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FAQs About Moyamoya Syndrome

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by R. Michael Scott, MD

The cause of the syndrome is unknown. The process of narrowing of the brain arteries seems to be a non-specific reaction of the brain's blood vessels to a wide variety of stimuli, injuries, or genetic defects. For example, in our own series of patients, we have seen the syndrome in association with Asian birth (nine children), neurofibromatosis -- the congenital condition that cases tumors to grow on nerves -- (12), Down Syndrome ( a chromosome defect -- 9 children), following cranial x-ray or chemotherapy treatments (10 children), etc. There is also 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 our children have no known cause for their moyamoya syndrome. Our adult patients have usually had no definite cause detected either, but there have been some associations -- heavy cigarette smoking, the use of birth control pills in young women, and in one patient a long history of cocaine abuse. Cocaine is a powerful constrictor of blood vessels throughout the body, and so the association makes some sense.

Is the disease a progressive one, and will my child's condition worsen with time?

All patients with moyamoya syndrome have progressive narrowing of their brain blood vessels over time, and I have never seen an exception to this rule after many years of studying these patients. Along with this progressive narrowing of the brain blood vessels, the patient's clinical condition will worsen also; this is why surgery to increase the brain's borderline blood supply is so important for these children.

What is my child's prognosis now that the moyamoya syndrome has been diagnosed?

Our data suggest that the patient's prognosis is very definitely linked to their status at the time the diagnosis is first made and surgical treatment instituted. Many of the references on this condition link prognosis to age at diagnosis; this indicator is not an accurate one. For example, if a three year-old child is diagnosed with the syndrome, we have found that the youngster's ultimate outcome is dependent on whether there have been strokes in both sides of the brain and how badly impaired the child is at the time of diagnosis and surgery. That child's prognosis seems to be just the same as an older youngster with a similar scan and clinical history, in other words.

How many patients with moyamoya syndrome have you actually taken care of?

Since 1983 and up to February 15, 1999, I have operated on 96 children with the syndrome. There are roughly twice as many girls than boys in the group, and the average age at surgery has been a little more than 7 years of age, although patients have been as young as 4 months at the time of operation.

What is actually done during the surgical procedure "pial synangiosis" that you have recommended for my child?

This operation is designed to take advantage of the tendency of the brains of children with moyamoya syndrome to attract new blood vessels from any source that is made available. We make an incision on the scalp over an artery supplying blood only to the skin over the head. We separate this artery from the tissues around it, keeping blood flowing through it. We open up a window of bone beneath the artery, and then use a microscope to carefully open all of the coverings of the brain right down to the brain surface. The artery is then placed directly onto the brain, and the tissues around its walls are sewn with tiny sutures to the brain surface to keep it in contact with the brain. Then the bone window is replaced securely, and the skin incision closed. In some patients, we may also place an extra small hole (a "burr hole") in the skull away from the first incision, and at this hole we also make tiny openings in all of the coverings of the brain before closing the incision. To operate on one side of the brain takes about 3 to 4 hours; in many patients, we will try to do both sides of the brain at the same time.

Is it dangerous to operate on both sides of the brain at once?

Operating on both sides of the brain during the same anesthesia probably reduces the patient's risk of having a stroke with surgery. Most of the patients with moyamoya syndrome have a very tenuous blood supply to their brain that can be reduced very easily. Anesthesia can alter brain blood flow, and in particular, the starting and ending of the anesthesia are critical times when blood flow to the brain can be dramatically changed. To make the surgery safer, we monitor the patient's brain waves ("EEG") throughout the procedure using small button electrodes placed over the scalp except in the areas where we are operating. As we are carrying out the surgery, we can tell whether our anesthetic or surgical techniques are affecting the patient's brain function. If all is going well after the first side is completed, we will go on to get the other side done to avoid having to administer another anesthetic on a separate occasion.

How many patients have undergone bilateral surgery, and what have been the results?

Of the 96 patients with moyamoya syndrome operated on as of February 15, 1999, 66 patients have undergone synangiosis on both sides of the head under the same anesthetic and using EEG monitoring. We have had to stop the operation after the first side was completed in ten patients for various reasons, and the surgery was completed later safely in all of these. Depending on the patient's status and the reasons for stopping the surgery, the opposite side will be done in a period ranging from several days to three months from following the first operation.

What is the chance of another stroke during or following the operation?

The surgery has been safe, and has a low complication rate. There have been seven patients, however, who suffered new strokes of varying degrees of severity either at the time of surgery or during the first post-operative week. Many of these patients were unstable before surgery, having frequent strokes or numerous transient ischemic attacks ("TIA's") -- brief periods of neurological dysfunction that are often warning signs of an impending stroke -- and we believe that such patients are at a higher risk for stroke during a surgical procedure than patients who have had no recent events of this type. That is why we usually wait for four to six weeks after a stroke before we proceed with surgery. In four patients, I thought that unstable blood pressure or medication problems were the likely causes of any new post-operative strokes. Most of these patients, by the way, have made excellent recoveries.

Why does the surgery work?

The surgery works by inducing the development of new blood vessels from the donor artery in the area of the area of the synangiosis which provides an additional source of blood to the underlying brain. These blood vessels develop not only from the scalp artery, which is the major source of new blood, but also from blood vessels which sprout from the coverings of the brain around the skull opening. That is why even making a small skull opening (the "burr hole" mentioned above) can also help these patients. We are not sure why these new blood vessels sprout and grow. This response is usually not seen in other patients having brain surgery for other reasons. Our research work has demonstrated that there are growth factors in the fluid surrounding the brain of patients with moyamoya syndrome which seem to be responsible for the development of the new blood vessels. Our research work in this area is ongoing, and we have recently published the results of some of this work.

What diagnostic studies need to be done prior to carrying out the surgery?

Recent studies to document the extent of preexisting- strokes and brain injury need to be obtained -- in particular an MRI of the brain, and if possible, an MRA (MR angiogram, which demonstrates some of the brain blood vessels). Because we need to know flow patterns of blood around the brain, and also to determine whether any blood flow is getting to the brain from arteries outside the skull, all patients need to undergo formal cerebral arteriography (or angiography). This test involves the placement of a small tube ("catheter") through an artery in the groin up to the neck where its tip is placed in the individual blood vessels supplying the brain, x-ray visible dye is injected, and x-ray pictures taken. This part of the diagnostic evaluation is extremely important in planning the surgery and estimating its risk. In the past, it has been thought that this study was risky in children with marginal blood flow to the brain, but our radiology group has recently published data regarding arteriogram complications in our own patients, and the complication rate is in fact quite low, with no post-arteriogram strokes and minimal minor problems. For this reason, if at all possible, we prefer that patients undergo arteriography at The Children's Hospital, unless there are significant practical reasons why this cannot be done. If time is available, we may also obtain MRI perfusion studies and SPECT scans. Both of these essentially risk- and pain-free studies are still of theoretical value only. They both demonstrate areas in the brain where blood flow is diminished or unstable, and we hope that they will be of benefit in planning surgery and demonstrating its long-term benefit.

How long will the hospital stay be?

Most patients are admitted the night before surgery for intravenous administration of fluids to ensure adequate volume of fluid within the body's blood vessels. The night following the operation, the patient stays in the intensive care unit so that blood pressures and body hydration status can be carefully assessed and maintained. The patients are then transferred to a patient floor, where the usual hospital stay is another three to four days. There are no restrictions on airplane travel after surgery, and patients and their families can usually return home one week after the operation. The skin sutures are taken out by the family physician or pediatrician ten days following the procedure; recently we have begun to use sutures that will dissolve on their own and that do not require removal.

What is the usual follow-up of the operated patients?

If distance permits, I see patients again in four to six weeks after the procedure. Many patients live too far away for this visit to be practicable, so a visit to the patient's local neurologist must often serve as a substitute. I ask that all patients return to Boston in one year for follow up studies, which include formal arteriography and repeats of any pre-op cerebral blood flow studies , such as MR-MRA and perfusion studies and SPECT scanning. The arteriogram is usually the last one that the patient will need to undergo, with subsequent follow ups consisting of yearly MRI-MRA studies only (which can be carried out locally).

I ask that all my patients stay in contact with me on a yearly basis. Follow-up in patients with moyamoya syndrome is extraordinarily important and really forms the basis of our knowledge regarding prognosis and ultimate outcome of the condition, and I rely on my patients to help me in this effort.

What will happen to a patient with moyamoya syndrome decades from now? Will there be problems with bleeding in the brain or further strokes? Will my daughter ever be able to marry and raise a family?

No one knows whether the form of moyamoya syndrome prevalent in most children, which causes strokes and TIA's, will be replaced in adulthood by the bleeding form seen more commonly in adults. The evidence in my own series suggests that this change in pattern is unlikely, since most adult patients don't have histories of stroke and TIA when they were younger. I do have several patients now, treated surgically in the 80's, who have married and had uncomplicated pregnancies and deliveries. One of these women has two children, one of whom unfortunately has moyamoya syndrome also. This familial form of the syndrome is extremely rare in the Western hemisphere. There is no current method of determining before birth whether the fetus is likely to have the syndrome, but I do believe that the likelihood of this phenomenon occurring in mother and child is very low.

My doctor has recommended medical treatment of the syndrome. Are medications effective?

Certain medications can be very helpful in the treatment of the symptoms caused by moyamoya syndrome. I believe that the basis for some of the strokes and TIA's 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 moyamoya syndrome, and I believe that all moyamoya patients need to be on the medication permanently. [The small risk of Reye's Syndrome -- an inflammatory swelling of the brain following chicken pox infection when aspirin is given -- is outweighed by the consistent long-term benefit of the aspirin administration}. Calcium channel blockers such as verapamil are also often prescribed for patients with moyamoya 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 moyamoya vessels from developing, and I firmly believe that surgery is the mainstay of treatment for the syndrome.

My doctor has recommended a surgical procedure different from the pial synangiosis to treat the condition. Does it matter which procedure is used?

A detailed answer to this question is beyond the scope of this question and answer format, because there are many different surgical procedures, with varying technical considerations and implications in various patient groups. No one surgical technique is the right answer for every patient with the syndrome, and the patient needs to review the surgical recommendation with the involved surgeon, determine his or her rationale for the recommendation, and inquire about the surgeon's results and experience with the technique recommended.

Written February 15, 1999

Previous On-Line Lectures

Letter from John Shillito, M.D.

Potential Cost of Non-Invasive Telemetric Monitoring in Patients with Shunted Hydrocephalus, by David Frim, M.D., Ph.D.

Neurosurgical Treatment of Spasticity, by Joseph R. Madsen, M.D.

Tethered Cord Syndrome: Questions and Answers, by Joseph R. Madsen, M.D.

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