• Brandon Smith, Jennifer Strahle, Hugh Garton, Karin M Muraszko, and Cormac O Maher.
• Neurosurgery. 2015 Aug 1;62 Suppl 1:232.

IntroductionClinical observations of patients with both Chiari Malformation Type I (CIM) and tethered spinal cord (TSC), have led some to speculate that there may be an association between the two entities. However, the level of evidence for this association is anecdotal. We examined a large group of subjects to evaluate the association between CIM and TSC.MethodsCases were identified for a case-control study from a pediatric CIM database of 509 subjects, aged 0 to 18. Control subjects were selected from a database of 2549 patients undergoing MRI and were matched to cases 1:1 by age and sex. For eligibility, the cases and controls had both brain or c-spine MRI and lumbar MRI. All imaging studies were reviewed for conus position as well as cerebellar tonsil position and morphology. Low conus position was defined as conus at or below the L2-3 disk space. Descriptive statistics and conditional logistic regression were utilized.ResultsTwo hundred three case-control pairs were identified. One hundred twenty-one (60%) of the pairs were female, and 82 (40%) of the pairs were male. Seven of 203 (3.4%) of the cases had low conus levels. Nine of 203 (4.4%) of the controls had low conus levels. All 7 cases that met the definition of low conus position had conus levels at L2-3. Of the 9 controls with low conus position, 4 had conus levels at L2-3, 3 had conus levels at L3, and 2 had conus levels at L4. In the matched analysis, the prevalence of TSC did not differ significantly between the cases and controls (3.4% vs 4.4%; odds ratio 0.5, with a 95% CI of 0.045-3.489, P = .6875).ConclusionThere was no statistically significant association between CIM and low conus position. We conclude that patients with CIM do not have lower conus position compared with matched normals, and that TSC is not associated with CIM for most patients.

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