Moyamoya disease



What is moyamoya disease?

Moyamoya disease is a chronic and progressive narrowing of the internal carotid arteries at the base of the brain where they divide into middle and anterior cerebral arteries. The walls of the arteries become thickened, which narrows the inside diameter of the vessel. The narrowing can eventually result in complete blockage and stroke.

To compensate for the narrowing arteries, the brain creates collateral blood vessels in an attempt to deliver oxygen-rich blood to deprived areas of the brain. These tiny collateral vessels, when seen on an angiogram, have a hazy, filmy appearance. The Japanese were the first to describe the condition, and they named it “moyamoya,” the Japanese term for “puff of smoke.” More fragile than normal blood vessels, the tiny moyamoya collaterals can break and bleed into the brain, causing hemorrhages. Moyamoya usually affects both sides of the brain and is often accompanied by aneurysms.

The progression of Moyamoya follows a typical course and can be classified into stages based on angiography findings.

  • Stage I: Narrowing of internal carotid arteries
  • Stage II: Development of moyamoya vessels at the base of the brain
  • Stage III: Intensification of moyamoya vessels and internal carotid artery narrowing (most cases diagnosed at this stage)
  • Stage IV: Minimization of moyamoya vessels and increased collateral vessels from the scalp
  • Stage V: Reduction of moyamoya vessels and significant internal carotid artery narrowing
  • Stage VI: Disappearance of moyamoya vessels, complete blockage of internal carotid arteries, and significant collateral vessels from the scalp

Once the process of blockage (vascular occlusion) begins, it tends to continue. No known medication can reverse the blockage. Once a major stroke or bleeding has occurred, the patient may be left with permanent loss of function. It is important, therefore, to treat this condition promptly.

How common is moyamoya disease?

Moyamoya disease is quite rare.  It 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. Please discuss with your doctor for further information.


What are the symptoms of moyamoya disease?

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:

  • Headache
  • Seizures
  • 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.

There may be some symptoms not listed above. If you have any concerns about a symptom, please consult your doctor.

When should I see my 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:

  • Ask the person to smile. Does one side of the face droop?
  • Ask the person to raise both arms. Does one arm drift downward? Or is one arm unable to raise up?
  • Ask the person to repeat a simple phrase. Is his or her speech slurred or strange?
  • If you observe any of these signs, call emergency immediately.

Call 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.


What causes moyamoya disease?

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.

Risk factors

What increases my risk for moyamoya disease?

There are many risk factors for moyamoya disease, such as:

  • 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.

Diagnosis & treatment

The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.

How is moyamoya disease diagnosed?

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.

How is moyamoya disease treated?

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.

Revascularization surgery

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.

Other Surgery

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.

Lifestyle changes & home remedies

What are some lifestyle changes or home remedies that can help me manage moyamoya disease?

Please discuss with your doctor for further information.

If you have any questions, please consult with your doctor to better understand the best solution for you.

Hello Health Group does not provide medical advice, diagnosis or treatment.


Review Date: November 23, 2017 | Last Modified: November 24, 2017

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