discussed in Variant 10. Sensitivities for MRI detection of perineural spread of a tumor range from 73% to 100% and vary according to the nerve evaluated and timing of imaging relative to tissue sampling [65,104,123-125].


Cranial Neuropathy

Cranial Neuropathy. In patients with clinical features of hemifacial spasm, 3-D heavily T2-weighted MRI sequences and MRA are noninvasive methods for characterizing the anatomy of vascular loops potentially compressing the centrally myelinated portion of the facial nerve and correlate well with surgical findings [76,78,100,101,110]. Both false- positive and false-negative imaging studies occur when assessing for neurovascular contact in the setting of hemifacial spasm; consequently MRI is supportive rather than diagnostic in selecting candidates for microvascular


Cranial Neuropathy

Cranial Neuropathy

Cranial Neuropathy. Cranial Neuropathy


Cranial Neuropathy

Cranial Neuropathy. decompression [78,100]. In patients with failed initial microvascular decompression surgery, heavily T2-weighted MRI may be helpful to delineate the cause [101].


Cranial Neuropathy

Cranial Neuropathy. DTI is an advanced imaging technique that may be useful in assessing the facial nerve. Several studies suggest that DTI is accurate for the preoperative localization of the cisternal facial nerve to avoid iatrogenic injury in patients with cerebellopontine angle tumors [107,126-128]. Research indicates that DTI may have future use localizing the intraparotid facial nerve and detecting perineural spread of a tumor [129,130].


Cranial Neuropathy


Cranial Neuropathy

Cranial Neuropathy. In general, Bell palsy patients do not need to be imaged unless the symptoms are atypical, recurrent, or persistent for 2 to 4 months [102]. When imaging is considered, MRI is the method of choice. Variable abnormal enhancement patterns may be seen in the canalicular, labyrinthine, geniculate, tympanic, and mastoid portions of the nerve [106,117-122]. There is a lack of consensus regarding the prognostic value of MRI in Bell palsy [118-121], and MRI is most useful for excluding other causes of facial nerve palsy.


Cranial Neuropathy

Cranial Neuropathy. In patients with clinical features of hemifacial spasm, 3-D heavily T2-weighted MRI sequences and MRA are noninvasive methods for characterizing the anatomy of vascular loops potentially compressing the centrally myelinated portion of the facial nerve and correlate well with surgical findings [76,78,100,101,110]. Both false- positive and false-negative imaging studies occur when assessing for neurovascular contact in the setting of hemifacial spasm; consequently MRI is supportive rather than diagnostic in selecting candidates for microvascular decompression [78,100]. In patients with failed initial microvascular decompression surgery, heavily T2-weighted MRI may be helpful to delineate the cause [101].


Cranial Neuropathy

Cranial Neuropathy. DTI is an advanced imaging technique that may be useful in assessing the facial nerve. Several studies suggest that DTI is accurate for the preoperative localization of the cisternal facial nerve to avoid iatrogenic injury in patients with cerebellopontine angle tumors [107,126-128]. Research indicates that DTI may have future use localizing the intraparotid facial nerve and detecting perineural spread of tumor [129,130].


Cranial Neuropathy

Cranial Neuropathy. US Neck There is no relevant literature to support the use of US neck in the evaluation of isolated unilateral facial nerve palsy or hemifacial spasm.


Cranial Neuropathy

Cranial Neuropathy. Variant 4: Multiple different middle cranial nerve palsies (CN V-VII). Initial imaging. Multiple CN nuclei are closely approximated within the brainstem, from which motor fibers originate and sensory fibers terminate. A small single brainstem lesion can produce severe and mixed neurologic deficits, including multiple cranial neuropathies, often times with some component of cerebellar, motor, or somatosensory deficit helping in clinically localizing the lesion. The pons connects the midbrain to the medulla. The dorsal pontine tegmentum contains white matter tracts and CN V through CN VIII nuclei, and the ventral pons contains corticospinal, corticobulbar, and corticopontine tracts [1,131]. After exiting the pons, the first and second divisions of the trigeminal nerve course along the lateral wall of the cavernous sinus, the abducens nerve courses through the cavernous sinus, and CNs VII and VIII extend through the cerebellopontine angle toward the porus acusticus. The third division of the trigeminal exits the skull base via foramen ovale.


Cranial Neuropathy

Cranial Neuropathy. Pontine lesions can affect CNs V, VI, VII, and/or VIII. Ischemic and hemorrhagic infarcts are the most frequent cause of acute brainstem syndromes with the pons most frequently affected [1,132]. Nonischemic lesions affecting


Cranial Neuropathy

Cranial Neuropathy. the brainstem include trauma, demyelinating disease, encephalitis, neoplasms, central pontine myelinolysis, neurodegenerative disorders, and syringobulbia [18,131,132]. Pontine syndromes causing variable involvement of CNs V-VIII, along with other neurologic deficits, include Millard-Gubler syndrome, Foville syndrome, locked-in syndrome, and facial colliculus syndrome [131].


Cranial Neuropathy

Cranial Neuropathy. The internal carotid artery with its surrounding sympathetic plexus and the abducens nerve extend through the center of the cavernous sinus, and the oculomotor, trochlear, and trigeminal nerves (1st and 2nd division) extend along the lateral wall of the cavernous sinus. Cavernous sinus lesions can result in isolated or multiple cranial neuropathies including involvement of the abducens and trigeminal nerves. Tumors, vascular lesions, infection, and inflammatory disorders can lead to cavernous sinus syndrome [18].


Cranial Neuropathy

Cranial Neuropathy. The cerebellopontine angle spans a craniocaudal extent that encompasses the cisternal portions of CNs V-X and is most frequently affected by benign tumors. Sensorineural hearing loss and tinnitus are the most common symptoms but can be accompanied by neuropathies of CNs V, VI, VII, IX, and X with larger tumors [18]. The combination of ipsilateral CN V and CN VII palsies raises concern for perineural spread of tumor, which is discussed in Variant 10. Additionally, leptomeningeal processes can lead to variable patterns of cranial neuropathy [18,132].


Cranial Neuropathy

Cranial Neuropathy. CT Maxillofacial There is no relevant literature to support the use of maxillofacial CT in the initial evaluation of multiple middle CN palsies. Depending on institutional protocols used for high-resolution skull base imaging, maxillofacial CT may be complementary to an MRI exam if a skull base lesion is found to be the cause of multiple middle CN palsies and can be useful to characterize the osseous integrity of the skull base, intratumoral calcification, and skull base foramina [134]. Contrast should be administered. Noncontrast CT may also be an alternate option when used as complementary to the MRI. There is no relevant literature to support the use of combined pre- and postcontrast imaging.


Cranial Neuropathy

Cranial Neuropathy. CT Temporal Bone There is no relevant literature to support the use of temporal bone CT in the initial evaluation of multiple middle CN palsies. Depending on institutional protocols used for high-resolution skull base imaging, temporal bone CT may be complementary to contrast-enhanced MRI if a skull base lesion is found to be the cause of multiple middle CN palsies and can be useful to characterize the osseous integrity of the base, intratumoral calcification, and skull base foramina [134]. Contrast should be administered. Noncontrast CT may also be an alternate option when used as complementary to the MRI. There is no relevant literature to support the use of combined pre- and postcontrast imaging.


Cranial Neuropathy

Cranial Neuropathy. CT Neck There is no relevant literature to support routine use of neck CT in the initial evaluation of multiple middle cranial palsies. If perineural tumor spread (discussed in Variant 10) is suspected based on clinical features, most notably involving both CNs V and VII, neck CT is complementary to MRI for characterizing osseous changes of skull base neural foramina and may be useful to characterize perineural fat and stage the neck [64,66]. Contrast should be administered if possible. There is no relevant literature to support the use of combined pre- and postcontrast imaging.


Cranial Neuropathy

Cranial Neuropathy. CTA Head There is no relevant literature to support routine use of CTA head in the initial evaluation of multiple middle cranial palsies. Ischemic and hemorrhagic infarcts are the most frequent cause of acute brainstem syndromes, which can result in multiple middle CN palsies [131,132,135]. CTA may be complementary to brain MRI or head CT to characterize the vasculature in these clinical scenarios.


Cranial Neuropathy

Cranial Neuropathy

Cranial Neuropathy. Cranial Neuropathy


Cranial Neuropathy

Cranial Neuropathy. FDG-PET/CT Skull Base to Mid-Thigh There is no relevant literature to support the use FDG-PET/CT skull base to mid-thigh in the initial evaluation of multiple middle cranial palsies.


Cranial Neuropathy

Cranial Neuropathy. MRA Head There is no relevant literature to support routine use of MRA head in the initial evaluation of multiple middle cranial palsies. Ischemic and hemorrhagic infarcts are the most frequent cause of acute brainstem syndromes, which can result in multiple middle CN palsies [131,132,135]. MRA may be complementary to MRI brain to characterize the vasculature in these clinical scenarios.