Role of aneurysm projection in "A2" fork orientation for determining the side of surgical approach

To determine factors that help decide the side of approach for anterior communicating artery (AComA) aneurysms, based on a prospective study.

Between January 2004 and January 2006, 93 cases with AComA aneurysms were treated through pterional approach. They were classified as Type I, II (IIa, IIb), III and IV, based on the various projections and size of aneurysm. The principle for the choice of operative side was designed based on the type of aneurysm and the A2 fork orientation (the interrelations between the plane of bilateral A2, AComA, and mid-saggital plane).

There were 55 aneurysms of Type I, 10 of Type IIa, 14 of Type IIb, 12 of Type III, and 2 of Type IV. In Types I and IIa, the side posteriorly placed to A2 was chosen for the approach. In Type IIb, the side of the dominant A1 was selected. In Type III, the side anteriorly placed to A2 was chosen. Type IV aneurysms were difficult to handle even if approached from the dominant A1. There were 11 cases treated from the side of non-dominant A1. The overall outcome in the treatment of AComA aneurysms were considered excellent in 90.8% of cases according to the Glasgow Outcome Scale, with complete occlusion of aneurysms and complete patency of parent or perforating arteries.

Applying three-dimensional computed tomography and magnetic resonance angiography, we classified AComA aneurysms as four types and undertook surgical clipping from the chosen side of approach, according to the type of aneurysm and the A2 fork orientation. The selective side of approach on the basis of individual decision-making has led to favourable outcomes.