[Natural History of Asymptomatic Moyamoya Disease].

Emerging evidence obtained as a result of recent advancements in non-invasive diagnostic modalities indicates that the incidence of asymptomatic moyamoya disease may be much higher than previously reported. However, there are currently no established guidelines for managing asymptomatic moyamoya disease because of the lack of sufficient information regarding its clinical features, prognosis, and treatment strategies. To address these issues, we conducted a multicenter prospective cohort study, the Asymptomatic Moyamoya Registry(AMORE), in Japan. The interim analysis of the AMORE revealed that affected hemispheres may carry a 1.0% annual risk of stroke, mainly hemorrhagic stroke, in asymptomatic moyamoya disease. Grade-2 choroidal anastomosis was found to be an independent predictor of stroke, whereas microbleeds and Grade-2 choroidal anastomosis were independent predictors of hemorrhagic stroke. The annual risk of disease progression, transient ischemic stroke(TIA), and de novo microbleeds were 5.9%, 2.3%, and 2.3%, respectively. Younger age and hypercholesterolemia were predictors of disease progression; disease progression prior to TIA was a significant predictor of TIA, and microbleeds at the time of enrollment were significant predictors of de novo microbleeds. Further research on the impact of genetic mutations and cerebral hemodynamics on the prognosis of asymptomatic moyamoya disease is warranted.