Moyamoya Disease

What is Moyamoya Disease?

Overview

Moyamoya disease is a rare neurovascular condition that can affect both children and adults and is caused by progressive narrowing or blockage of the major blood vessels supplying the brain.

As the arteries become blocked, the brain receives less oxygen-rich blood, which can cause ischemic stroke, mini-stroke (transient ischemic attack, or TIA), or bleeding into the brain. In response, the body forms tiny collateral vessels to try to restore circulation. On imaging, these small vessels appear as a hazy “puff of smoke,” giving the disease its name—moyamoya means “puff of smoke” in Japanese.

3D Vascular Imaging

3D vascular imaging of the brain showing successful revascularization surgery for moyamoya disease with extracranial-to-intracranial bypass.

Brain Perfusion Heatmap

Brain perfusion heatmap demonstrating successful changes (reduction in areas of low blood flow) after revascularization surgery.

Who is Affected?

While moyamoya disease is often diagnosed in people of Asian descent, it has now been recognized worldwide across all ethnic groups. It can present in both children and adults, often with different patterns of symptoms:

• Children tend to present with strokes or TIAs.
• Adults are more likely to present with brain hemorrhage.

Moyamoya Disease Symptoms & Causes

Symptoms

Patients with moyamoya disease experience the symptoms of ischemic stroke, hemorrhagic stroke or TIA. Symptoms can include:

• Weakness or numbness in an arm or leg
• Difficulty speaking
• Paralysis affecting one side of the body
• Seizures
• Cognitive difficulty or developmental delays (in children)
• Headache
• Weakness or numbness in an arm or leg
• Sudden loss of vision or difficulty seeing

These symptoms may come on suddenly, especially during times of stress, fever, dehydration, or exertion when blood flow demands are higher.

Causes

The exact cause of moyamoya disease is not fully understood, but genetics are believed to play a role. In some families, the disease is inherited, and mutations in the RNF213 gene have been associated with increased risk. In other cases, moyamoya may occur secondary to other conditions such as:

• Sickle cell disease
• Neurofibromatosis type 1
• Down syndrome
• Prior cranial radiation therapy

When to See a Doctor

Seek medical attention immediately if you or a loved one experiences symptoms of stroke, TIA, or sudden neurological decline. Early diagnosis and treatment are critical to preventing permanent brain injury.

Moyamoya Disease Diagnosis

Diagnosis typically involves:

Moyamoya Disease Treatment & Outcomes

Treatment Options

The narrowing of the arteries to the brain is irreversible. Medications may help reduce stroke risk (e.g., aspirin or other antiplatelet drugs), but they cannot restore adequate blood flow to the brain.

The mainstay of treatment for moyamoya disease is minimally invasive surgical revascularization, which creates new pathways for blood to reach brain tissue.

Direct bypass (EC-IC, Extracranial-to-intracranial bypass): A scalp artery (superficial temporal artery) is directly connected to a brain artery (middle cerebral artery) to restore flow.

Indirect bypass (EDAS, encephalo-duro-arterio-synangiosis): Scalp or muscle tissue is placed on the brain surface to encourage new vessel growth over time.

Combined techniques: Sometimes used to maximize blood flow restoration.

Patient Outcomes

With timely surgical treatment, most patients with moyamoya disease experience reduced risk of recurrent strokes and improved brain perfusion. Long-term outcomes are generally favorable, especially in children, who tend to recover brain function more effectively. Without treatment, moyamoya disease often progresses, leading to repeated strokes and cognitive decline.

Managing Moyamoya Disease

While surgery is the cornerstone of treatment for moyamoya disease, patients can also protect brain health by:

• Avoiding dehydration, which can worsen symptoms.
• Treating high blood pressure and other cardiovascular risk factors.
• Avoiding smoking and excessive alcohol use.
• Taking prescribed medications such as antiplatelet agents (e.g., aspirin) to lower stroke risk.
• Attending regular follow-up appointments and imaging to monitor brain circulation.

Meet our Expert Specialists & Surgeons

Samuel Hou, MD, PhD

Neurointerventional Surgery

Adi Iyer, MD, MS

Neurosurgery, Neuro-interventional Surgery

Ashkan Mowla, MD

Neurointerventional Surgery

Sandra Narayanan, MD

Vascular Neurology, Neurointerventional Surgery

Christopher Putman, MD

Neurointerventional Surgery

Experience Compassionate, Expert Care

At Pacific Neuroscience Institute, our neurosurgeons and experts specialize in advanced imaging, minimally invasive keyhole surgery, and personalized treatment for moyamoya disease. We provide comprehensive care, from diagnosis through long-term follow-up.

Learn More About Moyamoya Disease

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