Does embryologic basilar fusion type impact basilar apex aneurysm treatment outcomes?

Basilar apex aneurysms can be challenging entities for both open and endovascular treatment. The basilar artery forms from fusion of the paired longitudinal neural arteries that produces several anatomical morphologies known to correlate with basilar aneurysm formation. There is paucity of literature on these morphologic types on aneurysm treatment. The aim of this study was to examine endovascular treatment outcomes of basilar apex aneurysms based on embryologic fusion type.

We performed a retrospective review of aneurysm databases from one American and one Japanese institution for basilar apex aneurysms treated using endovascular modalities. Angiographic studies were reviewed, and embryologic fusion type was assigned. Outcomes of interest included treatment type, angiographic and complications.

151 patients were included in the analysis. There were 76 patients (50.3 %) with cranial fusion, 28 patients (18.6 %) with caudal fusion, and 47 patients (31.1 %) with asymmetric fusion. Mean aneurysm height was largest in the asymmetric fusion group (5.2 mm; [IQR] 3.7-7.0) compared to cranial (4.3 mm; [IQR] 2.9-5.8) and caudal (4.8 mm; [IQR] 3.5-8.0) groups (p = 0.03). Treatment modality did not differ among embryologic fusion types; stent assisted coil embolization was the most frequent treatment modality (58.9 %). There were no differences in complication rates between groups. One-year complete occlusion rates were lowest in the asymmetric fusion group (40.7 %) and highest in the cranial fusion group (72.9 %) (p = 0.03).

There are differences in one-year complete occlusion rates following endovascular treatment of basilar apex aneurysms among varying embryologic fusion types. Asymmetric fusion is associated with the lowest complete occlusion rate. Embryologic fusion type may portend differences in outcomes among patients undergoing treatment for basilar apex aneurysms.