Moyamoya Disease

When you hear that your child may need brain surgery due to Moyamoya disease, you may feel overwhelmed. Our neurosurgery team is highly trained in rare children’s disorders and has decades of experience treating Moyamoya. We will be with your family from diagnosis throughout your child’s growth to ensure the best possible outcome.

What is Moyamoya?

Moyamoya is a rare brain disease caused by a blockage in the artery supplying blood to the brain. Moyamoya means “puff of smoke” in Japanese, which describes the look of the blood vessels that are tangled together to form the blockage, as seen on an MRI.

What causes and risk factors are related to Moyamoya disease?

There is no known direct cause of Moyamoya, but it is more commonly found in children of Asian descent, or children who have had brain radiation.

Children with other disorders that affect blood flow to the brain can be diagnosed with Moyamoya, including:

What are the symptoms of Moyamoya disease?

Moyamoya can occur at any age, but doctors find there are two peak incidence periods—between the ages of five and 10 years in children, and between 30 to 50 years in adults.

One of the most common symptoms seen in a child with Moyamoya syndrome is a stroke caused by the lack of blood supply to the brain. Other symptoms may include:

  • Partial temporary paralysis
  • Headaches
  • Seizures
  • Involuntary movements
  • Vision problems

What tests are used to diagnose Moyamoya disease?

To diagnose Moyamoya, there are a few tests that will be done to map the blood flow to the brain and give an accurate visualization of the existing blood flow to various areas of the brain.

  • Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) – An MRI and MRA, when used together, provide two useful diagnostic images: the MRI gives an in-depth image of the brain and the MRA offers proper visualization of the blood flow.
  • Cerebral angiogram – Once initial testing shows the appearance of Moyamoya, a cerebral angiogram is often used to determine the level of blockage and severity of the problem, and to help doctors decide on treatment. Using a small needle, contrast dye is injected and followed through the veins, mapping out the exact routes that blood flows to and from the brain.
  • CT angiography – In certain cases, low-dose computerized tomography (CT) angiography can be used, especially when emergent studies need to be performed.

What are the treatment options for Moyamoya disease?

A child with Moyamoya brain disease will often be put on aspirin, a blood thinner, to help ease blood flow and reduce the risk of stroke.

Your neurosurgeon will then discuss the best surgery that should be performed based on the level of blockage. These surgeries will help regenerate blood flow to the brain. If both sides of the brain are affected, your doctor may schedule two separate surgeries to reduce the potential for complications.

  • Microsurgical encephaloduroarteriosynangiosis (EDAS) – This is the most advanced surgery used to treat Moyamoya because it uses blood flow that is already available, sometimes called revascularization. A small portion of the skull is removed so that a branch of the temporal artery, found on the side of the head near the temple, can be laid directly on the surface of the brain. This allows a new blood supply to reach the affected area.
  • Encephalo-myo-synangiosis (EMS) – An indirect bypass of the blockage is created by dissecting the temporalis muscle and placing it on the surface of the brain to allow a new blood supply to develop from the muscle tissue.

Recovery time depends on the severity of the surgery, but most families can expect to spend about three days in the hospital.

Follow-Up Care

After surgery, your child will be followed closely by your team of specialists at CHOC to ensure proper recovery. Some tests such as MRAs will be requested every year to recheck the blood flow created by the surgery, and in some cases another surgery could be required in the future.

Why CHOC?

As a parent, your top priority is choosing a hospital and team of doctors who can provide the best outcome for your child and your family. The CHOC Children’s Neuroscience Institute is a place dedicated to caring for kids with complex and rare medical issues. Our specialists have devoted their training, research and practice to caring specifically for children.

  • During his 20+ years as a neurosurgeon, Dr. Michael G. Muhonen has helped more than 100 patients and their families with Moyamoya brain disease through diagnosis, surgery and recovery.
  • We practice a team approach to healing. Neurological conditions in children require a team of caregivers including neurologists, orthopedic specialists, nurses, social workers, rehabilitation therapists and more. Our team works together on every aspect of your child’s care from diagnostics to surgery and follow-up care.
  • We care about your child deeply, and will care for the whole family. We make the experience seamless, from coordinating care, communicating with your child’s primary care physician, or discussing your child’s treatment with your family as long as you need to get all of your questions answered. CHOC is here for you.
  • We understand that a hospital can seem frightening for both the child and their family. Our child life specialists work with families to “normalize” hospital equipment and procedures so you can concentrate on healing instead.
  • Our surgical center is outfitted with advanced imaging, communication and robotics technologies, specific to children and their needs. This ensures a high level of skill and safety for the children under our care.

US News and World Report Best Children's Hospitals Neurology and Neurosurgery

Contact Us

Our neurosurgeons are available for appointments and referrals at the following office.

CHOC Children’s Specialists Neurosurgery
1010 W. La Veta Ave., Suite 710
Orange, CA 92868
Appointments: 714-509-7070
Hours and Directions

Meet Our Pediatric Neurosurgeons

Loudon, William G. MD, PhD

Specialty: Neurosurgery
Appointments: 714-509-7070

Dr. William Loudon is a board-certified pediatric neurosurgeon at CHOC Children's.

Muhonen, Michael G. MD

Specialty: Neurosurgery
Appointments: 714-509-7070

Dr. Michael Muhonen is a board certified neurosurgeon at CHOC Children's and serves as medical director of the CHOC Children's Neuroscience Institute.

Olaya, Joffre E. MD

Specialty: Neurosurgery
Appointments: 714-509-7070

Dr. Joffre Olaya specializes in neurosurgery. He sees kids and teens at CHOC Children's Hospital in Orange and CHOC Children's at Mission Hospital.