Moyamoya Disease: The Rare Brain Condition You’ve Probably Never Heard Of

Have you ever heard of Moyamoya disease? If not, you're not alone. This rare but serious condition affects the brain’s blood vessels and can lead to strokes—even in children. Although its name might sound unusual, this disease is very real and can be life-changing if left untreated. Understanding Moyamoya could be the key to saving lives.

What is Moyamoya Disease?

Moyamoya disease is a rare, progressive disorder of the blood vessels in the brain. It causes the main arteries at the base of the brain (especially the internal carotid arteries) to become narrow or blocked over time. As a result, the brain tries to compensate by creating a network of tiny blood vessels. These small vessels appear like a “puff of smoke” on imaging scans—hence the name Moyamoya, which means "something hazy like smoke" in Japanese.

Epidemiology: Who Gets It?

Moyamoya disease is most commonly found in East Asian countries, particularly Japan, Korea, and China, but cases are increasing worldwide, including in Europe and North America. It can affect people of all ages, though it often strikes in childhood (around 5–10 years old) or again in early adulthood (30–40 years old). Females are slightly more likely to be affected than males.

What Causes It?

The exact cause of Moyamoya disease is still unknown, but research suggests it may be linked to:

• Genetics: Certain genetic mutations, like RNF213, are strongly associated with the disease in East Asian populations.

• Autoimmune factors: In some cases, the immune system may mistakenly attack blood vessels.

• Other diseases: Moyamoya can be secondary to conditions like Down syndrome, neurofibromatosis, or sickle cell disease.

How Does It Develop?

In Moyamoya, the internal carotid arteries, which supply blood to the brain, gradually narrow (stenosis) that happens due to abnormal thickening of the vessel walls. More specifically, the inner layer of the artery (called the intima) begins to grow excessively, a process known as intimal hyperplasia. This abnormal growth may be triggered by genetic factors, particularly mutations that affect how blood vessels develop and repair themselves. In many patients, especially in East Asian populations, a mutation in the RNF213 gene has been strongly linked to this process. 

Over time, this thickened layer reduces the space inside the artery, making it harder for blood to pass through. This leads to reduced blood flow to critical areas of the brain. In response, the brain tries to form new, smaller vessels to keep blood moving. However, these tiny vessels are fragile and prone to rupture, causing hemorrhagic strokes, or they may not supply enough blood, leading to ischemic strokes.

Signs and Symptoms

Symptoms depend on age and the severity of the disease. Common signs include:

In Children:

• Transient ischemic attacks (TIAs) or “mini-strokes”

• Sudden weakness or paralysis (often on one side)

• Seizures

• Headaches

• Learning or behavior difficulties

In Adults:

• Stroke

• Cognitive decline

• Visual disturbances

• Speech difficulties

• Hemorrhagic stroke (bleeding in the brain)

These symptoms may come and go, which can delay diagnosis.

Treatment Overview

There is no known cure, but early diagnosis and treatment can significantly improve outcomes.

Main Treatments:

• Surgery is the most effective option to restore blood flow. The most common procedures include:

  • Direct revascularization: Connecting an external artery to a brain artery directly.

  • Indirect revascularization: Encouraging new blood vessels to grow over time.

• Medications may include:

  • Antiplatelets (e.g., aspirin) to reduce stroke risk.

  • Drugs to manage seizures or blood pressure.

Treatment plans are tailored individually, often requiring neurologists, neurosurgeons, and rehabilitation specialists.

Can It Be Prevented?

Since Moyamoya disease often has a genetic component and no known environmental triggers, prevention is difficult. However, you can take steps to reduce complications:

• Get regular check-ups if there’s a family history.

• Seek immediate care if you or your child shows stroke-like symptoms.

• Manage related health conditions such as hypertension or diabetes.

• Follow post-treatment plans strictly to prevent further strokes.