Anomalous medial origin of the anterior choroidal artery with associated aneurysm.

Injury to the anterior choroidal artery (AchA) can be devastating owing to the importance of the territory it supplies. The AchA is a known site of aneurysm formation, and is often exposed during various surgical and endovascular procedures. We report a patient with an aneurysm at the origin of the AchA, and an anomalous medial take off of the artery from the internal carotid artery, then a sharp lateral turn followed by a normal course toward the choroidal fissure, unreported to date to our knowledge. The aneurysm was treated successfully by endovascular therapy. The typical anatomy of the AchA, and reported variations in its origin are discussed. Thorough knowledge of the normal cerebrovascular anatomy and attention to variations play an important role in the successful management of patients with neurological vascular conditions.