Best Pediatric Clinical Abstract: Rates of low-lying conus position and symptomatic tethered cord syndrome are not different between pediatric patients with and without Chiari Malformation Type 1

Introduction: The relationship between Chiari malformation type I (CMI) and tethered cord syndrome (TCS) is not well understood. The aim of this study was to examine conus position and rates of TCS and tethered cord release (TCR) in pediatric patients with and without CMI.

Methods: A retrospective review of medical records was performed from 2000-2023 to identify pediatric patients with a diagnosis of CMI from international classification of disease codes. Patients with Chiari malformation type II, complex Chiari malformation, and acquired Chiari malformation (posterior fossa tumors/vascular malformations, complex craniosynostosis, etc) were excluded. Patients with a diagnosis of CMI, defined as cerebellar ectopia of at least 5 mm below the foramen magnum, who had MRI of their lumbar spine available for review were used to create the cohort. An age- and sex-matched control cohort was created by identifying pediatric patients without CMI with an MRI of their lumbar spine. Conus position on MRI was coded numerically (T12=1, T12-L1 =2, etc) and presence of fatty filum or filum terminale lipoma, and rates of TCR were recorded. Wilcoxon signed rank test was used to compare coded conus position between the matched cohorts and McNemar’s test of symmetry was used to compare dichotomous variables between the matched groups.

Results: Four hundred and eight pediatric patients were included (204 with CMI and 204 matched controls). Conus position was statistically significantly higher in the CMI group compared to controls (p < 0.001). There was no difference in the number of patients with a conus position below L2 between groups (p=0.13). There was no difference in the number of radiologically identified fatty filums (p=0.39), intradural lipomas and lipomyelomeningocele (p=1) and symptomatic TCS requiring surgery (p=0.45).

Conclusion : Pediatric patients with CMI have similar rates of low lying conus medullaris, fatty filums, intradural lipomas, lipomyelomeningocele, and symptomatic TCS requiring TCR as compared to the general pediatric population. Patients with CMI do not appear to have an increased associated with TCS compared to patients without CMI.