human
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Objective Many patients with symptomatic Chiari I malformation experience symptom recurrence after surgical decompression . Improved radiographic predictors of outcome are needed to better select patients most likely to benefit from surgical intervention . We examined whether ventral or dorsal cerebrospinal fluid ( CSF ) flow dynamics assessed by cine phase-contrast MRI scans could predict response to posterior fossa decompression for Chiari I malformation . Methods Forty-four consecutive pediatric patients undergoing pre-operative cine phase-contrast MRI followed by posterior fossa decompression for Chiari I malformation were retrospectively review ed . The association of pre-operative ventral or dorsal CSF flow abnormalities at the foramen magnum with symptom-free survival after surgical decompression was assessed via Kaplan – Meier plots and log-rank analysis . Results Mean ± SD age at time of surgery was 8 ± 6 years . Sixteen ( 36 % ) patients demonstrated decreased CSF flow dorsal to the cervico-medullary brainstem alone . Fourteen ( 32 % ) patients demonstrated abnormal CSF flow both ventral and dorsal to the cervico-medullary brainstem . Fourteen ( 32 % ) had normal hindbrain CSF flow . Overall , 13 ( 30 % ) patients experienced some degree of symptom recurrence by last follow-up ( mean of 27 ± 16 months post-operatively ) . Symptom recurrence did not differ as a function of degree of tonsilar ectopia ( p = 0.55 ) . Abnormal CSF flow dorsal to the cervico-medullary brainstem was not associated with symptom recurrence after surgical decompression ( p = 0.10 ) . However , combined pre-operative ventral and dorsal CSF flow abnormality was associated with a significant reduction ( 2.6-fold ) in the risk of post-operative symptom recurrence ( p < 0.05 ) . Only one patient ( 7 % ) with pre-operative ventral and dorsal CSF flow pathology experienced symptom recurrence 3.5 years after surgery versus 12 ( 40 % ) patients without ventral CSF flow pathology . There were otherwise no differences in baseline clinical , radiological , or operative variables between patients with abnormal versus normal ventral CSF flow . Conclusion The presence of decreased CSF flow both ventral and dorsal to the cervico-medullary brainstem was associated with improved response to hindbrain decompression for Chiari I malformation in children . Cine phase-contrast MRI may be a useful tool for surgical risk stratification and identifying patients that may be optimal surgical c and i date s. Combined ventral and dorsal hindbrain CSF flow pathology may better predict response to posterior fossa decompression compared to dorsal CSF flow pathology alone OBJECT There is little information about the long-term effectiveness and complications following decompressive surgery for syringomyelia related to Chiari malformation Type I ( CM-I ) . METHODS Examining long-term clinical and radiological follow-up , the authors studied a mixed retrospective and prospect i ve single-institution cohort of 109 consecutive surgically treated adult patients with syringomyelia and CM-I. All patients underwent a st and ardized surgical protocol : decompression of the craniocervical junction , arachnoid exploration , and shrinkage of the cerebellar tonsils . Factors predicting outcome were investigated . RESULTS The retrospective arm consisted of 41 cases treated between 1990 and 1994 , and the prospect i ve arm comprised 68 patients treated between 1994 and 2001 . The mean overall age was 45.9 years , and 58.8 % of the population was female . The median follow-up period was 12.7 years . The most frequent initial symptoms were pain and sensory and gait disturbances . There was no perioperative death or neurological deterioration . The comprehensive perioperative complication rate was approximately 11 % , with 3 cases ( 2.7 % ) of CSF leakage . Regression analysis showed that the best combination of clinical and radiological outcome predictors was age and duration of symptoms . Clinical follow-up confirmed surgical result stability with clinical improvement of greater than 90 % of the spinal and cranial manifestations over a long-term period . Two patients had radiological recurrences of syringomyelia without clinical signs 85 and 124 months after surgery . CONCLUSIONS Certain clinical predictors of poor clinical and radiological prognosis were identified-namely , age at time of surgery and symptom duration . The results of the study provide additional long-term data that support the effectiveness and safety of relieving CSF block at the craniocervical junction in CM-I-related syringomyelia Background : This study compared the use of two commonly utilized dural closure techniques used in augmentation duraplasty for Chiari malformation I ( CM I ) and evaluated their efficacy and outcome in terms of quality of life assessment s. Methods : This prospect i ve r and omized study compared sutureless ( DuraGen ) and suturable ( Dura-Guard ) techniques in CM I decompression . Clinical parameters , cost analysis , and SF-36 Quality of Life Question naire ( QLQ ) were utilized to assess outcome . Results : Thirty-four patients were enrolled . Average age was 38.7 ± 12.2 years ( mean ± SD ( St and ard Deviation ) ) and 82 % of patients were female . Sixteen patients received DuraGen and 18  Dura-Guard . Age and gender were similar among groups . Postoperative complications did not differ between groups . Operative cost and time were less for DuraGen , whereas hospital stay was less with Dura-Guard , neither was statistically significant . Average QLQ scores at months 1 , 2 , and 3 improved in both groups . Dura-Guard patients showed greater improvement in quality of life at month 2 ( P < 0.05 ) but groups did not differ at final survey . All patient 's physical health ( P < 0.005 ) and function ( P < 0.005 ) were significantly improved . Outcome did not differ between groups and all patients showed significant improvement ( P < 0.05 ) . Conclusion : Both techniques are effective in reaching the goals of decompressive surgery for CM I and did not differ in quality of life at final survey . All patients showed significant improvement in physical function , physical health , and outcome following surgery . With all variables being equal the choice of duraplasty material may be based upon surgeon 's preference OBJECT The choice of surgical technique for decompressive surgery in patients with Chiari I malformation is controversial . Good preliminary postoperative outcomes have been achieved in patients with Chiari I malformation ( without syringomyelia ) after using a dura-splitting technique . The authors evaluated safety , re source use , and early outcome after this surgery in patients without syringomyelia and compared the findings associated with duraplasty in patients with syringomyelia . METHODS A prospect i ve series of 24 patients with Chiari I malformation ( 12 with a syrinx ) underwent decompression of the craniocervical junction ( CCJ ) .  An allograft-augmented duraplasty was performed in patients with syringomyelia . Intraoperative ultrasonography confirmed adequate tonsillar decompression after lysis of the periosteal b and s at the foramen magnum and C-1 arch as well as partial resection of the outer leaf of the dura in patients without syringomyelia . Patients in each group were of similar mean age ( syringomyelia 10.8 years and no syringomyelia 7.6 years old ; p = 0.07 ) and functional status . The mean follow-up period was 15.3 months ( range 3 - 30 months ) . Dura-splitting decompression required significantly less mean operative time ( 99 minutes compared with 169 minutes , respectively ; p < 0.001 ) , total operating room time ( 166 minutes compared with 249 minutes , respectively ; p < 0.001 ) , duration of hospitalization ( 3 days compared with 3.75 days , respectively ; p < 0.05 ) , perioperative charges ( $ 3615 compared with $ 5538 , respectively ; p < 0.001 ) , and overall hospital charges ( $ 7705 compared with $ 9759 , respectively ; p < 0.001 ) than the duraplasty . Mean clinical outcome scores were similar ( syringomyelia 1.53 of 2 ; no syringomyelia 1.67 of 2 ; not statistically significant ) . CONCLUSIONS Dura-splitting CCJ decompression in pediatric patients with Chiari I malformation and without syringomyelia is safe , provides good early clinical results , and significantly reduces re source use . A r and omized controlled trial of dura-splitting decompression in a uniform population of patients with Chiari I malformation is indicated Summary Background . This prospect i ve study , conducted in patients with Chiari I malformation ( C I ) related syringomyelia who underwent posterior decompression and duroplasty  , utilizes radionuclide cisternography in order to study the cerebrospinal fluid ( CSF ) dynamics at the foramen magnum and to predict the clinical outcome following surgery . Methods . 17 consecutive patients of C I with syringomyelia ( but without hydrocephalus or fixed atlanto-axial dislocation ) , underwent a detailed neurological examination and were assigned a clinical disability score based on the modified Klekamp and Samii score . A radionuclide cisternography ( using Tc99m-DTPA ) was performed via the lumbar route and the ascent of the tracer was followed utilizing a gamma camera immediately after injection and then sequentially after 1 , 2 , 4 , 6 and 24 hours . After posterior decompression and duroplasty , the modified Klekamp and Samii score was repeated at follow-up visits ( range : 3 months to one year ) along with radionuclide cisternography at 3 months , and MR imaging at 6 months . Findings . Three patterns of tracer flow were observed : a ) rapid flow ( n=7 ) ; b ) supratentorial subarachnoid delay ( n=7 ) ; and , c ) foramen magnum block ( n=3 ) . The patients having foramen magnum block had the poorest clinical scores on admission . At follow up , there was an improvement in the clinical scores so that the mean scores in all three categories reached nearly the same level . Following posterior decompression , the radionuclide cisternography performed in 10 patients showed a rapid flow of the tracer without any obstruction . The syrinx resolved in 4 of the 11 patients in whom an MRI was done . Interpretation . The patients with C I with syringomyelia may often have a free flow of tracer across the FM . Posterior decompression and duroplasty provides maximum clinical relief in patients with a demonstrable foramen magnum block on radionuclide cisternography while those with a normal flow have less relief . The symptomatology related to brain-stem compression immediately responds to the surgical procedure but the syrinx-induced signs and symptoms of spinal cord dysfunction persist OBJECT Craniocervical decompression for Chiari malformation Type I ( CM-I ) and syringomyelia has been reported to fail in 10%-40 % of patients . The present prospect i ve clinical study was design ed to test the hypothesis that in cases in which syringomyelia persists after surgery , craniocervical decompression relieves neither the physiological block at the foramen magnum nor the mechanism of syringomyelia progression . METHODS The authors prospect ively evaluated and treated 16 patients with CM-I who had persistent syringomyelia despite previous craniocervical decompression .  Testing before surgery included the following : 1 ) clinical examination ; 2 ) evaluation of the anatomy using T1-weighted MR imaging ; 3 ) assessment of the syrinx and CSF velocity and flow using cine phase-contrast MR imaging ; and 4 ) appraisal of the lumbar and cervical subarachnoid pressures at rest , during a Valsalva maneuver , during jugular compression , and following the removal of CSF ( CSF compliance measurement ) . During surgery , ultrasonography was performed to observe the motion of the cerebellar tonsils and syrinx walls ; pressure measurements were obtained from the intracranial and lumbar intrathecal spaces . The surgical procedure involved enlarging the previous craniectomy and performing an expansile duraplasty with autologous pericranium . Three to 6 months after surgery , clinical examination , MR imaging , and CSF pressure recordings were repeated . Clinical examination and MR imaging studies were then repeated annually . RESULTS Before reexploration , patients had a decreased size of the CSF pathways and a partial blockage in CSF transmission at the foramen magnum . Cervical subarachnoid pressure and pulse pressure were abnormally elevated . During surgery , ultrasonographic imaging demonstrated active pulsation of the cerebellar tonsils , with the tonsils descending during cardiac systole and concomitant narrowing of the upper pole of the syrinx . Three months after reoperation , patency of the CSF pathways was restored and pressure transmission was improved . The flow of syrinx fluid and the diameter of the syrinx decreased after surgery in 15 of 16 patients . CONCLUSIONS Persistent blockage of the CSF pathways at the foramen magnum result ed in increased pulsation of the cerebellar tonsils , which acted on a partially enclosed cervical subarachnoid space to create elevated cervical CSF pressure waves , which in turn affected the external surface of the spinal cord to force CSF into the spinal cord through the Virchow-Robin spaces and to propel the syrinx fluid caudally , leading to syrinx progression . A surgical procedure that reestablished the CSF pathways at the foramen magnum reversed this pathophysiological mechanism and resolved syringomyelia . Elucidating the pathophysiology of persistent syring 
    Output:
    
agent
Development , validation , and incorporation of a small number of disease-specific patient-based instruments will improve the quality of research and care of CM-I patients
***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Objective Many patients with symptomatic Chiari I malformation experience symptom recurrence after surgical decompression . Improved radiographic predictors of outcome are needed to better select patients most likely to benefit from surgical intervention . We examined whether ventral or dorsal cerebrospinal fluid ( CSF ) flow dynamics assessed by cine phase-contrast MRI scans could predict response to posterior fossa decompression for Chiari I malformation . Methods Forty-four consecutive pediatric patients undergoing pre-operative cine phase-contrast MRI followed by posterior fossa decompression for Chiari I malformation were retrospectively review ed . The association of pre-operative ventral or dorsal CSF flow abnormalities at the foramen magnum with symptom-free survival after surgical decompression was assessed via Kaplan – Meier plots and log-rank analysis . Results Mean ± SD age at time of surgery was 8 ± 6 years . Sixteen ( 36 % ) patients demonstrated decreased CSF flow dorsal to the cervico-medullary brainstem alone . Fourteen ( 32 % ) patients demonstrated abnormal CSF flow both ventral and dorsal to the cervico-medullary brainstem . Fourteen ( 32 % ) had normal hindbrain CSF flow . Overall , 13 ( 30 % ) patients experienced some degree of symptom recurrence by last follow-up ( mean of 27 ± 16 months post-operatively ) . Symptom recurrence did not differ as a function of degree of tonsilar ectopia ( p = 0.55 ) . Abnormal CSF flow dorsal to the cervico-medullary brainstem was not associated with symptom recurrence after surgical decompression ( p = 0.10 ) . However , combined pre-operative ventral and dorsal CSF flow abnormality was associated with a significant reduction ( 2.6-fold ) in the risk of post-operative symptom recurrence ( p < 0.05 ) . Only one patient ( 7 % ) with pre-operative ventral and dorsal CSF flow pathology experienced symptom recurrence 3.5 years after surgery versus 12 ( 40 % ) patients without ventral CSF flow pathology . There were otherwise no differences in baseline clinical , radiological , or operative variables between patients with abnormal versus normal ventral CSF flow . Conclusion The presence of decreased CSF flow both ventral and dorsal to the cervico-medullary brainstem was associated with improved response to hindbrain decompression for Chiari I malformation in children . Cine phase-contrast MRI may be a useful tool for surgical risk stratification and identifying patients that may be optimal surgical c and i date s. Combined ventral and dorsal hindbrain CSF flow pathology may better predict response to posterior fossa decompression compared to dorsal CSF flow pathology alone OBJECT There is little information about the long-term effectiveness and complications following decompressive surgery for syringomyelia related to Chiari malformation Type I ( CM-I ) . METHODS Examining long-term clinical and radiological follow-up , the authors studied a mixed retrospective and prospect i ve single-institution cohort of 109 consecutive surgically treated adult patients with syringomyelia and CM-I. All patients underwent a st and ardized surgical protocol : decompression of the craniocervical junction , arachnoid exploration , and shrinkage of the cerebellar tonsils . Factors predicting outcome were investigated . RESULTS The retrospective arm consisted of 41 cases treated between 1990 and 1994 , and the prospect i ve arm comprised 68 patients treated between 1994 and 2001 . The mean overall age was 45.9 years , and 58.8 % of the population was female . The median follow-up period was 12.7 years . The most frequent initial symptoms were pain and sensory and gait disturbances . There was no perioperative death or neurological deterioration . The comprehensive perioperative complication rate was approximately 11 % , with 3 cases ( 2.7 % ) of CSF leakage . Regression analysis showed that the best combination of clinical and radiological outcome predictors was age and duration of symptoms . Clinical follow-up confirmed surgical result stability with clinical improvement of greater than 90 % of the spinal and cranial manifestations over a long-term period . Two patients had radiological recurrences of syringomyelia without clinical signs 85 and 124 months after surgery . CONCLUSIONS Certain clinical predictors of poor clinical and radiological prognosis were identified-namely , age at time of surgery and symptom duration . The results of the study provide additional long-term data that support the effectiveness and safety of relieving CSF block at the craniocervical junction in CM-I-related syringomyelia Background : This study compared the use of two commonly utilized dural closure techniques used in augmentation duraplasty for Chiari malformation I ( CM I ) and evaluated their efficacy and outcome in terms of quality of life assessment s. Methods : This prospect i ve r and omized study compared sutureless ( DuraGen ) and suturable ( Dura-Guard ) techniques in CM I decompression . Clinical parameters , cost analysis , and SF-36 Quality of Life Question naire ( QLQ ) were utilized to assess outcome . Results : Thirty-four patients were enrolled . Average age was 38.7 ± 12.2 years ( mean ± SD ( St and ard Deviation ) ) and 82 % of patients were female . Sixteen patients received DuraGen and 18  Dura-Guard . Age and gender were similar among groups . Postoperative complications did not differ between groups . Operative cost and time were less for DuraGen , whereas hospital stay was less with Dura-Guard , neither was statistically significant . Average QLQ scores at months 1 , 2 , and 3 improved in both groups . Dura-Guard patients showed greater improvement in quality of life at month 2 ( P < 0.05 ) but groups did not differ at final survey . All patient 's physical health ( P < 0.005 ) and function ( P < 0.005 ) were significantly improved . Outcome did not differ between groups and all patients showed significant improvement ( P < 0.05 ) . Conclusion : Both techniques are effective in reaching the goals of decompressive surgery for CM I and did not differ in quality of life at final survey . All patients showed significant improvement in physical function , physical health , and outcome following surgery . With all variables being equal the choice of duraplasty material may be based upon surgeon 's preference OBJECT The choice of surgical technique for decompressive surgery in patients with Chiari I malformation is controversial . Good preliminary postoperative outcomes have been achieved in patients with Chiari I malformation ( without syringomyelia ) after using a dura-splitting technique . The authors evaluated safety , re source use , and early outcome after this surgery in patients without syringomyelia and compared the findings associated with duraplasty in patients with syringomyelia . METHODS A prospect i ve series of 24 patients with Chiari I malformation ( 12 with a syrinx ) underwent decompression of the craniocervical junction ( CCJ ) .  An allograft-augmented duraplasty was performed in patients with syringomyelia . Intraoperative ultrasonography confirmed adequate tonsillar decompression after lysis of the periosteal b and s at the foramen magnum and C-1 arch as well as partial resection of the outer leaf of the dura in patients without syringomyelia . Patients in each group were of similar mean age ( syringomyelia 10.8 years and no syringomyelia 7.6 years old ; p = 0.07 ) and functional status . The mean follow-up period was 15.3 months ( range 3 - 30 months ) . Dura-splitting decompression required significantly less mean operative time ( 99 minutes compared with 169 minutes , respectively ; p < 0.001 ) , total operating room time ( 166 minutes compared with 249 minutes , respectively ; p < 0.001 ) , duration of hospitalization ( 3 days compared with 3.75 days , respectively ; p < 0.05 ) , perioperative charges ( $ 3615 compared with $ 5538 , respectively ; p < 0.001 ) , and overall hospital charges ( $ 7705 compared with $ 9759 , respectively ; p < 0.001 ) than the duraplasty . Mean clinical outcome scores were similar ( syringomyelia 1.53 of 2 ; no syringomyelia 1.67 of 2 ; not statistically significant ) . CONCLUSIONS Dura-splitting CCJ decompression in pediatric patients with Chiari I malformation and without syringomyelia is safe , provides good early clinical results , and significantly reduces re source use . A r and omized controlled trial of dura-splitting decompression in a uniform population of patients with Chiari I malformation is indicated Summary Background . This prospect i ve study , conducted in patients with Chiari I malformation ( C I ) related syringomyelia who underwent posterior decompression and duroplasty  , utilizes radionuclide cisternography in order to study the cerebrospinal fluid ( CSF ) dynamics at the foramen magnum and to predict the clinical outcome following surgery . Methods . 17 consecutive patients of C I with syringomyelia ( but without hydrocephalus or fixed atlanto-axial dislocation ) , underwent a detailed neurological examination and were assigned a clinical disability score based on the modified Klekamp and Samii score . A radionuclide cisternography ( using Tc99m-DTPA ) was performed via the lumbar route and the ascent of the tracer was followed utilizing a gamma camera immediately after injection and then sequentially after 1 , 2 , 4 , 6 and 24 hours . After posterior decompression and duroplasty , the modified Klekamp and Samii score was repeated at follow-up visits ( range : 3 months to one year ) along with radionuclide cisternography at 3 months , and MR imaging at 6 months . Findings . Three patterns of tracer flow were observed : a ) rapid flow ( n=7 ) ; b ) supratentorial subarachnoid delay ( n=7 ) ; and , c ) foramen magnum block ( n=3 ) . The patients having foramen magnum block had the poorest clinical scores on admission . At follow up , there was an improvement in the clinical scores so that the mean scores in all three categories reached nearly the same level . Following posterior decompression , the radionuclide cisternography performed in 10 patients showed a rapid flow of the tracer without any obstruction . The syrinx resolved in 4 of the 11 patients in whom an MRI was done . Interpretation . The patients with C I with syringomyelia may often have a free flow of tracer across the FM . Posterior decompression and duroplasty provides maximum clinical relief in patients with a demonstrable foramen magnum block on radionuclide cisternography while those with a normal flow have less relief . The symptomatology related to brain-stem compression immediately responds to the surgical procedure but the syrinx-induced signs and symptoms of spinal cord dysfunction persist OBJECT Craniocervical decompression for Chiari malformation Type I ( CM-I ) and syringomyelia has been reported to fail in 10%-40 % of patients . The present prospect i ve clinical study was design ed to test the hypothesis that in cases in which syringomyelia persists after surgery , craniocervical decompression relieves neither the physiological block at the foramen magnum nor the mechanism of syringomyelia progression . METHODS The authors prospect ively evaluated and treated 16 patients with CM-I who had persistent syringomyelia despite previous craniocervical decompression .  Testing before surgery included the following : 1 ) clinical examination ; 2 ) evaluation of the anatomy using T1-weighted MR imaging ; 3 ) assessment of the syrinx and CSF velocity and flow using cine phase-contrast MR imaging ; and 4 ) appraisal of the lumbar and cervical subarachnoid pressures at rest , during a Valsalva maneuver , during jugular compression , and following the removal of CSF ( CSF compliance measurement ) . During surgery , ultrasonography was performed to observe the motion of the cerebellar tonsils and syrinx walls ; pressure measurements were obtained from the intracranial and lumbar intrathecal spaces . The surgical procedure involved enlarging the previous craniectomy and performing an expansile duraplasty with autologous pericranium . Three to 6 months after surgery , clinical examination , MR imaging , and CSF pressure recordings were repeated . Clinical examination and MR imaging studies were then repeated annually . RESULTS Before reexploration , patients had a decreased size of the CSF pathways and a partial blockage in CSF transmission at the foramen magnum . Cervical subarachnoid pressure and pulse pressure were abnormally elevated . During surgery , ultrasonographic imaging demonstrated active pulsation of the cerebellar tonsils , with the tonsils descending during cardiac systole and concomitant narrowing of the upper pole of the syrinx . Three months after reoperation , patency of the CSF pathways was restored and pressure transmission was improved . The flow of syrinx fluid and the diameter of the syrinx decreased after surgery in 15 of 16 patients . CONCLUSIONS Persistent blockage of the CSF pathways at the foramen magnum result ed in increased pulsation of the cerebellar tonsils , which acted on a partially enclosed cervical subarachnoid space to create elevated cervical CSF pressure waves , which in turn affected the external surface of the spinal cord to force CSF into the spinal cord through the Virchow-Robin spaces and to propel the syrinx fluid caudally , leading to syrinx progression . A surgical procedure that reestablished the CSF pathways at the foramen magnum reversed this pathophysiological mechanism and resolved syringomyelia . Elucidating the pathophysiology of persistent syring 
    Output:
    