Combination of olfactory course anterior cerebral artery and accessory middle cerebral artery (MCA) with occluded in situ MCA and related moyamoya phenomenon.

We describe a rare case of congenital persistence of a primitive olfactory anterior cerebral artery in association with an ipsilateral accessory middle cerebral artery. The normally and anatomically positioned, or in situ, middle cerebral artery was occluded. This, along with a well-developed anastomotic network of lenticulostriate artery domains and leptomeningeal collaterals suggested a moyamoya phenomenon. To our knowledge, ours is the first report of this anatomic variant and the altered conventional vascular territories of supply.