[Subarachnoid hemorrhage due to ruptured dissecting aneurysm of peripheral superior cerebellar artery].

The peripheral superior cerebellar artery (SCA) dissecting aneurysm (DA) is extremely rare, with only 4 cases (including our case) having been reported. Here we report a case of subarachnoid hemorrhage due to ruptured DA of peripheral SCA and summarize the 23 cases of the DA of peripheral arteries in the posterior fossa. A 64-year-old woman was found unconscious at home and was admitted to our hospital on December 12, 1998. A computed tomography scan revealed a diffuse subarachnoid hemorrhage (Fisher's classification Group 3), mainly in the prepontine cistern. Her neurological state on admission was Hunt and Kosnik grade III. A cerebral angiogram was performed on admission, and revealed a slightly enlarged lesion at the anterior pontine segment of the left SCA. The day after admission, a second angiogram was performed and revealed that the lesion was not well-defined. She was treated conservatively, with no change in condition. On the 16th day after admission, a third angiogram was performed and revealed a saccular aneurysm-like lesion arising at that region with intra luminal pooling sign. She was treated, using the left subtemporal approach. In the operation, organized clots and hemosiderin were identified in the prepontine cistern. However, saccular aneurysm was not found at all and only the arterial wall was thin and discolored. These serial angiogram and operative findings revealed a DA of peripheral SCA. In this case, serial angiogram showed singular change of findings within a short period. We emphasize the need to repeat the angiogram taking due timing into account.