[A case of peripheral, fusiform type aneurysm originating from the superior cerebellar artery].

We reported a case of a 33-year-old woman who presented a subarachnoid hemorrhage due to rupture of an aneurysm arising from the ambient segment of the superior cerebellar artery (SCA). The patient who complained of severe headache and nausea was admitted on April 6, 1996. A CT scan revealed subarachnoid hemorrhage in the left cerebellopontine cistern. Left vertebral angiography showed a fusiform type aneurysm of the ambient segment of the left SCA. Trapping of the aneurysm was successfully performed via the subtemporal approach on the day of admission, April 6, 1996. She was discharged with no deficits on May 2, 1996. Fusiform type aneurysm arising from SCA is very rare. Only 3 cases have been reported in the literature. We discussed the pathogenesis of this aneurysm and the timing of surgery.