Moyamoya disease is an uncommon chronic cerebrovasculopathy, characterized by progressive stenosis of the terminal portion of the internal carotid artery and its main branches, in association with the development of compensatory collateral vessels at the base of the brain.
The etiology is unknown, and was originally considered exclusive to East Asia, with particular prevalence in Japan. Moyamoya disease is increasingly diagnosed throughout the world, and represents an important cause of childhood stroke in Western countries. In some cases, similar angiographic features are evident in children with other medical conditions, such as sickle cell disease and Down syndrome. In these instances, the term “moyamoya syndrome” is used. Diagnosing the vasculopathy, excluding possible associated conditions, and planning treatment and follow-up imaging comprise important aspects of clinical management.
Source: Stuart Currie, Ashok Raghavan, Ruth Batty, Daniel J.A. Connolly, Paul D. Griffiths, Childhood Moyamoya Disease and Moyamoya Syndrome: A Pictorial Review, Pediatric Neurology, Volume 44, Issue 6, June 2011, Pages 401-413, ISSN 0887-8994, 10.1016/j.pediatrneurol.2011.02.007.