Background Basilar artery (BA) trunk aneurysms are rare, and the clinical characteristics and outcomes of endovascular treatment (EVT) remain unclear. The purpose of this study was to report clinical and angiographic outcomes of BA trunk aneurysm treated with EVT and to analyze risk factors for unfavorable outcomes.

Methods From October 2004 to December 2020, a total of 40 patients with BA trunk aneurysms underwent EVT. Clinical characteristics and outcomes were evaluated retrospectively from a prospectively collected database. Of the 40 enrolled patients, nine were treated by coiling without stents, 17 were treated by stent-assisted coiling, six by stent only, five by flow diverters, and three by vertebral artery occlusion.

Results In total, 27 (67.5%) patients had subarachnoid hemorrhage as an initial presentation, and 20 (50.0%) had large/giant aneurysms. Procedure-related complications occurred in five patients (12.5%); favorable clinical outcome was achieved in 27 patients (67.5%); and six patients (15.0%) died. Favorable angiographic outcome was achieved in 26 (83.9%) of 31 patients who underwent follow-up angiography. Poor initial Hunt-and-Hess grade (OR 7.67, 95% CI 1.55 to 37.80; p=0.018) was the only independent risk factor for unfavorable clinical outcome. Large/giant aneurysm (OR 8.14, 95% CI 1.88 to 27.46; p=0.047) and long lesion (OR 14.25, 95% CI 1.48 to 69.80; p=0.013) were independent risk factors for unfavorable angiographic outcomes during follow-up.

Conclusions EVT might be a feasible option for this rare disease entity. Unfavorable angiographic outcome might be expected in a large/giant aneurysm or a long lesion. It can be difficult to treat BA trunk aneurysms by EVT, needing multiple procedures or various techniques due to diverse clinical and angiographic features.