Moyamoya Syndrome

Moyamoya syndrome is a rare condition in which blood vessels at the base of the skull progressively narrow, limiting the flow of oxygenated blood to the brain. Surgical treatment options for Moyamoya syndrome include direct revascularization procedures such as an EC-IC bypass as well as indirect revascularization procedures like encephaloduroarteriosynangiosis (EDAS) and pial synangiosis. Here at Columbia University Irving Medical Center/NewYork-Presbyterian Hospital, our neurosurgeons have particular expertise using these and other surgeries to treat patients with Moyamoya syndrome.

“Moyamoya” means “puff of smoke” in Japanese, and the condition is so named because the body grows a secondary network of small vessels in an effort to compensate for the restricted blood flow. On an arteriogram, the network of new vessels resembles a cloud–or puff of smoke. Moyamoya is more common in Japan than in the U.S., but it is unusual everywhere.

The blood vessel network that gives Moyamoya its name may lead to complications. As blood flow becomes increasingly restricted, the supplementary network may become inadequate as an alternative blood supply to the brain. This can lead to cerebral ischemia. In addition, the new vessels are fragile and may rupture.


The type and severity of symptoms vary. Possible symptoms include:

  • Weakness
  • Paralysis in a limb or on one side of the body
  • Sensory impairment
  • Involuntary movements
  • Headaches
  • Speech problems
  • Dizziness
  • Seizures

Sudden, severe problems can include:

  • Transient ischemic attack (TIA or “mini-stroke”)
  • Stroke
  • intracranial hemorrhage

TIA, stroke, and intracranial hemorrhage are neurological emergencies that require immediate treatment.

Moyamoya is a progressive condition. Untreated, it carries not only the risk of hemorrhage or stroke, but also the risk of other consequences that may emerge over time, such as mental retardation and sustained neurological problems. For most patients, however, surgery halts the progression of the disease.


Moyamoya is a rare condition, and physicians who do not specialize in cerebrovascular disorders sometimes do not consider it as a diagnosis.

Computed tomography (CT) and magnetic resonance imaging (MRI) scans may provide the first indications of the disease.

If the disease is suspected, cerebral angiography is conducted to establish the diagnosis. For this test, a catheter is inserted in a large blood vessel in the groin and threaded up to the blood supply of the brain. A special dye visible on X-ray is injected into the blood vessels, and a series of X-rays are taken. In this way, a specialist can study the blood flow in the brain. Magnetic resonance angiography (MRA), another imaging study that shows the blood vessels in the brain, also may be used.

In addition, single photon emission computerized tomography (SPECT) scans may be used to identify the regions of the brain that are not receiving sufficient oxygen.

Risk Factors

Physicians distinguish between true “moyamoya disease” and “moyamoya syndrome.”

True moyamoya disease is caused by the continual growth of the inner lining of certain arteries. It is most common in people of Japanese ancestry, and it is generally more common in people with Asian ancestry than in people of other ancestries. It is somewhat more common in women than in men. About 10% of people with true moyamoya disease have a direct relative with the disease.

Sometimes a moyamoya-like pattern of vessel blockage and compensatory new vessel growth is caused by other conditions. This is called moyamoya syndrome. Many conditions can be associated with moyamoya syndrome. Some of the more common are:

  • Neurofibromatosis type I (NFI)
  • Atherosclerosis
  • Vasculitis
  • Radiation therapy for parasellar tumors
  • Cranial trauma
  • Down syndrome
  • Marfan syndrome
  • Sickle cell disease

The information on this page applies both to moyamoya disease and to moyamoya syndromes associated with these and other conditions.

Moyamoya can affect children or adults.


Untreated, moyamoya is a progressive condition. No medications can currently stop the disease, though in some cases medication may buy some time and reduce some symptoms. However, surgery is the mainstay of moyamoya treatment, and it usually stops the progression of the disease. Following surgery, most patients never experience another stroke or any further neurological decline.

Surgical moyamoya treatment consists of restoring blood flow to the brain with procedures known as revascularization procedures. There are two main types of revascularization procedures: direct and indirect.

In a direct revascularization, the surgeon directly sutures a healthy extracranial blood vessel to an incision made in the wall of a blood-deprived intracranial vessel, giving the intracranial vessel a full blood supply. Most often, the surgeon connects a healthy artery called the Superficial Temporal Artery (STA) with the blood-deprived Middle Cerebral Artery (MCA); this particular procedure is called an STA/MCA bypass. But there are a number of these procedures to choose from; as a group, they known as extracranial/intracranial, or EC-IC bypass procedures.

The main advantage of a direct revascularization is that the new blood supply is immediate. A healthy blood flow through the previously blood-deprived artery begins as soon as the surgical clamps are removed. The main disadvantage of a direct revascularization is that it often cannot be used in children due to the exceedingly small diameter of their arteries.

In an indirect revascularization, a surgeon places an existing blood supply on the surface of the oxygen-deprived region of the brain. This existing blood supply may be a blood vessel that is otherwise attached to the scalp, or it may be a nearby muscle, like one in the temple area. New blood vessels grow like roots from the vessel or muscle on the surface of the brain into the oxygen-deprived region. The most common indirect revascularization procedures are encephaloduroarteriosynangiosis (EDAS) and pial synangiosis.

EDAS and pial synangiosis are excellent options for pediatric moyamoya patients, and for adult patients who cannot undergo an EC/IC bypass. Following these procedures, it takes approximately 3-6 months for new blood vessels to grow and begin to supply the brain.

Like all other surgical procedures, revascularization surgeries do carry some risk, including bleeding and stroke. However, these risks are usually far outweighed by the benefits of surgery. Surgery generally provides a good long-term outlook for moyamoya.

Though moyamoya is a rare condition, our neurosurgeons are skilled and experienced in treating it, both in children and adults.