I think of you so often and remember all the fun times we had. Your smile and laughter always made me realize what life should be all about at times when I may have forgotten.
-- Mary Jane Blaney
Moya Moya Disease
What is
Moya Moya Disease?
The term "Moya Moya" is of Japanese origin meaning "puff of
smoke." This comes from the appearance of the brain blood
vessels affected by Moya Moya syndrome during an angiogram (a
special picture of the brain where an x-ray is taken after a
special injection is given that allows your doctor to see the
blood vessels). 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.
Signs and Symptoms
In young children transient ischemic attack (mini-stroke) is the
most common initial symptom. Some children may experience
seizures or involuntary movements and even exhibit signs of
mental retardation. In young patients, Moya Moya disease is
usually associated with headaches, speech difficulties, and
episodes of paralysis involving the feet, legs or upper
extremities, hemorrhage and anemia.
In adults, presenting features are those of intracranial
hemorrhage (bleeding within the skull). Disturbances of
consciousness or subarachnoid hemorrhage is prominent. The
arachnoid is a connective tissue sheath that covers the brain.
The patient may have fainting episodes (black outs). In
addition, the patient may also suffer visual abnormalities may
occur alone or in combination -- loss of sight in one eye (hemianopia),
blurry vision (diplopia), poor vision in both eyes (bilaterally
diminished visual acuity), and the inability to recognize
objects. Papilledema, or localized swelling of the tissues
affected may indicate subarachnoid or cerebral hemorrhage.
Epidemiology
The "Moya Moya" disease is often found among Japanese. The onset
is the highest in the ages around 5 years and next in the 4th
decade. The cause of the syndrome is unknown.
The process of narrowing of the brain arteries seems to be a
reaction of the brain's blood vessels to a wide variety of
external stimulus, injuries, or genetic defects. In a series of
patients, the syndrome was associated with Asian birth (nine
children), neurofibromatosis -- the congenital condition that
causes tumors to grow on nerves (12 children), Down Syndrome (a
chromosome defect -- 9 children), following cranial x-ray or
chemotherapy treatments (10 children). There also seems to be an
association with a previous history of surgery for congenital
heart disease, suggesting that there may be a genetic defect in
the blood vessel wall in these patients. But more than half of
the children seen with this disease have no known cause for
their Moya Moya syndrome.
The disease often progresses despite any known medical
management unless treated with surgery. The repeated strokes can
lead to severe problems with functions related to the area of
the brain affected and may even cause death. It is important to
recognize these lesions and treat them early on.
How is it diagnosed?
Once a diagnosis is suspected by CT or MRI, the next step is
usually an angiogram to confirm the diagnosis and to see the
what the blood vessels involved look like. Often nuclear
medicine studies such as SPECT (single photon emission
computerized tomography) are used to show the decreased blood
and oxygen supply to areas of the brain affected with the Moya
Moya disease.
How is it treated?
There is no cure for Moya Moya disease. Treatment is symptomatic
and supportive. Certain medications can be very helpful in the
treatment of the symptoms caused by Moya Moya syndrome. The
basis for some of the strokes in this condition is sludging of
blood within the narrowed arteries at the base of the brain, the
formation of tiny blood clots at these areas, and the subsequent
breaking off of these clots into downstream blood vessels --
which blocks them off temporarily or permanently.
Medicines which prevent this micro-clot formation, such as
aspirin, are essential in Moya Moya syndrome, and some doctors
believe that all Moya Moya patients need to be on the medication
permanently as a preventive step.
Calcium channel blockers such as Verapamil are also often
prescribed for patients with Moya Moya syndrome. These
medications are often helpful in reducing the headache that
certain patients may suffer during various stages of the
illness, but they need to be given under the supervision of a
neurologist. It is important to understand, however, that no
medications prevent the arterial narrowing process from
progressing or keep the Moya Moya vessels from developing, and
surgery is the mainstay of treatment for the syndrome.
The neurosurgeon has to decide what type of operation is best
suited for the child. There are many operations that have been
developed for the condition. Surgical treatment has less success
for an adult.
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EDAS (encephaloduroarteriosynangiosis) procedure. This procedure requires freeing up, without severing, 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.
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EMS (encephalomyosynangiosis) operation. Here a muscle which on the temple and slightly on the forehead region of the skull, is freed from some attachments. A hole it then made in the skull under this muscle and it is then placed onto the surface of the brain.
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STA-MCA (superficial temporal artery-middle cerebral artery) in which a scalp artery is directly sutured to a brain surface artery.
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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 work on 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, this then
bypasses the areas of blockage.
Are there risks involved with surgery?
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 problem is the sensitivity of the affected vessels and the
part of the brain affected. These areas are very sensitive to
changes in blood pressure, volume and also the relative amount
of carbon dioxide. All these things may vary dramatically under
general anesthesia and surgery. 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. The anesthesiologist must 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 brain surgery.
Outlook
The long term outlook for children with treated Moya Moya
appears good. It will take probably 6-12 months before new
vessels can develop after surgery and symptoms may seem to
improve almost immediately after surgery. Unfortunately, once
major strokes or seizures occur there may be permanent damage to
the brain that cannot be corrected with surgery.
No one knows whether the form of Moya Moya syndrome prevalent in
most children, which causes strokes and transient ischemic
attacks (mini-stroke), will be replaced in adulthood by the
bleeding form seen more commonly in adults. There is some
evidence to suggests that this change in pattern is unlikely,
since most adult patients don't have histories of stroke after
surgery for Moya Moya when they were younger.
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An Example of Moya Moya Disease These angiograms are antero-posterior views of the right carotid artery injection. Contrary to the top normal angiogram (A), the angiogram of a Moya Moya patient shows marked development of the Moya Moya vessels at the base of the brain and marked narrowing of the terminal portion of the internal carotid artery. The middle cerebral and anterior cerebral arteries are poorly visualized (B).
(A) |
(B)