Chronic isolated trochlear nerve palsy produced by intracavernous internal carotid artery aneurysm. Report of a case.

The fourth cranial nerve is rarely affected by intracranial aneurysms, and when this occurs other motor ocular nerves and the trigeminal nerve are almost always involved as well. In the case reported, a middle-aged woman presented with a long-standing selective and stationary palsy of the right superior oblique muscle. Neuroradiologic studies disclosed an aneurysm arising at the C-3 segment of the right internal carotid artery.