Cerebellar Ectopia Associated with Unilateral Agenesis of Posterior Arch of Atlas

ABSTRACT

Chiari type I malformation(CM-I) is a congenital disorder recognized by caudal displacement of the cerebellar tonsils through the foramen magnum and into the cervical canal. Though bony anomalies associated with CM including platybasia, small posterior fossa and occipitalization, are relatively frequent, but the incidence rate associated with agenesis of posterior arch of atlas is very low. We report our experience of surgical treatment for patient who had CM-I with unilateral agenesis of posterior arch of atlas.