Medically reviewed on March 7, 2018
Moyamoya disease is a rare, progressive blood vessel (vascular) disorder in which the carotid artery in the skull becomes blocked or narrowed, reducing blood flow to your brain. Tiny blood vessels then open up at the base of the brain in an attempt to supply the brain with blood. The word "moyamoya" means "puff of smoke" in Japanese, a term describing the appearance of this cluster of tiny blood vessels.
These tiny clusters of blood vessels cannot supply the necessary blood and oxygen to the brain, resulting in temporary or permanent brain injury.
The condition may cause a ministroke (transient ischemic attack, or TIA), stroke, bulge or ballooning in a blood vessel (aneurysm) or bleeding in the brain. It can also affect how well your brain functions and cause cognitive and developmental delays or disability.
Moyamoya disease most commonly affects children, but adults may have the condition. Moyamoya disease is found all over the world, but it's more common in East Asian countries, especially Korea, Japan and China and in people of East Asian descent.
In moyamoya disease, arteries to your brain become narrow and may even close, leading to reduced delivery of oxygen-rich blood to your brain. This lack of blood flow to the brain can cause stroke and other symptoms.
Moyamoya disease may occur at any age, though symptoms most commonly occur between 5 and 10 years of age in children and between 30 and 50 years of age in adults.
The first symptom of moyamoya disease is usually stroke or recurrent transient ischemic attacks (TIAs), especially in children. Adults may also experience these symptoms but more often experience bleeding in the brain (hemorrhagic stroke) from abnormal brain vessels.
Accompanying signs and symptoms of moyamoya disease related to reduced blood flow to the brain include:
- Weakness, numbness or paralysis in your face, arm or leg, typically on one side of your body
- Visual disturbances
- Difficulties with speaking or understanding others (aphasia)
- Developmental delays
- Involuntary movements
- Cognitive decline
These symptoms can be triggered by exercise, crying, coughing, straining or fever.
When to see a doctor
Seek immediate medical attention if you notice any signs or symptoms of a stroke or TIA, even if they seem to fluctuate or disappear.
Think "FAST" and do the following:
- Face. Ask the person to smile. Does one side of the face droop?
- Arms. Ask the person to raise both arms. Does one arm drift downward? Or is one arm unable to raise up?
- Speech. Ask the person to repeat a simple phrase. Is his or her speech slurred or strange?
- Time. If you observe any of these signs, call 911 immediately.
Call 911 or your local emergency number right away. Don't wait to see if symptoms go away. Every minute counts. The longer a stroke goes untreated, the greater the potential for brain damage and disability.
If you're with someone you suspect is having a stroke, watch the person carefully while waiting for emergency assistance.
The exact cause of moyamoya disease is unknown. Moyamoya disease is more common in Japan, Korea and China, but it also occurs in other parts of the world.
Researchers believe the higher concentration of moyamoya disease in these Asian countries strongly suggests the disease may have genetic causes.
Moyamoya is also associated with certain conditions, such as Down syndrome, sickle cell anemia, neurofibromatosis type 1 and hyperthyroidism.
Though the cause of moyamoya disease is unknown, certain factors may increase your risk of having the condition, including:
- Being of Asian descent. Moyamoya disease is found all over the world, but it's more common in East Asian countries, especially Korea, Japan and China. This may possibly be due to certain genetic factors in those populations. Higher rates of moyamoya disease have been documented among Asians living in western countries.
- Having a family history of moyamoya disease. If you have a family member with moyamoya disease, your risk of having the condition is 30 to 40 times higher than the general population — a factor that strongly suggests a genetic component to the disease and may justify screening of family members.
- Having a certain medical condition. Moyamoya disease sometimes occurs in association with another disorder, including neurofibromatosis type 1, sickle cell anemia and Down syndrome, among others.
- Being female. Females have a slightly higher incidence of moyamoya disease.
- Being young. Though adults can have moyamoya disease, children younger than 15 years old are most commonly affected.
Most complications from moyamoya disease are associated with the effects of stroke, such as:
- Vision problems. As a result of stroke, some people with moyamoya disease experience visual disturbances.
- Weakness (hemiparesis).
- Language disturbance (aphasia).
- Movement disorders. Though rare, some people with moyamoya disease experience involuntary movement of certain muscles.
- Learning or developmental issues. Following a stroke, a child may have problems with mental processing, which can affect schoolwork as well as cause emotional difficulties and low self-esteem. Adults may experience memory decline as well as challenges with other areas of cognitive function.
To diagnose moyamoya disease, your doctor will review your symptoms and your family and medical history. Your doctor will perform a physical examination and may order several tests to diagnose moyamoya disease and any underlying conditions.
Tests may include:
- Magnetic resonance imaging (MRI). An MRI uses powerful magnets and radio waves to create detailed images of your brain. Your doctor may inject a dye into a blood vessel to view your arteries and veins and highlight blood circulation (magnetic resonance angiography). If available, your doctor may recommend a type of imaging that can measure the amount of blood passing through the vessels (perfusion MRI).
- Computerized tomography (CT) scan. A CT scan uses a series of X-rays to create a detailed image of your brain. Your doctor may inject a dye into a blood vessel to highlight blood flow in your arteries and veins (CT angiogram).
- Cerebral angiography. During a cerebral angiogram, your doctor inserts a long, thin tube (catheter) into a blood vessel in your groin and guides it to your brain using X-ray imaging. Your doctor then injects dye through the catheter into the blood vessels of your brain to make them visible under X-ray imaging.
- Transcranial Doppler ultrasound. In a transcranial Doppler ultrasound, sound waves are used to obtain images of your brain. Doctors may use this test to obtain information about the blood vessels in the brain.
- Positron emission tomography (PET) scan or single-photon emission computerized tomography (SPECT). In these tests, your doctor injects you with a small amount of a safe radioactive material and places emission detectors over your brain. PET provides visual images of brain activity. SPECT measures blood flow to various regions of your brain.
- Electroencephalography (EEG). An EEG monitors the electrical activity in your brain via a series of electrodes attached to your scalp. Children with moyamoya disease often exhibit abnormalities on EEG.
If necessary, your doctor may order other tests to rule out other conditions.
Mayo Clinic doctors utilize the latest tools and techniques to diagnose moyamoya disease.
Doctors will evaluate your condition and determine the most appropriate treatment for your condition. The goal of treatment is to reduce your symptoms, improve your blood flow and lower your risk of serious complications such as an ischemic stroke caused by a lack of blood flow, bleeding in your brain (intracerebral hemorrhage) or death.
Your treatment may include:
Medications may be prescribed to reduce the risk of stroke or to aid in seizure control, including:
- Blood thinners. After you're diagnosed with moyamoya disease, if you have mild or no symptoms at first, then your doctor may recommend you take aspirin or other blood thinner to prevent strokes.
- Calcium channel blockers. Also known as calcium antagonists, this type of medication may improve symptoms of headache and possibly reduce symptoms related to transient ischemic attacks.
- Anti-seizure medications. These may be prescribed if you or your child has an accompanying seizure disorder.
If your symptoms become worse or if tests show evidence of low blood flow, your doctor may recommend revascularization surgery.
In revascularization surgery, surgeons bypass blocked arteries to help restore blood flow to your brain. Your doctor may use direct or indirect revascularization procedures, or a combination of both.
Direct revascularization procedures. In direct revascularization surgery, surgeons stitch (suture) the scalp artery directly to a brain artery (superficial temporal artery to middle cerebral artery bypass surgery) to increase blood flow to your brain immediately.
Direct bypass surgery may be difficult to perform in children, due to the size of the blood vessels to be attached.
Direct revascularization surgery has a risk of complications, including stroke.
Indirect revascularization procedures. In indirect revascularization, the goal is to increase blood flow to your brain gradually over time.
Types of indirect revascularization procedures include encephaloduroarteriosynangiosis (EDAS) or encephalomyosynangiosis (EMS), or a combination of both.
In EDAS, your surgeon separates (dissects) a scalp artery over several inches.
Your surgeon makes a small temporary opening in your skull directly beneath the artery and attaches (sutures) the intact scalp artery to the surface of your brain, which allows blood vessels from the artery to grow into your brain over time. The surgeon then replaces the bone and closes the opening in your skull.
In EMS, your surgeon separates (dissects) a muscle in the temple region of your forehead and places it onto the surface of your brain through an opening in your skull to help restore blood flow.
Your surgeon may perform EMS with EDAS. In this procedure, your surgeon separates (dissects) a muscle in the temple region of your forehead and places it onto the surface of your brain, after attaching the scalp artery to the surface of your brain. The muscle helps to hold the artery in place as blood vessels grow into your brain over time.
Your surgeon may peel the outer layer of your skull bone (pericranium), which may serve as an additional source of new blood vessels to the brain. This may be important in areas that cannot be reached by a scalp artery.
Your surgeon may make multiple holes (burr holes) in your skull to allow new blood vessels to grow, either as a separate procedure or in combination with other procedures.
Some people with moyamoya disease develop a bulge or ballooning of a blood vessel in the brain known as a brain aneurysm. If this occurs, surgery may be necessary to prevent or treat a ruptured brain aneurysm.
To address the physical and psychological effects of stroke on you or your child, your doctor may recommend other therapies.
Physical and occupational therapy can help to attempt to regain any lost physical function caused by stroke. Speech therapy also may be recommended if needed.
Cognitive behavioral therapy can help address emotional issues related to having moyamoya disease, such as how to cope with fears and uncertainties about future stroke.
Mayo Clinic doctors provide comprehensive treatment for people with moyamoya.
In a direct revascularization procedure, your surgeon connects a scalp artery (superficial temporal artery) directly to the middle brain (cerebral) artery in order to increase blood flow to the brain.
Preparing for an appointment
If you or your child has been diagnosed with moyamoya disease, you'll most likely be referred to a doctor who specializes in brain conditions (neurologist). You can prepare to discuss the subject with your doctor at your next appointment.
What you can do
- Write down any symptoms you or your child has experienced. Include any that may seem unrelated to the reason you scheduled the appointment.
- Make a list of all medications. Include vitamins and supplements you or your child is taking, including dosages. Write down the reasons any were discontinued, whether because of side effects or lack of effectiveness.
- Ask a family member to come with you to the doctor. Sometimes it can be difficult to remember all the information provided during an appointment. Someone who goes with you may remember something you missed or forgot.
- Write down questions. Preparing a list of questions for your doctor will help you make the most of your time together.
Some basic questions to ask include:
- What is likely causing my or my child's symptoms or condition?
- What kinds of tests are necessary? Do they require any special preparation?
- What treatments are available, and which do you recommend?
- What types of side effects can be expected from treatment?
- Is surgery a possibility?
- Are you prescribing medication? If so, is there a generic alternative?
- My child has other medical problems. How can they be managed together?
- Will I or my child have any restrictions on physical activity?
- Are there brochures or other printed materials that I can take with me? What websites do you recommend?
What to expect from your doctor
Your doctor is likely to ask you or your child a number of questions, such as:
- When did symptoms first occur?
- How often do the symptoms occur?
- Do certain activities trigger symptoms?
- Has anyone in your immediate family ever had moyamoya disease?