[A Case of Ruptured Peripheral Cerebral Aneurysm at Abnormal Vessels Associated with Middle Cerebral Artery Stenosis:Similarity to Moyamoya Disease].

We report a case of ruptured peripheral cerebral aneurysm at abnormal vessels associated with severe stenosis at the middle cerebral artery (MCA). A 66-year-old woman was admitted at our hospital with headache on foot. Computed tomography (CT) showed intracerebral hemorrhage in the left fronto-basal area. Three-dimensional-CT and conventional angiogram revealed abnormal vessels, which were similar to those seen in moyamoya disease, with a small enhancement close to the hematoma. On day 11, subsequent cerebral angiogram demonstrated an aneurysm at the peripheral portion of an abnormal vessel arising from the left A2. On day 17, soon after the diagnosis of the ruptured aneurysm was made (while still at the subacute stage), we operated on the aneurysm. Superficial temporal artery (STA)-MCA anastomosis was also performed to preserve cerebral blood flow and reduce hemodynamic stress. Several days after the operation, she had transient aphasia due to hyperperfusion of the MCA territory, but eventually recovered with no neurological deficit at discharge. Follow-up study revealed revascularization from the branches of the external carotid artery as well as the STA. On admission, we initially thought that this patient had abnormal vessels associated with arteriosclerotic MCA stenosis. However, the postoperative clinical course as well as the histopathological specimens of both the abnormal artery with the aneurysm and the STA revealed similar findings to those of moyamoya disease. Although this case did not satisfy the criteria for moyamoya disease, it is conceivable that a single arterial occlusive lesion associated with moyamoya-like vessels might develop in the same mechanism with that of moyamoya disease.