Brain, Nervous System and Mental Conditions


What is moyamoya?

Carotid artery – moyamoyaMoyamoya (pronounced MOY-a-MOY-a) is a problem with blood flow to the brain. It happens when the major blood vessels to the brain (internal carotid arteries) become narrowed (stenosis). This narrowing decreases the space inside the vessels, making it harder for oxygen-rich blood to get through.

In response, small blood vessels form to create a new path for blood to flow. On a cerebral angiogram, the new vessels look like a puff of smoke. In Japan, where the condition was first documented, “moyamoya” means “hazy puff of smoke.”

Moyamoya slows blood flow to the brain, increasing the chance that a transient ischemic attack (TIA) or stroke will happen. These events can cause lasting brain damage or death. If your child has symptoms of a TIA or stroke, get medical help right away.

Because of the risk of stroke, moyamoya needs urgent treatment. Moyamoya does not get better on its own; it tends to gets worse over time. Young children with moyamoya are at greater risk for the condition getting worse. Seizures caused by reduced blood flow are another major risk for children with moyamoya.

Doctors often use the term “moyamoya” alone. They may also call this condition:

  • Moyamoya syndrome when the child has moyamoya along with a linked condition, like neurofibromatoses (NF) type 1 or Down syndrome.
  • Moyamoya disease when the child has no linked condition but has moyamoya on both sides of the brain.

Moyamoya at Seattle Children’s

Because moyamoya is rare, most doctors never see a child with this condition. Seattle Children’s treats many children with moyamoya each year. We see patients from babies to young adults and can provide all aspects of care — from diagnosis to surgery to long-term follow-up. We also provide second opinions.

The experts you need are here

Your child will be cared for by a team of moyamoya and stroke experts, starting with specialists from Neurology.

Seattle Children’s has the Pacific Northwest’s only Pediatric Vascular Neurology Program. The program is headed by a doctor who specializes in blood flow to a child’s brain, Catherine Amlie-Lefond, MD. Children with suspected or diagnosed moyamoya typically begin by seeing this doctor, who does a complete neurological evaluation and plans further evaluation. We will see your child promptly to assess their condition and plan for treatment.

Richard G. Ellenbogen, MD, and others from Neurosurgery have developed a special focus in treating moyamoya. Children come here from across the country for surgery called pial synangiosis (pronounced PEE-ul sin-an-JOE-sis) to improve blood flow to their brain. Dr. Ellenbogen performs many of these operations every year on infants, children and teens, and he has taught the operation to many other neurosurgeons.

Each child’s case is unique. Based on your child’s needs, your team may include specialists from Interventional Radiology, Neuropsychology, Rehabilitation Medicine, Social Work and other areas. If your child has another condition sometimes linked with moyamoya, team members partner closely with each other and with you to develop the best treatment plan to take care of all your child’s health needs.

Your whole team works together to explain your child’s condition and treatment and to answer your questions so you know what is happening and what to expect.

We treat infants, children and young adults

At Seattle Children’s, we diagnose and treat moyamoya patients from birth through young adulthood. We see patients who:

  • Have symptoms but haven’t been diagnosed.
  • Have been diagnosed and need surgery. (Some have had no moyamoya symptoms, but they had a brain scan for another reason that revealed the small blood vessels that form in moyamoya.)
  • Had surgery somewhere else for moyamoya and have moved to the Northwest, want to change doctors or want a second opinion about the best treatment.

We have the specialized equipment and expertise needed to operate on babies, children and young adults. Our neurosurgeons also operate on adults with moyamoya and similar conditions at Harborview Medical Center.

Your child gets long-term care and support

We take care of your child over the long term — not only in the weeks and months right before and after surgery, but for years to come.

Pial synangiosis is a surgery that creates a way for more blood to get to your child’s brain, but it takes time for the blood supply to improve. Even after surgery, children may have symptoms and be at risk for stroke. Children who had moyamoya on only one side of the brain may develop it later on the other side. And those who have had a stroke may need rehabilitation or other services if the stroke affected their movement, speech, thinking, mood or other aspects of their health or function.

We provide follow-up care to monitor your child’s health, prevent complications, manage symptoms or other health problems and give your child the best quality of life. Our commitment to lifelong care includes helping patients with moyamoya transition to care at Harborview Medical Center when they become adults. We prepare our moyamoya patients to take on a greater role in their own care, and we make sure they are connected with experts who can meet their adult healthcare needs.

We understand that dealing with moyamoya can be stressful and challenging. Social workers, Child Life specialists and many others are available to provide support for you and your child.

Moyamoya in Children

How common is moyamoya?

Moyamoya is rare. It affects about one in 1 million people in the United States. It is more common in people of Asian descent (especially Japanese, Korean and Chinese) than in people of other backgrounds. Girls are almost twice as likely as boys to have it.

When does moyamoya develop?

Some people have moyamoya from very early childhood. Others develop it as they get older. Doctors diagnose moyamoya most often in children under age 10 and in adults in their 30s or 40s.

Does it happen on both sides of the brain?

Most often, blood vessels on both sides of the brain are affected. If only one side is affected, the same problem may develop later on the other side. Some people only have moyamoya on one side of the brain. Long-term follow-up care is important to watch the blood vessels.

What other health problems are linked to moyamoya?

Some children who develop moyamoya had no major health problems before. But children with other medical conditions or certain procedures may be at greater risk for moyamoya. This includes:

Does moyamoya run in families?

Usually, moyamoya affects only one person in a family. But in some families, there is a history of moyamoya. If a child with moyamoya is an identical twin, the other twin should be screened for it. If other family members develop symptoms, they should get checked right away.