Associated Disorders of Chiari Type I Malformations

A Review

Marios Loukas, M.D., Ph.D.; Brian J. Shayota, B.S.; Kim Oelhafen, B.S.; Joseph H. Mill er, M.D.; Joshua J. Chern, M.D., Ph.D.; R. Shane Tubbs, M.S., P.A.-C., Ph.D.; W. Jerry Oakes, M.D.


Neurosurg Focus. 2011;31(3):e3 

In This Article


Morphometric studies by Schady et al.[59] and Milhorat et al.[36] have provided evidence that the volume of the posterior cranial fossa in patients with CM-I was 23% less than controls. Furthermore, Badie and colleagues[3] discovered the ratio of posterior fossa volume to supratentorial space was significantly lower in symptomatic CM-I patients compared with control patients. Marin-Padilla and Marin-Padilla[32] added to the understanding of this anatomical pathology by inducing underdevelopment of the basiocciput and posterior fossa in hamsters through high doses of vitamin A. In doing so, these authors demonstrated how impairing posterior fossa development could induce caudal displacement of the cerebellum. Others, however, have challenged this proposition with studies showing no difference in posterior fossa volume.[79] Additional morphological findings in CM-I may include an underdeveloped supraocciput and exocciput, large foramen magnum, short clivus, and longer anterior cranial fossa.[44,62,80] Therefore, while it may be a common school of thought, a smaller posterior fossa does not necessarily lead to CM-I.