Moyamoya Disease and Syndrome

Medically reviewed by Dina Mohammed, MD · Last updated: August 25, 2026

Our Specialists for Moyamoya Disease and Syndrome

Moyamoya care at UChicago is delivered by a team that treats both adults and children, with decades of combined experience in direct and indirect bypass surgery. Experience matters here — bypass surgery for moyamoya is technically demanding, and outcomes are closely tied to surgeon volume.

Issam A. Awad, M.D., M.Sc., FACS

Section Chief, Vascular Neurosurgery

Dr. Awad directs the Neurovascular Surgery Program at UChicago and has spent four decades operating on complex cerebrovascular disease, including moyamoya. If you have moyamoya at UChicago, Dr. Awad is typically involved in planning the revascularization strategy and coordinating care across neurology, neuroradiology, and the operating room.

Sean P. Polster, M.D.

Co-Director, Stroke Center; Safadi Faculty Scholar

Dr. Polster performs direct, indirect, and combined bypass for adults and older children with moyamoya, and his NIH-funded lab studies the vascular biology of cerebrovascular disease. He works closely with Dr. Awad on the moyamoya service, handling both the microsurgical anastomosis and long-term follow-up imaging.

Arthur J. DiPatri Jr., M.D.

Director, Pediatric Neurosurgery

Dr. DiPatri is the pediatric neurosurgeon who sees children with moyamoya at UChicago Medicine Comer Children's Hospital, including kids with moyamoya syndrome from sickle cell disease, Down syndrome, and neurofibromatosis. He favors pial synangiosis and other indirect revascularization techniques that work particularly well in young, developing brains.

What Is Moyamoya?

Moyamoya is a rare cerebrovascular disease in which the large arteries that carry blood to the front of the brain — the terminal portions of the internal carotid arteries and their main branches — slowly narrow and eventually close off. In response, the brain grows a tangled network of tiny, fragile backup vessels to try to keep blood flowing.

On an angiogram, those collateral vessels look like a hazy cloud. The Japanese neurosurgeons who first described the disease in the 1960s called it moyamoya, which means 'puff of smoke' in Japanese. The name stuck.

When the narrowing happens on its own, with no underlying cause, we call it moyamoya disease. When it happens in someone who has another condition known to damage arteries — sickle cell disease, Down syndrome, neurofibromatosis type 1, prior radiation to the head, or certain genetic syndromes — we call it moyamoya syndrome. The surgical treatment is very similar, but the underlying disease matters for long-term management.

Moyamoya is most common in East Asia, but it occurs in every population. In the United States it shows up in two age peaks: children around age 5-10, and adults in their 30s and 40s. Women are affected slightly more often than men.

What Does It Feel Like?

Symptoms depend on age. Children and adults tend to present very differently, and recognizing the pattern is the first step toward getting the right test.

In children

Kids almost always present with symptoms of not enough blood flow to the brain — what doctors call ischemia. Parents often notice episodes that come and go:

• Transient weakness or numbness on one side of the body, sometimes triggered by crying, blowing out birthday candles, or hot soup (anything that causes rapid breathing and lowers blood CO2)
• Slurred speech or trouble finding words that lasts a few minutes and resolves
• Headaches, often severe and recurrent
• Seizures
• Involuntary movements (chorea) of an arm or leg
• A gradual drop in school performance or cognitive changes
• In young children, developmental delay or loss of previously learned skills

These spells are often mistaken for migraines, seizures, or behavioral problems for months before the diagnosis is made.

In adults

Adults more often present with sudden, dramatic events:

• Intracranial hemorrhage — bleeding into the brain or ventricles, causing sudden headache, confusion, weakness, or loss of consciousness. This is more common in adult moyamoya than in children.
• Ischemic stroke with sudden weakness, numbness, or speech problems that does not fully resolve
• Transient ischemic attacks (TIAs) — brief, stroke-like symptoms that recover
• Cognitive slowing, memory problems, or personality change from repeated small strokes
• Severe or new-pattern headaches

How Is It Diagnosed?

Most patients start with an MRI and MRA (magnetic resonance angiography) of the brain. MRI shows any strokes, old or new. MRA shows the blood vessels and can reveal the telltale narrowing of the carotid arteries and the wispy collateral network.

If moyamoya is suspected, the next test is usually a catheter cerebral angiogram. This is still the gold standard: a neurointerventional specialist threads a thin catheter up to the vessels of the brain and injects contrast to produce a detailed, real-time map of every artery. Catheter angiography is what lets your surgical team see exactly which arteries are narrowed, how extensive the collateral network is, and what the target vessels on the brain surface look like for a bypass.

We also assess how well the brain is compensating. Perfusion imaging — either MRI, CT, or a specialized study called acetazolamide-challenge SPECT or BOLD-MRI — measures whether the brain still has any 'reserve' left. A brain that is running on empty, with no reserve, is at high risk for stroke and generally needs surgery sooner rather than later.

Because moyamoya can run in families and because an RNF213 founder variant is strongly linked to the disease in East Asian populations, genetic testing and evaluation of first-degree relatives are increasingly part of the workup. In children, we also screen for the conditions associated with moyamoya syndrome — sickle cell disease, Down syndrome, neurofibromatosis, and others.

Types and Stages of Moyamoya

Disease vs. syndrome

• Moyamoya disease — the arterial narrowing occurs on its own, with no underlying cause. It is often bilateral and may have a genetic basis (RNF213 is the major susceptibility gene in East Asian populations).
• Moyamoya syndrome — the same vessel changes occur in someone with a predisposing condition such as sickle cell disease, Down syndrome, neurofibromatosis type 1, prior cranial radiation, Graves disease, or certain connective tissue disorders. Treatment of the underlying condition matters as much as the bypass.

Suzuki angiographic stages

In 1969 the Japanese neurosurgeons Suzuki and Takaku described six angiographic stages that trace the progression of moyamoya over time. Your surgical team will often refer to them:

• Stage I — narrowing of the internal carotid artery at its top, no visible collaterals yet
• Stage II — the characteristic 'puff of smoke' collateral network begins to appear at the base of the brain
• Stage III — collaterals become more prominent as the normal arteries narrow further; this is the stage at which many patients are first diagnosed
• Stage IV — the collaterals start to fade and new collaterals begin recruiting from the external carotid circulation
• Stage V — the classic moyamoya network further diminishes as external-to-internal collaterals take over
• Stage VI — the original moyamoya vessels are gone and the brain is perfused almost entirely through collaterals from the external carotid and posterior circulation

The stage helps predict how aggressive the disease is and how quickly you may need surgery, but it does not replace clinical judgment and perfusion imaging.

How Is It Treated?

Taking medication—like aspirin, controlling blood pressure, and managing risk factors—alone cannot halt the progression of moyamoya. For patients who have experienced symptoms, such as a stroke, TIA, or hemorrhage, and for many others with abnormal perfusion imaging, surgical revascularization is considered the standard treatment. The objective is to redirect blood flow from vessels outside the skull into the brain, thereby supporting the impaired circulation.

Direct bypass: STA-MCA

In a superficial temporal artery to middle cerebral artery (STA-MCA) bypass, the surgeon identifies a branch of the scalp artery you can feel pulsating in front of your ear, carefully dissects it free, and sews it directly into a small artery on the surface of the brain using sutures thinner than a human hair. The moment the clamp comes off, blood flows immediately through the new connection.

Direct bypass provides immediate improvement in blood flow. It is the preferred first option in most adults and works especially well when the target arteries on the brain are large enough to sew to.

Indirect bypass: EDAS, EMS, EDAMS, pial synangiosis

Indirect methods don't link directly. Instead, the surgeon places vascularized tissue—like a scalp artery, a muscle strip, or dura—right on the brain's surface, enabling new blood vessels to form within the brain over weeks to months. Typical techniques include:

• EDAS (encephaloduroarteriosynangiosis) — a scalp artery is laid onto the brain surface
• EMS (encephalomyosynangiosis) — a piece of temporalis muscle is laid onto the brain
• EDAMS (encephaloduroarteriomyosynangiosis) — a combination of artery, dura, and muscle
• Pial synangiosis — a refinement developed at Boston Children's, particularly well suited to children, in which the scalp artery is carefully sewn to the pia (the thin membrane covering the brain) to encourage ingrowth of new vessels

Indirect procedures are often the technique of choice in young children, whose vessels are too small for a reliable direct anastomosis and whose brains are especially good at growing new blood vessels.

Combined bypass

At UChicago and other centers, adults often undergo a combined direct + indirect bypass. This method provides the benefits of both techniques: immediate blood flow from the direct connection and enhanced long-term revascularization from the indirect part.

What the evidence says

For adult hemorrhagic moyamoya, the Japan Adult Moyamoya (JAM) Trial — the only randomized controlled trial in this field — showed that bilateral direct bypass reduced the rate of rebleeding and adverse events compared with medical therapy alone over 5 years of follow-up. For ischemic presentations and for children, large observational studies and meta-analyses consistently show that revascularization markedly lowers future stroke risk.

Medical management

Aspirin is commonly used to reduce the risk of small-vessel clots, particularly in ischemic moyamoya. Dehydration, low blood pressure, and hyperventilation should all be avoided because they further reduce blood flow to the brain. Blood pressure, cholesterol, and diabetes are managed aggressively.

What Are the Outcomes?

Untreated, symptomatic moyamoya carries a high risk of repeat stroke or hemorrhage. After bypass surgery, that risk drops dramatically — but the procedure itself carries some perioperative risk, which is why experience matters.

Most patients feel and function better after revascularization — headaches improve, TIAs stop, and cognitive symptoms often stabilize or improve, particularly in children operated on early. The most important predictors of a good outcome are the severity of any baseline deficits, the quality of the operation, and how closely your long-term medical and imaging follow-up is managed. At UChicago, every moyamoya patient is followed with serial MRI and perfusion studies to ensure the bypass remains durable.

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