Supply of the unilateral circulation of the brain by an occipital artery anastomosis--a case report.

The author presents a case of occlusion of the right internal carotid artery in which the vertebral artery, the basilar artery and the entire right-sided anterior and posterior circulations were supplied by the right external carotid artery by way of an occipital-vertebral artery anastomosis. In this case, the usually small muscular branches of the occipital artery developed into collaterals capable of supplying the entire right side of the brain.