Cat optic nerve imaging with metrizamide.

Metrizamide is a water-soluble, nonionic radiocontrast medium that penetrates better into narrow subarachnoid spaces than do oily contrast media or gas. We performed metrizamide optic nerve thecography on five cats with iatrogenic orbital lesions. Optic thecograms successfully demonstrated displacement of the optic nerve, obstruction of the optic nerve sheath subarachnoid space, and extravasation of the contrast medium from a punctured optic nerve sheath. Metrizamide-induced seizures could be prevented by intramuscular preadministration of diazepam.