Everyone's Favorite Poison Scores Another Win

Medically Reviewed by Jacqueline Brooks, MBBCH, MRCPsych

Oct. 5, 2000 -- For a deadly poison, botulinum toxin A sure gets a lot of good press, being touted for treatment of everything from cerebral palsy to facial wrinkles. The latest feather in the toxin's cap comes out of Europe, where researchers have used it to relieve painful, disabling arm-muscle spasms in people who have had strokes.

People who suffer strokes often experience severe, painful muscle spasms in their arms and legs. The spasms can interfere with their ability to walk, dress, eat, bathe themselves, or use a toilet. Only about five out of every 100 stroke sufferers who develop arm-muscle spasms ever regain full use of the limb, according to A.M.O. Bakheit, MD, PhD, and colleagues from the United Kingdom, Austria, and Germany. So it's important to find a way to treat these spasms.

As the researchers showed in a study published in Stroke: Journal of the American Heart Association, patients whose arm, finger, or wrist muscles were injected with small doses of the botulinum toxin had a significant reduction in the spasms, compared with people who got injections of a harmless, inactive substance. But the toxin did not produce noticeable improvements in the patients' abilities to perform daily activities such as dressing, washing, or using a toilet, the authors say.

"We found that the effect of a single injection lasted, on average, about 12 weeks," Bakheit, a professor of neurological rehabilitation at Mount Gould Hospital in Plymouth, England, tells WebMD. "What we are trying to do now is to study the effect of repeated doses, and we're actually hoping to start a study later this year looking at that -- trying to see patients for a full year rather than just for one treatment session, and see how often they need their treatment repeated. I suspect that we will probably need to repeat the injection once every three or four months."

The botulinum toxin A is one of a family of naturally occurring bacterial toxins that can cause a potentially fatal form of food poisoning called botulism. The most common causes of botulism are home-canned or commercially prepared foods that haven't been handled or stored properly, or contaminated food that hasn't been cooked at a temperature high enough to kill the bacteria. The poison can shut down the muscles that control breathing.

But physicians have also known for about a decade that the toxin's paralyzing effects can also be used to advantage, to treat conditions in which a temporary and mild paralysis of muscles can result in an improvement in function. Such conditions include crossed eyes (the toxin is used to relax overly tight muscles that hold the eye in place); uncontrolled eyelid blinking; and the birth defect cerebral palsy, which causes a loss of body control due to muscle spasms.

The toxin prevents the release of a chemical messenger that tells muscles to contract, thus causing a temporary loss of muscle tone. Unlike oral drugs that are used to treat spasms, patients do not become 'immune' to the injections, which can, in some cases, be repeated many times over with good effect, says a researcher who uses the toxin A to alleviate muscle spasms in children with cerebral palsy.

"The average length of effect [of the treatment] in our group has been about 12 weeks, with a lot of variability -- anywhere from one week to one year," says Ross M. Hays, MD, a rehabilitative medicine specialist at Children's Hospital and Regional Medical Center in Seattle. "We have had some patients who have very nice responses to repeat treatments; we've had one child who has had up to 20 treatments."

In the current study, which involved 82 patients followed for up to 14 weeks, the European researchers found that botulinum toxin A was effective and safe at any of three doses they tested. The injections reduced arm stiffness and spasms and allowed patients to sit up or lie more comfortably, although they did not produce any real improvements in the patients' ability to care for themselves, the researchers say. They say there was not enough information to draw conclusions about whether the injections could reduce pain.

"How effective is it? That's the $64,000 question," Hays says. "We've seen a range of response: some of our children have had a dramatic reduction in [spasticity] and therefore improvement in functional skills, particularly their [walking], and ... we've had patients who had significant improvement in their hand use after treatments. But then we've had children who have had essentially no improvement at all.

"What we encourage families to expect when we counsel them prior to treatment is the effect is likely to be modest to moderate, and we spend a lot of time creating realistic expectations."