What is Moyamoya Disease?
Moyamoya disease is a rare but very serious condition affecting one or both of the internal carotid arteries. These arteries are located at the base of the brain. Moyamoya disease causes them to become narrowed over time. This restricts blood flow to the brain. As a result, blood clots may form, and the risk of having a stroke, mini-stroke or seizure may increase.
Moyamoya develops over the course of months or years. It is most common during childhood. As the arteries become narrower, the brain forms tiny blood vessels to create new pathways for blood to flow. The tiny blood vessels look like puffs of smoke on a cerebral angiogram. The word “moyamoya” means “puff of smoke” in Japanese.
How Often Does It Happen?
Moyamoya disease affects about one in 1 million people in the United States. The disease primarily affects children. The average age of diagnosis is 7, but it can occur in adults as well. Moyamoya disease is more common among those of Asian descent. Girls are about twice as likely as boys to have it.
What Causes Moyamoya?
Researchers are still trying to understand what causes Moyamoya disease. Some believe that an inherited, defective blood vessel may cause the disease. The cause may also be related to associated conditions, including Down syndrome and sickle cell disease, among others.
What Are the Signs of Childhood Moyamoya?
The first sign of Moyamoya usually is an ischemic stroke. An ischemic stroke happens when a blood clot blocks blood flow to the brain. When brain tissue is cut off from its supply of oxygen for more than three minutes, it begins to die.
The symptoms of an ischemic stroke can occur suddenly, or slowly over time. They include:
- Weakness or numbness on one side of the body
- Vision loss or double vision
- Trouble speaking or understanding others
- Inability to stand upright or walk
- Severe headache, especially with vomiting and sleepiness
Sometimes these symptoms go away quickly and do not result in damage to brain tissue. This is often referred to as a transient ischemic attack (TIA) or a “mini-stroke.” If symptoms last for days, weeks or longer, a true ischemic stroke has occurred.
If you think your child is experiencing stroke-like symptoms, seek medical help right away! Immediate treatment can reduce the risk of permanent brain damage.
Some children who develop Moyamoya disease are otherwise healthy. But some have pre-existing medical conditions that damage blood vessels to the brain. These diseases may increase a child’s risk of developing Moyamoya and may include:
- Neurofibromatosis Type1 (NF1)
- Down syndrome
- Sickle cell disease
- Noonan syndrome
- Other syndromes caused by chromosome problems
- A previous brain tumor that was treated with radiation therapy
Children who have Moyamoya disease and one of the conditions listed above are considered to have Moyamoya syndrome, rather than Moyamoya disease.
What Tests Will My Child Need?
Imaging technologies help doctors diagnose Moyamoya, confirm a diagnosis and plan for surgery, if needed. Those used most often include:
- Magnetic resonance imaging (MRI). This test uses a magnetic field and radio waves to produce detailed pictures of the brain and brain stem.
- Magnetic resonance angiogram (MRA). This test uses a magnetic field and pulses of radio wave energy. It provides detailed pictures of blood vessels inside the body.
- Computed tomography (CT). This procedure uses special X-ray equipment. It creates detailed, cross-sectional images of internal organs, bones, soft tissue and blood vessels.
- Cerebral angiography. This procedure uses a special dye (contrast material) and X-rays. It helps doctors see how blood flows through the brain.
How Is Moyamoya Treated?
Moyamoya disease does not get better without treatment. In fact, it tends to get worse − especially in young children.
Immediate treatment for Moyamoya disease is essential, since the disease increases a child’s risk for stroke and seizures. Treatment may include surgery and/or medication.
Surgery for Children with Moyamoya
The only proven, long-term treatment for Moyamoya disease is surgery. The goal of surgery is to create a healthy, new supply of blood for the part of the brain affected by this disease.
There are two kinds of surgery for Moyamoya disease:
The surgeon connects a blood vessel from outside the skull (usually the artery by the temple) to a blood vessel inside the skull (middle cerebral artery). This creates an immediate new pathway for the blood to flow.
This type of surgery involves laying an artery, muscle or other tissue on the surface of the brain. Over time, new blood vessels form and branch off from the new artery, leading to improved blood flow to the brain.
Your child’s doctor will talk to you about which surgery is likely to be most effective for your child.
Medication for Children with Moyamoya
Medication cannot cure Moyamoya disease or stop its progression. But, it still plays an important role. Your child’s doctor may prescribe:
- Calcium channel blockers. These drugs cause the blood vessels to dilate. They help lower blood pressure. This reduces the risk of severe headaches, strokes and mini-strokes.
- Anti-clotting medication. These medications thin the blood and help prevent blood clots from forming. This reduces the risk of mini-strokes and strokes. The most common anti-clotting drug that doctors prescribe is aspirin. Many patients who receive treatment for Moyamoya follow a daily regimen of aspirin for the rest of their lives.
After the initial diagnosis of Moyamoya, children who suffered a stroke may need rehabilitation therapy. A personalized therapy plan may include physical, occupational and/or speech therapy. It can help patients regain as much lost function as possible. Depending on your child’s needs, therapy may take place before and/or after surgery.
What Happens after Surgery?
After surgery, your child will probably be discharged from the hospital in two to three days. Children usually can return to most of their regular activities within two to four weeks. Over the next three to six months, they can return to regular activates including gym class and sports.
In addition to taking any medication prescribed by the doctor, your child must stay well hydrated at all times. This helps boost blood volume in the body and provide an adequate blood flow through the arteries.
Most children will return to the hospital for an initial follow-up visit within several weeks of surgery. After that, they will come back for regularly scheduled check-ups. These appointments may happen every six months to a year.
At the one-year mark, patients may undergo a cerebral angiogram. This can help the neurosurgeon assess the results of surgery.
What Is My Child’s Outlook?
Most children who receive treatment for Moyamoya disease experience a very good outcome and are at low risk for stroke.
A child’s long-term outlook depends largely on whether a stroke occurred before treatment, and what its effects were. Other factors include:
- Overall health
- Symptoms at the time of diagnosis
- Whether a stroke affected one or both internal carotid arteries
- The amount of time between diagnosis and surgery
- The effectiveness of surgery
Your child’s treatment team can talk to you about your child’s expected recovery. You also will learn what you can do to help your child reach their full potential.
Concerns in Adulthood
Patients who had Moyamoya in only one internal carotid artery may be at risk for developing it in the other artery. They should be followed closely to watch for signs that this may be happening.
In order to lower their risk for stroke, people who have been treated for Moyamoya should check their blood pressure for the rest of their lives, and seek care if it becomes elevated. They also should not take birth control pills. These medications can increase the risk of blood clots forming.