What Is Moyamoya Disease? Understanding Symptoms, Causes, and Risk Factors

Moyamoya disease is a rare and progressive cerebrovascular disorder that affects the blood vessels in the brain. The name "moyamoya," which means "puff of smoke" in Japanese, was coined due to the hazy, smoke-like appearance of tiny, abnormal blood vessels that form around the blocked arteries in the brain when viewed on an angiogram. This distinctive visual pattern inspired the term, helping doctors identify the condition through imaging studies.

How Does Moyamoya Disease Develop?

The exact cause of moyamoya disease remains unclear, but researchers believe it may result from a combination of genetic and environmental factors. Normally, major arteries like the internal carotid artery supply steady blood flow to the brain. However, in patients with moyamoya, these arteries gradually narrow and eventually close off. To compensate for the reduced blood flow, the body forms a network of fragile, microscopic collateral vessels at the base of the brain. While these new vessels attempt to restore circulation, they are weak and prone to complications such as bleeding or clotting.

Who Is Most at Risk?

Moyamoya disease tends to affect two primary age groups: children under 10 years old and adults between the ages of 30 and 50. In young patients, the most common symptoms stem from ischemic events—sudden interruptions in blood flow to parts of the brain. These can manifest as transient ischemic attacks (TIAs), often described as mini-strokes, leading to temporary weakness, speech difficulties, or vision problems. Some children may also experience seizures or convulsions due to inadequate oxygen delivery to brain tissue.

Symptoms in Adults: A Different Presentation

In contrast, adults with moyamoya are more likely to present with hemorrhagic strokes—bleeding within the brain, particularly into the ventricles (fluid-filled spaces). Interestingly, some individuals may not show classic neurological deficits like paralysis or aphasia immediately after a bleed, which can delay diagnosis. Because the abnormal vessels are prone to rupture and re-bleed, adult patients face a higher risk of recurrent hemorrhages, making early detection and management critical.

Why Early Diagnosis Matters

Given its variable presentation across age groups, moyamoya disease can be challenging to diagnose without advanced neuroimaging such as MRI, MRA, or cerebral angiography. Delayed recognition increases the risk of permanent brain damage. Surgical interventions, including bypass procedures like EDAS (encephaloduroarteriosynangiosis), are often recommended to improve cerebral blood flow and reduce the likelihood of future strokes.

While still relatively unknown in many regions, awareness of moyamoya disease is growing among neurologists and vascular specialists. Ongoing research aims to uncover genetic markers and refine treatment protocols, offering hope for better outcomes in both pediatric and adult populations affected by this complex condition.