What is Moyamoya Disease and How Does It Affect Blood Flow to the Brain?
Moyamoya disease is a rare, progressive cerebrovascular disorder characterized by narrowing or blockage of the internal carotid arteries at the base of the brain. As these arteries gradually become constricted, the brain receives less oxygen-rich blood. In response, the body develops a network of tiny collateral vessels to compensate. These fragile vessels appear like a “puff of smoke” on angiography — which is what the Japanese term “Moyamoya” describes.
Although these vessels temporarily help maintain circulation, they are weak and prone to rupture or clot formation. This increases the risk of ischemic stroke, hemorrhagic stroke, transient ischemic attacks (TIAs), headaches, seizures, and cognitive decline. Moyamoya can occur in both children and adults, but symptoms and progression patterns differ across age groups. Children commonly present with recurrent ischemic events or developmental delay, while adults are more likely to experience brain hemorrhage.
The exact cause remains unclear, though genetic and environmental factors are suspected. It is seen more frequently in East Asian populations and may be associated with conditions such as Down syndrome, neurofibromatosis, thyroid disorders, or prior cranial irradiation.
Early diagnosis and intervention are critical because the disease progresses silently in many cases. Without treatment, repeated strokes may lead to neurological disability. With timely surgical revascularization and long-term monitoring, many patients can achieve improved blood flow and better quality of life.