[Frequency of vascular variations and anomalies accompanying intracranial aneurysms].

PURPOSE: Investigation of the sites of intracranial aneurysms and incidence of associated congenital variations or anomalies. MATERIALS AND METHODS: One hundred and ninety cerebral angiography examinations that were positive for aneurysm were evaluated retrospectively. Fourteen cases with vasospasm were excluded and the remaining 176 patients were assessed for the location of the aneurysm and co-incidental vascular variations and/or anomalies. There were two observers in the study, one of whom was an experienced vascular radiologist. RESULTS: The most frequent locations of aneurysms were the supraclinoid internal carotid artery (32%, n=74), anterior communicating artery (30%, n=68), and middle cerebral artery bifurcation (23%, n=52). Twenty-eight patients (17%) had multiple aneurysms. Ninety-one (52%) patients had a vascular anomaly or variation. Hypoplasia or agenesis of A1 segment of the anterior cerebral artery was found in 48 patients, an azygous anterior cerebral artery in 1, a frontoorbital artery in 1, a duplicated middle cerebral artery in 1, early bifurcation of the middle cerebral artery in 9, persistent fetal origin of the posterior cerebral artery in 26, fenestration of P1 segment of posterior cerebral artery in 1, agenesis of P1 segment of posterior cerebral artery in 1, fenestration of vertebral artery in 1, double trunk visualization of superior cerebellar artery in 2 patients. CONCLUSION: Due to an increased hemodynamic stress, congenital anomalies of the intracranial arteries predispose to the formation of saccular aneurysms. Nomalies such as A1 hypoplasia or agenesis, azygous anterior cerebral artery, accessory middle cerebral artery and persistent trigeminal artery are detected more frequently in patients with cerebral aneurysms compared to the normal population. The location of aneurysms and the frequency of arterial variations and anomalies in this study correlated well with data found in previous studies.