Category: Developmental Malformations

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The value of multimodality intraoperative neurophysiological monitoring in treating pediatric Chiari malformation type I

CMI

Acta Neurochir (2016) 158:335–340

Chiari malformation type I is defined as a descent of cerebellar tonsils below the level of the foramen magnum. The traditional treatment for symptomatic patients is foramen magnum decompression (FMD) surgery. Intraoperative neurophysiological monitoring (INM) is an established surgical adjunct, which is proposed to reduce the potential risk of various surgical procedures. Though INM has been suggested as being helpful in patient positioning and in determining the optimal surgical extent of FMD (i.e., duroplasty, laminectomy, tonsillectomy), its shortcomings include prolongation of anesthesia and surgery as well as monetary costs. Multimodality INM including transcranial-electric motor evoked potential (TcMEP) is not routinely employed in most practices. This study evaluates efficacy of multimodality INM during FMD.

Methods This work is a retrospective analysis of prospectively collected data. Twenty-two FMD surgeries in 21 pediatric patients (aged 1–18 years) were performed at our center utilizing multimodality INM. All patients presented Chiari malformation type I, 18 of which had presented with syringomyelia, underwent posterior fossa decompression (FMD+ C1 laminectomy), accompanied in some with additional cervical laminectomies, duroplasty, and partial tonsillectomies. TcMEP and somatosensory evoked potentials (SSEP) were monitored throughout the procedure including before and after positioning. INM alarms were correlated with perioperative and long-term patient outcomes.

Results INM data remained stable during 19 operations. Three cases displayed significant attenuation in the monitoring signals, all concomitant with patient positioning on the surgical table. One case showed attenuation in SSEP data only, which remained attenuated following repositioning. Another displayed altered TcMEP concomitant with positioning which partially stabilized following repositioning and resolved following bony decompression. The third case showed unilateral attenuation of both TcMEP and SSEP data, which did not rectify until closure. In each of these three cases, no new neurological deficits were observed post operatively.

Conclusions Multimodality INM can be useful in FMD surgery, particularly during patient positioning. TcMEP attenuations may occur independent of SSEPs. The clinical implications of these monitoring alerts have yet to be defined. There is a need to establish an optimal, cost-effective monitoring protocol for FMD.

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Pineal cyst resection in the absence of ventriculomegaly or Parinaud’s syndrome

Pineal cyst resection in the absence of ventriculomegaly or Parinaud’s syndrome

J Neurosurg 123:352–356, 2015

Surgical indications for patients with pineal cysts are controversial. While the majority of patients harboring a pineal cyst require no treatment, surgery is a well-accepted option for a subset of those patients with secondary hydrocephalus or Parinaud’s syndrome. The majority of pineal cysts are identified incidentally during workup for other potential conditions, which may or may not be related to the presence of the cyst. In the absence of clear obstruction of CSF pathways, the treatment of presumed symptomatic pineal cysts is debatable. To clarify the role of surgery in these borderline cases, the authors reviewed their experience with resection of pineal cysts in the absence of ventriculomegaly or Parinaud’s syndrome.

Methods The authors retrospectively reviewed medical records and imaging of all patients surgically treated between 2001 and 2014 with a pineal cyst in the absence of ventriculomegaly and Parinaud’s syndrome. The presenting symptoms, preoperative cyst size, preoperative radiographic aqueductal compression, extent of resection, and radiographic and clinical follow-up were documented.

Results Eighteen patients (14 female and 4 male; mean age 24 years, range 4–47 years) underwent cyst resection in the absence of ventriculomegaly or Parinaud’s syndrome. Presenting symptoms included headache (17 patients), visual disturbances (10 patients), gait instability (5 patients), dizziness (5 patients), episodic loss of consciousness (2 patients), and hypersomnolence (1 patient). The mean preoperative cyst diameter was 1.5 cm (range 0.9–2.2 cm). All patients had a complete resection. At a mean clinical follow-up of 19.1 months (range postoperative to 71 months), 17 (94%) patients had resolution or improvement of their presenting symptoms.

Conclusions: The authors’ results suggest that ventriculomegaly and Parinaud’s syndrome are not absolute requisites for a pineal cyst to be symptomatic. Analogous to colloid cysts of the third ventricle, intermittent occlusion of cerebrospinal fluid pathways may cause small pineal cysts to become intermittently symptomatic. A select cohort of patients with pineal cysts may benefit from surgery despite a lack of hydrocephalus or other obvious compressive pathology.

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Imaging-Based Features of Headaches in Chiari Malformation Type I

Imaging-Based Features of Headaches in Chiari Malformation Type I

Neurosurgery 77:96–103, 2015

Suboccipital cough-induced headaches are considered a hallmark symptom of Chiari malformation type I (CMI). However, non–Valsalva-related suboccipital headaches and headaches in other locations are also common in CMI. The diagnostic significance and the underlying factors associated with these different headaches types are not well understood.

OBJECTIVE: To compare cranial morphology and hydrodynamics in 3 types of headaches in CMI to better understand the pathophysiological basis for the different headache characteristics.

METHODS: Twenty-two cranial physiological and morphological measures were obtained with specialized magnetic resonance imaging scans from 63 symptomatic pretreated CMI patients, 40 with suboccipital headaches induced by Valsalva maneuvers (34 women; age, 36 6 10 years), 15 with non–Valsalva-related suboccipital headaches (10 women; age, 33 6 9 years), 8 with nonsuboccipital non–Valsalva-induced headaches (8 women; age, 39 6 13 years), and 37 control subjects (24 women; age, 36 6 12 years). Group differences were identified with the use of the 2-tailed Student t test. RESULTS: Posterior cranial fossa markers of CMI were similar among the 3 headache subtypes. However, the Valsalva-related suboccipital headaches cohort demonstrated a significantly lower intracranial compliance index than the non–Valsalva-related suboccipital headaches cohort (7.5 6 3.4 vs 10.9 6 4.9), lower intracranial volume change during the cardiac cycle (0.48 6 0.19 vs 0.61 6 0.16 mL), and higher magnetic resonance imaging–derived intracranial pressure (11.1 6 4.3 vs 7.7 6 2.8 mm Hg; P = .02). The Valsalva-related suboccipital headaches cohort had smaller intracranial and lateral ventricular volumes compared with the healthy cohort. The non–Valsalva-related suboccipital headaches cohort had reduced venous drainage through the jugular veins.

CONCLUSION: Valsalva-induced worsening of occipital headaches appears to be related to a small intracranial volume rather than the smaller posterior cranial fossa. This explains the reduced intracranial compliance and corresponding higher pressure measured in CMI patients with headaches affected by Valsalva maneuvers.

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Changes in cerebrospinal fluid flow assessed using intraoperative MRI during posterior fossa decompression for Chiari malformation

Changes in cerebrospinal fluid flow assessed using intraoperative MRI during posterior fossa decompression for Chiari malformation

J Neurosurg 122:1068–1075, 2015

The authors completed a prospective, institutional review board–approved study using intraoperative MRI (iMRI) in patients undergoing posterior fossa decompression (PFD) for Chiari I malformation. The purpose of the study was to examine the utility of iMRI in determining when an adequate decompression had been performed.

Methods Patients with symptomatic Chiari I malformations with imaging findings of obstruction of the CSF space at the foramen magnum, with or without syringomyelia, were considered candidates for surgery. All patients underwent complete T1, T2, and cine MRI studies in the supine position preoperatively as a baseline. After the patient was placed prone with the neck flexed in position for surgery, iMRI was performed. The patient then underwent a bone decompression of the foramen magnum and arch of C-1, and the MRI was repeated. If obstruction was still present, then in a stepwise fashion the patient underwent dural splitting, duraplasty, and coagulation of the tonsils, with an iMRI study performed after each step guiding the decision to proceed further.

Results Eighteen patients underwent PFD for Chiari I malformations between November 2011 and February 2013; 15 prone preincision iMRIs were performed. Fourteen of these patients (93%) demonstrated significant improvement of CSF flow through the foramen magnum dorsal to the tonsils with positioning only. This improvement was so notable that changes in CSF flow as a result of the bone decompression were difficult to discern.

Conclusions The authors observed significant CSF flow changes when simply positioning the patient for surgery. These results put into question intraoperative flow assessments that suggest adequate decompression by PFD, whether by iMRI or intraoperative ultrasound. The use of intraoperative imaging during PFD for Chiari I malformation, whether by ultrasound or iMRI, is limited by CSF flow dynamics across the foramen magnum that change significantly when the patient is positioned for surgery.

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Is atlantoaxial instability the cause of Chiari malformation? Outcome analysis of 65 patients treated by atlantoaxial fixation

Is atlantoaxial instability the cause of Chiari malformation?

J Neurosurg Spine 22:116–127, 2015

Understanding that atlantoaxial instability is the cause of Chiari malformation (CM), the author treated 65 patients using atlantoaxial stabilization. The results are analyzed.

Methods Cases of CM treated using atlantoaxial fixation during the period from January 2010 to November 2013 were reviewed and analyzed. Surgery was aimed at segmental arthrodesis.

Results The author treated 65 patients with CM in the defined study period. Fifty-five patients had associated syringomyelia. Forty-six patients had associated basilar invagination. Thirty-seven patients had both basilar invagination and syringomyelia. Three patients had been treated earlier using foramen magnum decompression and duraplasty. According to the extent of their functional capabilities, patients were divided into 5 clinical grades. On the basis of the type of facetal alignment and atlantoaxial instability, the patients were divided into 3 groups. Type I dislocation (17 patients) was anterior atlantoaxial instability wherein the facet of the atlas was dislocated anterior to the facet of the axis. Type II dislocation (31 patients) was posterior atlantoaxial instability wherein the facet of the atlas was dislocated posterior to the facet of the axis. Type III dislocation (17 patients) was the absence of demonstrable facetal malalignment and was labeled as “central” atlantoaxial dislocation. In 18 patients, dynamic images showed vertical, mobile and at-least partially reducible atlantoaxial dislocation. All patients were treated with atlantoaxial plate and screw fixation using techniques described in 1994 and 2004. Foramen magnum decompression or syrinx manipulation was not performed in any patient. Occipital bone and subaxial spinal elements were not included in the fixation construct. One patient died, and death occurred in the immediate postoperative phase and was related to a vertebral artery injury incurred during the operation. One patient had persistent symptoms. In the rest of the patients there was gratifying clinical improvement. More remarkably, in 7 patients, the symptoms of lower cranial nerve paresis improved. No patient worsened in their neurological function after surgery. Reductions in the size of the syrinx and regression of the CM were observed in 6 of 11 cases in which postoperative MRI was possible. During the follow-up period, there was no delayed worsening of neurological function or symptoms in any patient. Sixty-three patients improved after surgery, and the improvement was sustained during the average follow-up period of 18 months.

Conclusions On the basis of outcomes in this study, it appears that the pathogenesis of CM with or without associated basilar invagination and/or syringomyelia is primarily related to atlantoaxial instability. The data suggest that the surgical treatment in these cases should be directed toward atlantoaxial stabilization and segmental arthrodesis. Except in cases in which there is assimilation of the atlas, inclusion of the occipital bone is neither indicated nor provides optimum stability. Foramen magnum decompression is not necessary and may be counter-effective in the long run.

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Syrinx resolution is correlated with the upward shifting of cerebellar tonsil following posterior fossa decompression in pediatric patients with Chiari malformation type I

Sirinx resolution

Eur Spine J (2015) 24:155–161

Chiari malformation type I (CMI) is characterized by deformed hindbrain. This study aimed to quantitatively evaluate the alterations in position of hindbrain after Posterior fossa decompression (PFD), and to identify the factors associated with syrinx resolution in pediatric patients with CMI.

Methods Eighty-seven patients, aged from 5 to 18 years, who underwent PFD for CMI between September 2006 and September 2012 were retrospectively reviewed. On midsagittal MR images, the position of medulla oblongata and cerebellum was quantitatively evaluated preoperatively and at follow-up. The maximal syrinx/cord (S/C) ratio and syrinx length were also measured. Significant improvement of syrinx was defined as a more than 20 % decrease in maximal S/C ratio or length on follow-up MRI.

Results Neurological deficits were found in 51 of the 87 patients preoperatively and 37 (72.4 %) of them obtained improvement of their symptoms at the last visit. Overall, upward shifting of the tip of cerebellar tonsil was observed in 66 (75.9 %) patients at the last follow-up. Moreover, the mean longitudinal distance of the tip of cerebellar tonsil changed from 16.47 ± 5.00 to 13.89 ± 4.38 mm (P<0.001) at final follow-up. Significant syrinx resolution was noticed in 79 (90.8 %) cases. Pointed cerebellar tonsils were found in 85 (97.7 %) of our patients preoperatively and 78 (91.8 %) of them acquired round cerebellar tonsils after PFD. The improvement of maximal S/C ratio was significantly correlated with upward shifting of the tip of cerebellar tonsil (P = 0.023).

Conclusions Following PFD for CMI, position and morphology of the cerebellar tonsil could revert to normal in most of the pediatric patients, and the upward shifting of the tip of cerebellar tonsil is significantly correlated with syrinx improvement. From this study, PFD without shunting may be effective for syrinx secondary to CMI in pediatric population.

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Joint Indexes for the Craniovertebral Junction

New Indexes for the Craniovertebral Junction

Neurosurgery 10:621–630, 2014

Joint-distraction and intra-operative manipulation surgeries to correct basilar invagination (BI) and atlantoaxial dislocation (AAD) are becoming standard procedures. However, current data are unable to aid in the understanding of normal and abnormal morphology of the C1/C2 joints.

OBJECTIVE: To study various aspects of C1/C2 joint morphology to create normative and patient data on joint abnormalities that could provide the surgeon with objective data for surgical planning and approach.

METHODS: Seventy patients (age, 15-45 years) were compared with an equal number of age- and sex-matched control subjects (age, 21.9±8.2 years) with irreducible BI and AAD from a developmental origin (May 2010-July 2013). Joint anatomy was studied with the use of thin-slice computed tomography scans. The joint parameters studied included sagittal joint inclination, craniocervical tilt, coronal joint inclination, surface area, joint overlap index, and joint reciprocity. The severity of BI and the severity of AAD were compared.

RESULTS: Sagittal joint inclination and craniocervical tilt significantly correlated with both BI and AAD (P , .01). Coronal joint inclination correlated with BI (P = .2). The mean sagittal joint inclination value in control subjects was 87.15±5.65 and in patients with BI and AAD was 127.1±22.05. The mean craniocervical tilt value in controls was 60.2±9.2 and in patients with BI and AAD was 84.0±15.1. The mean coronal joint inclination value in control subjects was 110.3±4.23 and in patients with BI and AAD was 121.15±14.6.

CONCLUSION: This study has demonstrated for the first time the important role of joint orientation and its correlation with the severity of BI and AAD and has described new joint indexes.

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Magnetic Resonance Imaging Measures of Posterior Cranial Fossa Morphology and Cerebrospinal Fluid Physiology in Chiari Malformation Type I

Magnetic Resonance Imaging Measures of Posterior Cranial Fossa Morphology and Cerebrospinal Fluid Physiology in Chiari Malformation Type I

Neurosurgery 75:515–522, 2014

It has been well documented that, along with tonsillar herniation, Chiari Malformation Type I (CMI) is associated with smaller posterior cranial fossa (PCF) and altered cerebrospinal fluid (CSF) flow and tissue motion in the craniocervical junction.

OBJECTIVE: This study assesses the relationship between PCF volumetry and CSF and tissue dynamics toward a combined imaging-based morphological-physiological characterization of CMI. Multivariate analysis is used to identify the subset of parameters that best discriminates CMI from a healthy cohort.

METHODS: Eleven length and volumetric measures of PCF, including crowdedness and 4th ventricle volume, 4 measures of CSF and cord motion in the craniocervical junction, and 5 global intracranial measures, including intracranial compliance and pressure, were measured by magnetic resonance imaging (MRI) in 36 symptomatic CMI subjects (28 female, 37 6 11 years) and 37 control subjects (24 female, 36 6 12 years). The CMI group was further divided based on symptomatology into “typical” and “atypical” subgroups.

RESULTS: Ten of the 20 morphologic and physiologic measures were significantly different between the CMI and the control cohorts. These parameters also had less variability and stronger significance in the typical CMI compared with the atypical. The measures with the most significance were clival and supraocciput lengths, PCF crowdedness, normalized PCF volume, 4th ventricle volume, maximal cord displacement (P , .001), and MR measure of intracranial pressure (P = .007). Multivariate testing identified cord displacement, PCF crowdedness, and normalized PCF as the strongest discriminator subset between CMI and controls. MR measure of intracranial pressure was higher in the typical CMI cohort compared with the atypical.

CONCLUSION: The identified 10 complementing morphological and physiological measures provide a more complete and symptomatology-relevant characterization of CMI than tonsillar herniation alone.

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Posterior C1–C2 screw and rod instrument for reduction and fixation of basilar invagination with atlantoaxial dislocation

Basilar invagination with C1-C2 dislocation surgery

Eur Spine J (2014) 23:1666–1672

To report the surgical technique and preliminary clinical results for the treatment of basilar invagination (BI) with atlantoaxial dislocation (AAD) by posterior C1–C2 pedicle screw and rod instrument.

Methods Between July 2012 and August 2013, 33 patients who had BI with AAD underwent surgery at our institution. Pre and postoperative three-dimensional computed tomographic (CT) scans were performed to assess the degree of dislocation. Magnetic resonance (MR) imaging was used to evaluate the compression of the medulla oblongata. For all patients, reduction of the AAD was conducted by two steps: fastening nuts and rods was performed to achieve the horizontal reduction. Distraction between C1 and C2 screws was performed to obtain the vertical reduction.

Results No neurovascular injury occurred during surgery. Follow-up ranged from 6 to 15 months (mean 10.38 months) in 32 patients. Post-operative three-dimensional CT showed that complete horizontal reduction was obtained in 30/33 (90.9 %), and complete vertical reduction was obtained in 31/33 (93.9 %). The repeated threedimensional CT and MR image demonstrated that bony fusion and the decompression of the medulla oblongata were obtained in all patients. Clinical symptoms improved significantly 3 months after surgery.

Conclusions This C1–C2 pedicle screw and rod instrument is a promising technique for the treatment of BI with AAD.

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Chiari I malformation associated with syringomyelia: can foramen magnum decompression lead to restore cervical alignment?

Chiari I malformation associated with syringomyelia- can foramen magnum decompression lead to restore cervical alignment?

Eur Spine J (2013) 22:2520–2525

There are few researches that demonstrate the relationship between the extent of syringomyelia and sagittal alignment of the cervical spine. The purpose of this study is to investigate the correlation between the change of syrinx size and cervical alignment.

Methods From January 2001 to June 2008, we operated on 207 patients who had syringomyelia. The associated diseases were categorized by Chiari I malformation, tumor, trauma, spinal stenotic lesion, inflammatory disease and idiopathic causes. Thirty patients who had Chiari I malformation associated with syringomyelia and who underwent foramen magnum decompression (FMD), participated in this study. We excluded patients with scoliosis, cervical instrumentation, tumor, trauma, myelomeningocele, hydrocephalus, tethered cord and congenital vertebral anomalies. Lateral radiographs in neutral and magnetic resonance imaging were taken pre- and postoperatively.

Results Mean follow-up was 6.5 ± 1.5 years (ranged from 4.0 to 9.5 years). The mean pre- and postoperative lordosis angles at C2–C7 were −5.9° ± 1.0° and −10.4° ± 1.0°, respectively (P = 0.001). There was significant correlation between the differences of syrinx width and the cervical lordotic angles before and after surgery (P = 0.016). After FMD, syringomyelia and cervical alignment improved in 28 (93.3 %) and 25 (85.18 %) of 30 patients, respectively. There was significant correlation between recovery rate by Japanese Orthopaedic Association scores and the difference of the cervical lordotic angles before and after surgery (P = 0.022).

Conclusions The present results demonstrate that the decrease of syrinx size by FMD may restore the cervical lordosis. We suggest that the postoperative cervical alignment might be a predictive factor for neurological outcome.

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Management of subdural hygromas associated with arachnoid cysts

Subdural hygromas associated with cysts

J Neurosurg Pediatrics 12:434–443, 2013

Arachnoid cysts may occasionally be associated with subdural hygromas. The management of these concurrent findings is controversial.

Methods. The authors reviewed their experience with arachnoid cysts and identified 8 patients with intracranial arachnoid cysts and an associated subdural hygroma. The medical records and images for these patients were also examined.

Results. In total, 8 patients presented with concurrent subdural hygroma and arachnoid cyst. Of these 8 patients, 6 presented with headaches and 4 had nausea and vomiting. Six patients had a history of trauma. One patient was treated surgically at the time of initial presentation, and 7 patients were managed without surgery. All patients experienced complete resolution of their presenting signs and symptoms.

Conclusions. Subdural hygroma may lead to symptomatic presentation for otherwise asymptomatic arachnoid cysts. The natural course of cyst-associated subdural hygromas, even when symptomatic, is generally benign, and symptom resolution can be expected in most cases. The authors suggest that symptomatic hygroma is not an absolute indication for surgical treatment and that expectant management can result in good outcomes in many cases.

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De Novo Formation of a Cavernoma in a Thrombosed Developmental Venous Anomaly

Magnetic Resonance Evolution of De Novo Formation of a Cavernoma in a Thrombosed Developmental Venous Anomaly

Neurosurgery 73:E739–E745, 2013

Mechanisms that lead to de novo formations of nonfamilial-type cavernomas are not well understood. One of the interesting hypotheses is the causative relationship between developmental venous anomaly (DVA) and cavernoma formation. We report a unique case in which serial imaging demonstrated the evolution of de novo formation of a cavernoma in association with a thrombosed DVA. A detailed review of the causal hypothesis between a DVA and cavernoma is also provided.

CLINICAL PRESENTATION: We report a 37-year-old female patient in whom a cavernoma-like lesion arose 1 year after the progressive thrombosis of a medullary (or caput medusa) vein of a DVA. The presence of an acute angulation in the draining vein may have prompted an intrinsic outflow restriction. Possible worsening of venous disequilibrium led to subsequent thrombus progression, venous congestion, and occlusion of the vein with venous dilation and signs of stasis on follow-up magnetic resonance imaging. Finally, this developed into a lobulated lesion with salt-and-pepper appearance at the converging region of medullary tributaries, which typified the classic features of a cavernoma.

CONCLUSION: Compared with other published cases of de novo cavernoma formation in relation to a DVA, our case, for the first time, allows us to witness the temporal evolution from a thrombosed DVA to the birth of a cavernoma around it. This supports the hypothesis that the cavernoma can be an acquired disease that arises from a DVA.

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Increased body mass index in CM-I and syringomyelia

Increased body mass index in CM-I and syringomyelia

J Neurosurg 119:1058–1067, 2013

In this paper the authors describe an association between increased body mass index (BMI) and Chiari malformation Type I (CM-I) in adults, as well as its relationship to the development of syringomyelia.

Methods. In the period between January 2004 and December 2011, the senior author reviewed the data for all CM-I patients with or without syringomyelia and neurological deficit. Analyzed factors included clinical status (headaches and neurological signs), radiological characteristics of syringomyelia (diameter and vertical extent of syrinx), BMI, and relationship of age to BMI, syrinx diameter, and vertical extent of syrinx.

Results. Sixty consecutive adults had CM-I, 26 of whom also had syringomyelia. The mean BMI among all patients was 30.35 ± 7.65, which is Class I obesity (WHO), and was similar among patients with or without syringomyelia. Extension of the vertical syrinx was greater in overweight patients (p = 0.027) than in those with a normal body weight. Evidence of de novo syrinx formation was found in 2 patients who gained an average BMI of 10.8 points. After repeated decompression and no change in holocord syrinx width or vertical extent, a reduction in the syrinx was seen after BMI decreased 11.7 points in one individual. No correlation was found between patient age and BMI, age and vertical extension of the syrinx, and age and diameter of the syrinx.

Conclusions. An association between increased BMI and CM-I in adults was recognized. Gaining weight may influence the de novo creation of a syrinx in adults who previously had minimally symptomatic or asymptomatic CM-I, and reducing weight can improve a syrinx after unsuccessful surgical decompression. Therefore, a reduction in body weight should be recommended for all overweight and obese patients with CM-I.

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Outcome After Suboccipital Decompression for Chiari Malformation I in Adults

Assessment_of_1_Year_Outcomes_and

Neurosurgery 73:569–581, 2013

To date, there has been no study to comprehensively assess the effectiveness of suboccipital craniectomy (SOC) for Chiari malformation I (CMI) using validated patient-reported outcome measures.

OBJECTIVE: To determine the effectiveness and minimum clinically important difference thresholds of SOC for the treatment of adult patients with CMI using patientreported outcome metrics.

METHODS: Fifty patients undergoing first-time SOC and C1 laminectomy for CMI at a single institution were followed up for 1 year. Baseline and 1-year postoperative pain, disability, quality of life, patient satisfaction, and return to work were assessed. Minimum clinically important difference thresholds were calculated with 2 anchors: the Health Transition Index and North American Spine Society satisfaction questionnaire.

RESULTS: The severity of headaches improved in 37 patients (74%). Improvement in syrinx size was seen in 12 patients (63%) and myelopathy in 12 patients (60%). All patientreported outcomes showed significant improvement 1 year postoperatively (P,.05). Of the 38 patients (76%) employed preoperatively, 29 (76%) returned to work postoperatively at a median time of 6 weeks (interquartile range, 4-12 weeks). Minimum clinically important difference thresholds after SOC for CMI were 4.4 points for numeric rating scale for headache, 0.7 points for numeric rating scale for neck pain, 13.8 percentage points for Headache Disability Index, 14.2 percentage points for Neck Disability Index, 7.0 points for Short Form-12 Physical Component Summary, 6.1 points for Short Form-12 Mental Component Summary, 4.5 points for Zung depression, 1.7 points for modified Japanese Orthopaedic Association, and 0.34 quality-adjusted life-years for Euro-Qol-5D.

CONCLUSION: Surgical management of CMI in adults via SOC provides significant and sustained improvement in pain, disability, general health, and quality of life as assessed by patient-reported outcomes. This patient-centered assessment suggests that suboccipital decompression for CMI in adults is an effective treatment strategy.

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Distribution of cerebellar tonsil position: implications for understanding Chiari malformation

Cerebellar tonsil position

J Neurosurg 119:812–819, 2013

Prior attempts to define normal cerebellar tonsil position have been limited by small numbers of patients precluding analysis of normal distribution by age group. The authors’ objective in the present study was to analyze cerebellar tonsil location in every age range.

Methods. Two thousand four hundred patients were randomly selected from a database of 62,533 consecutive patients undergoing MRI and were organized into 8 age groups. Magnetic resonance images were directly examined for tonsil location, morphology, and other features. Patients with a history or imaging findings of posterior fossa abnormalities unrelated to Chiari malformation (CM) were excluded from analysis. The caudal extent of the cerebellar tonsils was measured at the midsagittal and lowest parasagittal positions.

Results. The mean tonsil height decreased slightly with advancing age into young adulthood and increased with advancing age in the adult age range. An increasing age in the adult age range was associated with a decreased likelihood of a tonsil position 5 mm or more below the foramen magnum (p = 0.0004). In general, the lowest tonsil position in each age group was normally distributed. Patients with pegged morphology were more likely to have a tonsil location at least 5 mm below the foramen magnum (85%), as compared with those having intermediate (38%) or rounded (2%) morphology (p < 0.0001). Female sex was associated with a lower mean tonsil position (p < 0.0001). Patients with a lower tonsil position also tended to have an asymmetrical tonsil position, usually lower on the right (p < 0.0001).

Conclusions. Cerebellar tonsil position follows an essentially normal distribution and varies significantly by age. This finding has implications for advancing our understanding of CM.

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Dura Splitting Decompression for Chiari I Malformation in Pediatric Patients

Dura_Splitting_Decompression_for_Chiari_I

Neurosurgery 72:922–929, 2013

Dural splitting decompression may be an effective and safe treatment for Chiari I malformation.

OBJECTIVE: To compare clinical outcomes, complications, and resource utilization for patients undergoing Chiari I decompression with or without duraplasty.

METHODS: Between 2000 and 2009, the senior author performed 113 Chiari I decompression operations with dural splitting or duraplasty in children less than 18 years of age; 110 were included in a retrospective cohort analysis of safety, efficacy, and treatment cost. Patients without significant syringomyelia underwent dural splitting decompression, and patients with syringomyelia underwent duraplasty.

RESULTS: Sixty-three patients without significant syringomyelia (57%) underwent dural splitting decompression. They were significantly younger than patients undergoing duraplasty (8.3 ± 4.9 years vs 10.4 ± 4.4 years; P < .05). Headaches improved or resolved in most patients in both groups (90.5% vs 93.6%; P = .59). Dysphagia, long tract signs, cranial nerve, and bulbar symptoms also improved similarly in both groups. Three duraplasty patients were treated medically for aseptic meningitis; one underwent reoperation for a symptomatic pseudomeningocele. No patient undergoing dural splitting decompression experienced a cerebrospinal fluid-related complication. Extradural decompression required less operative time than duraplasty (105.5 vs 168.9 minutes, P < .001), a shorter length of stay (2.4 vs 2.8 days, P = .011), and lower total cost for the primary hospitalization ($26 837 vs $29 862, P = .015).

CONCLUSION: In this retrospective cohort study, dural splitting decompression was equally effective, safer, and lower cost for treatment of Chiari I malformation without syringomyelia. A multicenter trial with groups balanced for the presence of syringomyelia is necessary to determine whether these results are generalizable.

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Risk Factors for Pediatric Arachnoid Cyst Rupture/Hemorrhage: A Case-Control Study

Risk_Factors_for_Pediatric_Arachnoid_Cyst

As the availability of imaging modalities has increased, the finding of arachnoid cysts has become common. Accurate patient counseling regarding physical activity or risk factors for cyst rupture or hemorrhage has been hampered by the lack of definitive association studies.

OBJECTIVE: This case-control study evaluated factors that are associated with arachnoid cyst rupture (intracystic hemorrhage, adjacent subdural hematoma, or adjacent subdural hygroma) in pediatric patients with previously asymptomatic arachnoid cysts.

METHODS: Patients with arachnoid cysts and intracystic hemorrhage, adjacent subdural hygroma, or adjacent subdural hematoma treated at a single institution from 2005 to 2010 were retrospectively identified. Two unruptured/nonhemorrhagic controls were matched to each case based on patient age, sex, anatomical cyst location, and side. Risk factors evaluated included arachnoid cyst size, recent history of head trauma, and altitude at residence.

RESULTS: The proportion of imaged arachnoid cysts that presented either originally or subsequently with a rupture or hemorrhage was 6.0%. Larger cyst size, as defined by maximal cyst diameter, was significantly associated with cyst rupture/hemorrhage (P < .001). When dichotomized with a 5-cm cutoff, 9/13 larger cysts ruptured and/or hemorrhaged, whereas only 5/29 smaller cysts ruptured/hemorrhaged (odds ratio = 16.5 (confidence interval [2.5, N]). A recent history of head trauma was also significantly associated with the outcome (P < .001; odds ratio = 25.1 (confidence interval [4.0, N]). Altitude was not associated with arachnoid cyst rupture or hemorrhage.

CONCLUSION: This case-control study suggests that larger arachnoid cyst size and recent head trauma are risk factors for symptomatic arachnoid cyst rupture/hemorrhage.

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Diastematomyelia: A 35-Year Experience

Dyastematomyelia

SPINE Volume 38, Number 6, pp E344–E349

Diastematomyelia is a rare entity, which presents distinct clinical characteristics and requires different managements compared with other more common occult spinal dysraphism.

Methods. A total of 156 patients with diastematomyelia were reviewed. All the patients underwent neurological and radiological examinations. Surgical excision of the lesion was performed for most patients and intradural exploration of the lumbar region was done to release tethering of conus in some patients. One patient died and autopsy was performed. Follow-up was carried out for all the patients, including surgical and nonsurgical approaches.

Results. There were 123 cases of type I diastematomyelia and 33 cases of type II diastematomyelia. The lumbar and thoracolumbar region was the most common site for diastematomyelia, and most spinal cords were split among 6 segments. The postoperative course was complicated by cerebrospinal fl uid leakage in 2 patients, temporary neurological deterioration in 4 patients, and epidural hematoma in 1 patient. All cases did not have aggravation of symptoms during the follow-up of 2 to 20 years (mean of 4.5 yr). For the 123 patients with type I diastematomyelia, clinical symptoms were improved in 96 after surgical intervention and no worsening or occurrence of new clinical signs were observed during the follow-up. Those who did not receive surgery showed stabilization of neurological manifestation. Of the 33 type II cases, 9 surgical patients remained neurologically stable during the postoperative years without signifi cant improvement in function, and 24 nonsurgical patients neither improved nor worsened in their neural defi cit.

Conclusion. Surgical treatment is the necessary management for type I diastematomyelia causing progressive neurological deterioration or with tethered fi lum, whereas conservative treatment is recommended to asymptomatic type I diastematomyelia and all type II diastematomyelia.

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Normalization of hindbrain morphology after decompression of Chiari malformation Type I

J Neurosurg 117:942–946, 2012

Chiari malformation Type I (CM-I) is characterized by hindbrain deformity. We investigated the effects of craniocervical decompression surgery on the anatomical features of hindbrain deformity with a prospective MRI study of patients with CM-I.

Methods. A prospective longitudinal study was conducted in 48 patients with CM-I (39 with syringomyelia) treated with craniocervical decompression. Clinical examinations and cervical MRI were performed before surgery and 1 week, 3–6 months, and annually after surgery. Hindbrain deformity was defined by tonsillar ectopia, pointed cerebellar tonsils, and/or cervicomedullary protuberance. The length of the clivus, basiocciput (sphenooccipital synchondrosis to basion), supraocciput (internal occipital protuberance to opisthion), and anteroposterior (AP) width of CSF pathways at the foramen magnum were measured and compared with those from 18 healthy volunteers (control group).

Results. Before surgery, the patients’ posterior fossa bones were short and their CSF pathways were narrow. All patients had tonsillar ectopia (mean [± SD] 12.3 ± 5.1 mm; normal 0.3 ± 1.0). The majority of patients had pointed tonsils and more than two-thirds exhibited a cervicomedullary protuberance. Clivus and basiocciput lengths were significantly shorter than the values obtained in the control group. However, the supraocciput length did not differ significantly from control measurements. The mean bulbopontine sulcus distance superior to the basion was 9.5 ± 2.6 mm (vs 13.6 ± 2.8 mm in controls; p < 0.0001). The AP widths of the CSF pathways at the level of the foramen magnum were significantly narrowed. After surgery, CSF pathways significantly expanded both ventrally and dorsally. By 3–6 months after surgery, pointed tonsils became round, cervicomedullary protuberance disappeared, and tonsillar ectopia diminished by 51% (to 6.0 ± 3.3 mm; p < 0.0001).

Conclusions. The cerebellar tonsils and brainstem assumed a normal appearance within 6 months after craniocervical decompression. These findings support the concept that the CM-I is not a congenital malformation of the neural elements but rather an acquired malformation that arises from pulsatile impaction of the cerebellar tonsils into the foramen magnum.

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Surgical Treatment of Chiari I Malformation

Neurosurgery 71:365–380, 2012 DOI: 10.1227/NEU.0b013e31825c3426

Foramen magnum decompression is widely accepted as the treatment of choice for Chiari I malformation. However, important surgical details of the procedure are controversial.

OBJECTIVE: This study analyzes 371 decompressions focusing on intraoperative findings, analysis of complications, and long-term outcomes.

METHODS: Among 644 patients between 1985 and 2010, 359 patients underwent 371 decompressions. Surgery for symptomatic patients consisted of suboccipital craniectomy, C1 laminectomy, arachnoid dissection, and duraplasty. Short-term results were determined after 3 months; long-term outcomes were evaluated with Kaplan-Meier statistics.

RESULTS: The mean age was 40 ± 16 years; mean follow-up was 49 ± 56 months; 75.8% demonstrated syringomyelia. The complication rate was 21.8% with permanent surgical morbidity of 3.2% and surgical mortality of 1.3%. Of the patients, 73.6% reported improvement after 3 months; 21% were unchanged. Overall, 14.3% demonstrated a neurological deterioration within 5 years and 15.4% within 10 years. The severity of neurological symptoms correlated with the grade of arachnoid pathology. Outcome data correlated with the number of previous decompressions, severity of arachnoid pathology, handling of the arachnoid, type of duraplasty, and surgical experience. Firsttime decompressions with arachnoid dissection and an alloplastic duraplasty resulted in surgical morbidity for 2.0%, a 0.9% mortality rate, postoperative improvement after 3 months for 82%, and neurological recurrence rates of 7% after 5 years and 8.7% after 10 years.

CONCLUSION: Arachnoid pathology in Chiari I malformation has an impact on clinical symptoms and postoperative results. Decompressions with arachnoid dissection and an alloplastic duraplasty performed by surgeons experienced with this pathology offer a favorable long-term prognosis.

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