Intracranial embolization via external carotid artery: report of a case with angiographic documentation.

This report describes our experiences with a patient who developed delayed recurrent retinal and hemispheric ischemia distal to an old internal carotid artery occlusion in the neck. Fundoscopy and sequential cerebral arteriography documented that recurrent ischemic symptoms in this individual were the result of embolic fragments arising from the "stump" of the occluded internal carotid artery and from a diseased external carotid artery. These emboli traversed the external carotid artery and its orbital and intracranial anastomotic connections to reach the symptomatic eye and hemisphere. Ischemic symptoms in this patient were effectively terminated with anticoagulant therapy. We believe that this patient graphically documents that post-occlusion microembolism via the external carotid artery does indeed occur, and probably accounts for post-occlusion recurrent ischemic attacks more frequently than is currently appreciated. Recognition of this phenomenon is of importance because of its significant therapeutic implications. In these situations treatment modalities which terminate embolic phenomena would appear to have a more rational basis than do surgical procedures designed primarily to augment collateral blood flow to the symptomatic organ(s).