Moyamoya is a progressive disorder that affects the brain’s blood vessels (cerebrovascular). It is characterized by the stenosis (narrowing) and/or occlusion (closure) of the carotid artery in the skull, the main artery that carries blood to the brain. At the same time, tiny blood vessels at the base of the brain open up in an apparent effort to carry blood to the brain distal to the blockage. MMD can occur at any ages, though symptoms that usually occur in 30-50-years-old adults and 5-10-years-old children. The first symptom of MMD is usually recurrent transient ischemic attack (TIA) or stroke, particularly in children. Adults may experience these symptoms and also bleeding in the brain (hemorrhagic stroke) from abnormal blood vessels in the brain. Diagnosis may include MRI, CT, Cerebral angiogram, Transcranial Doppler ultrasound, PET, SPECT, and EEG. Medication may be prescribed to help in seizure control or decrease the risk of stroke, including Calcium channel blockers, Blood thinners, Anti-seizure medications, and Revascularization surgery are also performed for MMD. This article evaluates the types, causes, diagnosis, symptoms, and treatment of MMD.