A Rare Anatomic Variant of a Solitary Internal Carotid Artery Associated with Moyamoya Phenomenon of the Middle Cerebral Artery

SUMMARY: A case of a congenital solitary internal carotid artery with complicated anastomosis is presented. This rare anomaly was an incidental finding at cerebral angiography in a patient with a poor-grade subarachnoid hemorrhage and a ruptured anterior communicating artery aneurysm. We describe a case of a congenital solitary internal ca-rotid artery arising from the right side in a patient with a poor-grade subarachnoid hemorrhage and a rup-tured anterior communicating artery aneurysm. There was also complete occlusion of the proximal right middle cere-bral artery with collaterals reconstituting the terminal branches of the right middle cerebral artery. Such findings are extremely rare. Case Report An 81-year-old woman presented with sudden collapse. On admis-sion to our institution, the patient was unconscious. The Glasgow Coma Scale score on examination was 9/15. Blood pressure and pulse were stable. Noncontrast cranial CT findings were diffuse subarach