Moyamoya disease is a rare condition in which the large arteries at the base of the brain slowly narrow, forcing tiny backup vessels to develop. These smaller vessels look like a “puff of smoke” on imaging, but they cannot carry enough blood, so the brain is starved of oxygen. Symptoms often start in childhood or early adulthood and can build up gradually or appear suddenly. The earliest warning is usually repeated transient ischemic attacks (TIAs)—brief episodes of weakness, numbness, or trouble speaking that resolve within minutes to hours. Children may complain of a sudden weak arm or leg, slurred speech,... Learn more