Moyamoya Syndrome: What You Need to Know

What is moyamoya syndrome?

Moyamoya syndrome is a disorder that causes certain arteries in the brain to constrict (tighten or shrink) and thicken. The arteries affected are called internal carotid arteries. They help carry blood to the brain. The constricted blood vessels can put a person at a higher risk for a stroke (when blood supply to the brain is interrupted by a blockage or blood flow issue).

Moyamoya syndrome is 3 times more common in people with Down syndrome than people without Down syndrome. Doctors do not know why people with Down syndrome have a higher risk of developing moyamoya syndrome.

What are the signs and symptoms of moyamoya syndrome?

People with moyamoya syndrome may not have any symptoms for many years. Over time, the thickening of the internal carotid arteries can cause different neurological (brain and nerve) related issues. The most common sign of moyamoya syndrome is a stroke.

• Ischemic strokes are caused by lack of blood flow to the brain because of constricted blood vessels. This is the most common cause of stroke in young people with moyamoya syndrome.
• Hemorrhagic strokes are when poorly formed blood vessels burst or tear because of the constricted blood vessels. This type of stroke is less common in young people with moyamoya syndrome.

What are the signs of a stroke?

• Weakness or difficulty moving arms or legs
• Numbness, tingling or a feeling of heaviness in the arms or legs
• Slurred speech
• Trouble swallowing or food/liquid falling out of the mouth
• Sudden weakness in the dominant hand
• Inability to speak or language that does not make sense
• Unsteadiness or falling to one side
• Facial weakness
• Severe and sudden headaches, possibly with vomiting
• In rare cases, seizures

If your child has any of these symptoms, see a doctor right away or call 911. Children who are actively having a stroke can be given medicine or have treatments that can help lessen the amount of injury to the brain. Remember, TIME = BRAIN!

Rev. 7/2019. Created by Jonathan Santoro, MD. Mass General for Children and Massachusetts General Hospital do not endorse any of the brands listed on this webpage. This webpage is intended to provide health information so that you can be better informed. It is not a substitute for medical advice and should not be used to treatment of any medical conditions.