Moyamoya Disease.

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 is unknown, recent genetic studies have identified RNF213 in the 17q25-ter region as an important susceptibility gene of MMD among East Asian populations. A c.14576G>A polymorphism in RNF213 was identified in 95% of MMD patients with a family history and in 79% of sporadic cases, and patients carrying this polymorphism exhibited significantly earlier disease onset and a more-severe form of MMD. Due possibly to genetic differences, the prevalence of MMD is higher in East Asia (e.g., Korea and Japan) than in Western countries. The MMD prevalence peaks at two ages with different clinical presentations: around 10 years and at 30-45 years. Ischemic symptoms, including transient ischemic attacks, are the most important clinical manifestation in both children and adults. Intracranial hemorrhages are more frequent in adults than in children. Catheter angiography is a diagnostic method of choice. Magnetic resonance angiography and computed tomography angiography are noninvasive diagnostic methods. High-resolution vessel-wall magnetic resonance imaging also helps in diagnosing MMD by revealing concentric vessel-wall narrowing with basal collaterals. Surgical revascularization such as extracranial-intracranial bypass is the preferred procedure for MMD patients presenting with ischemic stroke. Surgical therapy may also be effective in patients with hemorrhages, based on recent observations in the Japan Adult Moyamoya trial. Procedure-related cerebral infarction and hyperperfusion syndrome are potential complications that can lead to neurological deterioration.