Radiologic demonstration of the dorsal medullocervical spur in adult Chiari malformation.

An adolescent female with downbeat nystagmus and long tract signs was evaluated by a number of diagnostic radiologic procedures. Metrizamide CT cisternography was the procedure that established the diagnosis by showing not only the tonsillar herniation, but also the medullocervical deformity characteristic of the Chiari type II malformation. This case report emphasizes the superior diagnostic capability of this technique with respect to conventional radiography in the diagnosis of Arnold-Chiari malformation.