[Ruptured aneurysm of bihemispheric anterior cerebral artery bifurcation: case report].

It is well known that distal anterior cerebral artery (ACA) aneurysms are often associated with the anomalies of the ACA, of which azygos ACA and triple ACA have frequently been described. In this report, we present a rare case with a ruptured aneurysm arising from the bifurcation of the bihemispheric ACA, a rare anomaly of the ACA. A 63-year-old male suddenly developed severe headache, consciousness disturbance, and left hemiparesis, and was admitted to our hospital. Plain CT scans revealed subarachnoid clots that were densely distributed in the supracallosal cistern. Cerebral angiography demonstrated that the left pericallosal artery supplied blood flow to the bilateral parietal lobes through the bihemispheric arteries. A saccular aneurysm was found at their bifurcation. He underwent clipping surgery through interhemispheric approach. Postoperative course was uneventful. Special care should be taken not to occlude the bihemispheric arteries supplying to the bilateral parietal lobes during surgery.