Moyamoya

Moyamoya is a rare disorder that causes a blockage to the main blood vessels serving the brain as they enter the skull. The name is a Japanese phrase meaning puff of smoke since that is how the lesion looks on an angiogram.

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Symptoms

Adults with moyamoya experience bleeding or strokes. An adult with moyamoya may have spells of fainting or blacking out. He or see may have vision problems that include loss of sight in one eye, blurry vision, poor vision in both eyes or not being able to recognize objects. The condition tends to get worse without treatment. Moyamoya can cause severe brain damage or death.

In children, moyamoya tends to cause mini-strokes (transient ischemic attack) or seizures. Some children may have movements they can't control. Others may show signs of developmental disabilities. Other signs of moyamoya are headaches, speech difficulties or bouts of being unable to move their feet, legs or arms. Because this condition involves bleeding, they may also experience anemia (low levels of iron in their blood).

 

Causes and Risk Factors

It's not yet known what causes Moyamoya. 

The narrowing of the brain's blood vessels may be due to injuries or genetic abnormalities. There may be some links between having moyamoya and having neurofibromatosis or having procedures such as X-rays of the skull, chemotherapy or heart surgery. 

Moyamoya tends to affect children or adults in their 30s or 40s. It is often found among people of Japanese origin.

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Diagnosis

Because moyamoya can cause severe brain damage or even death, it is important to diagnose and treat the condition as quickly as possible.

Your doctor may recommend these tests or imaging scans:

  • Computed tomography (CT), which can diagnose the presence of a block in the blood vessels going to the brain
  • Magnetic resonance imaging (MRI), which can also diagnose the presence of a block
  • Angiogram. This is used to confirm the diagnosis of moyamoya. It also shows the doctor the structure of the blood vessels involved.
  • Single photo emission computerized tomography (SPECT). This is a nuclear medicine study that can show whether the affected areas of the brain have a loss of blood and oxygen supply.
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Treatments

Surgery is the preferred way to treat moyamoya. The goal of surgery is to go around the blockage and allow new blood vessels to develop to bring blood and oxygen to the brain.

The moyamoya blood vessels and the areas of the brain they affect are sensitive. They can be affected by changes in blood pressure, the amount of blood flow and the amount of carbon dioxide in the blood. Under anesthesia it can be hard to control all these factors, especially in children.

Children undergoing treatment for moyamoya need a different type of anesthesia for this surgery than is given for almost any other type of neurosurgical procedure.

With trained, experienced neurovascular surgeons, the risks of this surgery are generally low. The long-term outlook for children who have been treated for moyamoya is good.

Drug therapy

Medicines that prevent clots from forming can be helpful. This includes aspirin. Sometimes a calcium channel blocker such as verapamil is prescribed for people with moyamoya. Verapamil helps with the headache that some patients with moyamoya get. The drug needs to be given under the supervision of a neurologist. No drug, however, can prevent the arteries to the brain from narrowing.

Surgical Approaches for Moyamoya

Surgery for moyamoya uses the idea that a brain starved for blood and oxygen will reach out to grasp and develop new and more efficient means of bringing blood to the brain. The brain does this by bypassing the areas of blockage.

Encephaloduroarteriosynangiosis (EDAS) - This procedure requires freeing up, without severing, a scalp artery over a course of several inches and then making a small temporary opening in the skull directly beneath the artery. The artery is then sutured to the surface of the brain and the bone replaced.

Encephalomyosynangiosis (EMS) operation - In this procesure a muscle from the temple region of the forehead is freed from some attachments. A hole is then made in the skull through which this muscle is directed and then placed onto the surface of the brain.

Superficial temporal artery-middle cerebral artery (STA-MCA) - This procedure directly sutures a scalp artery to a brain surface artery.

Multiple small holes (burr holes) are placed in the skull to allow for growth of new vessels into the brain from the scalp.

Recovery from Surgery for Moyamoya

While symptoms may seem to improve almost immediately after surgery, it will usually takes six to 12 months before new vessels can develop sufficiently.

If a patient has had major bleeding into the tissues of the brain from moyamoya, the damage is usually permanent. Prompt treatment is important to prevent a permanent loss of function as much as possible.

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