Anterior communicating artery aneurysms with associated anomalies.

In 296 cases with a single aneurysm of the anterior communicating artery (ACoA), fenestration or the presence of more than two ACoA's was observed in 17 cases (5.7%), and abnormal vessels of ACoA origin, such as a median artery of the corpus callosum, were observed in 13 cases (4.4%). As more than one anomaly was found in some of these cases, anomalies of the ACoA were found in total of 26 cases (8.8%). This occurrence rate was no higher than that observed in other cerebral aneurysm cases and in the control cases, which were reported previously. There was no significant increase of hypoplasia of the A1 portion if the ACoA aneurysm was complicated by other arterial anomalies.