What is Moyamoya?

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Moyamoya disease is a progressive disorder in which the large arteries that carry blood to the brain narrow and often completely close off. The cause of the narrowing is unknown. When the arteries narrow, small branches of these arteries enlarge to bypass the blockage. These small branches, which grow larger (and maybe more numerous) give the disorder its name. “Moyamoya” is a Japanese term that means “puff of smoke,” which is used to describe the hazy appearance of these small vessels on an angiogram.

Why rely on Washington University experts to treat your moyamoya disease?

The Moyamoya Center at Washington University School of Medicine is a leading national program that is advancing the understanding and treatment of moyamoya disease.

Our department chair Gregory Zipfel, MD, has performed surgical revascularization on hundreds of patients with moyamoya disease with excellent results. Patients with the disease also are treated by vascular neurologists and receive well-coordinated care in the Neuroscience Center at the Center for Advanced Medicine at Washington University School of Medicine.

Washington University School of Medicine is the site for a research study on Moyamoya sponsored by National Institute of Neurological Disorders and Stroke (NINDS). For more information, contact study coordinator Christina Moore at or call 314-362-3466.


Cerebral angiography – an X-ray study of the blood vessels using a dye – is the principal form of imaging used for the diagnosis of moyamoya disease. The characteristic findings of moyamoya disease on an angiogram are traditionally described in stages, which progress from early narrowing of the carotid arteries to the formation of moyamoya vessels and then to the disappearance of these vessels with maintenance of blood flow by the external carotid and vertebral arterial systems.

 Stage INarrowing of carotid arteries
 Stage IIInitial appearance of moyamoya vessels
 Stage IIIIntensification of moyamoya vessels
 Stage IVMinimization of moyamoya vessels
 Stage VReduction of moyamoya vessels
 Stage VIDisappearance of moyamoya vessels

Suzuki J. Moyamoya Disease. Tokyo, Japan: Springer-Verlag; 1986.

Noninvasive imaging techniques also may be used in the diagnosis of moyamoya disease. When magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) demonstrate blockage of carotid arteries and moyamoya vessels on both sides, a cerebral angiogram is not needed for a diagnosis.

Once the diagnosis is confirmed, other imaging techniques may be used to measure blood flow and other aspects of the recovery and disease. Washington University neuroradiologists are experts in diagnosing and following moyamoya disease.

In an NINDS-sponsored clinical trial, positron emission tomography (PET) is used to study blood flow to the brain and oxygen use in patients with moyamoya.

Moyamoya treatment

Surgical revascularization has become the treatment of choice for patients with moyamoya disease. Although various drugs have been investigated for the treatment of this disease, at this point all have proven ineffective. In adults, surgical revascularization that directly bypasses blocked arteries is the most common treatment, if feasible. Indirect revascularization procedures are more frequently used in children.

STA-MCA Bypass

The superficial temporal artery to middle cerebral artery (STA-MCA) bypass for adult patients with moyamoya disease is performed by neurosurgeon Gregory Zipfel, MD, co-director of the Moyamoya Center at Washington University School of Medicine. After opening of the scalp, the STA is cut along its length. Care is taken to gently move the STA out of the operative field, and a portion of the skull is removed to expose the brain.

The dura – the outermost membrane enveloping the brain – is opened in a way that preserves the main branches of the middle meningeal artery (MMA), which delivers blood to the meninges, or connective tissues that cover the brain. Once the MCA is identified, the arachnoid – the middle layer of membrane surrounding the brain – is opened and the MCA is positioned so that the bypass can be completed.

The MCA is opened, and the STA is connected to it. In contrast to indirect revascularization procedures, the direct STA-MCA bypass provides an immediate increase to blood flow in the brain. Dr. Zipfel has performed hundreds of these direct bypass procedures with relief of symptoms and excellent results for patients.

Indirect revascularization procedures

Indirect revascularization procedures involve laying an artery or muscle on the surface of the brain. This can lead to blood vessel formation and increased blood flow to the brain over a longer period of time. Indirect procedures are more frequently used in children and are performed in adults only when direct surgical bypass is not feasible. Two of the most common indirect procedures are:

  • Encephaloduroarteriosynangiosis (EDAS) During this procedure, one of the main scalp arteries, usually the STA, is laid directly on the surface of the brain. Over time (6-8 weeks), this may cause the growth of new arteries in the brain and provide more blood flow. Once an EDAS is performed, the STA cannot be used for a direct bypass procedure.
  • Encephalomyosynangiosis (EMS) This procedure involves taking the temporalis muscle, which is in the temple region of the forehead, opening the skull, and placing the muscle on the brain. Once again, over 6-8 weeks, this may result in the development of arteries and increased blood flow.