OCCLUSION of the internal carotid artery is a common cause of cerebral ischemia or infarction. Occlusion usually results from thrombosis secondary to atherosclerosis at or near the origin of the artery.1 Internal carotid artery occlusion is therefore more common in older patients (arbitrarily defined as persons above the age of 40) in whom arteriosclerosis is a frequent finding.2 In younger patients the causes of internal carotid artery occlusion are more variable. Humphrey and Newton3 listed trauma, hypertension, blood dycrasias, various vascular inflammatory diseases, and the postpartum state, in that order, as the main contributing and precipitating factor in nearly half of the cases in the below-40 age group. In the remaining cases no precipitating or contributory factors could be found.
The purpose of this paper is to report the case of a 35-year-old man in whom spontaneous dissecting aneurysm of the internal carotid artery in the neck was the cause of its sudden occlusion and resultant massive cerebral infarction. Study of this case and review of the literature of this rare condition emphasize the role of medial necrosis in the pathogenesis of the dissection, although considerable doubt persists concerning the etiology of the medial necrosis.