Metrizamide CT cisternography and perioptic subarachnoid space imaging.

Opacification of the perioptic subarachnoid space (PSAS) is a normal occurrence. Opacification depends on the anatomy of the meningeal layers surrounding the optic nerves. To determine the reliability and the most efficacious technique for opacifying the PSAS, a retrospective study of 200 computed tomographic cisternography studies with water soluble contrast medium (metrizamide or iopamidol) was undertaken. Of these patients, 32.5% had opacification of the PSAS. Opacification was facilitated by examining the patients in the prone position. Demonstration of the PSAS was frequently noted in patients with empty sella and rhinorrhea.