The Abnormally Tangled Artery Simulating an Intracranial Aneurysm with Complete Defect of the Terminal Portion of the Internal Carotid Artery: Report of a Case

A peculiar case of abnormally tangled cerebral artery with complete defect of the terminal portion of the internal carotid artery is reported. The patient suffered from an intraventricular hemorrhage. Preoperative angiography suggested an aneurysm at the junction of the right internal carotid and posterior communicating arteries and also an occlusion of the terminal portion of the right internal carotid artery which was thought to have developed asymptomatically prior to the hemorrhage. The right cerebral hemisphere was supplied mainly by an artery arising from the anterior cerebral artery and partly by several cortical arteries of the anterior and posterior cerebral arteries. Abnormal fine arteries originating from the internal carotid artery also supplied the basal part of the hemisphere. Operative findings, however, revealed that the aneurysm-like mass was not a true aneurysm, but rather was abnormally elongated tangled arteries composed of the posterior communicating and posterior cerebral arteries. Furthermore, no vessels were found where the terminal portion of the internal carotid artery and the horizontal portion of the anterior and middle cerebral arteries were considered to exist. This case offers the first example in which the complete defect was localized at the terminal portion of the internal carotid artery. The radiological findings and the pathogenesis of these peculiar lesions are discussed.