Importance of the external carotid artery in extracranial cerebrovascular occlusive disease.

We have encountered 12 patients whose symptoms of transient ischemic attacks were due to total occlusion of the internal carotid artery with patency of the intracranial circulation being maintained by collateral circulation from the external carotid artery. In each case there was either tight stenosis or total occlusion at the origin of the external carotid artery. Eleven of the 12 patients were operated upon, receiving either thromboendarterectomy of the external carotid artery or a saphenous vein bypass to the patent distal portion of this artery. Ten of these 11 had complete or significant relief of symptoms. Although this condition represents only a small percentage of the total number of clinically significant extracranial occlusive lesions, studies suggest that the external carotid artery may be involved more commonly than previously suspected. Adequate radiographic visualization of the cerebral circulation is essential to evaluate the collateral pathways.