Frequently Asked Questions about Moyamoya Disease (FAQ)

Moyamoya disease is a rare, progressive cerebrovascular disorder caused by blocked arteries at the base of the brain in an area called the basal ganglia. Moyamoya means “puff of smoke” in Japanese and is used to describe the tangled appearance of tiny vessels compensating for the blockage.  

Moyamoya disease causes different symptoms in adults and children. In children, the first symptom is usually a stroke or recurrent transient ischemic attack (TIA). Adults may experience these symptoms, as well. But adults also may experience bleeding in the brain, known as a hemorrhagic stroke. The bleeding occurs because of the way blood vessels in the brain formed.

Symptoms of moyamoya disease related to reduced blood flow to the brain include:

• Headache.

• Seizures.

• Weakness, numbness or paralysis in your face, arm or leg. This is typically on one side of your body.

• Vision problems.

• Trouble speaking or understanding others, known as aphasia.

• Cognitive or developmental delays.

• Involuntary movements.

These symptoms can be triggered by exercise, crying, coughing, straining or a fever.

The genetics of moyamoya disease are not well understood. Research suggests that the condition can be passed through families, and changes in one gene, RNF213, have been associated with the condition. Other genes that have not been identified may be involved in moyamoya disease. It is also likely that other factors (such as infection or inflammation) in combination with genetic factors play a role in the condition's development.

Moyamoya disease is usually diagnosed by a neurologist who specializes in the condition. The specialist will review your symptoms and your family and medical history. The specialist also will likely perform a physical exam. Several tests are generally needed to diagnose moyamoya disease and any underlying conditions. These include:

• MRI

• CT Scan

• Cerebral Angiogram

• PET Scan

• SPECT Scan

• EEG

• Transcranial Doppler Ultrasound

Up to 15 percent of Japanese people with moyamoya disease have one or more family members with the condition, indicating that the condition can be passed through generations in families; however, the inheritance pattern is unknown. Research suggests that the condition follows an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. However, some people who have a copy of the altered gene never develop the condition, which is a situation known as reduced penetrance.

Moyamoya disease was first identified in Japan, where it is most prevalent, affecting about 5 in 100,000 individuals. The condition is also relatively common in other Asian populations. It is ten times less common in Europe. In the United States, Asian Americans are four times more commonly affected than whites. For unknown reasons, moyamoya disease occurs twice as often in females as in males.

The goal of treatment is to reduce your symptoms and improve brain blood flow. Treatment also aims to lower your risk of complications. Complications include ischemic stroke caused by a lack of blood flow, bleeding in your brain and death.

The prognosis for moyamoya disease depends on several factors, such as:

• How early the disease was diagnosed

• How much damage has occurred when you seek treatment

• Whether or not you undergo treatment

• Age

• Direct revascularization surgery: This bypass procedure provides immediate new blood flow to the brain. The moyamoya blockages are bypassed by connecting a scalp artery to an artery on the surface of the brain to restore blood flow.

• Indirect revascularization surgery: This procedure involves placing an artery near the surface of the brain to enable blood vessels to eventually grow into and connect with other brain blood vessels, typically over the course of months after surgery.