**1. Introduction**

Moyamoya disease (MMD) is a rare vascular syndrome most commonly found among the Japanese and other Asiatic peoples, its is chareacterized by the angiographic appearance of widespread cerebral collaterals due to occlusion of one or both internal carotid arteries [1]. The aetiology is unclear, but is perhaps related to an acquired lesion of the blood vessels at the brain's base. MMD was first described in Japan in 1957 by Takeuchi and Shimizu [2]. Although it is more common in Japan, clinical cases of the pathology have been reported in other parts of the world [3]. The incidence of MMD peaks in two age groups: int those around 4 years-old (pediatric MoyaMoya Disease, pMMD), and those in their 40s (adult MoyaMoya Disease, aMMD) [4]. There are almost twice as many female patients as there are male [5]. MMD is the most common pediatric cerebrovascular disorder in Japan, with a prevalence of about three cases per 100,000 children [6], while the incidence in Europe is approximately one- tenth of that observed in Japan [7]. A 2005 review result suggest an incidence of 0.086 cases per 100,000 people in the U.S. [8]. There are two main etiological categories of symptoms: those due to cerebral ischemia (stroke, transient ischemic attacks, and seizures, more frequent in pMMD) [9], and hemorrhagic symptoms due to the secondary effects of compensatory mechanisms that are triggered in response to the ischemia (hemorrhage of fragile collateral vessels and headache due to dilated transdural vessels, more frequent in aMMD). Individual variations in the degree of arterial involvement, the progression of stenosis, the regions of the ischemic cortex, and the response to reduced blood supply

explain the wide range of clinical presentations of the disease [10]. This chapter reviews the literature on moyamoya disease, specifically on neuropsychological aspects, in both pediatric and adult populations.
