Injected into a localized area and in extremely low concentrations, the potent toxin botulinum A blunts the nerve endings responsible for muscle spasms. For patients receiving treatment at the LSU Pain Management Service, researchers found that this therapy significantly decreased patients' muscle pain; increased their range of motion; and improved their ability to perform routine activities, such as washing and dressing.

The medication derived from botulinum has been used for several years to treat writer's cramp, tremors, eye muscle problems and other conditions marked by muscle spasms. The medication is used by some plastic surgeons to minimize wrinkles as well.

"Pain management specialists also reported success with botulinum for chronic low back pain, but few clinical studies have been done," Professor and Chair of Anesthesiology Randall C. Cork, M.D., Ph.D., said.

The LSU study included 19 patients, nine of whom received two injections of botulinum toxin into both sides of the lower back and 10 patients who had not received treatment for their back problems.

All patients completed questionnaires regarding the intensity of their pain and the impact of that discomfort on their ability to function. The researchers also rated range of motion and severity of muscle spasms in the experimental group before treatment.

The group receiving botulinum reported significant reductions in pain, improvements in their ability to function, and fewer muscle spasms. The other group reported an increase in pain and no improvement in muscle spasms.

"Unlike acute back pain, which tends to resolve on its own, chronic back pain tends to worsen over time due to a vicious, self-perpetuating cycle of muscle spasms," Dr. Cork said. "This study shows botulinum effectively breaks that cycle."

Botulinum injections begin working in two to three days, but their effects can last for months, Dr. Cork said. One drawback is the medication's tendency to become less and less effective with repeated injections as the body builds up antibodies to the toxin. "But most patients never need another injection," he said. Anesthesiologists at the LSU pain service may administer up to three injections for patients whose pain persists.