Anomalous internal carotid artery-anterior cerebral artery anastomosis associated with fenestration and cerebral aneurysm.

A 69-year-old female presented with a ruptured aneurysm at the distal tip of a fenestrated anomalous artery which originated in the ophthalmic segment of the internal carotid artery (ICA), passed between the optic nerves, ascended along the midline, and formed the fenestration before dividing into the bilateral pericallosal arteries. The anomalous artery manifested as subarachnoid hemorrhage. Four days later, she died from severe pulmonary edema. The angiographic finding was confirmed by postmortem examination. Numerous perforating vessels from the anomalous artery and the distal ICA supplied the optic nerves and chiasm. This finding supports the idea that this anomalous vessel may be an extreme developmental variation of the prechiasmal arterial plexus.