Moyamoya Disease: Narrowing of the Brain’s Blood Vessels That Increases the Risk of Stroke in Children and Adults

Stroke is more commonly associated with older adults. However, there is a rare condition that can cause stroke in both children and young adults, known as moyamoya disease. This disease causes narrowing of the major blood vessels in the brain, reducing blood flow to brain tissue. In its early stages, the symptoms often go unnoticed, so the condition is frequently diagnosed only after a stroke or other neurological complications have occurred.

Although considered rare, moyamoya disease should be recognized as early as possible because it can significantly increase the risk of stroke, impaired brain function, and a reduced quality of life if left untreated.

What Is Moyamoya Disease?

Moyamoya disease is a cerebrovascular disorder characterized by progressive narrowing of the internal carotid arteries and their major branches at the base of the brain. This narrowing reduces blood flow to the brain, preventing brain tissue from receiving adequate oxygen and nutrients.

In response, the body forms a network of tiny blood vessels as alternative pathways (collateral vessels) to maintain blood flow to the brain. However, these collateral vessels are small and fragile, making them unable to fully replace the function of the main arteries. They are also prone to rupture, which can lead to bleeding in the brain.

On Digital Subtraction Angiography (DSA), this network of tiny blood vessels appears as a cloud of smoke. In Japanese, the word "moyamoya" means "a puff of smoke," which is how the disease got its name.

Moyamoya disease may affect one side or both sides of the brain. However, in most patients, the narrowing gradually progresses to involve both sides over time if left untreated.

Symptoms of Moyamoya Disease

The symptoms of moyamoya disease vary from person to person, depending on age and the severity of blood vessel narrowing. Symptoms develop either because of reduced blood flow to the brain or due to rupture of the fragile collateral blood vessels.

In children, the disease most commonly presents as a Transient Ischemic Attack (TIA) or an ischemic stroke. In adults, intracranial hemorrhage (hemorrhagic stroke) is also commonly observed in addition to ischemic stroke.

Symptoms that should not be ignored include:

1. Weakness or numbness of the face, arm, or leg
2. Temporary episodes of weakness that improve afterward (TIA)
3. Difficulty speaking or slurred speech
4. Visual disturbances
5. Recurrent headaches
6. Seizures
7. Dizziness
8. Balance problems
9. Declining learning ability, concentration, or academic performance in children
10. Decreased level of consciousness in certain situations

In some patients, symptoms may be triggered by strenuous physical activity, crying, fever, coughing, or hyperventilation, as these conditions can further reduce blood flow to the brain.

Causes and Risk Factors of Moyamoya Disease

To date, the exact cause of moyamoya disease remains unknown. However, several factors are known to be associated with an increased risk of developing the condition.

1. Genetic Factors or Family History

Genetic factors play an important role in the development of moyamoya disease. One of the genes most commonly associated with the disease is RNF213, particularly among East Asian populations. However, not everyone who carries this genetic variant will develop moyamoya disease.

The risk is also higher in individuals who have a family member—especially a parent or sibling—with moyamoya disease.

2. Age

Moyamoya disease most commonly occurs in two age groups: children between 5 and 10 years old and adults between 35 and 50 years old. In children, the disease typically presents as an ischemic stroke or TIA. In adults, symptoms may include ischemic stroke, intracranial hemorrhage, or chronic headaches.

3. Certain Genetic Disorders

Several genetic disorders are known to increase the risk of developing moyamoya disease, including:

1. Down syndrome
2. Neurofibromatosis type 1
3. Certain chromosomal abnormalities

These conditions may affect the development and structure of blood vessels, increasing susceptibility to narrowing of the brain's arteries.

4. Conditions Associated with Moyamoya Syndrome

In addition to moyamoya disease, there is another condition known as moyamoya syndrome, which refers to blood vessel narrowing that resembles moyamoya disease but occurs secondary to another underlying medical condition.

Several conditions associated with moyamoya syndrome include:

1. Sickle cell disease
2. A history of radiation therapy to the head
3. Certain autoimmune diseases

5. Environmental Factors

The role of environmental factors is still being investigated. To date, no environmental factor has been conclusively proven to cause moyamoya disease. However, it is believed that an interaction between genetic and environmental factors may contribute to the development of the disease.

How Is Moyamoya Disease Diagnosed?

The diagnosis of moyamoya disease is established through a combination of medical history taking, physical examination, neurological examination, and brain imaging studies.

Diagnostic tests that may be performed include:

1. Brain MRI, to evaluate brain tissue damage caused by reduced blood flow.
2. Magnetic Resonance Angiography (MRA) or CT Angiography (CTA), to assess the condition of the brain's blood vessels.
3. Digital Subtraction Angiography (DSA), which is considered the gold standard for diagnosing moyamoya disease because it clearly demonstrates the characteristic narrowing of the blood vessels and the formation of collateral vessels.

An accurate diagnosis is essential so that appropriate treatment can be initiated before recurrent strokes occur.

Treatment of Moyamoya Disease

The goals of treatment are to reduce the risk of stroke, preserve brain function, and improve the patient's quality of life.

1. Medical Therapy

Depending on the patient's condition, doctors may prescribe medications such as:

1. Antiplatelet medications to help reduce the risk of blood clot formation.
2. Blood pressure medications, when necessary.
3. Anti-seizure medications for patients who experience seizures.

It is important to note that medications cannot reverse the narrowing of the blood vessels. Instead, they help reduce the risk of complications.

2. Revascularization Surgery

Surgery is the primary treatment for most patients with moyamoya disease. The purpose of this procedure is to create a new pathway to improve blood flow to the brain. Common surgical techniques include:

1. Direct bypass, in which a blood vessel from outside the skull is directly connected to a blood vessel in the brain.
2. Indirect bypass, in which vascularized tissue is placed on the surface of the brain, allowing new blood vessels to gradually develop over time.

In some patients, both techniques may be combined to achieve the best possible outcome. The choice of surgical procedure depends on the patient's age, the condition of the blood vessels, imaging findings, and the neurosurgeon's clinical judgment.

Numerous studies have shown that revascularization surgery can reduce the risk of recurrent stroke while improving patients' long-term quality of life.

Conclusion

Moyamoya disease is a cerebrovascular disorder that can cause stroke in both children and adults. Although it is considered a rare condition, the disease is progressive, making early diagnosis and timely treatment essential to prevent recurrent strokes, permanent brain damage, and a decline in quality of life.

Do not ignore symptoms such as sudden weakness on one side of the body, speech difficulties, seizures, or recurrent headaches, especially when they occur in children or young adults. The earlier moyamoya disease is recognized, the greater the opportunity to preserve brain function and prevent more serious complications.

The National Hospital Neuroscience Center is supported by an experienced team of neurologists and neurosurgeons, along with advanced diagnostic facilities such as MRI, CT Scan, and Digital Subtraction Angiography (DSA) to help establish an accurate diagnosis and determine the most appropriate treatment plan for each patient.