Aneurysm at the origin of accessory middle cerebral artery associated with middle cerebral artery aplasia: case report.

A case of ruptured aneurysm at the origin of accessory middle cerebral artery associated with ipsilateral middle cerebral artery aplasia is reported. The angiograms did not show a middle cerebral artery shadow on the lesion side. Instead, the accessory middle cerebral artery ran toward the Sylvian fissure and supplied the middle cerebral artery territory along with multiple hypertrophied perforating branches. The operative findings confirmed that the cord-like, rudimentary middle cerebral artery had no internal blood flow. The effect of these combined anomalies on the hemodynamic equilibrium between the arteries of the same embryologic trees and the genesis of aneurysm is worthy of notice.