Moyamoya disease appears when the walls of the carotid arteries at the base of the brain become thick and narrow. It became difficult for blood to flow freely, up to a complete blockage and stroke.
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When the brain is short of oxygen the body starts to fights back: It creates new collateral blood vessels, trying to make new paths for the blood. However, those new vessels are small, they appears hazy on an angiogram and that's why this condition got the name moyamoya - "puff of smoke" in Japanese. Since they are very fragile they can break and bleed into the brain and that is a very bad condition.
Moyamoya usually occurs on both sides of the brain and is often accompanied by aneurysms. This conditions grows in several stages, from start of narrowing to the point when carotid arteries are completely blocked.
During the third stage, a half way between the first appearance of narrowing and a complete block, visible symptoms occur and that's the phase when the most cases are diagnosed. The problem is, when blockage begins it can't be stopped with drugs so it is important to discover the condition as soon as possible.
Now, how to recognize that dangerous health condition? In the most cases symptoms of moyamoya first appear with a mini-stroke (transient ischemic attack, TIA), ischemic stroke, or hemorrhagic stroke. During a mini stroke, a vessels block interrupts the flow of blood to the brain. Hemorrhagic stroke happens when a blood vessel burst and leak blood into the brain.
Ischemic and hemorrhagic stroke symptoms include weakness or numbness in an arm or leg, difficulty speaking, or paralysis on one side of the body. Other symptoms are seizures, cognitive, and learning difficulties. Here is important to say that headache is also common in hemorrhagic stroke.
The cause of moyamoya disease is not very well known, we known that it is common in Japan, while in the USA, for example, 1 person in 100,000 will get it, and we know that age 5 to 15 and 30 to 40 are dangerous for some reason. There are some diseases related to vessels blocking but we can't say that a particular condition leads to moyamoya.
Diagnosing is done via different image techniques, trying to find the characteristic "puff of smoke" vessels, such as MRI, angiography, CTA, Doppler ultrasonography, xenon-enhanced CT, PET scan, and single photon emission computed tomography (SPECT). We can say that using multiple imaging techniques we make sure that the condition won't pass unnoticed.
There are no medications that can reverse the artery narrowing, so treatment is focused on reducing the risks of repeated strokes.
Surgery is recommended for patients with progressive or frequents transient ischemic attacks. Several methods are available and, speaking in general, direct bypass procedures are performed in adults and older children, while indirect procedures are preferred for children under the age of 10. The goal of all procedures is to make new vessels, or give the body chance to make new vessels, that can get the blood to the brain.
After the surgery the physical activity must be kept at minimum until new blood vessels are formed, that's especially important at children, and it may take from six to 12 months for the body to build new blood vessels. It's hard to give a general prognosis because it depends heavily on the individual patient and his state. However, as a rule of thumb: without surgery the prognosis is bad, with surgery it varies from better to very good. ■