Background: Moyamoya disease (MMD) is a progressive cerebrovascular occlusive disease of the bilateral internal carotid arteries that leads to a compensatory abnormal vascular network at the base of the brain. Its average annual incidence 0.54 per 100,000 population but it is the most common pediatric cerebrovascular disease in East Asia. The reported incidence in USA is approximately 0.086 per 100,000 patients.
Case Report: We present a case of Moyamoya disease that was to detected in a 7-year-old female who presented with transient altered mental status.
Conclusions: Moyamoya disease can be diagnosed if history, physical exam and brain imaging is highly suspicious. Conventional angiography remains the gold standard for diagnosis and aids in surgical planning for patients with suspected Moyamoya disease.

Keywords: Altered mental status, CADASIL, familial MMD, moyamoya disease