Medical Conditions

Moyamoya Disease in Children

Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist

Content reviewed against published AHA, NIH, AAP guidelines

Editorial policy

Last reviewed:

If your baby has been diagnosed with or you suspect moyamoya disease in children, here is what the evidence says.

The short answer

Moyamoya disease is a rare, progressive condition in which the major arteries at the base of the brain gradually narrow, reducing blood flow. The body compensates by forming fragile collateral blood vessels (the "puff of smoke" appearance on angiography that gives the disease its Japanese name). It affects approximately 1 in 100,000 children and is more common in children of East Asian descent, though it occurs in all ethnic groups. Moyamoya puts children at risk for stroke and TIAs (transient ischemic attacks). Surgical revascularization is the mainstay of treatment and can significantly reduce stroke risk. Early recognition and treatment are key to preventing irreversible brain damage.

Key takeaways

  • Moyamoya disease is a rare, progressive condition in which the major arteries at the base of the brain gradually narrow, reducing blood flow. The body compensates by forming fragile collateral blood vessels (the "puff of smoke" appearance on angiography that gives the disease its Japanese name). It affects approximately 1 in 100,000 children and is more common in children of East Asian descent, though it occurs in all ethnic groups. Moyamoya puts children at risk for stroke and TIAs (transient ischemic attacks). Surgical revascularization is the mainstay of treatment and can significantly reduce stroke risk. Early recognition and treatment are key to preventing irreversible brain damage.
  • Usually normal when: Your child has occasional headaches that respond to hydration, rest, or appropriate pain medication and have no associated neurological symptoms
  • Call your doctor if: Your child develops sudden weakness on one side of the body, facial droop, speech difficulty, or vision loss — this may be a stroke and requires calling 911 immediately
  • Varies by age — see the age-by-age breakdown below
“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”
— Fever and Your Child, American Academy of Pediatrics (AAP)

Parents everywhere have the same worry. You are doing the right thing by looking into it.

What Parents Should Know

According to AHA, NIH, AAP guidelines, moyamoya disease is a rare, progressive condition in which the major arteries at the base of the brain gradually narrow, reducing blood flow. The body compensates by forming fragile collateral blood vessels (the "puff of smoke" appearance on angiography that gives the disease its Japanese name). It affects approximately 1 in 100,000 children and is more common in children of East Asian descent, though it occurs in all ethnic groups. Moyamoya puts children at risk for stroke and TIAs (transient ischemic attacks). Surgical revascularization is the mainstay of treatment and can significantly reduce stroke risk. Early recognition and treatment are key to preventing irreversible brain damage. At 0-2 years, moyamoya disease is uncommon in infancy but can present in the first two years of life, particularly in children with associated conditions such as Down syndrome, sickle cell disease, neurofibromatosis type 1, or prior cranial radiation. In young children, the presentation may include seizures, developmental regression, or stroke-like episodes with sudden weakness. An infant or toddler presenting with a stroke should be evaluated for moyamoya as part of the stroke workup. Brain MRI with MR angiography (MRA) is the initial screening test. It is generally considered normal when your child has occasional headaches that respond to hydration, rest, or appropriate pain medication and have no associated neurological symptoms. However, you should contact your pediatrician promptly if your child develops sudden weakness on one side of the body, facial droop, speech difficulty, or vision loss — this may be a stroke and requires calling 911 immediately.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Your child has occasional headaches that respond to hydration, rest, or appropriate pain medication and have no associated neurological symptoms
Your child develops sudden weakness on one side of the body, facial droop, speech difficulty, or vision loss — this may be a stroke and requires calling 911 immediately
Your child had a single episode of clumsiness or dizziness that resolved quickly and was attributable to dehydration or viral illness
Your child with known moyamoya develops a severe sudden headache, vomiting, or loss of consciousness — possible hemorrhagic stroke requiring emergency care
Your child has a condition associated with moyamoya (such as Down syndrome) but screening MRA is normal
Your child has recurrent TIA-like episodes — even if they resolve, each episode indicates the brain is at risk for a completed stroke, and urgent neurosurgical evaluation is needed
Your child was evaluated for moyamoya and brain imaging showed normal blood vessels
Your child has recurrent, unexplained headaches, especially if they occur in the morning or worsen with activity

When to Seek Immediate Care

  • Your child develops sudden weakness on one side of the body, facial droop, speech difficulty, or vision loss — this may be a stroke and requires calling 911 immediately
  • Your child with known moyamoya develops a severe sudden headache, vomiting, or loss of consciousness — possible hemorrhagic stroke requiring emergency care
  • Your child has recurrent TIA-like episodes — even if they resolve, each episode indicates the brain is at risk for a completed stroke, and urgent neurosurgical evaluation is needed

By Age

What to expect by age

0-2 years

Moyamoya disease is uncommon in infancy but can present in the first two years of life, particularly in children with associated conditions such as Down syndrome, sickle cell disease, neurofibromatosis type 1, or prior cranial radiation. In young children, the presentation may include seizures, developmental regression, or stroke-like episodes with sudden weakness. An infant or toddler presenting with a stroke should be evaluated for moyamoya as part of the stroke workup. Brain MRI with MR angiography (MRA) is the initial screening test.

2-5 years

This is one of the peak onset periods for moyamoya in childhood. Children may present with transient ischemic attacks (TIAs) — brief episodes of weakness, numbness, speech difficulty, or vision changes that resolve within minutes to hours. A characteristic trigger is hyperventilation (such as during crying, blowing on hot food, or playing a wind instrument), which causes cerebral vasoconstriction and can precipitate TIA symptoms in the setting of already reduced blood flow. Recurrent morning headaches may also occur. These symptoms are often initially attributed to other causes, delaying diagnosis.

5-10 years

School-age children may present with recurrent TIAs, completed strokes (causing lasting weakness on one side), seizures, or cognitive decline. Some children are diagnosed after being noted to have progressive difficulty in school. The gold standard diagnostic test is conventional cerebral angiography, which shows the characteristic narrowing of the internal carotid arteries and the network of small collateral vessels. Surgical treatment — either direct bypass (STA-MCA bypass) or indirect revascularization (EDAS, EMS, or multiple burr holes) — is recommended to improve blood flow and prevent future strokes.

10+ years

Adolescents with moyamoya may present similarly to adults, with TIAs, stroke, or hemorrhage (though hemorrhagic presentation is more common in adults than children). Post-surgical outcomes in children are generally excellent, with new vessel growth into the brain typically more robust than in adults. Long-term follow-up with periodic imaging is essential, as the disease can progress. Aspirin therapy is often used to reduce clotting risk. Children who undergo successful revascularization can often return to normal activities, though contact sports may be restricted.

What to Tell Your Pediatrician

  • Describe when you first noticed moyamoya disease in children and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child has recurrent, unexplained headaches, especially if they occur in the morning or worsen with activity.
  • Mention if your child has brief episodes of weakness, numbness, or speech difficulty that resolve completely, particularly triggered by crying, hyperventilation, or exertion.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

What Should You Do?

When to take action

Probably normal when...
  • Your child has occasional headaches that respond to hydration, rest, or appropriate pain medication and have no associated neurological symptoms
  • Your child had a single episode of clumsiness or dizziness that resolved quickly and was attributable to dehydration or viral illness
  • Your child has a condition associated with moyamoya (such as Down syndrome) but screening MRA is normal
  • Your child was evaluated for moyamoya and brain imaging showed normal blood vessels
Mention at your next visit when...
  • Your child has recurrent, unexplained headaches, especially if they occur in the morning or worsen with activity
  • Your child has brief episodes of weakness, numbness, or speech difficulty that resolve completely, particularly triggered by crying, hyperventilation, or exertion
  • Your child has a condition known to be associated with moyamoya (Down syndrome, sickle cell disease, NF1, prior head radiation) and has not been screened
Act now when...
  • Your child develops sudden weakness on one side of the body, facial droop, speech difficulty, or vision loss — this may be a stroke and requires calling 911 immediately
  • Your child with known moyamoya develops a severe sudden headache, vomiting, or loss of consciousness — possible hemorrhagic stroke requiring emergency care
  • Your child has recurrent TIA-like episodes — even if they resolve, each episode indicates the brain is at risk for a completed stroke, and urgent neurosurgical evaluation is needed

What You Can Do at Home

  • Keep track of when you notice moyamoya disease in children — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that your child has occasional headaches that respond to hydration, rest, or appropriate pain medication and have no associated neurological symptoms — this is generally within the range of normal.
  • At 0-2 years, focus on observation rather than intervention unless your pediatrician advises otherwise.
  • Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
  • While monitoring at home, seek immediate care if your child develops sudden weakness on one side of the body, facial droop, speech difficulty, or vision loss — this may be a stroke and requires calling 911 immediately.

Perinatal and Childhood Stroke

Stroke in babies and children is more common than many people realize, affecting approximately 1 in 2,500 to 4,000 births (perinatal stroke) and about 2-8 per 100,000 children per year (childhood stroke). Perinatal stroke occurs around the time of birth and may not be noticed until months later when the baby favors one side. Childhood stroke presents more suddenly, similar to adult stroke. Seizures are the most common presenting symptom of neonatal stroke. Rapid recognition and treatment can minimize brain damage and improve long-term outcomes.

Recognizing Signs of a Brain Tumor in Babies and Toddlers

Brain tumors are the second most common childhood cancer after leukemia. In babies and toddlers, symptoms can be subtle and overlap with common childhood complaints. Key warning signs include persistent morning vomiting (especially without nausea), rapidly increasing head size, bulging fontanelle, new-onset seizures, developmental regression, balance and coordination problems, vision changes, and persistent headache. These symptoms are usually caused by other conditions, but persistent or progressive symptoms deserve medical evaluation.

Neurofibromatosis Type 1 (NF1) in Babies

Neurofibromatosis type 1 (NF1) is one of the most common genetic conditions, affecting about 1 in 2,500 to 3,000 births. It is autosomal dominant, meaning a child needs only one copy of the altered NF1 gene (about half of cases are new mutations with no family history). The hallmark early sign is six or more cafe-au-lait spots larger than 5mm before puberty. NF1 has highly variable severity — many children have mild symptoms, while others develop complications requiring monitoring. Early diagnosis enables proactive surveillance for learning difficulties, vision changes, and tumor growth.

Milestone

Month-by-Month Development

Detailed monthly development guides from birth through 24 months.

Guide

When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is moyamoya disease in children normal?
Moyamoya disease is a rare, progressive condition in which the major arteries at the base of the brain gradually narrow, reducing blood flow. The body compensates by forming fragile collateral blood vessels (the "puff of smoke" appearance on angiography that gives the disease its Japanese name). It affects approximately 1 in 100,000 children and is more common in children of East Asian descent, though it occurs in all ethnic groups. Moyamoya puts children at risk for stroke and TIAs (transient ischemic attacks). Surgical revascularization is the mainstay of treatment and can significantly reduce stroke risk. Early recognition and treatment are key to preventing irreversible brain damage.
When should I call the doctor about moyamoya disease in children?
Your child develops sudden weakness on one side of the body, facial droop, speech difficulty, or vision loss — this may be a stroke and requires calling 911 immediately Your child with known moyamoya develops a severe sudden headache, vomiting, or loss of consciousness — possible hemorrhagic stroke requiring emergency care Your child has recurrent TIA-like episodes — even if they resolve, each episode indicates the brain is at risk for a completed stroke, and urgent neurosurgical evaluation is needed
When is moyamoya disease in children normal?
Your child has occasional headaches that respond to hydration, rest, or appropriate pain medication and have no associated neurological symptoms Your child had a single episode of clumsiness or dizziness that resolved quickly and was attributable to dehydration or viral illness Your child has a condition associated with moyamoya (such as Down syndrome) but screening MRA is normal
What causes moyamoya disease in children?
Moyamoya disease is a rare, progressive condition in which the major arteries at the base of the brain gradually narrow, reducing blood flow. The body compensates by forming fragile collateral blood vessels (the "puff of smoke" appearance on angiography that gives the disease its Japanese name). It affects approximately 1 in 100,000 children and is more common in children of East Asian descent, though it occurs in all ethnic groups. Moyamoya puts children at risk for stroke and TIAs (transient ischemic attacks). Surgical revascularization is the mainstay of treatment and can significantly reduce stroke risk. Early recognition and treatment are key to preventing irreversible brain damage. Common explanations include: Your child has occasional headaches that respond to hydration, rest, or appropriate pain medication and have no associated neurological symptoms. Your child had a single episode of clumsiness or dizziness that resolved quickly and was attributable to dehydration or viral illness.
What should I mention to my pediatrician about moyamoya disease in children?
You should mention moyamoya disease in children at your next visit if: Your child has recurrent, unexplained headaches, especially if they occur in the morning or worsen with activity. Your child has brief episodes of weakness, numbness, or speech difficulty that resolve completely, particularly triggered by crying, hyperventilation, or exertion. Your child has a condition known to be associated with moyamoya (Down syndrome, sickle cell disease, NF1, prior head radiation) and has not been screened.
Is moyamoya disease in children normal at 0-2 years?
Moyamoya disease is uncommon in infancy but can present in the first two years of life, particularly in children with associated conditions such as Down syndrome, sickle cell disease, neurofibromatosis type 1, or prior cranial radiation. In young children, the presentation may include seizures, developmental regression, or stroke-like episodes with sudden weakness. An infant or toddler presenting with a stroke should be evaluated for moyamoya as part of the stroke workup. Brain MRI with MR angiography (MRA) is the initial screening test.
Is moyamoya disease in children normal at 2-5 years?
This is one of the peak onset periods for moyamoya in childhood. Children may present with transient ischemic attacks (TIAs) — brief episodes of weakness, numbness, speech difficulty, or vision changes that resolve within minutes to hours. A characteristic trigger is hyperventilation (such as during crying, blowing on hot food, or playing a wind instrument), which causes cerebral vasoconstriction and can precipitate TIA symptoms in the setting of already reduced blood flow. Recurrent morning headaches may also occur. These symptoms are often initially attributed to other causes, delaying diagnosis.
Should I go to the ER for moyamoya disease in children?
Seek emergency care if your child develops sudden weakness on one side of the body, facial droop, speech difficulty, or vision loss — this may be a stroke and requires calling 911 immediately, or if your child with known moyamoya develops a severe sudden headache, vomiting, or loss of consciousness — possible hemorrhagic stroke requiring emergency care. When in doubt, call your pediatrician's after-hours line for guidance.
Does moyamoya disease in children go away on its own?
In many cases, moyamoya disease in children resolves on its own, especially when your child has occasional headaches that respond to hydration, rest, or appropriate pain medication and have no associated neurological symptoms. By 10+ years, adolescents with moyamoya may present similarly to adults, with TIAs, stroke, or hemorrhage (though hemorrhagic presentation is more common in adults than children). Post-surgical outcomes in children are generally excellent, with new vessel growth into the brain typically more robust than in adults. Long-term follow-up with periodic imaging is essential, as the disease can progress. Aspirin therapy is often used to reduce clotting risk. Children who undergo successful revascularization can often return to normal activities, though contact sports may be restricted.
AHANIHAAP

References

  1. [1]Scott RM, Smith ER. Moyamoya Disease and Moyamoya Syndrome. New England Journal of Medicine. 2009;360:1226-1237. AHA
  2. [2]National Institute of Neurological Disorders and Stroke. Moyamoya Disease. NINDS, 2023. NIH
  3. [3]Smith ER. Moyamoya Disease and Syndrome: Surgical Considerations. Seminars in Pediatric Neurology. 2023;45:101030. AAP

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Moyamoya Disease in Children.

Things to mention

  • Describe when you first noticed moyamoya disease in children and how it has changed over time.
  • Note your baby's current age and which age-specific patterns you are seeing.
  • Mention if your child has recurrent, unexplained headaches, especially if they occur in the morning or worsen with activity.
  • Mention if your child has brief episodes of weakness, numbness, or speech difficulty that resolve completely, particularly triggered by crying, hyperventilation, or exertion.
  • Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
  • Bring a list of any questions or observations you want to discuss at the appointment.

Observations to share

  • Your child has recurrent, unexplained headaches, especially if they occur in the morning or worsen with activity
  • Your child has brief episodes of weakness, numbness, or speech difficulty that resolve completely, particularly triggered by crying, hyperventilation, or exertion
  • Your child has a condition known to be associated with moyamoya (Down syndrome, sickle cell disease, NF1, prior head radiation) and has not been screened

Urgent signs to report immediately

  • Your child develops sudden weakness on one side of the body, facial droop, speech difficulty, or vision loss — this may be a stroke and requires calling 911 immediately
  • Your child with known moyamoya develops a severe sudden headache, vomiting, or loss of consciousness — possible hemorrhagic stroke requiring emergency care
  • Your child has recurrent TIA-like episodes — even if they resolve, each episode indicates the brain is at risk for a completed stroke, and urgent neurosurgical evaluation is needed

My notes

From ismybabyalright.com — free, evidence-based baby health guides

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members

Related Resources

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Bottom line

Most cases of moyamoya disease in children are normal. Talk to your pediatrician if your child develops sudden weakness on one side of the body, facial droop, speech difficulty, or vision loss — this may be a stroke and requires calling 911 immediately.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

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Related Medical Concerns

Perinatal and Childhood Stroke

Stroke in babies and children is more common than many people realize, affecting approximately 1 in 2,500 to 4,000 births (perinatal stroke) and about 2-8 per 100,000 children per year (childhood stroke). Perinatal stroke occurs around the time of birth and may not be noticed until months later when the baby favors one side. Childhood stroke presents more suddenly, similar to adult stroke. Seizures are the most common presenting symptom of neonatal stroke. Rapid recognition and treatment can minimize brain damage and improve long-term outcomes.

Recognizing Signs of a Brain Tumor in Babies and Toddlers

Brain tumors are the second most common childhood cancer after leukemia. In babies and toddlers, symptoms can be subtle and overlap with common childhood complaints. Key warning signs include persistent morning vomiting (especially without nausea), rapidly increasing head size, bulging fontanelle, new-onset seizures, developmental regression, balance and coordination problems, vision changes, and persistent headache. These symptoms are usually caused by other conditions, but persistent or progressive symptoms deserve medical evaluation.

Neurofibromatosis Type 1 (NF1) in Babies

Neurofibromatosis type 1 (NF1) is one of the most common genetic conditions, affecting about 1 in 2,500 to 3,000 births. It is autosomal dominant, meaning a child needs only one copy of the altered NF1 gene (about half of cases are new mutations with no family history). The hallmark early sign is six or more cafe-au-lait spots larger than 5mm before puberty. NF1 has highly variable severity — many children have mild symptoms, while others develop complications requiring monitoring. Early diagnosis enables proactive surveillance for learning difficulties, vision changes, and tumor growth.

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Achondroplasia (Dwarfism) in Babies

Achondroplasia is the most common form of short-limbed dwarfism, affecting about 1 in 15,000 to 40,000 births. It is caused by a mutation in the FGFR3 gene and is usually apparent at birth with characteristic features including short limbs, a larger head, and a prominent forehead. Intelligence is normal. With monitoring for specific complications and supportive care, children with achondroplasia lead full, active, and independent lives.

Adenoid Hypertrophy and Breathing

Adenoids are lymphoid tissue located behind the nose that help fight infection in young children. When adenoids become enlarged (adenoid hypertrophy), they can block the nasal airway, causing chronic mouth breathing, snoring, nasal speech, and sleep-disordered breathing. Enlarged adenoids are most common between ages 2-7 and are a leading cause of obstructive sleep apnea in young children. Treatment ranges from watchful waiting and nasal steroids to surgical removal (adenoidectomy) if breathing or sleep is significantly affected.