[Moyamoya disease associated with a false aneurysm--case report and review of the literature].

A 67-year-old male was admitted to our clinic on May 1, 1981, because of mild confusion and a left hemiparesis. About 6 years ago, when he had a left-sided homonymous hemianopia, carotid angiography revealed moyamoya disease. CT scan on the admission showed an intracerebral hematoma in the right temporal lobe, which ruptured to the lateral ventricle. An angiogram demonstrated the net work of moyamoya vessels in the base of the brain and a "newly-appeared" aneurysm at the peripheral portion of the right anterior choroidal artery. This artery was shown on the previous angiogram also but did not bear the aneurysm. At the emergent operation the hematoma was evacuated and the aneurysm was excised, which was proved histologically to be a false aneurysm. Thirty-six cases of moyamoya diseases associated with aneurysm including the present case were reviewed. There were 44 aneurysms in this series. They were classified into groups--1) the major artery aneurysms arising from the major cerebral arterial segments; 2) the peripheral artery aneurysms arising from the distal segments of the peripheral cerebral arteries. The major artery aneurysms were found more frequently in the vertebro-basilar system, and the peripheral artery aneurysms in the basal ganglia, near or in the moyamoya vessels. Of 26 major artery aneurysms 12 were proved to be saccular aneurysms, 9 by surgeries and 3 by autopsy studies respectively. Of 18 cases of the peripheral group the aneurysms were excised operatively in two cases, and autopsy studies were performed in other two cases. The peripheral artery aneurysms were examined histologically in three cases; one was proved to be a false aneurysm, the other was thought to be a true aneurysm, and the third one was not verified. In 8 cases, the peripheral artery aneurysms disappeared on the follow-up angiograms and were supposed to be false aneurysms. From these reported cases, it may be suggested that major artery aneurysms are mainly true aneurysms and peripheral artery aneurysms are false aneurysms.