Introduction: Triplicate A2 segment of the anterior cerebral artery (ACA) is a rare anatomical variant (1-3% prevalence) that is thought to result mainly from persistence of the embryonic median artery of the corpus callosum (Figure). We sought to determine if triple-A2 variant is specifically associated with anterior communicating artery (AComA) aneurysm.
Methods: We reviewed two- and three-dimensional digital-subtraction angiography (DSA) images of 55 patients with AComA aneurysms treated between 2009 and 2014 at our institution. The criteria to obtain definitive accounting of all A2 segments were presence of adequate cross-filling across the AComA or ability to fuse rotational 3D-DSA images of left and right internal carotid artery injections. Patients whose imaging did not meet the above criteria were excluded from further analysis.
Results: In 36 patients we were able to obtain a definitive count of all A2 segments. Among these, 16 patients including 5 with the triple-A2 variant were treated surgically, and 20 patients including 2 with the triple-A2 variant were treated endovascularly. A total of 7 patients had the triple-A2 variant. The prevalence of triple-A2 variant among patients with AComA aneurysm was 19.4%.
Conclusions: Compared to normal population, patients with AComA aneurysm have a significantly higher likelihood of having triplicate A2 segment of the ACA (P<0.0001). Knowledge of this variation is of critical importance in planning and executing endovascular and open surgical treatment of AComA aneurysms.
Patient Care: Knowledge of triple-A2 variant is crucial for open surgical or endovascular treatment of anterior communicating artery aneurysms. This research highlights the significant association of these two conditions and the importance of looking for this variant prior to treatment planning.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the triple-A2 variant, its main developmental origin, and its prevalence in the normal population, 2) Understand the association of the triple-A2 variant with anterior communicating artery aneurysms, and 3) Discuss the importance of knowledge of this variant for treatment of anterior communicating artery aneurysms.