Asymmetric laterality of Chiari type I malformation in patients with non-syndromic single-suture craniosynostosis.

BACKGROUND: Chiari type I malformation is a frequent incidental finding commonly associated with craniosynostosis. However, there seems to be a paucity of literature concerning the asymmetry of tonsillar herniation in patients with non-syndromic single-suture craniosynostosis.

METHODS: To study the asymmetry in this cohort, measurements of the right and left tonsils were made from sagittal images from both pre-operative and post-operative images from 11 patients with non-syndromic single-suture craniosynostosis.

RESULTS: Pre-operatively, the mean difference between the caudal descent of all tonsils ranged from 0 to 7 mm, with a mean difference between sides of 2.45 mm. In three cases, cerebellar tonsils were symmetrically herniated. Post-operatively, the mean difference between caudal descent of all tonsils ranged from 0 to 4 mm, with a mean difference between sides of 1.45 mm. Four were symmetrically herniated. In patients with non-syndromic single-suture craniosynostosis, the tonsillar herniation is asymmetric in the majority of cases.

CONCLUSIONS: Asymmetry of cerebellar tonsil herniation is a frequent finding in this cohort. The right tonsil is more inferiorly located in majority of cases, with predominance to the synostotic suture side in asymmetric craniosynostosis cases.