Association of Anterior Communicating Artery Aneurysms with Triplicate A2 Segment of the Anterior Cerebral Artery

Abstract

Triplicate A2 segment of the anterior cerebral artery is a rare anatomical variant (1%-3% prevalence) that which is thought to result mainly from persistence of the embryonic median artery of the corpus callosum. We sought to determine whether the triple-A2 variant is specifically associated with anterior communicating artery (ACoA) aneurysm. We reviewed 2-dimensional digital-subtraction angiography (2D-DSA) as well as 3-dimensional rotational angiography (3D-RA) images of 55 patients with ACoA aneurysms who presented for evaluation and treatment between 2009 and 2014 at our institution. The criteria for definitively obtaining an accurate accounting of all A2 segments was presence of adequate cross-filling across the ACoA on 2D-DSA or 3D-RA imaging, or ability to fuse left and right 3D-RA images. Patients whose imaging did not meet these criteria were excluded from further analysis. We obtained a definitive count of all A2 segments in 36 patients. Among these, 19 patients (5 with the triple-A2 variant) were treated surgically, and 17 patients (2with the triple-A2 variant) were treated endovascularly. The triple-A2 variant was seen in 7 patients. The prevalence of triple-A2 variant among patients with ACoA aneurysm was 19.4%. Patients with ACoA aneurysms had a significantly higher prevalence of the triple-A2 variant compared with the general population (P < 0.00001). Compared with the normal population, patients with ACoA aneurysms deemed to require treatment have a significantly higher likelihood of having triplicate A2 segment. Knowledge of this anatomical variation is of critical importance in planning and executing endovascular and microsurgical treatment of ACoA aneurysms.