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Distribution of thrombotic lesions in the cerebral arteries in spontaneous occlusion of the circle of Willis: cerebrovascular moyamoya disease.

In this paper, we have attempted to discuss the role of thrombogenesis in the formation or progression of the obstructive vascular lesions in so-called "spontaneous occlusion of the circle of Willis" (cerebrovascular Moyamoya disease) through histopathological observation on the cerebral arteries in this disease. Using the autopsy cases with this disease (28 cases), we examined the histological details of the cerebral arteries, including the circle of Willis and its major branches, to describe the distribution and the nature of thrombotic lesions. Thrombotic lesions were observed in up to 15 out of the 28 cases (54%). Predominant sites of the thrombi were the internal carotid arteries, the posterior communicating arteries, and the posterior cerebral arteries. The high incidence of thrombi formation as well as their distribution which closely correlated with the progression of the intimal lesion of this disease strongly suggested the importance of abnormal thrombogenesis as an etiologic factor in this disease.