What is Moyamoya disease? What does it mean?

Moyamoya disease (MMD) is a rare, progressive cerebrovascular disease that causes stenosis or a blockage to one or both of the primary blood vessels (internal carotid arteries) that supply the brain as they enter the skull.

Moyamoya disease was first noted in Japan in 1957 and it is seen mainly in Japan and other countries in Asia. The disease is diagnosed less frequently in Europe and North America. "Moyamoya" is a Japanese word that means "puff of smoke," which describes the hazy and tangled appearance of the vascular collateral network (small blood vessels) that forms to compensate for the blockage.

Is Moyamoya disease inherited (genetic)?

The cause of Moyamoya disease is unknown. It is believed there may be a genetic factor, as up to 15 percent of Japanese people with Moyamoya have family members with the condition.

How Serious Is a TIA or Mini-Stroke? Is It Fatal?

A transient ischemic attack (TIA, mini-stroke) should be considered a major warning sign of an impending future stroke.

  • Up to 15% of people will experience a stroke within three months of TIA.
  • There is no way of predicting that stroke-like symptoms will resolve.
  • In most hospitals, a drug can only be given within 4 1/2 hours of onset of stroke symptoms. The longer the delay, the greater the risk that the drug won't work, and that complications such as bleeding into the brain will occur, even death.

Use FAST to remember and recognize the following signs and symptoms of stroke, and call 911 immediately to get treatment fast. FAST means:

  • F: Face drooping. Ask the person to smile, and see if one side is drooping. One side of the face may also be numb, and the smile may appear uneven.
  • A: Arm weakness. Ask the person to raise both arms. Is there weakness or numbness on one side? One arm drifting downward is a sign of one-sided arm weakness.
  • S: Speech difficulty. People having a stroke may slur their speech or have trouble speaking at all. Speech may be incomprehensible. Ask the person to repeat a simple sentence and look for any speech abnormality.
  • T: Time to call 911! If a person shows any of the symptoms above, even if the symptoms went away, call 911 and get the person to a hospital immediately.

What are the signs and symptoms of Moyamoya disease?

Moyamoya disease can occur in children and adults. There are two times the disease incidence peaks: most commonly, at about 10 years of age in children and between ages 30 to 50 in adults. Moyamoya disease may present differently in adults and children.

In adults, the most common symptoms include bleeding in the brain (hemorrhagic strokes). Other symptoms of Moyamoya disease in adults include:

  1. Lightheadedness or fainting
  2. Visual disturbances
  3. Blurred vision
  4. Loss of vision in one eye
  5. Poor vision in both eyes
  6. Inability to recognize objects
  7. Seizures
  8. Headaches
  9. Unilateral (on one side) weakness, numbness, or paralysis in your face, arm, or leg
  10. Cognitive decline
  11. Moyamoya disease in children often results in transient ischemic attacks (TIAs), also called "ministrokes," and seizures.

In addition to the symptoms that can occur in adults, other symptoms of Moyamoya disease in children may include:

  1. Headaches
  2. Developmental delays
  3. Problems with speech
  4. Difficulty understanding others
  5. Involuntary movements
  6. Periods of inability to move feet, legs, or arms
  7. Anemia (symptoms include fatigue and pale skin)

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What causes Moyamoya disease?

The cause of Moyamoya disease is unknown. In some cases, there appears to be a genetic factor and the disease seems to run in families. Other possible causes of Moyamoya disease include:

  1. Injuries
  2. Neurofibromatosis (nf)
  3. Procedures such as X-rays of the skull
  4. Heart surgery
  5. Chemotherapy
  6. Moyamoya syndrome is a secondary disorder that may occur in association with some conditions, such as:
  7. Infections
  8. Atherosclerosis
  9. Heart disease
  10. Vasculitis
  11. Blood disorders (such as sickle cell disease or beta thalassemia)
  12. Autoimmune conditions (such as Lupus, thyroid disorders, Sneddon syndrome)
  13. Connective tissue disorders (such as neurofibromatosis type 1 or Tuberous sclerosis)
  14. Chromosome disorders
  15. Metabolic diseases
  16. Head trauma
  17. Radiation therapy of the brain
  18. Brain tumors
  19. Down syndrome or Williams syndrome

What are the 6 stages of Moyamoya disease?

There are 6 stages of Moyamoya disease, called Suzuki stages. Each stage refers to an angiographic finding (imaging of blood vessels).

  • Stage 1: Narrowing of carotid arteries
  • Stage 2: Initial appearance of basal Moyamoya with dilatation of all main cerebral arteries
  • Stage 3: Intensification of Moyamoya vessels together with reduction of flow in the middle and anterior cerebral arteries
  • Stage 4: Minimization of Moyamoya vessels; the proximal portions of the posterior cerebral arteries become involved
  • Stage 5: Reduction of Moyamoya vessels and absence of all main cerebral arteries
  • Stage 6: Disappearance of Moyamoya vessels; the cerebral circulation is supplied only by the external carotid system

What tests diagnose Moyamoya disease?

Along with a history and physical, imaging tests to help find the blockage and may be ordered to diagnose Moyamoya disease, including:

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What is the treatment for Moyamoya disease?

Treatment for Moyamoya disease is aimed at reducing symptoms with attempts to decrease intracranial pressure, improve blood flow in the blood vessels of the brain, and control seizures.

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What types of surgery treat Moyamoya disease?

Revascularization is a type of surgical procedure used to treat Moyamoya disease. This procedure repairs the narrowed arteries, improves blood flow, and reduces the risk of stroke. Without surgery, Moyamoya is a progressive condition and patients will experience multiple strokes and a mental decline.

There are several types of revascularization procedures:

  • EDAS (encephaloduroarteriosynangiosis): A scalp artery is rerouted onto the surface of the brain. Over time, new blood vessels form and ideally will provide a new blood supply to the ischemic area of the brain.
  • A modification of EDAS is pial synangiosis: Reroutes healthy scalp blood vessels to the brain, bypassing the narrowed vessels.
  • EMS (encephalomyosynangiosis): A muscle in the temple of the forehead is partially detached. A hole is drilled in the skull and the muscle is placed onto the surface of the brain, where it will eventually produce new blood vessels.
  • External carotid to internal carotid (EC-IC) bypass: One of the arteries in the scalp (superficial temporal artery) is attached to one of the major arteries in the brain (middle cerebral artery).
  • Direct arterial bypass, also called STA-MCA (superficial temporal artery-middle cerebral artery) bypass: A blood vessel from the scalp is joined directly to a brain surface artery to transport blood directly to where it is needed.
  • Omental transposition/transfer: The omentum, a blood-rich lining surrounding the abdominal organs, is placed over the surface of the brain so new blood vessels can generate and grow into the brain.
  • Dural inversion: The flaps of fibrous dural tissue on the meningeal vessel, a large artery within the skull, are inverted. The outer dural surface with a large number of blood vessels comes into direct contact with the parts of the brain that need blood flow.

In some cases, minimally invasive procedures may be used such as angioplasty and stenting to widen a narrowed artery.

How successful is surgery for Moyamoya disease?

Full recovery from revascularization surgery for Moyamoya disease may take six to 12 months, but patients notice improvements in their symptoms almost immediately. Surgical revascularization surgery is effective in preventing both ischemic and hemorrhagic stroke. Surgery for Moyamoya disease is most effective when performed before a patient suffers a stroke or hemorrhage, which may cause long-term damage.

If there has been major bleeding into the brain, there may be permanent damage that surgery cannot repair. In these cases, prompt treatment can help preserve as much brain function as possible.

What are the complications of surgery for Moyamoya disease?

Complications of revascularization surgery for Moyamoya include:

Is there a cure for Moyamoya disease? 

Moyamoya is a progressive disease and without treatment patients will not improve. Moyamoya itself is not curable, but revascularization surgery that allows for alternative blood supply to the brain prevents symptoms and can reduce the risk of future strokes.

Is Moyamoya disease fatal?

Without surgery, most patients with Moyamoya disease will suffer from multiple stokes and a mental decline because of the progressive narrowing of arteries. If left untreated, Moyamoya disease can be fatal as the result of intracerebral hemorrhage (bleeding within the brain).

What is the prognosis and life-expectancy for Moyamoya disease?

In general, the earlier patients are diagnosed and treated, the better the outcome. Patients who are diagnosed early and treated promptly with surgical intervention can have a normal life expectancy.

Moyamoya disease is progressive, and patients who are not treated often suffer cognitive and neurologic decline due to repeated ischemic stroke or hemorrhage.

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Medically Reviewed on 12/13/2019
References
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Chang, MD, et al. Surgical Management of Moyamoya Disease. Department of Neurosurgery and the Stanford Stroke Center, Stanford University Medical Center, Stanford. California, U.S.A 2018.
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Genetic and Rare Diseases Information Center (GARD). Moyamoya disease . Updated: Jul 01, 2014.
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Nijasri Charnnarong Suwanwela, MD. Moyamoya disease: Etiology, clinical features, and diagnosis. Updated: Aug 20, 2019.
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Moyamoya disease: Treatment and prognosis. UpToDate. Updated Aug 14, 2019.
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