[Clinical features and outcomes in patients with asymptomatic moyamoya disease--from the results of nation-wide questionnaire survey].

After induction of noninvasive diagnostic tools, asymptomatic moyamoya disease is occasionally being diagnosed. However, there is no epidemiological or clinical data concerning this condition because of its rarity. To elucidate clinical features and outcomes in patients with asymptomatic moyamoya disease we conducted a nation-wide questionnaire survey. Questionnaires were sent to 88 neurosurgical institutes in 1994 and we received answers from 66 institutions (75% recovery). Diagnosis of moyamoya disease is based on the guidelines established by the research committee on moyamoya disease of the Ministry of Health and Welfare, Japan. Thirty three asymptomatic moyamoya disease patients were collected (11 male, 22 female) and divided into 2 groups; group 1 defined as patients without any symptoms, and group 2 as patients who did not show any symptoms except headache. 80% of group 1 patients were adults, whereas in group 2, children and adults were equally distributed. Follow-up periods were 3 years and 8 months on average. Among conservatively treated 28 patients, 2 patients died from suspected bleeding (mortality 7%) and 4 patients with TIAs resulted in good outcome. Among surgically treated 5 patients, 1 patient showed poor outcome due to post-operative infarction. Other 26 patients showed excellent outcome. Natural course of asymptomatic moyamoya disease seemed benign, but mortality from bleeding is not negligible. A prospective study of asymptomatic moyamoya disease is necessary to clarify its natural course and appropriate management strategy.