Angiographic demonstration of congenital absence of both internal carotid arteries. Case report.

The authors present angiographic demonstration of bilateral, congenital, total absence of the internal carotid arteries in a patient with subarachnoid hemorrhage. Angiography demonstrated complete absence of both internal carotid arteries. The intracranial blood supply had been provided by communication between a hypertrophied basilar artery and the circle of Willis through the posterior communicating arteries. An aneurysm, believed to be the site of the subarachnoid hemorrhage, arose from the basilar artery. Absence of the carotid canals substantiated the congenital nature of the anomaly. The related embryology is reviewed.