Multiple aneurysms associated with agenesis of internal carotid artery

Agenesis of internal carotid artery (ICA) is a rare anomaly. The contralateral dominant artery has a high incidence of aneurysms. A 50-year-old male patient had aneurysmal subarachnoid hemorrhage due to rupture of a paraclinoid aneurysm. He also had an anterior communicating artery (Acom) aneurysm and the contralateral ICA was absent. To the best of the authors knowledge, the combination of agenesis of unilateral internal carotid artery with the unique association of a paraclinoid and an Acom aneurysm has not been previously reported. A meticulous assessment of the collateral blood circulation prior to surgery is mandatory in these cases for avoiding postoperative ischemic injury.