Optic chiasmal compression by venous aneurysm: magnetic resonance imaging diagnosis.

The overwhelming majority of traumatic carotid cavernous fistulas present with a bruit, arterialization of conjunctival vessels, or an elevated intraocular pressure. Described herein is a patient who presented with progressive deterioration of vision, without any of the above signs. Magnetic resonance imaging demonstrated compression of the optic ch asm by a venous aneurysm arising from a carotid cavernous fistula. This entity should be considered in patients who present with progressive visual loss.