Moyamoya disease and moyamoya syndrome (MMD/S) are a considerable source of neurologic morbidity in adults as a result of both ischemic and hemorrhagic events. Unfortunately, there is a paucity of literature detailing the natural course of MMD/S in the USA. To elucidate epidemiological information, stroke rates, hemorrhage rates, and risk factors for these events in patients with MMD/S, we reviewed our own institutional cohort of 42 North American adults with MMD/S. The mean patient age was 38.8 (standard deviation [SD] 12.7) with a 5:1 female-to-male predominance. About 74% of patients had an ischemic presentation while only 17% presented with hemorrhage. The mean Suzuki grade was higher in patients presenting with hemorrhage (3.7 compared to 2.9, p=0.03) but similar in those who presented with a stroke as compared to those who did not (3.00 compared to 3.05, p=0.88). The overall annual stroke and hemorrhage rates were 13.3% and 1.7%, respectively. Statistically significant risk factors for stroke or hemorrhage were female sex (p=0.031) and stroke presentation within 3 years (hazard ratio [HR]=4.08, p=0.035). Smoking was another risk factor, but it did not meet statistical significance (HR=1.56, p=0.38). We conclude that these results favor intervention for MMD/S to mitigate the high annual stroke risk. This particularly applies to females and/or those presenting with a recent stroke/hemorrhage. Our results also serve as a baseline for comparison of hemorrhage rates after intervention.
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