Intradural pathology and pathophysiology associated with Chiari I malformation in children and adults with and without syringomyelia

OBJECTIVEThe pathophysiology underlying tonsillar herniation and CSF obstruction in Chiari malformation Type I (CM-I) is unclear, and the cause of CM-I–associated syringomyelia is not well understood. A better understanding of this pathophysiology is important for an improved treatment strategy. Therefore, the authors sought to identify, characterize, and examine the intradural pathology and CSF flow pathophysiology in the posterior fossa and at the level of the foramen magnum that occurs in the setting of CM-I. They determined the incidence of these intradural findings and assessed differences across age, with the degree of tonsillar herniation, and in the presence and absence of syringomyelia.METHODSA prospective database initiated in March 2003 recorded all intraoperative findings during surgical treatment of children and adults with CM-I with or without syringomyelia. A total of 389 surgeries for CM-I were performed in 379 patients between March 2003 and June 2016. A total of 109 surgeries were performed in 109 patients with CM-I (without osseoligamentous abnormalities) in whom both a posterior fossa extradural and intradural decompression with duraplasty was performed (first-time intradural procedures). Using a surgical microscope, intradural pathology and obstruction of CSF channels were identified and assessed. Student t-tests and Fisher’s exact tests compared groups in a series of univariate analyses, followed by multivariate logistic regression.RESULTSThe following intradural pathological entities were observed (prevalence noted in parentheses). These include those that did not obstruct CSF flow channels: opacified arachnoid (33.0%), thickened arachnoid (3.7%), ischemic and gliotic tonsils (40.4%), tonsillar cysts (0.9%), and inferior descent of the fourth ventricle and cervicomedullary junction (CMJ) (78.0%). The following intradural pathological entities were observed to obstruct CSF flow channels: medialized tonsils (100%), tonsil overlying and obstructing the foramen of Magendie (21.1%), intertonsillar and tonsil to CMJ arachnoid adhesions (85.3%), vermian posterior inferior cerebellar artery branches obstructing the foramen of Magendie (43.1%), and arachnoid veils or webs obstructing or occluding the foramen of Magendie (52.3%). Arachnoid veils varied in type and were observed in 59.5% of patients with CM-I who had syringomyelia, which was significantly greater than the 33.3% of patients with CM-I without syringomyelia who had an arachnoid veil (p = 0.018). The presence of CM-I with an arachnoid veil had 3.22 times the odds (p = 0.013, 95% CI 1.29–8.07, by multivariate logistic regression) of being associated with syringomyelia, adjusting for tonsillar herniation. The inferior descent of the fourth ventricle and CMJ occurred with a greater degree of tonsillar herniation (p < 0.001) and correlated with a cervicomedullary kink or buckle on preoperative MRI.CONCLUSIONSIntradural pathology associated with CM-I with or without syringomyelia exists in many forms, is more prevalent than previously recognized in patients of all ages, and may play a role in the pathophysiology of CM-I tonsillar herniation. Arachnoid veils appear to partially obstruct CSF flow, are significantly more prevalent in cases of CM-I with syringomyelia, and therefore may play a role in the pathophysiology of CM-I–associated syringomyelia.

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Posterior fossa arachnoid cyst, tonsillar herniation, and syringomyelia in trichorhinophalangeal syndrome Type I

Journal of Neurosurgery ◽

10.3171/jns/2008/109/10/0746 ◽

2008 ◽

Vol 109 (4) ◽

pp. 746-750 ◽

Cited By ~ 7

Author(s):

Juan F. Martínez-Lage ◽

Antonio Ruiz-Espejo ◽

Encarna Guillén-Navarro ◽

María-José Almagro

Keyword(s):

Posterior Fossa ◽

Arachnoid Cyst ◽

Endochondral Ossification ◽

Spinal Pain ◽

Type I ◽

Syndrome Type ◽

Tonsillar Herniation ◽

Chiari Malformation Type I ◽

Trichorhinophalangeal Syndrome ◽

Tonsillar Descent

The authors report the case of a patient with Chiari malformation Type I (CM-I) and syringomyelia probably caused by a retrocerebellar arachnoid cyst. The patient's phenotype corresponded to trichorhinophalangeal syndrome Type I. The authors attributed the origin of both the retrocerebellar cyst and the abnormal posterior fossa to endochondral ossification anomalies that occur in this syndrome. The patient's spinal pain was most likely a result of the combination of CM-I and syringomyelia. To the best of the authors' knowledge, this is the first report on the association of CM-I and syringomyelia with a retrocerebellar arachnoid cyst occurring in a patient with trichorhinophalangeal syndrome Type I. The authors discuss the pathogenetic mechanisms involved in the production of tonsillar descent and syringomyelia in this patient, and review the current literature on related conditions that can result in this association.

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Fourth ventricle roof angle as a measure of fourth ventricle bowing and a radiographic predictor of brainstem dysfunction in Chiari malformation type I

Journal of Neurosurgery Pediatrics ◽

10.3171/2021.1.peds20756 ◽

2021 ◽

pp. 1-8

Author(s):

Scott C. Seaman ◽

Luyuan Li ◽

Arnold H. Menezes ◽

Brian J. Dlouhy

Keyword(s):

Fourth Ventricle ◽

Foramen Magnum ◽

Clinical Severity ◽

Type I ◽

Healthy Controls ◽

Tonsillar Herniation ◽

Chiari Malformation Type I ◽

Brainstem Dysfunction ◽

Roof Angle ◽

Tonsillar Descent

OBJECTIVE Chiari malformation type I (CM-I) is a congenital and developmental abnormality that results in tonsillar descent 5 mm below the foramen magnum. However, this cutoff value has poor specificity as a predictor of clinical severity. Therefore, the authors sought to identify a novel radiographic marker predictive of clinical severity to assist in the management of patients with CM-I. METHODS The authors retrospectively reviewed 102 symptomatic CM-I (sCM-I) patients and compared them to 60 age-matched normal healthy controls and 30 asymptomatic CM-I (aCM-I) patients. The authors used the fourth ventricle roof angle (FVRA) to identify fourth ventricle “bowing,” a configuration change suggestive of fourth ventricle outlet obstruction, and compared these results across all three cohorts. A receiver operating characteristic (ROC) curve was used to identify a predictive cutoff for brainstem dysfunction. Binary logistic regression was used to determine whether bowing of the fourth ventricle was more predictive of brainstem dysfunction than tonsillar descent, clival canal angle, or obex position in aCM-I and sCM-I patients. RESULTS The FVRA had excellent interrater reliability (intraclass correlation 0.930, 95% CI 0.905–0.949, Spearman r2 = 0.766, p < 0.0001). The FVRA was significantly greater in the sCM-I group than the aCM-I and healthy control groups (59.3° vs 41.8° vs 45.2°, p < 0.0001). No difference was observed between aCM-I patients and healthy controls (p = 0.347). ROC analysis indicated that an FVRA of 65° had a specificity of 93% and a sensitivity of 50%, with a positive predictive value of 76% for brainstem dysfunction. FVRA > 65° was more predictive of brainstem dysfunction (OR 5.058, 95% CI 1.845–13.865, p = 0.002) than tonsillar herniation > 10 mm (OR 2.564, 95% CI 1.050–6.258, p = 0.039), although increasing age was also associated with brainstem dysfunction (OR 1.045, 95% CI 1.011–1.080, p = 0.009). A clival canal angle < 140° (p = 0.793) and obex below the foramen magnum (p = 0.563) had no association with brainstem dysfunction. CONCLUSIONS The authors identified a novel radiographic measure, the FVRA, that can be used to assess fourth ventricular bowing in CM-I and is more predictive of brainstem dysfunction than tonsillar herniation. The FVRA is easy to measure, has excellent interrater variability, and can be a reliable universal radiographic measure. The FVRA will be useful in further describing CM-I radiographically and clinically by identifying patients more likely to be symptomatic as a result of brainstem dysfunction.

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Effect of craniovertebral decompression on CSF dynamics in Chiari malformation Type I studied with computational fluid dynamics

Journal of Neurosurgery Spine ◽

10.3171/2014.6.spine13950 ◽

2014 ◽

Vol 21 (4) ◽

pp. 559-564 ◽

Cited By ~ 8

Author(s):

Svein O. Linge ◽

Kent-A. Mardal ◽

Anders Helgeland ◽

John D. Heiss ◽

Victor Haughton

Keyword(s):

Fluid Dynamics ◽

Spinal Cord ◽

Posterior Fossa ◽

Flow Dynamics ◽

Decompression Surgery ◽

Type I ◽

Pressure Gradients ◽

Normal Model ◽

Csf Flow ◽

Chiari Malformation Type I

Object The effect of craniovertebral decompression surgery on CSF flow dynamics in patients with Chiari malformation Type I (CM-I) has been incompletely characterized. The authors used computational fluid dynamics to calculate the effect of decompression surgery on CSF flow dynamics in the posterior fossa and upper cervical spinal canal. Methods Oscillatory flow was simulated in idealized 3D models of the normal adult and the CM-I subarachnoid spaces (both previously described) and in 3 models of CM-I post–craniovertebral decompressions. The 3 postoperative models were created from the CM model by virtually modifying the CM model subarachnoid space to simulate surgical decompressions of different magnitudes. Velocities and pressures were computed with the Navier-Stokes equations in Star-CD for multiple cycles of CSF flow oscillating at 80 cycles/min. Pressure gradients and velocities were compared for 8 levels extending from the posterior fossa to the C3–4 level. Relative pressures and peak velocities were plotted by level from the posterior fossa to C3–4. The heterogeneity of flow velocity distribution around the spinal cord was compared between models. Results Peak systolic velocities were generally lower in the postoperative models than in the preoperative CM model. With the 2 larger surgical defects, peak systolic velocities were brought closer to normal model velocities (equal values at C-3 and C-4) than with the smallest surgical defect. For the smallest defect, peak velocities were decreased, but not to levels in the normal model. In the postoperative models, heterogeneity in flow velocity distribution around the spinal cord increased from normal model levels as the degree of decompression increased. Pressures in the 5 models differed in magnitude and in pattern. Pressure gradients along the spinal canal in the normal and CM models were nonlinear, with steeper gradients below C3–4 than above. The CM model had a steeper pressure gradient than the normal model above C3–4 and the same gradient below. The postoperative models had lower pressure gradients than the CM model above C2–3. The most conservative decompression had lower pressure gradients than the normal model above C2–3. The two larger decompression defects had CSF pressure gradients below those in the normal model above C2–3. These 2 models had a less steep gradient above C-3 and a steeper gradient below. Conclusions In computer simulations, craniovertebral surgical defects generally diminished CSF velocities and CSF pressures.

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Diffusion tensor imaging assessment of microstructural brainstem integrity in Chiari malformation Type I

Journal of Neurosurgery ◽

10.3171/2015.9.jns151196 ◽

2016 ◽

Vol 125 (5) ◽

pp. 1112-1119 ◽

Cited By ~ 20

Author(s):

Vibhor Krishna ◽

Francesco Sammartino ◽

Philip Yee ◽

David Mikulis ◽

Matthew Walker ◽

...

Keyword(s):

Diffusion Tensor Imaging ◽

Posterior Fossa ◽

Chiari Malformation ◽

Diffusion Tensor ◽

Structural Parameters ◽

Ventricular Volume ◽

Neurological Dysfunction ◽

Type I ◽

Tonsillar Herniation ◽

Chiari Malformation Type I

OBJECTIVE The diagnosis of Chiari malformation Type I (CM-I) is primarily based on the degree of cerebellar tonsillar herniation even though it does not always correlate with symptoms. Neurological dysfunction in CM-I presumably results from brainstem compression. With the premise that conventional MRI does not reveal brain microstructural changes, this study examined both structural and microstructural neuroimaging metrics to distinguish patients with CM-I from age- and sex-matched healthy control subjects. METHODS Eight patients with CM-I and 16 controls were analyzed. Image postprocessing involved coregistration of anatomical T1-weighted with diffusion tensor images using 3D Slicer software. The structural parameters included volumes of the posterior fossa, fourth ventricle, and tentorial angle. Fractional anisotropy (FA) was calculated separately in the anterior and posterior compartments of the lower brainstem. RESULTS The mean age of patients in the CM-I cohort was 42.6 ± 10.4 years with mean tonsillar herniation of 12 mm (SD 0.7 mm). There were no significant differences in the posterior fossa volume (p = 0.06) or fourth ventricular volume between the 2 groups (p = 0.11). However, the FA in the anterior brainstem compartment was significantly higher in patients with CM-I preoperatively (p = 0.001). The FA values normalized after Chiari decompression except for persistently elevated FA in the posterior brainstem compartment in patients with CM-I and syrinx. CONCLUSIONS In this case-control study, microstructural alterations appear to be reliably associated with the diagnosis of CM-I, with a significantly elevated FA in the lower brainstem in patients with CM-I compared with controls. More importantly, the FA values normalized after decompressive surgery. These findings should be validated in future studies to determine the significance of diffusion tensor imaging–based assessment of brainstem microstructural integrity as an adjunct to the clinical assessment in patients with CM-I.

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Chiari malformation Type I and syrinx in children undergoing magnetic resonance imaging

Journal of Neurosurgery Pediatrics ◽

10.3171/2011.5.peds1121 ◽

2011 ◽

Vol 8 (2) ◽

pp. 205-213 ◽

Cited By ~ 111

Author(s):

Jennifer Strahle ◽

Karin M. Muraszko ◽

Joseph Kapurch ◽

J. Rajiv Bapuraj ◽

Hugh J. L. Garton ◽

...

Keyword(s):

Cervical Spine ◽

Mr Imaging ◽

Chiari Malformation ◽

Foramen Magnum ◽

Type I ◽

Csf Flow ◽

Tonsillar Herniation ◽

Chiari Malformation Type I ◽

Age Related ◽

Imaging Characteristics

Object Chiari malformation Type I (CM-I) with an associated spinal syrinx is a common pediatric diagnosis. A better understanding of the relative age-related prevalence and MR imaging characteristics of these associated conditions may lead to improved treatment decisions. Methods The authors performed a retrospective review of 14,116 consecutive individuals 18 years of age or younger who had undergone brain or cervical spine MR imaging at the University of Michigan between November 1997 and August 2008. In the patients with CM-I, demographic, clinical, and radiographic information was recorded. Results Five hundred nine children (3.6%) with CM-I were identified. Among these patients, 23% also had a spinal cord syrinx, and 86% of the syringes were found in the cervical spine. The MR imaging prevalence of CM-I with a syrinx was 1.2% in girls and 0.5% in boys (p < 0.0001). The severity of impaired CSF flow at the foramen magnum was associated with the amount of tonsillar herniation (p < 0.0001) and conformation of the tonsils (p < 0.0001). Patients with CM-I were treated surgically in 35% of cases; these patients exhibited more severe tonsillar herniation (p < 0.0001) and impaired CSF flow (p < 0.0001) as compared with those who did not undergo surgery. On imaging, 32% of all the patients with CM-I were considered symptomatic by the treating physician. Patients were more likely to be considered symptomatic if they were female, had a syrinx, displayed abnormal tonsillar pulsations, or had a greater amount of tonsillar herniation. Conclusions In this study the authors describe the age-related prevalence and MR imaging characteristics of CM-I and its association with a syrinx and other abnormalities in a large group of children who underwent MR imaging for any indication. Syringes are more common in older children, in girls, and in patients with a greater degree of tonsillar descent and CSF flow impairment.

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Syringobulbia in pediatric patients with Chiari malformation type I

Journal of Neurosurgery Pediatrics ◽

10.3171/2018.1.peds17472 ◽

2018 ◽

Vol 22 (1) ◽

pp. 52-60 ◽

Cited By ~ 8

Author(s):

Arnold H. Menezes ◽

Jeremy D. W. Greenlee ◽

Brian J. Dlouhy

Keyword(s):

Posterior Fossa ◽

Cranial Nerve ◽

Chiari Malformation ◽

Fourth Ventricle ◽

Pediatric Patients ◽

Posterior Fossa Decompression ◽

Type I ◽

Chiari Malformation Type I ◽

Presenting Symptoms ◽

Cranial Nerve Palsies

OBJECTIVESyringobulbia (SB) is a rare entity, with few cases associated with Chiari malformation type I (CM-I) in the pediatric population. The authors reviewed all pediatric cases of CM-I–associated SB managed at their institution in order to better understand the presentation, treatment, and surgical outcomes of this condition.METHODSA prospectively maintained institutional database of craniovertebral junction abnormalities was analyzed to identify all cases of CM-I and SB from the MRI era (i.e., after 1984). The authors recorded presenting symptoms, physical examination findings, radiological findings, surgical treatment strategy, intraoperative findings, and outcomes. SB cases associated with tumors, infections, or type II Chiari malformations were excluded.RESULTSThe authors identified 326 pediatric patients with CM-I who were surgically treated. SB was identified in 13 (4%) of these 326 patients. Headache and neck pain were noted in all 13 cases. Cranial nerve abnormalities were common: vagus and glossopharyngeal nerve dysfunction was the most frequent observation. Other cranial nerves affected included the trigeminal, abducens, and hypoglossal nerves. Several patients exhibited multiple cranial nerve palsies at presentation. Central sleep apnea was present in 6 patients.Syringomyelia (SM) was present in all 13 patients. SB involved the medulla in all cases, and extended rostrally into the pons and midbrain in 2 patients; in 1 of these 2 cases the cavity extended further rostrally to the cerebrum (syringocephaly). SB communicated with the fourth ventricle in 7 of the 13 cases.All 13 patients were treated with posterior fossa decompression with intradural exploration to ensure CSF egress out of the fourth ventricle and through the foramen magnum. The foramen of Magendie was found to be occluded by an arachnoid veil in 9 cases. Follow-up evaluation revealed that SB improved before SM. Cranial nerve palsies regressed in 11 of the 13 patients, and SB improved in all 13.CONCLUSIONSThe incidence of SB in our surgical series of pediatric patients with CM-I was 4%, and all of these patients had accompanying SM. The SB cavity involved the medulla in all cases and was found to communicate with the fourth ventricle in 54% of cases. Posterior fossa decompression with intradural exploration and duraplasty is an effective treatment for these patients.

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Multimodal evaluation of CSF dynamics following extradural decompression for Chiari malformation Type I

Journal of Neurosurgery Spine ◽

10.3171/2014.10.spine1433 ◽

2015 ◽

Vol 22 (6) ◽

pp. 622-630 ◽

Cited By ~ 10

Author(s):

Jennifer L. Quon ◽

Ryan A. Grant ◽

Michael L. DiLuna

Keyword(s):

Chiari Malformation ◽

Phase Contrast ◽

Clinical Symptoms ◽

Type I ◽

Csf Flow ◽

Tonsillar Herniation ◽

Csf Dynamics ◽

Chiari Malformation Type I ◽

Cisterna Magna ◽

Flow Mri

OBJECT Extradural decompression is a minimally invasive technique for treating Chiari malformation Type I (CM-I) that avoids the complications of dural opening. While there is no agreement on which surgical method is optimal, mounting evidence demonstrates that extradural decompression effectively treats clinical symptoms, with a minimal reoperation rate. Neurological symptoms such as headache may be related to obstructed flow of CSF, and one aspect of successful extradural decompression is improved CSF dynamics. In this series, the authors report on their use of phase-contrast cine flow MRI to assess CSF flow as well as satisfactory decompression. METHODS The authors describe their first surgical series of 18 patients with CM-I undergoing extradural decompression and correlate clinical improvement with radiological changes. Patients were categorized as having complete, partial, or no resolution of their symptoms. Posterior fossa area, cisterna magna area, and tonsillar herniation were assessed on T2-weighted MRI, whereas improvement of CSF flow was evaluated with phase-contrast cine flow MRI. All patients received standard pre- and postoperative MRI studies; 8 (44.4%) patients had pre- and postoperative phase-contrast cine, while the rest underwent cine studies only postoperatively. RESULTS All 18 patients presented with symptomatic CM-I, with imaging studies demonstrating tonsillar herniation ≥ 5 mm, and 2 patients had associated syringomelia. All patients underwent suboccipital decompression and C-1 laminectomy with splitting of the dura. Patients with complete resolution of their symptoms had a greater relative increase in cisterna magna area compared with those with only partial improvement (p = 0.022). In addition, in those with complete improvement the preoperative cisterna magna area was smaller than in those who had either partial (0.020) or no (0.025) improvement. Ten (91%) of the 11 patients with improved flow also had improvement in their symptoms. There was 1 postoperative complication of dysphagia and dysphonia. None of the patients have required a second operation. CONCLUSIONS Extradural decompression has the potential to be the first-line treatment for CM-I but has been lacking an objective measure by which to assess surgical success as well as the need for reoperation. An increase in the CSF spaces and improved CSF dynamics may be associated with resolution of clinical symptoms. Including cine imaging as part of routine pre- and postoperative evaluation can help identify which patients are most likely to benefit from surgery.

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Pediatric Chiari malformation Type 0: a 12-year institutional experience

Journal of Neurosurgery Pediatrics ◽

10.3171/2011.4.peds10528 ◽

2011 ◽

Vol 8 (1) ◽

pp. 1-5 ◽

Cited By ~ 52

Author(s):

Joshua J. Chern ◽

Amber J. Gordon ◽

Martin M. Mortazavi ◽

R. Shane Tubbs ◽

W. Jerry Oakes

Keyword(s):

Posterior Fossa ◽

Chiari Malformation ◽

Foramen Magnum ◽

Posterior Fossa Decompression ◽

Type I ◽

Csf Flow ◽

Chiari Malformation Type I ◽

Institutional Experience ◽

Physical Barriers ◽

Small Cohort

Object In 1998 the authors identified 5 patients with syringomyelia and no evidence of Chiari malformation Type I (CM-I). Magnetic resonance imaging of the entire neuraxis ruled out other causes of a syrinx. Ultimately, abnormal CSF flow at the foramen magnum was the suspected cause. The label “Chiari 0” was used to categorize these unique cases with no tonsillar ectopia. All of the patients underwent posterior fossa decompression and duraplasty identical to the technique used to treat patients with CM-I. Significant syrinx and symptom resolution occurred in these patients. Herein, the authors report on a follow-up study of patients with CM-0 who were derived from over 400 operative cases of pediatric CM-I decompression. Methods The authors present their 12-year experience with this group of patients. Results Fifteen patients (3.7%) were identified. At surgery, many were found to have physical barriers to CSF flow near the foramen magnum. In most of them, the syringomyelia was greatly diminished postoperatively. Conclusions The authors stress that this subgroup represents a very small cohort among patients with Chiari malformations. They emphasize that careful patient selection is critical when diagnosing CM-0. Without an obvious CM-I, other etiologies of a spinal syrinx must be conclusively ruled out. Only then can one reasonably expect to ameliorate the clinical course of these patients via posterior fossa decompression.

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