OBJECTIVETo investigate the etiology, pathology, and mechanism of pathogenesis of Moyamoya disease.

METHODSA total of 15 human autopsies were analyzed. In addition, in order to create an animal model of the disease, 21 Japanese rabbits were divided randomly into two groups and subjected to injections of horse serum either intravenously or locally in the area of the sympathetic ganglia. Pathological and immunohistochemical characteristics were observed.

RESULTSThe pathological features of the autopsies and the animal models both involved intima hyperplasia and stenosis or even occlusion of the lumen in the terminal ends of the internal carotid artery and the anterior and middle cerebral arteries. Disconnections or even breakages of the inner layer of the lumen were also observed, without an obvious inflammatory response. Hyperplasic smooth muscle cells of the medial membrane had extended inward through broken portions of the internal elastic lamina, with intima cell hyperplasia resulting in lumen stenosis. The hyperplastic vascular walls were positive for IgG and IgM.

CONCLUSIONSThe etiology of Moyamoya disease may involve allergic angiitis. A possible mechanism is that proximal portions of the circle of Willis first develop chronic stenosis or occlusion, leading to compensatory small vessel proliferation, which perforates into the cerebral parenchyma.