Moyamoya

Moyamoya (pronounced MOY-a-MOY-a) is a rare condition that limits blood flow to the brain. It happens when the main blood vessels to the brain (internal carotid arteries) become narrower (stenosis). This makes it harder for oxygen-rich blood to get through. Small blood vessels form to create a new path for blood to flow.

On a picture of the blood vessels in the brain (cerebral angiogram), the new vessels look like a puff of smoke. “Moyamoya” means “hazy puff of smoke” in Japanese. The condition was first reported in Japan.

Moyamoya slows blood flow to the brain and increases the chance of:

• Transient ischemic attack (TIA)
• Stroke
• Seizures

Because of the risk of stroke, moyamoya needs urgent treatment. A stroke or TIA can cause lasting brain damage or death.

If you think your child is having a stroke, call 911.

Some people have moyamoya from very early childhood. Others develop it as they get older. Moyamoya does not get better on its own.

Most often, a doctor who specializes in blood flow to the brain diagnoses moyamoya after a child has symptoms of stroke or TIA. Sometimes a brain scan done for another reason finds moyamoya.

To understand your child’s problems and plan treatment, experts in our Pediatric Vascular Neurology Program will ask about your child’s medical history and symptoms and examine your child. As needed, we do imaging studies to look at the arteries that carry blood to the brain.

If your child might have moyamoya, we will do a complete neurological evaluation to check:

• Balance
• Reflexes
• Motor skills
• Sense of touch
• Memory and thinking

Your child may have 1 or more of these imaging studies:

• MRI (magnetic resonance imaging) scan
• MRA (magnetic resonance angiography) scans of the arteries
• CT (computed tomography) scan
• Cerebral angiogram to map blood vessels in your child’s brain

Some children need other types of imaging to find out how well and how much blood flows to different parts of the brain. Your child’s team will explain which tests your child needs, why and what to expect.

Doctors treat moyamoya with surgery to bring new blood supply to the brain. Your child’s team at Seattle Children’s will also recommend steps to help reduce stroke risk.

Our Pediatric Vascular Neurology team will talk with you in detail about what they recommend for your child and why.

Surgery Options for Moyamoya  

There are 2 main surgeries to improve blood flow in children with moyamoya: 

• Indirect revascularization – Surgery that prompts new blood vessels to grow into the brain over time. This surgery is called pial synangiosis (PEE-ul sin-an-JOE-sis) or encephaloduroarteriosynangiosis.  
• Direct revascularization - Surgery that sends more blood into blood vessels already in the brain. This procedure is called superficial temporal artery-middle cerebral artery anastomosis, or STA-MCA anastomosis.

Both methods use your child’s superficial temporal artery (STA). Normally, this artery comes up from the neck and goes under the scalp on the side of the head. 

We tailor treatment to your child. The neurosurgeon considers your child’s anatomy and health and recommends the best surgery for your child. Whenever possible, we use the indirect method because:

• We believe it is safer for children.
• It does not depend on good blood flow through the middle cerebral artery. Sometimes moyamoya causes narrowing of that artery, which restricts blood flow.

Children who have frequent TIAs or who have a stroke before surgery are at greater risk of having a stroke during surgery or in the next 2 weeks. Overall, this risk is low. To help reduce the risk, we usually wait 4 to 6 weeks after a stroke to do surgery.

Care After Surgery

Most children do very well after surgery for moyamoya. Your child will have pain medicine for their comfort. We will watch your child in the intensive care unit for 1 to 2 days until we are sure they are doing well. Then your child will stay in a regular hospital room for 2 to 3 days. Most children can go home 4 to 5 days after surgery.

Before your child goes home, your child’s team will explain any special care or precautions needed after surgery.

After pial synangiosis, new arteries start growing into the brain. This continues for at least a year. During this time, your child may have headaches or TIAs. Over time, this should improve. We ask you to keep track of your child’s symptoms, so we can talk about them at follow-up visits and give your child any tests or treatments they need.

As part of follow-up care, we check to see if moyamoya is developing on the other side of your child’s brain. If it does, we will treat it.

We tailor the follow-up schedule to your child. Here is what usually happens:

• About 2 weeks after surgery, the neurosurgery team will see your child for a follow-up visit. We check your child’s healing and remove their stitches.
• In about 3 months, a neurosurgeon and a neurologist will see your child for a follow-up visit. Your child will have an MRI (magnetic resonance imaging) scan. These tests check blood flow in the affected areas of your child’s brain.
• Each year, your child will have a brain scan.

Seattle Children’s provides follow-up care to:

• Monitor your child’s health
• Prevent complications
• Manage symptoms or other health problems
• Improve your child’s quality of life

Ongoing care will depend on your child’s needs. For example, if reduced blood flow damaged your child’s brain, they may benefit from:

• Rehabilitation medicine
• Neuropsychology
• Physical therapy
• Occupational therapy
• Speech therapy

Our team is experienced in helping children return to school and other important activities after brain surgery or treatment for stroke. We also work with you to find resources in your community.

Because moyamoya is very rare, most doctors never see a child with this condition. Each year, Seattle Children’s treats many patients with moyamoya, from babies to young adults. Experts in our Pediatric Vascular Neurology Program work as a team to care for your child — from diagnosis to surgery to long-term follow-up. We also provide second opinions.

The program director, Dr. Catherine Amlie-Lefond, is a pediatric vascular neurologist and national leader in this field. Seattle Children’s is the only children’s hospital in our region with a program focused on children who have problems that affect the brain’s blood flow and vessels. Our region includes Washington, Alaska, Montana and Idaho (WAMI).

Children come here from across the country for surgery called pial synangiosis (PEE-ul sin-an-JOE-sis) to improve blood flow to their brain and reduce the risk of stroke. Dr. Richard G. Ellenbogen performs many of these operations every year on babies, children and teens. We have some of the best outcomes in the nation for revascularization surgery.

Each child’s case is unique. Pediatric experts in Neurosurgery and Neurology will care for your child. Based on your child’s needs, your team may include specialists from Interventional Radiology, Neuropsychology, Social Work and Rehabilitation Medicine. 

If moyamoya causes a stroke, we have the expertise to respond quickly for the best possible outcome. As needed, we provide rehabilitation for your child’s recovery. If your child has another condition linked with moyamoya, team members work together and with you to develop the best treatment plan to take care of all your child’s health needs.