Moya-moya is a rare disorder of uncertain cause that leads to irreversible blockage of the main blood vessels to the brain as they enter into the skull.
The name comes from the Japanese and means "puff of smoke".
This naming is due to the appearance of the lesion on an angiogram.
This is a lesion that tends to affect children and adults in the third to fourth decades of life.
In children it tends to cause strokes or seizures.
In adults it tends to cause bleeding or strokes.
The process of blockage (vascular occlusion) once it begins tends to continue despite any known medical management unless treated with surgery. The repeated strokes can lead to severe functional impairment or even death so that it is important to recognize these lesions and treat them early on.
Once a diagnosis is suspected by CT or MRI, the next step is usually an angiogram to confirm the diagnosis and to see the anatomy of the vessels involved.
Often nuclear medicine studies such as SPECT (single photon emission computerized tomography) are used to demonstrate the decreased blood and oxygen supply to areas of the brain involved with the Moya-moya disease.
The next step is for the neurosurgeon to decide what type of operation is best suited for the child.
There are many operations that have been developed for the condition, but currently the most favored are: EDAS, EMS, STA-MCA and multiple burr holes.
The EDAS (encephaloduroarteriosynangiosis)
procedure requires dissecting a scalp artery over a course of several inches and then making a small temporary opening in the skull directly beneath the artery.
The artery is then sutured to the surface of the brain and the bone replaced.
In the EMS (encephalomyosynangiosis) operation,
the temporalis muscle which is in the temple region of the forehead, is dissected and through an opening in the skull placed onto the surface of the brain.
Other operations include:
the STA-MCA (superficial temporal artery-middle cerebral artery)
in which a scalp artery is directly sutured to a brain surface artery; and a procedure in which multiple small holes (burr holes) are placed in the skull to allow for growth of new vessels into the brain from the scalp.
All of these operations have in common the concept of a blood and oxygen "starved" brain reaching out to grasp and develop new and more efficient means of bringing blood to the brain and bypassing the areas of blockage.
The risks of the surgery seem to be more due to the risk of being under general anesthesia for an extended period of time then to the actual surgical manipulations.
The Moya-moya vessels and the involved brain are very sensitive to changes in blood pressure, blood volume and the relative amount of carbon dioxide in the blood.
When awake, the child's brain is able to regulate these factors fairly well. However, under general anesthesia these parameters are much harder to artificially control and this can lead to bleeding or strokes.
It is crucial for surgery that the anesthesiologist have experience in managing these children as the type of anesthesia they require is very different from the standard anesthetic children get for almost any other type of neurosurgical procedure.
The long term outlook for children with treated moya-moya seems to be good.
While symptoms may seem to improve almost immediately after surgery, it will take probably 6-12 months before new vessels can develop sufficiently. Once major strokes or bleeding take place, even with treatment the child may be left with permanent loss of function so it is very important to treat this condition promptly.