What is moyamoya disease?
Moyamoya disease is a rare condition where the main arteries supplying blood to the brain become narrowed over time, reducing blood flow to the brain. As a result, new smaller blood vessels grow to try and supply the brain with blood. However, these new blood vessels often cannot supply enough blood to meet the brain’s needs, increasing the risk of stroke. Early diagnosis and treatment of moyamoya disease can reduce stroke risk and complications. Although moyamoya is a long-term condition, when followed closely and treated, it does not reduce life expectancy, and children can achieve a good quality of life.
Where does the term “moyamoya” come from?
The term “moyamoya” means “puff of smoke” in Japanese, describing the appearance of the small, fragile blood vessels that form as the body tries to supply the brain with enough blood. Moyamoya disease can occur alone (primary disease), as part of another condition—such as Down syndrome, neurofibromatosis type 1 and sickle cell disease—or after radiation treatment to the brain (moyamoya syndrome).
How moyamoya disease presents in children
Children with moyamoya disease may experience sudden neurological symptoms:
- weakness
- numbness
- speech problems (slurred speech, difficultly speaking, or trouble understanding words)
- vision loss
- seizures
- headaches
These symptoms can be temporary (transient ischemic attacks [TIAs]), going away within minutes to hours, or permanent (stroke), causing lasting brain injury. Over time, if untreated, moyamoya disease may affect learning or development.
A simple way to remember the warning signs of stroke is the BE FAST checklist:
- Balance – sudden loss of balance or coordination
- Eyes – sudden vision loss or double vision
- Face – face drooping or uneven smile
- Arm – weakness or numbness in an arm (or leg)
- Speech – slurred speech, difficultly speaking, or trouble understanding words
- Time – call 911 right away. Every minute counts
Causes, risk factors and prevalence of moyamoya disease
The cause of moyamoya disease is not fully understood, although genetic factors—including genetic variation of the RNF213 gene—play a role. Moyamoya disease is most common in East Asian populations but occurs worldwide. It affects males and females equally.
The risk of having moyamoya disease is increased in children with Down syndrome, Neurofibromatosis type 1, sickle cell disease and certain genetic syndromes. In North America, prevalence is estimated at 0.086 per 100,000 children, with peak presentation in childhood and middle adulthood.
Disease course
Moyamoya disease is progressive: the main blood vessels to the brain gradually narrow. Without treatment, most children with moyamoya disease will develop worsening symptoms and may experience repeated strokes, leading to permanent neurological injury. With medical and/or surgical treatment, stroke risk is reduced, improving long-term outcomes.
How is moyamoya disease diagnosed?
Diagnosis of moyamoya disease is confirmed with imaging. Magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) is a way of taking pictures inside the body that can show evidence of strokes or narrowed blood vessels within the brain. Once moyamoya disease is detected through MRI, the next step is to make a map of the blood vessels of the brain. This is done using cerebral angiography, a procedure that uses contrast dye and X-rays to see the blood vessels in more detail.
Genetic testing may also be considered.
How is moyamoya disease treated?
Moyamoya disease can be treated with medication and/or surgery. Medications that treat moyamoya disease include ones that keep certain cells in the blood (platelets) from sticking together and causing clots, such as acetylsalicylic acid and clopidogrel.
Moyamoya disease can also be treated with surgery that aims to improve blood flow (revascularization). Revascularization techniques can include directly bypassing the narrowed arteries (connecting a scalp artery to a brain artery) or indirect methods such as pial synangiosis (laying healthy tissue on the brain surface to promote new vessel growth).
Living a healthy lifestyle, including eating healthy foods, being physically active and sleeping well, can also improve health outcomes.
Can moyamoya disease be prevented?
There is no known way to prevent moyamoya disease itself. However, early recognition and medical/surgical treatment can prevent further strokes and disability. Families with a history of moyamoya disease may benefit from genetic counselling.
Complications
Complications of moyamoya disease can include:
- recurrent ischemic strokes—strokes caused by a lack of blood flow to the brain that happen more than once
- hemorrhagic stroke, especially in adulthood—stroke caused by bleeding in the brain
- cognitive decline and learning difficulties
- seizures
- movement disorders (rare)
- headaches and migraines
Helping your child at home
You can help your child by making sure they take their prescribed medications and encouraging them to hydrate. It is important for your child to live a healthy lifestyle and avoid situations that may reduce blood flow to their brain (such as dehydration, hyperventilation or illness). Accessing emotional support, school planning and stroke rehabilitation services are also important. Many children can return to regular activities with adjustments.
Long-term monitoring
Children with moyamoya disease require lifelong follow-up with a neurology and neurosurgery team. Your child will need regular MRI/MRA scans to track the blood flow in their brain, the narrowing of their blood vessels and any evidence of stroke. Rehabilitation, speech therapy and neuropsychological support may also be needed. Long-term outcomes of moyamoya disease are greatly improved when treatment occurs early.
When to seek medical attention
Go to the nearest Emergency Department or call 911 if your child has sudden neurological symptoms (weakness, numbness, speech problems, vision loss, seizures or loss of consciousness, persistent vomiting, persistent headache). An easy way to remember the signs of stroke is the BE FAST checklist:
- Balance – sudden loss of balance or coordination
- Eyes – sudden vision loss or double vision
- Face – face drooping or uneven smile
- Arm – weakness or numbness in the arm (or leg)
- Speech – slurred speech, difficulty speaking, or trouble understanding words
- Time – call 911 right away. Every minute counts.
At SickKids
Children with moyamoya disease are seen in a combined neurology and neurosurgery moyamoya clinic. This clinic brings together stroke neurologists and neurosurgeons, so families can receive coordinated care and treatment planning. The team also works closely with genetics, rehabilitation, and other specialists to support long-term care.
For appointments, please visit Neurology or contact the Neurosurgery Clinic.
Resources
American Stroke Association
www.stroke.org
National Organization for Rare Disorders (NORD)
www.rarediseases.org
Orphanet Moyamoya Disease
www.orpha.net
The Moyamoya Foundation
www.moyamoya.org
International Pediatric Stroke Organization (IPSO)
www.internationalpediatricstroke.org/
Boston Children’s Hospital Moyamoya Program
www.childrenshospital.org/services/moyamoya-program
Children’s Hospital of Philadelphia: Moyamoya Disease
www.chop.edu/conditions-diseases/moyamoya-disease
References
Scott R.M., & Smith E.R. (2009). Moyamoya Disease and Moyamoya Syndrome. New England Journal of Medicine. 360(12), 1226–1237. https://doi.org/10.1056/NEJMra0804622
Research Committee on the Pathology and Treatment of Spontaneous Occlusion of the Circle of Willis, Health Labour Sciences Research Grant for Research on Measures for Intractable Diseases. (2012). Guidelines for Diagnosis and Treatment of Moyamoya Disease (Spontaneous Occlusion of the Circle of Willis). Neurologia medico-chirurgica. 52(5), 245–266. https://doi.org/10.2176/nmc.52.245
Kleindorfer D.O., Towfighi A., Chaturvedi S., Cockroft K.M., Gutierrez J., Lombardi-Hill D., Kamel H., Kernan W.N., Kittner S.J., Leira E.C., Lennon O., Meschia J.F., Nguyen T.N., Pollak P.M., Santangeli P., Sharrief A.Z., Smith S.C. Jr, Turan T.N., Williams L.S. (2021). Guideline for the Prevention of Stroke in Patients With Stroke and Transient Ischemic Attack: A Guideline From the American Heart Association/American Stroke Association. Stroke. 52(7), e364–e467. https://doi.org/10.1161/STR.0000000000000375. Erratum in: Stroke. 2021. 52(7), e483–e484. https://doi.org/10.1161/STR.0000000000000383
Klijn, K. (2015). Moyamoya disease. Orphanet. https://www.orpha.net/en/disease/detail/2573?search=Moyamoya-angiopathy&mode=name
Nagiub, M., & Allarakhia, I. (2013). Pediatric Moyamoya disease. American Journal of Case Reports. 14, 134–8. https://doi.org/10.12659/AJCR.889170
