MEDICAL
WHAT IS MOYAMOYA DISEASE? a rare cerebrovascular fight.
A rare cerebrovascular condition that most doctors will never see in their entire career. Here is what every patient, family member, and supporter needs to know.
By Vince Murdock, moyamoya survivor · Published 15 March 2026 · Updated 10 April 2026 · 10 min read · Reviewed against peer-reviewed sources listed below.
Moyamoya is a Japanese word meaning "puff of smoke." It describes the tangled web of tiny blood vessels that form at the base of the brain when the main arteries supplying it begin to narrow and close. On an angiogram, these fragile collateral vessels look like wisps of smoke rising from the blocked arteries below.
The disease was first identified by Japanese researchers Takeuchi and Shimizu in 1957. It primarily affects the internal carotid arteries and their branches, the anterior and middle cerebral arteries. As these vessels narrow over months and years, the brain attempts to compensate by growing new, smaller pathways. But these makeshift vessels are fragile. They can rupture, causing hemorrhagic stroke. Or they can fail to deliver enough blood, causing ischemic stroke.
Both outcomes are devastating. And both can happen without warning in a patient who has never been diagnosed.
Moyamoya disease affects roughly 1 in 100,000 people worldwide. In Japan and East Asia, incidence is higher, closer to 3 in 100,000. The condition has two peak onset periods: children between ages 5 and 10, and adults between 30 and 50. Women are affected approximately twice as often as men, though researchers have not fully determined why.
Because of its rarity, most general practitioners and even many neurologists will never encounter a moyamoya patient in their career. According to published research, an estimated 62% of moyamoya patients receive at least one incorrect diagnosis before the disease is properly identified. Misdiagnoses range from migraines and anxiety to multiple sclerosis and epilepsy. That delay can cost years, and it can cost lives.
Vince Murdock was fortunate. His moyamoya was discovered during a routine UFC pre-fight MRI in September 2019. Most patients are not scanned until they have already suffered a stroke or transient ischemic attack (TIA).
62%
MISDIAGNOSED.
The average patient is told it is anxiety, migraines, or stress before moyamoya is correctly identified. Earlier diagnosis means earlier surgery. Earlier surgery means better outcomes.
See symptoms in detail →Symptoms vary by age and by how far the disease has progressed. In children, the most common presentation is ischemic stroke or TIA. A child may experience sudden weakness on one side of the body, difficulty speaking, or vision changes. These episodes often occur during physical activity, crying, or hyperventilation, anything that changes blood flow to the brain.
In adults, moyamoya more frequently presents with hemorrhagic stroke (bleeding in the brain) due to rupture of the fragile collateral vessels. Adults may also experience chronic headaches, seizures, cognitive decline, or involuntary movements. Some patients describe a progressive "brain fog" that worsens over months before diagnosis.
The challenge is that many of these symptoms mimic other conditions. Headaches are attributed to stress. Weakness is blamed on fatigue. Cognitive changes are written off as anxiety. That is why the 62% misdiagnosis rate exists, and why awareness campaigns like Miles for Moyamoya matter.
For decades, the cause of moyamoya disease remained a mystery. Researchers knew it ran in families in approximately 10-15% of cases, suggesting a genetic component. In 2011, a breakthrough study identified RNF213 as the primary susceptibility gene for moyamoya disease. This gene, located on chromosome 17, encodes a protein involved in blood vessel formation and immune response.
A specific variant of RNF213 (p.R4810K) is found in roughly 80% of Japanese moyamoya patients. In European and North American populations, different RNF213 variants have been linked to the disease, though at lower frequencies. Having the variant does not guarantee developing moyamoya. Environmental factors, infections, autoimmune conditions, and other genetic modifiers likely play a role in triggering arterial narrowing.
Current research at Stanford and other centres focuses on understanding how RNF213 mutations alter blood vessel biology. The goal is earlier genetic screening for at-risk families and eventually targeted therapies that could slow or prevent arterial narrowing before surgery becomes necessary.
Diagnosis begins with brain imaging. MRI (magnetic resonance imaging) and MRA (magnetic resonance angiography) can reveal the characteristic narrowing of the internal carotid arteries and the presence of collateral "moyamoya" vessels. These non-invasive scans are usually the first step when a doctor suspects cerebrovascular disease.
Conventional cerebral angiography remains the gold standard for confirming moyamoya. This procedure involves threading a catheter through an artery (usually in the groin) to inject contrast dye directly into the brain's blood vessels. The resulting images show the exact location and severity of arterial narrowing, the extent of collateral vessel formation, and the overall blood flow pattern. This detailed map is essential for surgical planning.
Additional tests may include CT perfusion studies to measure blood flow in different brain regions, and transcranial Doppler ultrasound to assess blood velocity in major cerebral arteries. Together, these tools give neurosurgeons the information they need to determine whether and when surgery is required.
Surgery is the primary treatment for moyamoya disease. There is no medication that can reverse the arterial narrowing. The two main surgical approaches are direct revascularisation and indirect revascularisation, and many patients receive a combination of both.
Direct bypass surgery involves connecting a healthy artery from the scalp (usually the superficial temporal artery) directly to a brain artery beyond the point of narrowing. This creates an immediate new pathway for blood flow. Indirect procedures, such as encephaloduroarteriosynangiosis (EDAS), involve placing tissue rich in blood vessels onto the surface of the brain and allowing new connections to grow naturally over weeks and months.
Vince Murdock underwent direct bypass surgery at Stanford on 13 November 2019, performed by Dr Gary Steinberg, one of the world's leading moyamoya surgeons. The procedure quadrupled the blood flow through the bypass vessel. Within months, Vince was back on a bicycle, and within 11 months, he returned to professional MMA competition.
Recovery varies by patient, but many people return to full, active lives after revascularisation surgery. The bypass vessels mature over 3 to 6 months, gradually taking over from the failing original arteries. During this period, patients are closely monitored with follow-up imaging to ensure the new pathways are functioning properly.
Long-term outcomes are generally positive when surgery is performed by an experienced team. Studies from Stanford's moyamoya programme show that bypass surgery significantly reduces the risk of future strokes and improves cognitive function in both children and adults. However, moyamoya is a lifelong condition. The original arterial narrowing continues even after surgery, which means patients need ongoing monitoring and occasional additional procedures.
Cardiovascular exercise plays a significant role in recovery. Research suggests that sustained aerobic activity promotes the growth and maturation of bypass vessels. For Vince, cycling became both rehabilitation and purpose. Over 10,000 miles on the bike, including ultra-endurance events like the Unbound XL (350 miles), have demonstrated what is possible after moyamoya surgery. Read more about cycling and recovery.
The 62% misdiagnosis rate is not just a statistic. It represents real people who lost time, lost function, and in some cases lost their lives because a doctor did not know to look for moyamoya disease. Earlier diagnosis means earlier surgery. Earlier surgery means better outcomes. It is that simple.
Awareness serves multiple purposes. For potential patients, it means recognising symptoms and advocating for proper imaging. For medical professionals, it means keeping moyamoya on the differential diagnosis list when a young person presents with stroke-like symptoms. For researchers, public awareness drives the funding needed to pursue genetic screening tools, improved surgical techniques, and eventually non-surgical interventions.
Miles for Moyamoya exists to close the gap between what we know about this disease and what the general public (and many doctors) understand. Every article shared, every mile ridden, and every conversation started brings us closer to a world where moyamoya is caught before it causes irreversible damage.
Stanford's Department of Neurosurgery maintains one of the most comprehensive moyamoya research programmes in the world. Dr Gary Steinberg and his team have performed thousands of revascularisation procedures and published extensively on surgical outcomes. The National Institute of Neurological Disorders and Stroke (NINDS) also provides accessible information for patients and families.
If you suspect you or someone you know may have moyamoya disease, seek a referral to a neurovascular specialist. Request brain MRI and MRA imaging. Do not accept a diagnosis of "just migraines" or "anxiety" without proper investigation, particularly if symptoms include sudden weakness, speech difficulty, or vision changes. Early detection saves lives.
Last updated: 10 April 2026.
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