Abstract
A 28-year-old woman was referred to our hospital with a sudden, very severe headache. Brain computed tomographic angiography showed a saccular cerebral aneurysm at the bifurcation of the left middle cerebral artery and infraoptic courses of both anterior cerebral arteries. The anterior cerebral arteries were seen to arise from the ipsilateral internal cerebral arteries at the level of the origin of the ophthalmic artery, passed underneath the ipsilateral optic nerve, and turned upward at ventral portion of the optic chiasm.Infraoptic course of the proximal anterior cerebral artery is an extremely rare anomaly and is often associated with cerebral aneurysms. We report the clinical features, radiological findings, and possible genesis of this anomaly with a literature review.