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  • Author or Editor: Hugh J. L. Garton x
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Brandon W. Smith, Jennifer Strahle, J. Rajiv Bapuraj, Karin M. Muraszko, Hugh J. L. Garton and Cormac O. Maher

Object

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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Jennifer Strahle, Karin M. Muraszko, Joseph Kapurch, J. Rajiv Bapuraj, Hugh J. L. Garton and Cormac O. Maher

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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Jennifer Strahle, Karin M. Muraszko, Joseph Kapurch, J. Rajiv Bapuraj, Hugh J. L. Garton and Cormac O. Maher

Object

The natural history of the Chiari malformation Type I (CM-I) is incompletely understood. The authors report on the outcome of a large group of patients with CM-I that were initially selected for nonsurgical management.

Methods

The authors identified 147 patients in whom CM-I was diagnosed on MR imaging, who were not offered surgery at the time of diagnosis, and in whom at least 1 year of clinical and MR imaging follow-up was available after the initial CM-I diagnosis. These patients were included in an outcome analysis.

Results

Patients were followed clinically and by MR imaging for a mean duration of 4.6 and 3.8 years, respectively. Of the 147 patients, 9 had new symptoms attributed to the CM-I during the follow-up interval. During this time, development of a spinal cord syrinx occurred in 8 patients; 5 of these patients had a prior diagnosis of a presyrinx state or a dilated central canal. Spontaneous resolution of a syrinx occurred in 3 patients. Multiple CSF flow studies were obtained in 74 patients. Of these patients, 23 had improvement in CSF flow, 39 had no change, and 12 showed worsening CSF flow at the foramen magnum. There was no significant change in the mean amount of cerebellar tonsillar herniation over the follow-up period. Fourteen patients underwent surgical treatment for CM-I. There were no differences in initial cerebellar tonsillar herniation or CSF flow at the foramen magnum in those who ultimately underwent surgery compared with those who did not.

Conclusions

In patients with CM-Is that are selected for nonsurgical management, the natural history is usually benign, although spontaneous improvement and worsening are occasionally seen.

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Jennifer Strahle, Brandon W. Smith, Melaine Martinez, J. Rajiv Bapuraj, Karin M. Muraszko, Hugh J. L. Garton and Cormac O. Maher

OBJECT

Chiari malformation Type I (CM-I) is often found in patients with scoliosis. Most previous reports of CM-I and scoliosis have focused on patients with CM-I and a spinal syrinx. The relationship between CM-I and scoliosis in the absence of a syrinx has never been defined clearly. The authors sought to determine if there is an independent association between CM-I and scoliosis when controlling for syrinx status.

METHODS

The medical records of 14,118 consecutive patients aged ≤ 18 years who underwent brain or cervical spine MRI at a single institution in an 11-year span were reviewed to identify patients with CM-I, scoliosis, and/or syrinx. The relationship between CM-I and scoliosis was analyzed by using multivariate regression analysis and controlling for age, sex, CM-I status, and syrinx status.

RESULTS

In this cohort, 509 patients had CM-I, 1740 patients had scoliosis, and 243 patients had a spinal syrinx. The presence of CM-I, the presence of syrinx, older age, and female sex were each significantly associated with scoliosis in the univariate analysis. In the multivariate regression analysis, older age (OR 1.02 [95% CI 1.01–1.03]; p < 0.0001), female sex (OR 1.71 [95% CI 1.54–1.90]; p < 0.0001), and syrinx (OR 9.08 [95% CI 6.82–12.10]; p < 0.0001) were each independently associated with scoliosis. CM-I was not independently associated with scoliosis when controlling for these other variables (OR 0.99 [95% CI 0.79–1.29]; p = 0.9).

CONCLUSIONS

A syrinx was independently associated with scoliosis in a large pediatric population undergoing MRI. CM-I was not independently associated with scoliosis when controlling for age, sex, and syrinx status. Because CM-I is not independently associated with scoliosis, scoliosis should not necessarily be considered a symptom of low cerebellar tonsil position in patients without a syrinx.