Morphological study of aneurysms at the junction of the superior cerebellar artery

Superior cerebellar artery (SCA) aneurysms sometimes involve the origin of the SCA making treatment difficult. We focused on the morphological characteristics of SCA aneurysms and adjacent vascular structures to apply clinical decision-making for the treatment strategy. Sixty-nine SCA aneurysms, including 34 ruptured and 35 unruptured ones, had been treated for over 12 years. Multiple aneurysms were associated in 30 patients. The pattern of the neck position of aneurysms was classified into three types: Type A: no SCA-involved type; Type B: half involved type with SCA originating from the aneurysmal neck; Type C: pure SCA aneurysm with all the neck mounting on SCA. Morphological and clinical analysis was done between ruptured and unruptured aneurysms and among the three types. There was no difference in patient profile between ruptured and unruptured aneurysms. The angle formed by the posterior cerebral artery and SCA on the aneurysm side was obtuse in 62 (90%) patients. From the morphological point of view the SCA-involved type (types B + C) was significantly more prevalent in ruptured aneurysms (77%). Bleb formation was particular in ruptured aneurysms. As for the treatment, the risk of SCA occlusion and incomplete and attempted operation was particularly high in cases with SCA-involved type. Although SCA aneurysms may grow due to the hemodynamic stress at the opened bifurcation between the PCA and SCA, the neck shifting to the origin of SCA, particularly in ruptured lesions,may suggest some other etiological mechanism. SCA-involved type aneurysms had a high treatment risk of SCA occlusion and tended to incomplete treatment to avoid such ischemic complications.