Carotid-cavernous fistula with brainstem congestion mimicking tumor on MRI

A 65-year-old woman presented with a left abduction deficit and "red eye," mild proptosis, chemosis, arterialization of the conjunctival vessels, inte ntion tremor, and bilateral pyramidal signs. MRI showed significant left-si ded brainstem involvement that mimicked a tumor. Right hemiplegia ensued 1 week later. Venous congestion of the brainstem with hemiplegia resulting fr om shunting of blood flow from both carotid arteries is an extremely rare c omplication of carotid-cavernous fistula.