Moyamoya is a rare, progressive medical condition that affects the arteries that carry blood to the brain (the internal carotid arteries). This condition causes the internal carotid arteries and their branches to become narrowed. This limits the flow of blood to the brain and puts the brain at risk for stroke. The brain tries to make up for the decreased blood flow by growing new blood vessels at the base of the brain, called collateral vessels. These new arteries tend to be more fragile than normal brain arteries. While these blood vessels can temporarily help increase blood supply to the brain, they eventually stop working. The name “moyamoya,” which means “puff of smoke” in Japanese, refers to the wispy, smoke-like appearance of these new blood vessels on a special X-ray called an angiogram. Moyamoya primarily affects children but can also occur in adults.
Signs and Symptoms
The symptoms of moyamoya are caused by reduced blood flow to the brain. Moyamoya can affect one or both sides of the brain. The first sign is often a transient ischemic attack or a stroke. Symptoms include:
- Stroke or stroke-like symptoms
- Recurrent transient ischemic attacks (ministrokes)
- Weakness/paralysis or numbness on one side of the body alternating with weakness or numbness on the other side of the body if both sides of the brain are affected by moyamoya (the side of the body that is affected is opposite the side of the brain with moyamoya)
- Vision problems
- Involuntary movements
- Migraine-like headaches
- Cognitive impairment
Without treatment, children with moyamoya can experience multiple strokes that can lead to progressive neurological decline and possible permanent neurological deficits.
If your child shows signs of moyamoya, neurologists and neurosurgeons will perform specific tests to make an accurate diagnosis. Surgery is the only cure for moyamoya. Most children make a complete recovery and can return to normal activities within a month if their condition is diagnosed and treated before a major stroke occurs.
Moyamoya is a progressive condition, meaning that it gets worse over time, so children diagnosed with this condition need treatment to reduce their risk of stroke. In most cases, there is no known cause for moyamoya. However, it can be found in association with other medical conditions such as:
- Down syndrome
- Sickle cell disease
- Congenital heart disease
- Connective tissue disorders such as Ehlers-Danlos and Marfan syndrome
- Brain tumors at the base of the brain such as craniopharyngiomas and hypothalamic gliomas
The cerebral angiogram is performed by an interventional radiologist who specializes in the care of children. This is extremely important because children have smaller blood vessels, limitations on dye administration and specific radiation recommendations. It is a minimally invasive procedure that uses a special contrast, or dye, to observe blood flow in the brain.
During the procedure, the radiologist places a small IV or catheter in a blood vessel in the groin, which he or she then uses to reach the blood vessels that supply the brain. With the help of the special contrast or dye, an X-ray machine moves at different angles and takes pictures of the blood vessels. A team consisting of a radiologist, an anesthesiologist, radiology technologists and nurses will care for your child throughout the procedure. Following the procedure, your child will have to lie flat for approximately 4 hours due to puncture of a large blood vessel in the groin. Being flat will decrease the risk of bleeding. If needed, your child will receive medication to help him or her relax and rest during this time. This can be an outpatient procedure; however, if treatment is performed, such as embolization, your child will be admitted for observation by our team.
If diagnostic tests determine that moyamoya is present, your child will be referred to a pediatric neurosurgeon to discuss the condition with you and your child and work to create a surgery plan for definitive treatment. Some individuals have a close relative who is also affected. In these cases, researchers think that it is caused by inherited genetic abnormalities. Studies that look for the abnormal gene(s) may help reveal the biomechanisms that cause the disorder.
The goal of treatment is to restore blood flow to the brain and remove the risk of stroke. Without surgery, many individuals will experience mental decline and multiple strokes because of the progressive narrowing of arteries. Several types of surgery can restore blood flow (revascularization) to the brain. Children usually respond better to revascularization surgery than adults. Many children have no further strokes or related problems after surgery and can go on to live normal productive lives.
Treatment for moyamoya includes:
- Microneurosurgery for revascularization, called pial synangiosis Surgery is the only treatment for moyamoya. A pediatric neurosurgeon performs this type of revascularization surgery by transferring a healthy branch of the external carotid artery supplying the scalp to the surface of the brain. The healthy artery is secured to the surface of the brain, and new collateral blood vessels grow in and restore blood flow to the brain over time. This is a delicate procedure performed with the use of a high-powered operating microscope. If moyamoya is present on both sides of the brain, two separate surgeries will be performed for the best and safest results. Children typically spend two to three days in the hospital after surgery. They can return to school within two weeks and can take part in normal activities about four weeks after surgery.
- Moyamoya anesthesia protocol Children with moyamoya are at increased risk of stroke, especially when under anesthesia. The anesthesiologist will carefully monitor patients during surgery to maintain the proper blood pressure and hydration and prevent hyperventilation to avoid a stroke. Intraoperative electroencephalogram (EEG) monitoring is also used to track any potential seizure activity during surgery.
- Aspirin Children with moyamoya take a daily dose of aspirin for the rest of their lives as a method of stroke prevention.