Moyamoya syndrome (Japanese, "puff of cigar smoke") is aninherited disease in which certain arteries in the brain are constricted. Bloodflow is blocked by the constriction, and also by blood clots (thrombosis).
The blood vessels develop collateral circulation around the blockedvessels to compensate for the blockage, but the collateral vessels are small,weak, and prone to hemorrhage, aneurysm and thrombosis. On X-rays, these collateral vesselshave the appearance of a "puff of cigar smoke" ("Moyamoya"in Japanese).
The disease causes constrictions primarily in the internal carotid artery, which travelsfrom the neck up to the Circle of Willis inside the skull just underthe brain. At the Circle of Willis, the internal carotid artery flows into the middle cerebral artery, which continuesinto the brain, and the anterior cerebral artery, which is part ofthe Circle of Willis. Moyamoya disease often extends to the middle and anteriorcerebral arteries.
When the internal carotid artery becomes completely blocked, the finecollateral circulation that it supplies is obliterated. Patients often surviveon the collateral circulation from the back (posterior) of the Circle ofWillis, from the basilar artery.
Drugs such as antiplatelet agents (e.g. aspirin) are usuallygiven to prevent clots, but surgery is usually recommended. Since moyamoyatends to affect only the internal carotid artery and nearby sections of theadjacent anterior and middle cerebral arteries, surgeons can direct otherarteries, such as the external carotid artery or the superficial temporal artery to replace itscirculation. The arteries are either sewn directly into the brain circulation,or placed on the surface of the brain to reestablish new circulation after afew weeks. Although there is a 4% risk of stroke soon (30 days) after surgery,there is a 96% probability of remaining stroke-free over the next 5 years.
The constrictions of the arteries in moyamoya disease are unlike theconstrictions in atherosclerosis. In atherosclerosis, the innerlayer (lumen)of the arteries suffers an immune reaction, fills with inflammatory cells, andaccumulates fatty cells and debris. In moyamoya, the inner layer of the carotidartery overgrows inward to constrict the artery, and the artery also fills withblood clots, which cause strokes.
It is a disease that tends to affect children and adults in the third tofourth decades of life. In children it tends to cause strokes or seizures. Inadults it tends to cause strokes or bleeding. The clinical features are cerebralischemia (strokes), recurrent transient ischemic attacks (TIAs),sensorimotor paralysis (numbness in the extremities), convulsions and/or migraine-likeheadaches.