What is Moyamoya disease and how is it managed?

From the Guidelines

Moyamoya disease is a rare, progressive cerebrovascular disorder that requires prompt management to prevent strokes and reduce symptoms, with surgical revascularization being the definitive treatment, as supported by the most recent guidelines from the American Heart Association/American Stroke Association 1.

Overview of Moyamoya Disease

Moyamoya disease is characterized by the narrowing and blockage of the internal carotid arteries and their branches, leading to the formation of abnormal blood vessels at the base of the brain that resemble a "puff of smoke" (moyamoya in Japanese) 1. This condition has a bimodal distribution, with peaks in childhood and adulthood, and can be asymptomatic or present with ischemic or hemorrhagic strokes 1.

Management of Moyamoya Disease

Management of Moyamoya disease focuses on preventing strokes and reducing symptoms through both medical and surgical approaches. Medical management typically includes:

• Antiplatelet medications such as aspirin (81-325 mg daily) to prevent blood clots, though anticoagulants are generally avoided due to hemorrhage risk 1.
• Control of risk factors like hypertension.
• Regular neurological monitoring with MRI/MRA imaging for disease surveillance.

Surgical Revascularization

Surgical revascularization is the definitive treatment for Moyamoya disease, with direct procedures like superficial temporal artery to middle cerebral artery (STA-MCA) bypass or indirect procedures such as encephaloduroarteriosynangiosis (EDAS) or encephalomyosynangiosis (EMS) that promote new vessel formation 1. Children often receive indirect procedures, while adults may benefit from direct bypass. The goal of treatment is to improve cerebral blood flow, prevent ischemic events, and preserve neurological function.

Additional Considerations

Patients with Moyamoya disease should maintain adequate hydration, avoid hyperventilation and vasoconstrictive substances, and control risk factors like hypertension. Techniques to minimize anxiety and pain during hospitalizations may reduce the likelihood of stroke caused by hyperventilation-induced vasoconstriction 1. Management of systemic hypotension, hypovolemia, hyperthermia, and hypocarbia during the intraoperative and perioperative periods may reduce the risk of perioperative stroke in individuals with Moyamoya disease 1.

From the Research

Definition and Characteristics of Moyamoya Disease

• Moyamoya disease is a rare neurovascular disorder characterized by narrowing and occlusion of the internal carotid artery (ICA) branches 2.
• It is a chronic occlusive cerebrovascular disease involving bilateral stenosis or occlusion of the terminal portion of the ICAs and/or the proximal portions of the anterior cerebral arteries and middle cerebral arteries (MCAs) 3.
• The disease is named for the characteristic appearance of a "hazy puff of smoke" on angiography, which represents the formation of small, fragile blood vessels at the base of the brain 3.

Symptoms and Diagnosis

• Symptoms of moyamoya disease include recurrent ischemic or hemorrhagic strokes, transient ischemic attacks, and other neurological deficits 2, 4.
• The diagnosis of moyamoya disease is often delayed, and catheter-directed angiography is the gold standard test for diagnosis 2.
• Other diagnostic methods include magnetic resonance angiography, computed tomography angiography, and high-resolution vessel-wall magnetic resonance imaging 4.

Management and Treatment

• Medical management of moyamoya disease involves reducing the competing risks of ischemic and hemorrhagic stroke, as well as managing coexisting conditions such as headache, epilepsy, and neuropsychological sequelae 5.
• Antiplatelet therapy is commonly prescribed to prevent thromboembolic stroke, although data supporting this practice are limited 5.
• Surgical revascularization is the definitive treatment for moyamoya disease, aiming to augment perfusion to at-risk brain tissue and decrease the risk of hemorrhage from fragile moyamoya collaterals 5, 4, 6.
• Surgical procedures include direct, indirect, and combined bypass methods, with direct and combined bypasses being more effective in preventing recurrent ischemic stroke than indirect bypass surgery 6.

Epidemiology and Prognosis

• Moyamoya disease is more prevalent in East Asian countries, particularly Japan and Korea, and affects adults and children globally 5, 4.
• The disease has a high rate of incident and recurrent stroke, and the prognosis is generally poor if left untreated 2, 5.
• With proper management and treatment, patients with moyamoya disease can experience improved outcomes and reduced risk of recurrent stroke 5, 6.