Unilateral agenesis of internal carotid artery associated with superior cerebellar artery aneurysm and anomalous origin of ophthalmic artery arising from the ipsilateral posterior communicating artery.

Congenital agenesis of the unilateral internal carotid artery is a rare anomaly. The agenesis of the internal carotid artery is associated with a higher incidence of intracranial aneurysms. This report describes a rare case of internal carotid artery agenesis associated with an aneurysm of the left superior cerebellar artery in a 52-year-old woman. The left middle cerebral artery was supplied from the vertebrobasilar system through the dilated left posterior communicating artery associated with anomalous origin of the left ophthalmic artery from the left posterior communicating artery. This report demonstrates a rare combination of left internal carotid artery agenesis with associated intracranial aneurysm and anomalous origin of the ophthalmic artery, discussion of embryogenesis, clinical significance, and imaging findings.