A1-A2 anterior cerebral artery fenestration. A case report of a rare anatomical variant

Cerebral vascular anatomical variations are not uncommon in the human population. Their prevalence is not exactly known, as most of them are incidentally diagnosed on angiography or postmortem dissections. We present a rare fenestration of the A1 segment of the anterior cerebral artery presenting with a ruptured saccular aneurysm. A 42-year-old hypertensive patient presented unconscious following a ruptured saccular aneurysm. The computer tomography angiography showed a fenestration of the right A1 segment of the anterior cerebral artery (ACA). The medial segment of the A1 was communicating with the left ACA via the Anterior communicating artery, while the lateral segment was directly joining the A2 segment of the same side. Intraoperatively, the two segments were identified as separate vascular structures not sharing adventitia, and of equal caliber. The aneurysm arising from the bifurcation was clipped. The patient recovered with no neurological deficits. Many vascular anomalies like fenestrations and bifurcations are underdiagnosed, as many of them remain asymptomatic and are discovered incidentally on postmortem dissection or angiography for other pathologies. This has led to a paucity of cases to determine the prevalence in the human population. Good knowledge of the vascular anatomy variations and associated risk of aneurysm is important for the vascular neurosurgeons.