Caudal dislocation of the pons in the adult Arnold-Chiari malformation: an angiographic evaluation.

The position of the pons, determined angiographically, can be related to the clivus and sella. In adult patients with the Chiari malformation, a caudal dislocation of the pons is frequently associated with the well known anomalously low position of the cerebellar tonsils. This finding may aid in the angiographic diagnosis of the Chiari malformation.