110. Morphometric Parameters Associated with Syringomyelia in Pediatric Patients with Chiari I Malformation

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Authors: Catherine Peterson, MD; Neena Marupudi, MD; Hassan Fadel, MD; Bradley Kolb, MD; Steven Ham, DO; Sandeep Sood, MD (Detroit, MI)


Identifying factors that predict the development of syringomyelia in patients with Chiari I malformation (CM) may aid in surgical management and patient counseling. In this study, we investigate whether the morphometric variations in the skull base have predictive value for the development of syrinx in such patients.


We performed a retrospective analysis of all pediatric patients who had underwent suboccipital decompressive surgery for CM during a seven-year period at Children’s Hospital of Michigan. Various skull base angles/diameters were measured and analyzed. A case-control study was performed to analyze the predictive role of the morphometric parameters in development of syringomyelia. Statistical analyses were performed using SAS-9.0.


Eighty-five patients met the inclusion criteria for the study, 55 (64.7%) without syrinx and 30 (35.3%) with syrinx. The mean distance of tonsillar herniation below foramen magnum (12.6 v. 14.4mm, p=0.1131), C1-modified-tonsillar-ectopia (5.03 v. 5.59mm, p=0.6225), skull-base-angle (138.3 v. 139.8 p=0.5098), and foramen magnum diameter (33.83 v. 35.30mm, p = 0.081) were not statistically different between the two groups. Patients with syrinx tended to have larger sagittal-cerebellar-superior-inferior diameter (54.8 v. 57.0mm, p=0.0560), however when it came to final posterior fossa volume calculations, the two groups were similar (p=0.250). Patients with syrinx had a significantly smaller angle-of-occipital-protuberance, defined as the angle between the line connecting the inflection point of the internal occipital protuberance to the opisthion and the McRae line (132.5 v. 126.1mm, p=0.0021).


Our study suggests that there is a significant association between presence of syringomyelia and a smaller angle-of-occipital-protuberance in patients with CM. This association may help select patients at risk for developing syringomyelia for surgery.