Not the usual suspect.

An 82-year-old woman presented with right-sided proptosis, chemosis, and a supraorbital bruit. A dural carotid-cavernous fistula was suspected, but catheter angiography revealed an intraorbital inferior ophthalmic vein arteriovenous fistula supplied by the right ophthalmic artery and infraorbital branch of the internal maxillary artery. A primary orbital arteriovenous fistula can mimic the clinical and radiographic features of the more common carotid-cavernous fistula.