DALLAS, Oct. 6 - A toxin that causes botulism can also reduce the pain and muscle spasms that commonly paralyzes a limb after a stroke, according to a report in the October issue of Stroke: Journal of the American Heart Association.
European researchers tested three doses of Dysport, a drug derived from botulinum toxin type A (BtxA), against a placebo in a randomized study of 82 patients. All patients receiving the drug showed significant improvement compared to the placebo group.
"Stiffness in their arms was reduced, painful muscle spasms were reduced or abolished, and the patients were able to sit or lie in bed more comfortably," says lead author A. M. O. Bakheit, M.D., professor of neurological rehabilitation at Mount Gould Hospital in Plymouth, England.
Spasticity is severe muscle stiffness that commonly occurs in the arms or legs after a person has a stroke. Only about 5 percent of stroke survivors who develop it regain full use of a paralyzed arm, according to the authors.
"Spasticity causes severe pain in the muscle, which does not respond to treatment with other drugs," says Bakheit. "It causes frequent spasms - jerky movements of the arms or legs - that can interfere with sleep or sitting in a chair. It can be so severe as to throw a stroke survivor off a chair."
Two pharmacological forms of botulinum toxin type A, one of seven types of a bacterial toxin that can cause fatal food poisoning, are currently available - Dysport and Botox. Because of differences between the two drugs in their formulation, the European team said its findings apply only to Dysport.
In Bakheit's view, the Dysport injections used in the study offer distinct advantages over oral drugs used to treat spasticity in stroke patients. The oral drugs reduce muscle tone throughout the body and sometimes patients are unable to sit or walk because the good muscles are affected as well as the paralyzed muscles, he says.
The oral medications also produce several debilitating side effects such as sleepiness and mental confusion. Patients often develop tolerance to these drugs quickly and require higher doses, which usually increases the side effects.
In contrast, the Dysport injection targets specific muscles without interfering with other muscles. And a single injection is effective for three to four months, which would eliminate the need for patients to take oral medications once a day or more.
BtxA prevents the release of acetylcholine, a chemical that enables muscles to contract and cause movement. It is prescribed to treat a number of muscle conditions, including uncontrolled squinting of the eyes, cerebral palsy, and even to smooth facial wrinkles.
Researchers at 11 medical centers in the United Kingdom and Western Europe undertook the trial after several small studies suggested botulinum toxin could help patients who develop spasticity following a stroke. They wanted to confirm the findings in a large trial as well as determine the appropriate dose.
The study was double blind, meaning that neither the physicians nor the stroke patients knew who received the drug and which ones got an injection of an inactive fluid. Nineteen patients were randomized to placebo; 22 received 500 units of Dysport; another 22 got 1,000 units; and 19 were injected with 1,500 units. Researchers measured the degree of muscle stiffness and the ability to function before injection and at 2, 4, 8, 12, and 16 week intervals.
"We found that the botulinum toxin was much more effective in relieving spasticity than was the placebo, and that the patients who got the 1,000 unit-dose appeared to do much better," says Bakheit.
The drug did cause some minor side effects, including a red rash and mild flu-like symptoms of runny nose, aching joints and a slight fever. "The toxin has been used since 1989 in most European countries and North America and reports of serious side effects are rare," Bakheit says.
Although the patients who received Dysport had significantly less muscle stiffness and pain, their overall ability to function normally at tasks such as washing, dressing, and using a toilet did not improve significantly. This finding was not unexpected because the drug did not strengthen muscle. In fact, muscles injected with Dysport were weakened slightly.
Bakheit sees an advantage for caregivers as well as patients in using Dysport. Limb stiffness can make if difficult to dress a person or to open the hands for cleaning. "When the muscles become relaxed, the caregiver is better able to help the patient put his or her arms through sleeves or to open the hands for washing or for cutting finger nails," he says.
Co-authors are A. F. Thilmann, M.D.; A. B. Ward, M.D.; W. Poewe, M.D.; J. Wissel, M.D.; J. Muller, M.D.; R. Benecke, M.D.; C. Collin, M.D.; F. Muller, M.D.; C. D. Ward, M.D.; and C. Neumann, M.D. NR00-1176 (Circ/ Bakheit)
Materials provided by American Heart Association. Note: Content may be edited for style and length.
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