Risk factors of moyamoya disease in Canada and the USA.

Over the past 28 years, 39 patients with Moyamoya disease or syndrome defined as spontaneous occlusion of the circle of Willis with extensive basal collateral vessels have been treated by the author in Canada and the USA. All patients presented with clinical or radiologic evidence of hemorrhage (23) or ischemia and infarction (16). A total of 12 patients had associated cerebral aneurysms and seven of these patients with aneurysms presented with subarachnoid hemorrhage. The patients ages ranged from 5 to 47 years. Of these 58% were female. The patients racial origin included North American Indian, Innuit, East Indian/Pakistani, Japanese, Chinese, Filipino, Korean, Malayasian, Hispanic, African American and Caucasian. Familial clustering was seen in North American Indian, Innuit and Caucasian patients. Associated disorders (tuberculosis, pharyngitis, thalassemia, fibromuscular hyperplasia, polycystic kidney, sickle cell trait and hypertension) were common in these patients, as was the use of tobacco, alcohol and in the adult females, oral contraceptives. It may be concluded from this series that the etiology of Moyamoya disease or syndrome is probably multifactorial, but that some racial and familial groups are more susceptible. Furthermore, in that the clinical and angiographic features are identical, the separation between Moyamoya disease and syndrome may not be helpful in understanding the etiology and pathophysiology of this disorder.