The purpose of this study is to suggest a new and simple classification of anterior communicating artery (ACoA) aneurysms based on the relation between A1 direction and aneurysm projection. We analyzed the effect of morphological features on angiographic outcome after coil embolization for ACoA aneurysms.
We conducted a retrospective case review of 78 consecutive patients (35 men and 43 women) with ACoA aneurysms treated at our institution from September 2004 to October 2013. The patterns of A1 direction and aneurysm projection allowed the classification of ACoA aneurysms into four types: S-S type, A1 with superior direction and aneurysm with superior projection; S-I type, A1 with superior direction and aneurysm with inferior projection; I-I type, A1 with inferior direction and aneurysm with inferior projection; I-S type, A1 with inferior direction and aneurysm with superior projection. The percentage distribution of each type is as follows: S-S, 28.2%; I-I, 44.9%; S-I, 11.5%; and I-S, 15.4%. The I-I type is the most common type of aneurysm in this classification.
Thirty-five patients were treated with endovascular coil embolization, and the average volume embolization ratios were as follows: S-S, 34.2%; I-I, 28.2%; S-I, 25.8%; and I-S, 26.6%. Complete occlusion (Raymond grade 1) was achieved at 90% in S-S, 35.7% in I-I, 42.9% in S-I, and 0% in I-S. The S-S and I-I types are likely to result in complete occlusion or neck remnant. The S-I and I-S types are likely to result in body filling.
It is thought that coil embolization was likely to have resulted unfavorably in direction mismatch types (S-I, I-S) because the relation between A1 direction and aneurysm projection directly affects the intraoperative deliverability and stability of the microcatheter.
In conclusion, this classification provides useful information for ACoA aneurysm treatment in a simple and immediate manner.