What is Moya Moya (Moyamoya disease)?

From the Guidelines

Moyamoya disease should be treated with surgical revascularization procedures, such as direct bypass or indirect bypass, to restore blood flow to the brain and prevent future strokes, as supported by the most recent and highest quality study 1.

Overview of Moyamoya Disease

Moyamoya disease is a rare blood vessel disorder where the carotid arteries in the brain become narrowed or blocked, causing reduced blood flow to the brain. This condition leads to the formation of tiny, abnormal blood vessels that appear as a "puff of smoke" on imaging tests, which is what "moyamoya" means in Japanese. Symptoms include strokes, transient ischemic attacks (mini-strokes), seizures, headaches, and cognitive decline.

Treatment Options

Treatment typically involves surgical revascularization procedures such as direct bypass (STA-MCA bypass) or indirect bypass (EDAS, EMS, or multiple burr holes) to restore blood flow to the brain. These surgeries aim to prevent future strokes by creating new pathways for blood to reach brain tissue. The disease is more common in East Asian populations, particularly Japanese individuals, and can affect both children and adults. Early diagnosis through MRI, MRA, or cerebral angiography is crucial for effective management.

Key Considerations

• Surgical treatment for moyamoya consists of revascularization procedures that can be broadly categorized as direct, indirect, or combined 1.
• Direct bypass carries the benefits of immediate revascularization, whereas indirect bypass relies on angiogenic proliferation and arteriogenic maturation over days or weeks 1.
• The Japan Adult Moyamoya trial demonstrated a reduction in rebleeding with surgery (2.7%/y versus 7.6%/y; P=0.04) 1.
• A prespecified subgroup analysis of the Japan Adult Moyamoya trial showed that posterior hemorrhages are at higher risk of rebleeding and obtained greater benefit with the surgical intervention 1.

Recommendations

• Surgical revascularization procedures should be considered for patients with moyamoya disease to prevent future strokes and improve quality of life 1.
• Early diagnosis and treatment are crucial to prevent neurological deterioration and improve outcomes.
• Patients should be managed by a multidisciplinary team of healthcare professionals, including neurologists, neurosurgeons, and radiologists, to ensure optimal care.

From the Research

Definition and Characteristics of Moyamoya Disease

• Moyamoya 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.
• It is known to have a unique and dynamic nature to convert the vascular supply for the brain from internal carotid (IC) system to the external carotid (EC) system 3.
• The disease is predominantly seen in the East Asian population, with most cases being sporadic, but a small percentage being familial with an autosomal dominant mode of inheritance with incomplete penetrance 4.

Clinical Presentation and Diagnosis

• The clinical presentation of Moyamoya disease is variable and is influenced by the age and geographic region of the patient 4.
• Children mainly present with ischemia-related neurologic episodes, whereas adults can manifest as either an ischemic event or an intracranial hemorrhage (ICH) 4.
• The gold standard investigation for diagnosis is cerebral angiography, which reveals a smoky appearance of arteries at the base of the skull 4.

Treatment Options

• Surgical revascularization is the primary treatment option for preventing ischemic and hemorrhagic events, with direct and indirect revascularization procedures being used 2, 5.
• Combination revascularization procedures are now on the rise due to studies showing better long-term outcomes 4.
• Medical management also plays a role, particularly in cases involving asymptomatic patients or those at a high risk for surgical complications, with the importance of controlling risk factors and judicious use of antithrombotic therapy 2.
• Cerebral revascularization, in the form of extracranial-intracranial bypass, has been shown to prevent recurrent strokes in patients with Moyamoya syndrome associated with sickle cell disease 6.

Outcomes and Prognosis

• The long-term outcome of revascularization surgery for Moyamoya disease is favorable, but rapid increase in cerebral blood flow on the affected hemisphere could temporarily cause unfavorable phenomenon such as cerebral hyperperfusion syndrome 3.
• Early detection and surgical intervention, in addition to chronic transfusion therapy, could significantly reduce stroke recurrence and improve neurocognitive outcome in patients with Moyamoya syndrome associated with sickle cell disease 6.