Persistent carotid-vertebral anastomosis associated with contralateral accessory middle cerebral artery.

An exceptional case is reported of a complex anomaly of the brain arteries including low left carotid bifurcation, persistent carotid-vertebral anastomosis on the left and accessory middle cerebral artery on the right; the whole posterior circulation was only filled through the anomalous anastomotic vessel which joined with the vertebral artery because of a contralateral hypoplasic vertebral artery and the absence of both posterior communicating arteries. This association has not been previously reported in the literature. The embryological processes leading to these arterial anomalies are discussed. Risks related to a severe carotid stenosis or occlusion and to surgical or endovascular procedures in patients harboring these arterial anomalies are emphasized.