Moyamoya Disease

By Meg Marinis, Director of Medical Research May 02, 2013
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So… Many things seem to be happening at Grey-Sloan Memorial…

Paul still hasn't woken up. His son Ethan took his grandmother's sleeping pills. Arizona seems to be distracted by this visiting surgeon Lauren. Bailey's still not back in the operating room. And Jo has just shown up at Alex's door with a mysterious black eye.

Like I said, many things seem to be happening. And we're only a couple of episodes away from the season finale…

Iris suffers from Moyamoya disease.

Also known as Moyamoya syndrome and mostly seen in children, the disease is a rare condition in which the walls of the internal carotid arteries (the vessels that provide the blood supply to the brain) thicken and narrow. As the arteries narrow, less oxygen-rich blood reaches the brain, increasing the risk for the patient to have a complete blockage and suffer a stroke.

Due to the narrowing arteries, the brain will attempt to create new blood vessels in order to continue to provide oxygen-rich blood to the areas of the brain in need. When viewed on an angiogram, these tiny additional blood vessels resemble wisps – hence, the Japanese doctors named the disease Moyamoya, which means "puff of smoke" in Japanese. However, even though the brain forms these new vessels, they tend to be much more fragile and can even break off and bleed into the brain, causing hemorrhages.

As part of the progression of her disease, Iris lost muscle strength from having transient ischemic attacks (T.I.A.s or "mini-strokes").

During a T.I.A., a blockage occurs, disrupting the flow of blood to the brain. Symptoms appear similar to those of a stroke, such as:

• Weakness on one side of the body.
• Headache.
• Seizures.
• Slurred speech.
• Blurry vision.

Symptoms may come and go, depending on the individual patient and any treatment pursued. A rare and serious complication can be a brain hemorrhage. Warning signs include:

• Vomiting.
• Nausea.
• Severe headache.
• Numbness in part of the body.
• Fatigue.
• Vision changes.

Iris came to Grey-Sloan Memorial to have surgery to establish a new blood supply to her brain.

Unfortunately, Moyamoya disease is a progressive condition, and currently no medication can reverse the artery damage in the brain. However, some medications and various surgical treatments can successfully manage symptoms. Many doctors recommend children with Moyamoya disease regularly take aspirin to prevent blood clots from forming. Additionally, calcium channel blockers may be prescribed; these medications help lower blood pressure by keeping calcium from entering the cells in the heart and blood vessel walls. A lowered blood pressure can be instrumental in decreasing the headaches and possible T.I.A.s associated with the disease.

Surgery aims to either bypass narrowed arteries or create entirely new blood supplies for the affected areas of the brain. Surgical options can be divided into two groups – direct or indirect procedures. Cerebral bypass procedures are known as the direct method – a blood vessel from outside the brain will be connected to a vessel inside the brain to reroute the flow of blood around one of the damaged arteries. Surgeons commonly use a blood vessel from the patient's scalp (the superficial temporal artery) and join it to the middle cerebral artery in the brain. Abbreviated the STA-MCA, this bypass procedure may show improvement in blood flow in just a few months.

Derek and Alex performed an indirect procedure for little Iris with the goal of introducing a new blood supply to the brain over time. In many cases of a young pediatric patient, an indirect procedure is chosen because their arteries are not yet large enough for a bypass procedure. Several types of indirect surgeries exist, such as:

• The omental transposition procedure (what Iris had) uses the omentum – the lining of the abdominal organs, which serves as an excellent source of blood supply. The omentum is separated from the abdomen and placed on the surface of the brain; these vessels will then hopefully grow into the brain.

• The EDAS (encephalo-duro-arterio-synangiosis) procedure takes the superficial temporal artery and sutures it to the dura – the tissue that covers the brain. Over time, small arterial vessels will form.

• The EMS (encephalo-myo-synangiosis) procedure takes the temporalis muscle from the side of the head and places that onto the surface of the brain.

• Dural inversion involves flipping the flaps of the patient's dural tissue on the meningeal vessel, a large artery in the skull. Once reversed, the blood vessels on the outer surface provide supply to the starved areas of the brain.

For more information on Moyamoya disease, please visit the following:

http://www.ninds.nih.gov/disorders/moyamoya/moyamoya.htm