Left carotid-anterior cerebral artery anastomosis diagnosed by MR angiography: a case report.

Anastomosis of the carotid-anterior cerebral artery (ACA) is a rare anomalous vessel that arises from the internal carotid artery (ICA) at the level of the ophthalmic artery and takes an infraoptic and prechiasmatic path to anastomose with the ACA. It has known right-sided predominance. We report the case of an 83-year-old man with a left carotid-ACA anastomosis that was diagnosed by magnetic resonance (MR) angiography from the neck to the head during investigation of transient left hemiplegia. The right ICA was occluded at its origin. Our literature search revealed only six reported cases of left carotid-ACA anastomoses. We believe ours is the first case diagnosed by MR angiography.