Moyamoya disease (MMD) is a rare, progressive cerebrovascular condition where arteries at the base of the brain narrow, reducing blood flow. The body compensates by forming a network of fragile collateral vessels, which appear as a “puff of smoke” on diagnostic images. MMD can lead to serious neurological events, including strokes.
Understanding MMD Disease
Moyamoya disease involves the gradual narrowing of the internal carotid arteries and their main branches, diminishing the brain’s blood supply. To compensate, the body forms a network of smaller, abnormal collateral vessels around the blocked areas. This intricate web resembles a “puff of smoke” on angiograms, attempting to restore blood flow.
The development of MMD is not fully understood, but it involves a combination of genetic and environmental factors. Approximately 10-15% of cases are familial, with some linked to mutations in the RNF213 gene, particularly in East Asian populations. MMD is distinguished from moyamoya syndrome (MMS), where similar vessel changes occur as a complication of other underlying conditions such as Down syndrome, sickle cell disease, or neurofibromatosis type 1.
MMD has a bimodal age distribution, meaning it commonly presents in two distinct age groups. The first peak occurs in children, between 5 and 9 years old, and the second peak is observed in adults, often in their 30s or 40s. While MMD is found globally, its incidence is higher in East Asian countries, including Japan, Korea, and China, compared to Western nations. Females are slightly more susceptible to the condition than males.
Recognizing MMD Disease
The symptoms of moyamoya disease vary widely and depend on the patient’s age. Children often experience transient ischemic attacks (TIAs) or ischemic strokes, which result from reduced blood flow to the brain. These events can manifest as sudden weakness or paralysis on one side of the body, speech difficulties, or involuntary movements. Children may also present with headaches, seizures, or developmental delays.
Adults with MMD can also have TIAs and ischemic strokes, but they are more prone to hemorrhagic strokes, which involve bleeding into the brain. This bleeding occurs because the newly formed collateral vessels are fragile and prone to rupture. Headaches are a common symptom in adults, along with cognitive issues such as problems with memory, attention, or language. Seizures, dizziness, and vision problems can occur in both age groups.
Symptoms can fluctuate and may worsen over time without appropriate intervention. Early recognition is important for timely diagnosis and management, as untreated MMD can lead to progressive neurological decline.
Diagnosis and Treatment
Diagnosing moyamoya disease involves a combination of neurological examination, patient history, and specialized imaging techniques. Magnetic Resonance Imaging (MRI) and Magnetic Resonance Angiography (MRA) are commonly used to visualize the brain’s blood vessels and detect the characteristic narrowing of arteries and the presence of collateral circulation. Computed Tomography Angiography (CTA) can also provide detailed images of the cerebral arteries.
Cerebral angiography, also known as Digital Subtraction Angiography (DSA), is considered the gold standard for confirming the diagnosis. This invasive procedure provides the clearest view of the “puff of smoke” appearance and the extent of vessel narrowing.
Treatment for MMD primarily aims to prevent strokes, improve blood flow to the brain, and manage symptoms. Medical management includes medications such as antiplatelet agents to reduce the risk of blood clot formation and blood pressure control to protect the fragile vessels. However, these medications do not halt the progression of the arterial narrowing itself.
Surgical revascularization procedures are frequently performed to restore adequate blood supply to the brain. Direct bypass surgery, such as the superficial temporal artery-middle cerebral artery (STA-MCA) bypass, involves connecting a scalp artery directly to a brain artery to immediately augment blood flow. Indirect bypass procedures, like encephaloduroarteriosynangiosis (EDAS) or encephalomyosynangiosis (EMS), encourage the growth of new blood vessels from tissues outside the brain to its surface. These surgical interventions have been shown to reduce the risk of future strokes and improve outcomes for many patients. After treatment, rehabilitation services, including physical, occupational, and speech therapy, may be necessary to help individuals recover and adapt to any lingering neurological deficits.