Moyamoya Disease

Moyamoya is a rare cerebrovascular disease in which the internal carotid arteries and their main branches progressively narrow and eventually close — leaving the brain dependent on a fragile, smoke-like tangle of tiny collateral vessels that can neither supply blood reliably nor withstand the consequences. Without treatment, it is a disease of strokes and bleeds.

What Is Moyamoya Disease?

Moyamoya disease is a rare progressive occlusion of the internal carotid arteries and their proximal branches at the skull base, predominantly affecting the anterior circulation. As the main vessels close, the brain develops a network of tiny compensatory collateral vessels — these appear as a 'puff of smoke' on angiography (moyamoya in Japanese). The disease is most common in people of East Asian descent but affects all populations. It can present at any age but has two peaks: children (5–10 years) and adults (30–50 years).

At a Glance

Moyamoya is progressive narrowing of the internal carotid arteries — leaving the brain dependent on fragile tiny collateral vessels
In children: recurrent transient ischemic attacks and ischemic strokes, sometimes triggered by crying or hyperventilation
In adults: both ischemic stroke and hemorrhagic stroke (from rupture of fragile collaterals)
Surgical revascularization (STA-MCA bypass) is the only proven treatment — restores durable blood flow to the affected hemisphere
Outcomes after revascularization: ~80-90% of surgical patients are stroke-free at 5 years

Symptoms

Children: predominantly ischemic

Recurrent TIAs or strokes triggered by crying, exercise or hyperventilation (which causes cerebral vasoconstriction)
Progressive cognitive decline or school difficulties
Headaches

Adults: both ischemic and hemorrhagic

Ischemic stroke — weakness, speech problems, vision changes
Intracerebral hemorrhage — sudden severe headache, neurologic deficit (from rupture of the fragile collateral moyamoya vessels)

Diagnosis

MRI/MRA — shows bilateral ICA narrowing and white matter ischemic changes; collateral vessels visible
Digital subtraction angiography (DSA) — gold standard; shows the classical angiographic pattern and suzuki grade (I-VI)
Perfusion imaging (CTP or PET) — maps cerebral blood flow; identifies regions with hemodynamic compromise — directly guides which areas need bypass
Acetazolamide challenge SPECT — tests cerebrovascular reserve; areas that don't respond to vasodilatory challenge are most ischemic

Types

Treatment

Surgical revascularization — the only proven treatment to reduce stroke risk

Superficial temporal artery to middle cerebral artery (STA-MCA) direct bypass
The superficial temporal artery (a branch of the external carotid) is sewn directly onto a cortical branch of the MCA. Immediately increases blood flow to the ischemic hemisphere. This operation requires microsurgical expertise — each anastomosis is ~1.5-2 mm in diameter and must be performed under the microscope.

Indirect bypass (EDAS, EMS, pial synangiosis)
A branch of the scalp artery is laid directly on the brain surface and sutured to the pia, stimulating new vessel in-growth over 3-6 months. Preferred in children; often combined with direct bypass in adults.

Combined direct & indirect bypass
Standard approach at high-volume centers; provides both immediate and long-term augmentation of blood flow.

Medical management — antiplatelet therapy
Aspirin reduces platelet aggregation on the fragile collateral vessels; used in all patients including preoperatively and in patients not undergoing surgery.

Outcomes

Outcome	Rate after STA-MCA bypass	Notes
Stroke-free at 5 years	~80-90%	vs. ~60-70% for natural history without surgery
Neurologic improvement in ischemic patients	~70-80%	Higher in children
Reduction in hemorrhage (adult hemorrhagic form)	~60-80% reduction in rebleed rate	One of few treatments proven to reduce ICH in moyamoya
Perioperative stroke risk	~3-5%	Experienced centers

References

Scott RM, Smith ER. Moyamoya disease and moyamoya syndrome. NEJM. 2009;360:1226-1237. PMID: 19297575
Miyamoto S, et al. Effects of extracranial-intracranial bypass for patients with hemorrhagic moyamoya disease: results of the Japan Adult Moyamoya Trial. Stroke. 2014;45:1415-1421. PMID: 24668203
Guzman R, et al. Long-term follow-up after pial synangiosis for children with moyamoya disease. Neurosurg Focus. 2003;15:E5. PMID: 15323452

Our Specialists

Issam A. Awad, MD

Neurosurgery

Sean P. Polster, MD

Neurosurgery

Omer Doron, MD, PhD

Neurosurgery

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