Anatomic Risk Factors for S1 Segment Superior Cerebellar Artery Aneurysm Rupture : A Radiologic Study on 81 Consecutive Patients

Background: Due to treatment associated risks, it is still debatable which unruptured aneurysm should be treated. Anatomic and morphologic characteristics may aid to predict the rupture risk of superior cerebellar artery (SCA) aneurysm and possibly support in decision- making during treatment. Objectives: To identify morphologic characteristics that could predict the rupture of SCA aneurysms. Methods: A retrospective analysis of computed tomography angiography images of 81 consecutive patients harboring SCA aneurysm who were treated between 1980 to 2014 at Helsinki University Hospital was performed. Results: Of the 81 analyzed SCA aneurysms, 30 (37%) were unruptured and remaining 51 (63%) presented with subarachnoid hemorrhage. The mean ± SD size of unruptured SCA aneurysms was 6.2 ± 6.3 mm; mean size of ruptured SCA aneurysms was 5.9 ± 5.4 mm. The mean ± SD aspect ratio was 0.9 ± 0.3 in unruptured and 1.14 ± 0.44 in ruptured SCA aneurysms. The mean ± SD degree angle between basilar artery and aneurysm was 74.7 ± 24.4 in unruptured and 65.9 ± 23 ruptured SCA aneurysms. Patients with ruptured SCA aneurysm showed significantly higher aspect ratio (Mann-Whitney U, P = 0.01) and smaller aneurysm to basilar artery angle (Mann-Whitney U, P = 0.039). Aspect ratio >1.1 had 2.3 times higher risk of rupture (odds ration [OR] 2.3, 95% confidence interval [CI] 0.84–6.34). An aneurysm to basilar angle