Total spine MRI for the preoperative evaluation of adolescent idiopathic scoliosis: Part 2 - spinal cord tumors, dysraphisms, diastematomyelia, and vertebral anomalies.

Adolescent idiopathic scoliosis is a commonly encountered condition often diagnosed on screening examination. Underlying, asymptomatic neural axis abnormalities may be present at the time of diagnosis. At certain institutions, total spine MRI is obtained preoperatively to identify these abnormalities. We provide a framework for the radiologist to follow while interpreting these studies. In part 1, we discuss Arnold Chiari malformations, syringomyelia, and the tethered cord. In part 2, we focus on spinal cord tumors, dysraphisms, to include diastematomyelia, and vertebral anomalies.

The Effect of Posterior Fossa Decompression Surgery on Brainstem and Cervical Spinal Cord Dimensions in Adults with Chiari Malformation Type 1.

OBJECTIVE: Posterior fossa decompression (PFD) surgery creates more space at the skull base, reduces the resistance to the cerebrospinal fluid motion, and alters craniocervical biomechanics. In this paper, we retrospectively examined the changes in neural tissue dimensions following PFD surgery on Chiari malformation type 1 adults. METHODS: Measurements were performed on T2-weighted brain magnetic resonance images acquired before and 4 months after surgery. Measurements were conducted for neural tissue volume and spinal cord/brainstem width at 4 different locations; 2 width measurements were made on the brainstem and 2 on the spinal cord in the midsagittal plane. Cerebellar tonsillar position (CTP) was also measured before and after surgery. RESULTS: Twenty-five adult patients, with a mean age of 38.9 ± 8.8 years, were included in the study. The cervical cord volume increased by an average of 2.3 ± 3.3% (P = 0.002). The width at the pontomedullary junction increased by 2.2 ± 3.5% (P < 0.01), while the width 10 mm caudal to this junction increased by 4.2 ± 3.9% (P < 0.0001). The spinal cord width at the base of second cervical vertebra and third cervical vertebra did not significantly change after surgery. The CTP decreased by 60 ± 37% (P < 0.0001) after surgery, but no correlation was found between CTP change and dimension change. CONCLUSIONS: The brainstem width and cervical cord volume showed a modest increase after PFD surgery, although standard deviations were large. A reduction in compression after PFD surgery may allow for an increase in neural tissue dimension. However, clinical relevance is unclear and should be assessed in future studies with high-resolution imaging.

Exploring the Pathogenesis of Atlanto-Occipital Instability in Chiari Malformation With Type II Basilar Invagination: A Systematic Morphological Study.

BACKGROUND: Our previous study suggested that atlanto-occipital instability (AOI) is common in patients with type II basilar invagination (II-BI). OBJECTIVE: To further understand the pathogenesis of AOI in Chiari malformations (CM) and CM + II-BI through systematic measurements of the bone structure surrounding the craniocervical junction. METHODS: Computed tomography data from 185 adults (80 controls, 63 CM, and 42 CM + II-BI) were collected, and geometric models were established for parameter measurement. Canonical correlation analysis was used to evaluate the morphological and positional relationships of the atlanto-occipital joint (AOJ). RESULTS: Among the 3 groups, the length and height of the condyle and superior portion of the lateral masses of the atlas (C1-LM) were smallest in CM + II-BI cases; the AOJ had the shallowest depth and the lowest curvature in the same group. AOJs were divided into 3 morphological types: type I, the typical ball-and-socket joint, mainly in the control group (100%); type II, the shallower joint, mainly in the CM group (92.9%); and type III, the abnormal flat-tilt joint, mainly in the CM + II-BI group (89.3%). Kinematic computed tomography revealed AOI in all III-AOJs (100%) and some II-AOJs (1.5%) but not in type I-AOJs (0%). Morphological parameters of the superior portion of C1-LM positively correlated with those of C0 and the clivus and significantly correlated with AOI. CONCLUSION: Dysplasia of the condyle and superior portion of C1-LM exists in both CM and II-BI cases yet is more obvious in type II-BI. Unstable movement caused by AOJ deformation is another pathogenic factor in patients with CM + II-BI.

Posterior fossa volume in idiopathic intracranial hypertension: a magnetic resonance imaging-based study.

BACKGROUND: The etiology of idiopathic intracranial hypertension (IIH) is uncertain. Studies suggest the fundamental cause of the Chiari 1 malformation, a congenitally hypoplastic posterior fossa, may explain the genesis of IIH in some patients. PURPOSE: To assess the hypothesis that linear and volumetric measurements of the posterior fossa (PF) can be used as predictors of IIH. MATERIAL AND METHODS: A retrospective analysis of magnetic resonance imaging (MRI) studies on 27 patients with IIH and 14 matched controls was performed. A volumetric sagittal magnetization prepared rapid acquisition gradient echo sequence was used to derive 10 linear cephalometric measurements. Total intracranial and bony posterior fossa volumes (PFVs) were derived by manual segmentation. The ratio of PFV to total intracranial volume was calculated. RESULTS: In total, 41 participants were included, all women. Participants with IIH had higher median body mass index (BMI). No significant differences in linear cephalometric measurements, total intracranial volumes, and PFVs between the groups were identified. Linear measurements were not predictive of volumetric measurements. However, on multivariate logistic regression analysis, the likelihood of IIH decreased significantly per unit increase in relative PFV (odds ratio [OR]=3.66 × 10-50; 95% confidence interval [CI]=1.39 × 10-108 to 1.22 × 10-5; P = 0.04). Conversely, the likelihood of IIH increased per unit BMI increase (OR=1.19; 95% CI=1.04-1.47; P = 0.02). CONCLUSION: MRI-based volumetric measurements imply that PF alterations may be partly responsible for the development of IIH and Chiari 1 malformations. Symptoms of IIH may arise due to an interplay between these and metabolic, hormonal, or other factors.

Diagnostic performance evaluation of adult Chiari malformation type I based on convolutional neural networks.

PURPOSE: This study aimed to evaluate the diagnostic performance of convolutional neural network (CNN) models in Chiari malformation type I (CMI) and to verify whether CNNs can identify the morphological features of the craniocervical junction region between patients with CMI and healthy controls (HCs). To date, numerous indicators based on manual measurements are used for the diagnosis of CMI. However, the corresponding postoperative efficacy and prognostic evaluations have remained inconsistent. From a diagnostic perspective, CNN models may be used to explore the relationship between the clinical features and image morphological parameters. METHODS: This study included a total of 148 patients diagnosed with CMI at our institution and 205 HCs were included. T1-weighted sagittal magnetic resonance imaging (MRI) images were used for the analysis. A total of 220 and 355 slices were acquired from 98 patients with CMI and 155 HCs, respectively, to train and validate the CNN models. In addition, median sagittal images obtained from 50 patients with CMI and 50 HCs were selected to test the models. We applied original cervical MRI images (CI) and images of posterior cranial fossa and craniocervical junction area (CVI) to train the CI- and CVI-based CNN models. Transfer learning and data augmentation were used for model construction and each model was retrained 10 times. RESULTS: Both the CI- and CVI-based CNN models achieved high diagnostic accuracy. In the validation dataset, the models had diagnostic accuracy of 100% and 97% (p = 0.005), sensitivity of 100% and 98% (p = 0.016), and specificity of 100% (p = 0.929), respectively. In the test dataset, the accuracy was 97% and 96% (p = 0.25), sensitivity was 97% and 92% (p = 0.109), and specificity was 100% (p = 0.123), respectively. For patients with cerebellar subungual herniation less than 5 mm, three out of the 10 CVI-based retrained models reached 100% sensitivity. CONCLUSIONS: Our results revealed that the CNN models demonstrated excellent diagnostic performance for CMI. The models had higher sensitivity than the application of cerebellar tonsillar herniation alone and could identify features in the posterior cranial fossa and craniocervical junction area of patients. Our preliminary experiments provided a feasible method for the diagnosis and study of CMI using CNN models. However, further studies are needed to identify the morphologic characteristics of patients with different clinical outcomes, as well as patients who may benefit from surgery.

Rapid progression of acute cervical syringomyelia: A case report of delayed complications following spinal cord injury.

Context: Post-traumatic syringomyelia treatment usually focuses on restoring normal cerebrospinal fluid (CSF) flow. Herein, the first-reported case of delayed post-traumatic syringomyelia associated with an L2 compression fracture 30 years prior to syringomyelia symptoms that rapidly progressed to the brainstem within 5 months, leading to respiratory and circulatory impairments, is summarized. The improvement in symptoms and significant decrease in size of the syringomyelia/syringobulbia achieved in this patient suggest that the initial treatment of choice in such acute cases should be posterior fossa decompression (PFD). Intradural exploration in order to restore the normal CSF flow at the level of trauma can then be planned in a later time.Findings: A retrospective analysis of clinical manifestations and findings obtained from magnetic resonance (MR) imaging, including pre-operative and post-operative follow-up data acquired 6 months later, provided adequate comparisons of the neurological deficits and syrinx size. Interestingly, serial MR images showed that a cervical syrinx acutely progressed to the brainstem within 5 months. PFD and sectioning of the thick veil completely obstructing the foramen of Magendie resulted in partial resolution of the neurological deficits and syringomyelia regression after surgery.Conclusions: To our knowledge, this is the first case report to summarize the delayed complications of a spinal cord injury and acute syringomyelia progression to the brainstem in a short period. The symptoms were relieved by an emergency PFD, chosen due to the rapid progression of symptoms. An atypical treatment strategy is described for extremely rare cases, but with a good short-term prognosis.

Long-term surgical outcome of Chiari type-I malformation-related syringomyelia: an experience of tertiary referral hospital.

OBJECTIVE: Syringomyelia is a common condition seen in patients with Chiari type-I malformation (CM1). The purpose of this retrospective study was to evaluate the long-term clinical and radiological outcomes of posterior fossa decompression with duraplasty (PFDD) with coagulation of tonsillar ectopia in consecutive surgically treated adult patients with CM1-related syringomyelia (CRS). METHODS: Over 9 years' duration (1993-2001), medical charts of diagnosed patient with CM1 at our neurosurgical center were reviewed retrospectively. This study included adult patients with CM1 who had syringomyelia and underwent PFDD with coagulation of tonsillar ectopia surgery. The differences between the pre- and postoperative syrinx/cord ratio (S/C), the syrinx length, and the regression of herniated cerebellar tonsils on coronal and midsagittal MRIs were evaluated. RESULTS: A total of 87 surgical procedures (46 primary operations, 7 ventriculoperitoneal shunts, and 34 additional operations) for CRS were performed on 24 males and 22 females. The mean preoperative S/C was 0.59 ± 0.12. The means of regression in herniated cerebellar tonsils on mid-sagittal and coronal images were 11.8 ± 2.3 mm and 10.2 ± 2.2 mm (p < 0.0001), respectively. 35 (76.1%) patients were discharged after showing signs of recovery or improvement. Different complications occurred in 16 (34.8%) patients. Negative correlations were noticed between postoperative recovery/improvement and the long symptoms' duration, the herniated tonsils' extent, S/C, and the persistence of the herniated tonsils on the coronal images. CONCLUSION: Early diagnosis of patients with CRS can improve surgical outcomes. Due to its efficacy in resolving clinical symptoms and syrinx cavities, PFDD is still an optimal surgical approach for CRS.

Long-term outcomes of surgical management in subtypes of Chiari malformation.

Objective: Chiari malformations (CMs) are a heterogeneous group of disorders defined by anatomic anomalies of the cerebellum, brainstem, and craniovertebral junction (CVJ). The aims of this study are to establish the demographic and clinical features, incidence, surgical procedures, and outcomes in large series of old and new subtypes of CMs.Material and Methods: All patients were evaluated and operated on for CM-0, 1, and 1.5 between 1985 and 2016. The patients were grouped into various subtypes. Demographic data, additional diseases, clinical features, surgical procedures, complications and outcomes were recorded.Results: 191 patients who underwent various surgical procedures were evaluated. Their mean age was 37.21 ± 9.89. We detected 15 cases of CM-0 (7.8%), 121 cases of CM-1 (63.4%), 55 cases of CM-1.5 (28.8%). In total there were 191 cases, and 220 surgical procedures were performed. 29 (13.2%) of all surgical procedure was reoperations and secondary operations. SM Cyst is found to be decreased in 72 (76.5%) patients, unchanged in 14 (14.8%) and increased in 8(8.5%) of 94 patients radiologically. Clinical outcomes are better for 131 (65.8%), same for 31 (16.2%) and worse for 9 (15%).Conclusion: This study with 172 patients is a large series that includes CM-0, 1, and 1.5 subtypes. CM-1.5 also differs for symptom presentation and durations from CM-1. There are more neurological abnormalities in patients with SM. CVD alone are an effective, useful and safe surgical procedure for CM-0, CM-1 and CM-1.5. Surgical procedure, SM existence, and symptom duration have powerful effects on outcomes.

Hypothesis on the pathophysiology of syringomyelia based on analysis of phase-contrast magnetic resonance imaging of Chiari-I malformation patients.

Background: Despite several hypotheses, our understanding of syringomyelia's pathophysiology remains limited. The hypothesis proposed by Oldfield et al. suggests that piston-like movement of the cerebellar tonsils propels the cerebrospinal fluid (CSF) into the syrinx via the spinal perivascular space. However, a significant question remains unanswered: how does the CSF enter and stay in the syrinx, which has a higher pressure than the subarachnoid space. In the current study, we attempted to verify Oldfield's hypothesis using phase-contrast magnetic resonance imaging (MRI) data from patients with syringomyelia. Methods: We analyzed phase-contrast MRI scans of 18 patients with Chiari-I malformation associated with syringomyelia, all of whom underwent foramen magnum decompression, and 21 healthy volunteers. We obtained velocity waveforms for CSF and brain tissue from regions of interest (ROI) set at the various locations. These waveforms were synchronized at the peak timing of downward CSF flow. We compared the preoperative patient data with the control data and also compared the preoperative patient data with the postoperative patient data. Results: The syrinx shrank in 17 (94%) of the patients, and they experienced significant clinical improvement. When comparing pre- and postoperative MRI results, the only significant difference noted was the preoperative elevated velocity of the cerebellar tonsil, which disappeared post-surgery. The CSF velocities in the subarachnoid space were higher in the preoperative patients than in the controls, but they did not significantly differ in the postoperative MRI. The tonsillar velocity in the preoperative MRI was significantly lower than that of the CSF, suggesting that the elevated tonsillar velocity was more of an effect, rather than the cause, of the elevated CSF velocity. Conclusions: Given these findings, a completely new paradigm seems necessary. We, therefore, propose a novel hypothesis: the generative force of syringomyelia may be the direction-selective resistance to CSF flow in the subarachnoid space.

Laparoscopic Double Cholecystectomy in a Pediatric Patient for Gallbladder Duplication : An Unusual Case of Biliary Anatomy.

Gall bladder duplication is a rare congenital anomaly that can be identified clinically during the workup for gall bladder-related symptoms. This anatomic variation can complicate surgery, and yet there are few published reports of this variant causing symptoms in pediatric patients. This is a case of a 17-year-old female with a history of Arnold-Chiari malformation type I, presenting with right upper quadrant pain. Outside computed tomography reported a trilobed gall bladder, while magnetic resonance cholangiopancreatography demonstrated a duplicated gall bladder. Endoscopic resonance cholangiopancreatography (ERCP) showed a rare anatomic variant of duplicated gall bladder with an accessory right hepatic duct branching off the cystic duct. Due to complex anatomy, both indocyanine green and intraoperative cholangiogram (IOC) were utilized for a successful laparoscopic cholecystectomy. Only ERCP and IOC were able to clearly identify the aberrant right hepatic duct. Final pathology confirmed acute and chronic cholecystitis without dysplasia or cholelithiasis. This case highlights a rare anomaly of an aberrant right hepatic duct in the setting of gallbladder duplication in a pediatric patient. We would recommend both ERCP and IOC during the laparoscopic surgical approach as they were the only imaging modalities to identify the patient's correct anatomy, likely due to the size of pediatric biliary structures.

Chiari 1 Formation Redefined-Clinical and Radiographic Observations in 388 Surgically Treated Patients.

OBJECTIVE: The subject of Chiari formation is revisited and redefined. Results of surgical treatment of patients with Chiari formation by atlantoaxial fixation are presented. METHODS: Results were analyzed of 388 patients with Chiari formation surgically treated during 2010 to June 2019. RESULTS: Two hundred and sixty-six patients had syringomyelia. Two hundred and three patients had no craniovertebral bone abnormality and 74 patients had group A and 111 patients had group B basilar invagination. Twenty-nine patients had been earlier treated by foramen magnum decompression surgery with or without duroplasty. Clinical parameters, analysis of video recordings both before and after surgery, and patient self-assessment were included in the analysis of outcome. Immediate postoperative and sustained clinical improvement was observed in 385 patients (99.4%). CONCLUSIONS: Satisfactory clinical outcome in most patients after atlantoaxial fixation and without any manipulation of neural structures, dura, or bone in the region of foramen magnum consolidates the viewpoint that atlantoaxial instability is the nodal point of pathogenesis of Chiari 1 formation. The study suggests that Chiari 1 formation may be a secondary natural neural alteration in the face of atlantoaxial instability. The role of foramen magnum decompression surgery needs to be reassessed.

Severe and progressive neuronal loss in myelomeningocele begins before 16 weeks of pregnancy.

BACKGROUND: Despite undisputable benefits, midtrimester prenatal surgery is not a cure for myelomeningocele (MMC): residual intracranial and motor deficits leading to lifelong handicap question the timing of prenatal surgery. Indeed, the timing and intensity of intrauterine spinal cord injury remains ill defined. OBJECTIVE: We aimed to describe the natural history of neuronal loss in MMC in utero based on postmortem pathology. STUDY DESIGN: Pathology findings were analyzed in 186 cases of myelomeningocele with lesion level between S1 and T1. Using a case-control, cross-sectional design, we investigated the timewise progression and topographic extension of neuronal loss between 13 and 39 weeks. Motor neurons were counted on histology at several spinal levels in 54 isolated MMC meeting quality criteria for cell counting. These were expressed as observed-to-expected ratios, after matching for gestational age and spinal level with 41 controls. RESULTS: Chiari II malformation increased from 30.7% to 91.6% after 16 weeks. The exposed spinal cord displayed early, severe, and progressive neuronal loss: the observed-to-expected count dropped from 17% to ≤2% after 16 weeks. Neuronal loss extended beyond the lesion to the upper levels: in cases <16 weeks, the observed-to-expected motor neuron count was 60% in the adjacent spinal cord, decreasing at a rate of 16% per week. Progressive loss was also found in the upper thoracic cord, but in much smaller proportions. The observed-over-expected ratio of motor neurons was not correlated with the level of myelomeningocele. CONCLUSIONS: Significant neuronal loss is present ≤16 weeks in the exposed cord and progressively extends cranially. Earlier prenatal repair (<16 weeks) could prevent Chiari II malformation in 69.3% of cases, rescue the 17% remaining motor neurons in the exposed cord, and prevent the extension to the upper spinal cord.

Ventrolateral Tonsillar Position Defines Novel Chiari 0.5 Classification.

BACKGROUND: Cervicomedullary compression in young children has been described in the context of Chiari type 1 malformation, with symptoms associated with the extent of tonsillar herniation below McRae line. Historically, Chiari type 1 malformation has been defined by tonsillar herniation of at least 5 mm. However, in certain populations, including very young children, Chiari symptoms may be present without this finding. A new Chiari classification is thus necessary. METHODS: Cases involving patients up to 5 years of age evaluated for possible posterior fossa decompression were retrospectively reviewed. Preoperative symptoms, magnetic resonance imaging findings, surgical management, and short- and long-term outcome and follow-up were recorded. Tonsillar descent and presence of ventral herniation (VH) were recorded. We define VH as the tonsils crossing a line that bisects the caudal medulla at the level of the foramen magnum, thus creating a novel entity, Chiari type 0.5 malformation. Patients with ventrally herniated tonsils were compared with patients exhibiting more typical Chiari morphology. RESULTS: Of 41 cases retrospectively reviewed, 20 met criteria for VH. These differed from cases without VH because of the predominance of medullary symptoms. In the VH cohort, 11 patients underwent surgical decompression with symptom resolution; 9 were initially managed conservatively, but 3 subsequently required surgery. CONCLUSIONS: We define a novel Chiari entity, Chiari type 0.5 malformation, characterized by ventral tonsillar wrapping around the medulla in young children in the absence of classic Chiari type 1 malformation imaging findings. These patients are more likely to present with medullary symptoms than patients without VH. They are also more likely to require surgical decompression and respond favorably to intervention.

Multifocal Gorham-Stout disease associated with Chiari I malformation and recurrent aseptic meningitis: Case report and review of literature.

Gorham-Stout disease is a rare condition of uncertain aetiology characterised by lymphatic proliferation within osseous structures and subsequent massive osteolysis. This report describes the index case of a patient with multifocal Gorham-Stout disease involving the skull base with Chiari I malformation and recurrent aseptic meningitis without fistula. A five-year-old male presented following decompression of a Chiari I malformation with headaches, vomiting, and stiff neck and cerebrospinal fluid pleocytosis without growth of a pathogenic organism. Ongoing symptoms prompted a further three presentations over several months revealing persistent aseptic cerebrospinal fluid monocytic pleocytosis. Further investigation revealed multifocal osseous cystic disease and subsequent bone biopsy suggested Gorham-Stout disease. Suboccipital decompression was not repeated despite craniocervical junction re-stenosis. A literature review demonstrated the extreme rarity of Gorham-Stout disease associated with Chiari I malformation and meningitis. Potential mechanisms of these entities occurring in concert are discussed. Consideration of Gorham-Stout disease as a secondary cause for Chiari I malformation is important amid local bone changes or cerebrospinal fluid leakage prior to pursuing suboccipital decompression considering the poor outcomes reported.

Operative findings and surgical outcomes in patients undergoing Chiari 1 malformation decompression: relationship to the extent of tonsillar ectopia.

BACKGROUND: The diagnosis of Chiari 1 malformation is based on the extent of tonsillar ectopia. OBJECTIVE: To examine the relationship between the extent of tonsillar ectopia and the intra-operative findings and clinical outcome following Chiari decompression surgery. METHODS: Patients were divided into four groups depending on the position of the cerebellar tonsil (T): group 1: 0 < T < 3; group 2: 3 ≤ T ≤ 5; group 3: 5 < T ≤ 10; and group 4: T > 10. Intra-operative observations were recorded with regard to compression of the brain stem by posterior inferior cerebellar artery (pica), neuroma formation along the first cervical (C1), and accessory spinal nerves (XI), and pallor of the cerebellar tonsils. Brain stem auditory evoked potentials, (BAEP), were monitored in each case. One hundred sixty-eight patients accrued between 2009 and 2013 agreed to participate in an outcome study to determine the effectiveness of foramen magnum decompression. Findings across the four groups were compared using one-way ANOVA. Observed differences were further subjected to paired analysis. Intra-group comparisons were made using the paired t test. A P value less than 0.05 was considered statistically significant. RESULTS: There were 98 patients in group 1, 147 patients in group 2, 180 patients in group 3, and 63 patients in group 4. The mean extent of tonsillar ectopia was 0.4, 4.0, 7.1, and 14.3 mm in the four groups respectively. The prevalence of tonsillar pallor was greatest in group 4. Otherwise, there was no difference observed in the operative findings. A reduction of > 0.1 msec in the wave III-wave V latency of the BAEP was noted in all four groups with equal frequency. One hundred ten patients complied with at least 6 months follow-up. There was no difference in the prevalence of symptoms between the four groups at the time of initial evaluation and at 6 weeks and 6 months following surgery. There was a statistically significant reduction in the intensity of individual symptoms 6 months following surgery regardless of the extent of tonsil ectopia. CONCLUSION: Other than the finding of tonsillar pallor, there was no relationship between the extent of tonsillar ectopia and the intraoperative anatomical and physiological observations, nor was there any relationship to the likelihood of symptomatic improvement following surgery. These observations call into question the focus on the extent of tonsillar of ectopia in assessing the patient who presents with symptoms of the Chiari malformation.

Is there a relationship between the extent of tonsillar ectopia and the severity of the clinical Chiari syndrome?

BACKGROUND: Chiari 1 malformation is diagnosed if the cerebellar tonsils extend at least 5 mm below the opisthion-basion line. OBJECTIVE: To examine the correlation of the extent of tonsillar ectopia with the prevalence and severity of the symptoms associated with the Chiari malformation. METHODS: Patients (N = 428) were grouped according to the extent of tonsillar ectopia on the mid-sagittal MRI image (group 1, 0-< 3 mm; group 2, 3-5 mm; group 3, > 5 mm). Groups were compared regarding demographics, symptoms, neurological signs, pain score, and response to HADS and sf-36 questionnaires. Results were analyzed using one-way ANOVA, chi-square, and two sample Z test, and Student's t test for pairwise comparison, (statistical significance p < 0.05). A logistic regression analysis was performed to determine the relationship between tonsillar ectopia and the probability of a patient reporting any particular symptom. RESULTS: There were 97,148 and 183 patients in groups 1, 2, and 3 respectively. Groups did not differ with regard to antecedent trauma or female preponderance. Patients in group 1 were more symptomatic than those in groups 2 and 3 with regard to some symptoms, (p = 0.04-p = 0.000). Regression analysis confirmed an inverse relationship between the extent of tonsillar ectopia and the likelihood of many symptoms. The pain score was greatest in group 1, (p = 0.006). Prevalence of objective signs of myelopathy did not differ between groups except for Hoffmann sign which was more prevalent in group 1, (p = 0.034). HADS and sf-36 scores did not differ between groups. CONCLUSION: The severity of the symptoms associated with the Chiari malformation does not correlate directly with the extent of tonsillar ectopia. The extent of tonsillar ectopia should be re-evaluated as the threshold for diagnosis of Chiari 1 malformation.

Spontaneous Resolution of Syringomyelia with a 16-Year Serial Magnetic Resonance Imaging Follow-Up: A Case Report and Literature Review.

BACKGROUND: The natural course of syringomyelia is unpredictable. Only a few cases of adults with spontaneous resolution of syringomyelia associated with Chiari malformation type I (CM-I) have been reported. The timing of surgical intervention for syringomyelia remains controversial. The present report has documented a case with the longest medical history of syringomyelia reported, the associated imaging findings over 16 years, the mild symptom progression after the spontaneous resolution of syringomyelia, and a review of the relevant reported data. The natural history of our patient provides a unique view regarding the factors that might lead to the development and spontaneous resolution of syringomyelia. CASE DESCRIPTION: We present the case of a 36-year-old woman who had been monitored for 16 years for mild symptomatic CM-I and syringomyelia. After regular follow-up examinations for the initial 10 years, magnetic resonance imaging revealed partial spontaneous resolution of the syringomyelia and unchanged symptoms. However, after 6 additional years of follow-up examinations, her symptoms had mildly progressed, and the size of the syringomyelia had obviously decreased. CONCLUSIONS: The findings from our patient suggest that the natural course of mild symptomatic CM-I in adult patients will be benign and nonprogressive. Patients will commonly present with very few or mild symptoms, despite the presence of a large syrinx. It would be reasonable to observe patients with similar mild symptoms and syringomyelia. Surgery will be indicated by the type, severity, and duration of symptoms at the first clinical visit. Periodic follow-up examinations are also essential after spontaneous resolution because the pathophysiology of syringomyelia is incompletely understood and recurrence possible.

Cerebellar Tissue Strain in Chiari Malformation with Headache.

OBJECTIVE: The pathogenesis of Chiari malformation type 1 (CM-1)-associated Valsalva headache is unknown, but it may be caused by abnormal cerebellar tonsil tissue strain. Advances in cardiac-gated magnetic resonance imaging (MRI) techniques such as balanced fast-field echo (bFFE) allow quantification of the motion of anatomic structures and can be used to measure tissue strain. The current study investigated the relationship between Valsalva heachache and tonsillar motion in patients with CM-1. METHODS: A retrospective review of patients with CM-1 who had undergone cardiac-gated bFFE MRI was performed. Headache symptoms were retrieved from the medical records. Anatomic landmarks were manually selected on the cine bFFE, and a validated motion-tracking software was used to assess motion over the cardiac cycle in patients at rest. For each patient, displacement, strain, and strain rate were calculated for 3 anatomic segments. Patients undergoing surgery were examined before and after surgery. RESULTS: From 88 patients, a total of 108 bFFE sequences were analyzed. Valsalva headache was present in 50% of patients. Cerebellar tonsil displacement (P = 0.003), strain (P = 0.012), and maximum strain rate (P = 0.04) were reduced after surgery (n = 20). There was no statistically significant association between tissue motion and headache symptoms. CONCLUSION: The results of this study do not support a relationship between cardiac cycle cerebellar strain and Valsalva headache in patients with CM-1. It is possible that cerebellar strain related to respiratory maneuvers is associated with headache in Chiari patients. Further investigation of tissue strain is warranted because it represents a potential biomarker for outcomes after surgery.

Chiari Malformation Type 1 in EPAS1-Associated Syndrome.

A syndrome of multiple paragangliomas/pheochromocytomas, somatostatinoma, and polycythemia due to somatic mosaic gain-of-function mutation of EPAS1, encoding HIF-2α, was previously described. HIF-2α has been implicated in endochondral and intramembranous ossification. Abnormal bone growth of the skull base may lead to Chiari malformation type I. We report two cases of EPAS1 gain-of-function mutation syndrome with Chiari malformation and developmental skull base anomalies. Patients were referred to the Section on Medical Endocrinology, Eunice Kennedy Shriver NICHD, NIH for evaluation of recurrent and metastatic paragangliomas or pheochromocytoma. The syndrome was confirmed genetically by identification of the functional EPAS1 gain-of-function mutation in the resected tumors and circulating leukocytes. Both patients were confirmed for characteristics of EPAS1 gain-of-function mutation syndrome by complete blood count (CBC), plasma biochemistry, and computed tomography (CT) of the abdomen and pelvis. Chiari malformation type I and abnormal bony development of the posterior fossa was found on MRI and CT of the head. The present study implicates EPAS1 mutations in abnormal posterior fossa development resulting in Chiari malformation type I.

Dynamic cerebellar herniation in Chiari patients during the cardiac cycle evaluated by dynamic magnetic resonance imaging.

PURPOSE: Cerebellar herniation in Chiari patients can be dynamic, following the cerebrospinal fluid pulsatility during the cardiac cycle. We present a voxel intensity distribution method (VIDM) to automatically extract the pulsatility-dependent herniation in time-resolved MRI (CINE MRI) and compare it to the simple linear measurements. The degree of herniation is furthermore compared on CINE and static sequences, and the cerebellar movement is correlated to the presence of hydrocephalus and syringomyelia. METHODS: The cerebellar movement in 27 Chiari patients is analyzed with VIDM and the results were compared to linear measurements on an image viewer (visual inspection, VI) using a paired t test. Second, an ANOVA test is applied to compare the degree of herniation on static 3D MRI and CINE. Finally, the Pearson's correlation coefficient is calculated for the correlation between cerebellar movement and the presence of hydrocephalus and syringomyelia. RESULTS: VIDM showed significant movement in 85% of our patients. Assuming that movement < 1 mm cannot be detected reliably on an image viewer, VI identified movement in 29.6% of the patients (p = 0.002). The herniation was greater on static sequences than on CINE in most cases, but this was not statistically significant. The cerebellar movement was not correlated with hydrocephalus or syringomyelia (Pearson's coefficient < 0.3). CONCLUSIONS: VIDM is a sensitive method to detect tissue movement on CINE MRI and could be used for Chiari patients, but also for the evaluation of cyst membranes, ventriculostomies, etc. The cerebellar movement appears not to correlate with hydrocephalus and syringomyelia in Chiari patients.