Anatomic risk factors for S1 segment superior cerebellar artery aneurysm rupture: A radiological study on 81 consecutive patients.

Abstract Background Due to treatment associated risks, it is still debatable which unruptured aneurysm should be treated. Anatomical and morphological characteristics may aid to predict the rupture risk of SCA aneurysm and possibly support in decision making during treatment. Objectives To identify morphological characteristics that could predict the rupture of SCA aneurysms. Methods A retrospective analysis of CT 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 (OR=2.3, CI=0.84-6.34). An aneurysm to basilar angle Conclusion Ruptured SCA aneurysms are usually small in size. Higher aspect ratio and the smaler angle between SCA aneurysm and basilar artery had significantly higher risk of SCA (S1 segment) aneurysm rupture.