Moyamoya disease is a rare disease that translates to “Puff of Smoke” in Japanese. Normally, blood is taken to the brain through the internal carotid artery. Once it gets to the base of the brain, it splits into the anterior cerebral artery which goes to the front of the brain, and the middle cerebral artery which goes to the side of the brain.
In Moyamoya disease, the top of the internal carotid artery narrows over time, which prevents blood from flowing to the rest of the brain. The brain compensates by forming small, fragile blood vessels to supply blood around the area that is tightening.
Moyamoya disease can present in one of 2 ways. One way is a bleed that happens when these fragile blood vessels break and cause bleeding within the brain. Another way it presents is as an ischemic stroke which happens when not enough blood gets to the brain because of narrowing. A result is less oxygen traveling to the brain, which causes that part of the brain to die.
Treatment options for Moyamoya disease focus on resupplying the brain with blood so the surgeon can get blood past that area of stenosis. This can be done with two techniques which are referred to either as a direct bypass or an indirect bypass.
In a direct bypass, a small artery on the surface of the scalp is removed and reattached to an artery inside the brain. This allows blood to go from the external carotid artery, supplying the face, to the internal carotid artery which is supplying the brain.
The other option is an indirect bypass. In this procedure, instead of making a direct connection between an artery and an artery in the head, an indirect connection is made. This is done by laying the artery on the surface of the brain and possibly laying the muscle that's on the outside directly on the surface of the brain. Both the muscle and the artery will grow roots over time. These roots will enter the brain and supply blood to the brain in that manner.