Extreme pseudo-occlusion of the internal carotid artery.

Angiographic criteria for the identification of patients with angiographic internal carotid artery occlusion but with anatomical patency are presented. The presence of retained contrast material in a caudal atherosclerotic internal carotid artery stump, especially when accompanied by visualization of the internal carotid artery at the base of the skull, suggests that the internal carotid artery may be patent. Two cases of "extreme" pseudo-occlusion are presented, and the indications for extracranial-intracranial bypass and caudal internal carotid artery stump resection are reviewed.