Moyamoya Disease: Epidemiology, Clinical Features, and Diagnosis.

Moyamoya disease (MMD) is a chronic, occlusive cerebrovascular disease characterized by progressive stenosis at the terminal portion of the internal carotid artery and an abnormal vascular network at the base of the brain. Although its etiology remains unknown, recent genetic studies identified RNF213 in the 17q25-ter region as an important susceptibility gene of MMD among East Asian populations. Possibly because of genetic differences, MMD is relatively common in people living in East Asian countries such as Korea and Japan, compared to those in the Western Hemisphere. The prevalence of MMD appears to be slightly lower among Chinese, compared to Koreans or Japanese. There are two peaks of incidence with different clinical presentations, at around 10 years and 30-40 years. The peak appears to occur later in women than men. In children, ischemic symptoms, especially transient ischemic attacks, are predominant. Intellectual decline, seizures, and involuntary movements are also more common in this age group. In contrast, adult patients present with intracranial hemorrhage more often than pediatric patients. In patients with MMD, intracerebral hemorrhage is more often accompanied by intraventricular hemorrhage than in patients with hypertensive intracerebral hemorrhage. These different age peaks and different clinical presentations in each age group are also observed in MMD patients in the USA. Catheter angiography is the diagnostic method of choice. Magnetic resonance (MR) angiography and computed tomographic angiography are noninvasive diagnostic methods. High-resolution vessel wall MR imaging also helps diagnose MMD by revealing concentric vessel wall narrowing with basal collaterals.