Article by: Babu G. Welch, M.D., Neurological Surgery & Radiology, UT Southwestern Medical Center
Over the past 30 years, the stroke rate among younger Americans has been on the rise, even while it has fallen among individuals 75 and older.
Moyamoya, a Japanese word meaning “puff of smoke,” is frequently the term used to describe very small blood vessels seen in young patients with stroke. Associated with these small blood vessels is progressive narrowing of carotid arteries at the base of the brain. While some of the causes of the blood vessel narrowing may be genetic, many of the causes are related to reversible illnesses.
Any conversation about moyamoya should begin by differentiating between its two forms: Moyamoya disease (MMD) and moyamoya syndrome (MMS).
MMD can be diagnosed after a stroke occurs in a young patient – typically a child. The disease affects only about 5 in 100,000 people, predominantly of Asian descent, and predisposes patients to start developing stenotic arteries in childhood. Initial diagnosis may occur around age 5 but, if it isn’t prevalent then, the same findings can surface in patients who are between 20 and 30 years old.
MMS looks the same on imaging as MMD. But MMS is typically a complication of long-standing conditions such as diabetes, uncontrolled hypertension, inherited cholesterol diseases or even sickle cell disease. Blood vessels changes characteristic to MMS can also be seen in genetic conditions such as Down syndrome.
UT Southwestern’s Peter O’Donnell Jr. Brain Institute is one of only a handful of centers in the country that has a cerebrovascular team with advanced training in the diagnosis, imaging and treatment of MMD and MMS in children and adults.
My colleagues Rafael De Oliveira Sillero, M.D., Jon White, M.D., and I see patients from all over Texas and surrounding states. We are fortunate to work closely with talented neuroradiologists so we can offer specialized imaging to evaluate and personalize treatment options for each patient. All treatments start by providing patients with a thorough understanding of the options that give them the best chance of avoiding a stroke – or preventing another one.
Tracking mini-strokes and a gene mutation
The first signs of moyamoya disease usually appear as either a stroke or as repetitive symptoms that suggest patients are at risk for stroke. Some may call these mini-strokes, or transient ischemic attacks (TIAs). While MMS is related to other health conditions, some patients present without the presence of other illnesses.
Females are twice as likely as males to develop MMS. Research is ongoing as to what causes MMD/S, which may derive from a mutation of the RNF213 gene involved in blood vessel development.
Stroke and TIA may be the result of other health problems that lead to similar imaging of the blood vessels. These conditions can include:
- Atherosclerosis
- Diabetes
- Down syndrome
- Hyperthyroidism
- Neurofibromatosis type 1
- Sickle cell anemia
- Smoking
When an adult age 30 or older has a stroke, MMS and lifestyle risk factors are much more likely to be the cause than MMD, which is primarily a pediatric diagnosis.
MMS sometimes can be tricky to diagnose. Initially, changes in the blood vessel look similar to other aging-related diseases such as atherosclerosis. Getting an accurate diagnosis requires a team approach:
- Imaging: We start with a MRI and MRA to look for the characteristic arterial narrowing, as well as any evidence of past strokes. Both studies can also provide insight into how blood distribution (or perfusion) has changed in the brain. As the blood vessels get more narrow, they may slow down blood flow and decrease the volume that gets to parts of the brain.
- Arteriography: If those studies suggest MMD or MMS, we then recommend cerebral angiography to confirm the diagnosis.
- Neuropsychology: We will test memory and cognition as a baseline for post-treatment recovery.
Depending on the severity of the MMD/MMS and how the patient is tolerating the vessel changes, there are medical and surgical treatment options.
Medical management: Blood thinners, calcium channel blockers, and anti- seizure drugs may be able to manage symptoms for a time, but medications alone won’t stop the blood vessels from narrowing. Lifestyle modifications that address diet and weight changes are very important in management. In patients where symptoms are frequent, surgery may also become necessary to ensure adequate blood flow to the brain. We always say, “It is important to change your life to take care of the blood vessels that you have left.”
Surgery: Moyamoya brain surgeries are delicate procedures that require an experienced cerebrovascular neurosurgeon. Two effective procedures include:
- Direct bypass, a type of revascularization in which we reroute blood flow around the narrowed artery by connecting the superficial temporal (scalp) artery and middle cerebral artery – much like building a frontage road to the brain.
- Indirect bypass, which involves dissecting several inches of the superficial temporal artery and laying it onto the brain. This gives the brain an opportunity to grow new blood vessels. Frequently, the covering of the dura or muscle from the scalp can be used as another indirect blood donor. We use this approach only when direct bypass is not feasible, e.g., in children whose arteries are not developed enough or are too small to withstand rerouting.
The expected outcome from bypass surgery at UT Southwestern is excellent. Most patients will have more than 97% unobstructed blood flow after the procedure, with the potential to dramatically reduce stroke risk.
Some patients with MMD or MMS will need to take blood thinners for life to reduce the risk of stroke, but most return to normal activities four to six weeks after surgery.
UT Southwestern endocrinologists, cardiologists, neurologists, and hematologists work with referring physicians and their patients to optimize medications, nutrition, and exercise habits maximize their recovery.
Institutions throughout Texas and the Southwest refer moyamoya patients to UT Southwestern because of our team’s expertise and the array of evaluation and treatment options we offer. To refer a patient, call 214-645- 8300.
About UT Southwestern Medical Center
UT Southwestern, one of the nation’s premier academic medical centers, integrates pioneering biomedical research with exceptional clinical care and education. The institution’s faculty has received six Nobel Prizes, and includes 24 members of the National Academy of Sciences, 18 members of the National Academy of Medicine, and 14 Howard Hughes Medical Institute Investigators. The full-time faculty of more than 2,900 is responsible for groundbreaking medical advances and is committed to translating science- driven research quickly to new clinical treatments. UT Southwestern physicians provide care in more than 80 specialties to more than 100,000 hospitalized patients, more than 360,000 emergency room cases, and oversee nearly 4 million outpatient visits a year.