What is Moya Moya (Moyamoya disease)?

From the Guidelines

Moyamoya disease should be treated with surgical revascularization, such as direct or indirect extracranial-intracranial bypass, to prevent ischemic stroke or transient ischemic attack (TIA), as recommended by the 2021 guideline for the prevention of stroke in patients with stroke and TIA 1. 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.

Key Considerations

• Surgical revascularization procedures, such as direct bypass (STA-MCA bypass) or indirect procedures (EDAS, EMS, or multiple burr holes), are the primary treatment options for preventing strokes in moyamoya disease patients 1.
• Medical management includes antiplatelet therapy like low-dose aspirin (81-325 mg daily), avoiding dehydration, and maintaining adequate blood pressure 1.
• Patients should avoid vasoconstrictive medications and hyperventilation, which can worsen symptoms 1.
• Regular follow-up with neurosurgery and neurology is essential, including periodic brain imaging to monitor disease progression 1.

Treatment Benefits

• Surgical revascularization has been shown to reduce the risk of rebleeding in patients with hemorrhagic moyamoya, as demonstrated by the Japan Adult Moyamoya trial 1.
• A prespecified subgroup analysis of the Japan Adult Moyamoya trial found that posterior hemorrhages are at higher risk of rebleeding and obtained greater benefit with surgical intervention 1.
• Retrospective and prospective single- and multicenter case series have also supported the benefit of surgical revascularization 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 causes ischemic stroke, intracranial hemorrhage, headache, seizures, and transient ischemia attack in children and adults 3.
• Moya Moya disease has a progressive course, but may have a variable clinical presentation 3.

Types and Classification of Moya Moya

• The Ministry of Health and Welfare of Japan has defined 4 types of Moya Moya disease: ischemic, hemorrhagic, epileptic, and "other" 4.
• The ischemic type has been shown to predominate in childhood, while the hemorrhagic type is more often observed in the adult population 4.
• Moya Moya syndrome is a secondary process that occurs in response to another underlying pathological process that causes stenosis of intracranial blood vessels, such as radiation 5.

Diagnosis and Imaging

• Catheter-based diagnostic cerebral angiogram (DCA) is the current gold standard for obtaining a diagnosis of Moya Moya disease 5.
• CT perfusion allows preoperative identification of ischemic vascular territories, which may be amenable to surgical intervention 5.
• MRI enables rapid detection of acute ischemic stroke using diffusion-weighted Imaging (DWI) and apparent diffusion coefficient (ADC) sequences to assess for any diffusion restriction 5.

Treatment Options

• Surgical revascularization is the primary treatment option for preventing ischemic and hemorrhagic events in Moya Moya disease 2, 4, 5.
• Medical management has become increasingly recognized, particularly in cases involving asymptomatic patients or those at a high risk for surgical complications 2.
• Direct and indirect cerebrovascular bypass are common surgical options for Moya Moya disease 4, 5.

Epidemiology and Risk Factors

• Moya Moya disease is rare in the United States, with just 0.086 newly diagnosed cases per 100,000 individuals per year 5.
• Risk factors for Moya Moya disease include Eastern Asian ancestry and predisposing conditions such as neurofibromatosis and Down's syndrome 5.
• The highest prevalence of Moya Moya disease is found in Japan, with a higher female to male ratio 4.