Background: Carotid cavernous fistulas cause conjunctival hyperemia and orbital soft-tissue swelling because of increased flow directed anteriorly in ophthalmic veins. Less well recognized is that when fistular flow is directed posteriorly, these congestive features will be absent and the diagnosis of the "white-eyed shunt" will be missed unless angiography is performed.
Methods: Two patients who had oculomotor nerve palsies caused by posteriorly draining dural carotid cavernous fistulas were studied, and the 28 previously described cases were reviewed.
Results: One patient had a chronic painful palsy of the sixth cranial nerve, and the other, a palsy of the third cranial nerve. Cerebral angiography disclosed the fistulas. The clinical and imaging features of these cases conform to those of the 28 previously reported white-eyed shunts. Angiographic features do not explain why some posterior-draining fistulas cause sixth-nerve palsies and others cause third- (or rarely, fourth-) nerve palsies.
Conclusions: Dural carotid cavernous fistulas that drain primarily into the inferior petrosal sinus may cause painful oculomotor palsies that elude diagnosis because they lack congestive orbito-ocular features. Treatment by embolization leads to more rapid resolution of manifestations.