What is Moya Moya (Moyamoya disease)?

From the Guidelines

Moyamoya disease should be treated with surgical revascularization procedures, such as direct or indirect extracranial-intracranial bypass, to improve blood flow to the brain and prevent ischemic stroke or TIA, as recommended by the 2021 guideline from the American Heart Association/American Stroke Association 1.

Overview of Moyamoya Disease

Moyamoya disease is a rare, progressive cerebrovascular disorder characterized by narrowing of the internal carotid arteries and their branches, leading to reduced blood flow to the brain. This condition causes the body to develop small, fragile blood vessels (collaterals) as a compensatory mechanism, which appear as a "puff of smoke" on imaging studies—hence the Japanese name "moyamoya."

Diagnosis and Treatment

The diagnosis of Moyamoya disease has been refined over the years, with the most recent guidelines from the Research Committee on Moyamoya Disease (RCMD) in 2021 presenting important new accords regarding the locations and magnitude of involvement necessary for the definition of MMD 1.

• The treatment primarily involves surgical revascularization procedures to improve blood flow to the brain, with direct bypass procedures (STA-MCA bypass) or indirect procedures (EDAS, EMS) being the main options.
• While no medications can stop disease progression, aspirin may be prescribed to reduce stroke risk, and calcium channel blockers might help with headaches and symptoms of decreased blood flow, as supported by the 2021 guideline from the American Heart Association/American Stroke Association 1.

Management and Prevention

Patients should avoid dehydration, extreme physical exertion, and hyperventilation as these can worsen symptoms.

• Early diagnosis and treatment are crucial as the disease typically progresses without intervention, potentially leading to multiple strokes, cognitive decline, and neurological deficits.
• Regular follow-up with neurosurgeons and neurologists is essential for monitoring disease progression and managing symptoms.

Key Recommendations

• Surgical revascularization with direct or indirect extracranial-intracranial bypass can be beneficial for the prevention of ischemic stroke or TIA in patients with Moyamoya disease and a history of ischemic stroke or TIA, with a Class of Recommendation (COR) of 2a and a Level of Evidence (LOE) of C-LD 1.
• The use of antiplatelet therapy, typically aspirin monotherapy, for the prevention of ischemic stroke or TIA may be reasonable in patients with Moyamoya disease and a history of ischemic stroke or TIA, with a COR of 2b and a LOE of C-LD 1.

From the Research

Definition and Characteristics of Moya Moya

• Moya Moya disease is a rare and progressive cerebrovascular disorder characterized by stenosis or occlusion of the internal carotid arteries, resulting in the development of fragile collateral vessels at the base of the brain 2.
• The disease is also known as "Moyamoya" which means "hazy puff of smoke" in Japanese, describing the appearance of the collateral vessels on angiography 3.
• Moya Moya disease can be classified into different types, including ischemic, hemorrhagic, epileptic, and "other" types, with the ischemic type being more common in childhood and the hemorrhagic type being more common in adults 3.

Epidemiology and Risk Factors

• Moya Moya disease is more prevalent in Japan, with a higher female to male ratio 3.
• The disease has been linked to chromosome 17 in Japanese cases, as well as in cases from other demographics, suggesting a possible genetic association 3, 4.
• Risk factors for Moya Moya disease include Eastern Asian ancestry and predisposing conditions such as neurofibromatosis and Down's syndrome 5.

Diagnosis and Imaging

• Cerebral angiography is the gold standard for diagnosing Moya Moya disease, revealing the characteristic "puff of smoke" appearance of the collateral vessels at the base of the brain 3, 5, 4.
• Other imaging modalities, such as CT perfusion, MRI, and non-contrast CT, can also be used to assess the disease and identify ischemic vascular territories 5.

Treatment Options

• Surgical revascularization is the primary treatment option for Moya Moya disease, aiming to prevent ischemic and hemorrhagic events 2, 5, 4.
• Direct and indirect bypass surgery, as well as combined procedures, can be used to improve cerebral hemodynamics and reduce the risk of further ischemic events 6, 5, 4.
• Medical management, including controlling risk factors and antithrombotic therapy, may also play a role in the treatment of Moya Moya disease, particularly in asymptomatic patients or those at high risk for surgical complications 2.