A Ruptured Aneurysm at the Infraoptic Azygous Anterior Cerebral Artery with the Contralateral Internal Carotid Artery Agenesis Treated by Y-stent Assisted Coil Embolization.

Infraoptic anterior cerebral artery (ACA) is an extremely rare congenital anomaly. This anomalous artery usually arises from the intradural internal carotid artery (ICA) near the level of the ophthalmic artery (OA) or rarely from the extradural ICA. This anomaly frequently harbors a cerebral aneurysm, and may involve other coexisting vascular anomalies. In the case of this anomaly, surgical treatment of the aneurysm at the proximal ACA or anterior communicating artery (ACoA) may sometimes be difficult, because the veiled proximal ACA by the optic nerve would make proximal control inconvenient and the vertical midline segment of the proximal ACA would frequently form a superiorly directing aneurysm with a relatively high position. We report on an extremely rare case of a ruptured aneurysm at the infraoptic azygous ACA, possibly having an extradural origin, accompanied by contralateral ICA agenesis, and also introduce a feasible method for treatment by Y-stent assisted coil embolization.