Amir Dehdashti, MD, explains what you need to know about moyamoya disease
This rare stroke-related condition comes with an unusual name: Moyamoya is Japanese for “puff of smoke.” The disease was first identified by Japanese doctors, and they used the term to describe a wispy, tangle of new blood vessels that formed at the base of the brain — a sign of compromised blood flow. In an angiogram, or brain scan image, that mess of curled up vessels appears as a drifting haze, like an exhalation of smoke.
So, what is moyamoya disease?
Moyamoya disease occurs when carotid arteries —major arteries inside the skull that deliver blood to the brain — progressively narrow or become blocked. Gradually, tiny “moyamoya” vessels develop at the base of the brain to compensate for the blockage. “Those new vessels are technically taking over the blood supply to the brain,” explains Amir Dehdashti, MD, neurosurgeon and director of cerebrovascular neurosurgery research at North Shore University Hospital. But because these back-up vessels are smaller and weaker than the blocked artery, they can’t handle the same amount of blood pressure or supply enough blood to the brain — which may lead to a stroke, recurrent transient ischemic attacks (mini-strokes) or bleeding in the brain.
Who gets moyamoya disease?
Moyamoya can affect anyone at any age. However, it most often occurs between the ages of four and ten years old, and also in people between the ages of 40 and 60 years old, says Dr. Dehdashti, who also serves as professor of neurosurgery at the Zucker School of Medicine at Hofstra/Northwell.
Though the exact cause is unknown, moyamoya disease is more prevalent in the Asian population, which suggests genetic factors and family history may play a role. It’s also more common in women than men.
Moyamoya syndrome vs disease
Sometimes, moyamoya occurs with other conditions. When changes in brain blood vessels are associated with another underlying medical problem, the condition is called moyamoya syndrome. Medical conditions linked to moyamoya syndrome include:
- Down syndrome
- Sickle cell anemia
- Prior brain radiation therapy
- Neurofibromatosis type 1
- Hyperthyroidism
What are moyamoya symptoms?
The first sign of moyamoya disease in both children and adults is stroke or recurrent transient ischemic attack (TIA), or mini-strokes. Adults, however, are also more likely to suffer from bleeding in the brain. “That’s because there is a significant amount of pressure on those tiny moyamoya vessels that are trying to maintain blood flow to the brain,” explains Dr. Dehdashti. When it builds up too high, the vessels can shear or bulge and rupture and cause hemorrhagic stroke.
- Signs of moyamoya disease include:
- Headache
- Numbness or weakness, often on one side of the body.
- Involuntary movements
- Trouble with focus or memory
- Vision changes or other sensory problems
- Progressive developmental delays
In rare cases, patients with moyamoya disease are asymptomatic, and are identified incidentally, adds Dr. Dehdashti.
How is moyamoya disease diagnosed?
If your neurologist suspects moyamoya disease, he or she will work through a series of imaging tests to confirm a diagnosis. They include:
- Computerized tomography (CT) scan. “If a patient comes to the emergency department with symptoms of stroke, the first thing we do is a CT angiogram and CT perfusion,” says Dr. Dehdashti. These scans are used to help identify abnormal blood vessels in the head and neck and show which areas of the brain are adequately supplied with blood (perfused), as well as provide information about blood flow to the brain.
- Magnetic resonance imaging (MRI). If abnormal blood vessels are detected, the next test is an MRI, which uses a magnetic field, radio waves and a computer to create detailed images of the brain to help evaluate blood flow. Another test, called an MRA (magnetic resonance angiogram) may also be used to look inside blood vessels for any unusual features or malformations.
- Cerebral angiogram. This test provides the final confirmation for moyamoya disease, says Dr. Dehdashti. It uses a catheter, x-ray imaging guidance and in injections of contrast dye to examine blood vessels in the brain for narrowing and abnormalities, as well as map blood flow patterns to reveal moyamoya vessels.
Is there a cure for moyamoya disease?
There’s no cure for moyamoya disease, but treatments can help reduce symptoms and prevent strokes.
How is moyamoya disease treated?
Surgery is the standard of care for moyamoya disease, says Dr. Dehdashti, with the goal of increasing blood flow to the brain. “Patients who are symptomatic—meaning they have had a brain bleed, mini-stroke, or stroke — are at risk for recurrent symptoms. But with surgery, that risk is diminished by about 50%.”
To help treat patients quickly, Northwell experts follow a unique, focused sequence of tests that includes an advanced imaging system called NOVA (non-invasive optimal vessel analysis) MRA, which uses 3D modeling to quantify blood flow through brain arteries, assess risk of stroke and help plan for surgery.
For patients with mild or no symptoms, doctors may run additional tests — such as a single-photon emission computerized tomography (SPECT) — to evaluate brain flow activity and determine next steps.
In cases where surgery isn’t yet needed, doctors may prescribe aspirin to help manage symptoms and reduce the risk of stroke. “But medications don’t treat the actual condition,” says Dr. Dehdashti.
Moyamoya surgery types
Revascularization surgery can restore blood flow to the brain, and decrease pressure on the moyamoya vessels. In these delicate procedures, specialized surgeons connect blood vessels on the outside and inside of the skull to bypass blocked arteries. Two types include:
- Direct revascularization surgery. In this procedure, a blood vessel from the scalp (superficial temporal artery) is surgically attached to a brain blood vessel (middle cerebral artery), which immediately provides additional blood to the starved brain.
“Direct bypass is what we do for 99% of adult patients with Moyamoya disease,” says Dr. Dehdashti. The procedure typically takes about four hours, and patients need to stay in the hospital for about three days after surgery.
In children, however, direct bypass may be difficult due to the smaller size of their blood vessels.
- Indirect revascularization surgery. Surgeons may opt for this technique in adults where direct bypass isn’t possible or in children whose blood vessels are too small. The procedure involves stitching a scalp blood vessel to the surface of the brain (rather than to another blood vessel), which gradually increases blood flow over weeks or months.
Sometimes patients develop a bulge or ballooning in the tiny moyamoya vessels called an aneurysm. Surgery may be needed to prevent a rupture, or to treat an aneurysm rupture. Post-surgery, you can expect follow up scans at six months and one year to evaluate blood flow to the brain.
What is the life expectancy for moyamoya?
Without treatment, people with moyamoya disease can experience mental decline, multiple strokes as the disease progresses, and are at risk for fatal brain bleeds.
But with the right treatment, patients can live a healthy, normal life.
Find care for moyamoya
At the Moyamoya Center at Northwell Health’s Institute for Neurology and Neurosurgery, a multidisciplinary team led by Dr. Dehdashti can help diagnose, treat and support patients and their families with moyamoya disease.
The dedicatied specialists include vascular neurologists, neuropsychologists, neurosurgeons, endovascular specialists and more who have years of experience treating this rare condition.
Trained in cerebral vascular and skull-base surgery, Dr. Dehdashti has performed hundreds of cerebral bypass procedures to treat moyamoya disease over the course of his career—and brings that expertise to Northwell. “Currently we do about 30 to 40 bypasses a year at our hospitals—more than many other institutions,” he says.