**Abstract**

Moyamoya disease (MMD) is a rare disease affecting the cerebral vasculature of the central nervous system (CNS) with a reported incidence of 0.35–0.94 per 100,000 populations. It was first reported from Japan and later from other parts of the world. The pathology is narrowing of blood vessels supplying anterior circulation and rarely posterior circulation. It was believed that the disease is genetic in origin, but environmental factors also play a role. Patients with this rare disease may present with ischemic or hemorrhagic symptoms. Ischemic symptoms account for the disease in most of the pediatric patients, whereas in adults, hemorrhage is more common. Diagnostic imaging like CT angiogram and magnetic resonance angiogram helps in demonstrating the narrowing or the collateral vessels like "a puff of smoke" (moyamoya) formed at the base of the brain. Moyamoya disease is treated medically and/or surgically. Aspirin is the main medication used. Surgical options are direct or indirect revascularization techniques to bypass the stenosis. The disease is progressive in majority of the patients, but if treated early, they can have good prognosis especially children.

**Keywords:** moyamoya, vascular, CNS, MMD, MMS

## **1. Introduction**

Moyamoya disease (MMD) is a rare disease of the central nervous system (CNS). It was first reported in Japan in the year 1957 and later reported from other Asian countries. "Moyamoya" in Japanese means "a puff of smoke" alluding to the characteristic angiographic appearance of the collateral circulation in the brain of the patient with moyamoya disease [1]. It can present either as an isolated condition (moyamoya disease) or as a part of a syndrome associated with other conditions. In the latter case, it is called moyamoya syndrome (MMS). Moyamoya disease usually manifests bilaterally [2], and moyamoya syndrome manifests, unilaterally, to begin with, which may progress to become bilateral disease [3].
