December 6, 2005

Botox Injections Show Promise for ‘Tennis Elbow’

By Amy Norton

NEW YORK (Reuters Health) - The wrinkle fighter Botox may serve up a new therapy for the chronic pain of "tennis elbow," a new study suggests.

Researchers in Hong Kong found that among 60 adults with stubborn cases of tennis elbow, a single injection of botulinum toxin type A relieved some patients' pain for up to three months.

The findings, published in the Annals of Internal Medicine, add to the list of the conditions that are potentially treatable with botulinum toxin -- better known as Botox, one of its brand names.

Though Botox became a household name for its ability to smooth frown lines, the substance has long been used to treat the uncontrolled muscle contractions that mark a number of medical conditions, like cerebral palsy and chronic eye-muscle spasms.

Botox is a purified form of the toxin that causes botulism food poisoning. When injected in small doses, botulinum toxin helps relax spastic muscles by preventing nerve cells from releasing a chemical that triggers muscle contractions.

A number of recent studies have also suggested that Botox may aid chronic pain, including conditions like migraine and lower back and neck pain.

The new study is the first to find that botulinum toxin injections outperformed a placebo in the treatment of tennis elbow. In this case, injections of plain saline served as the placebo.

Tennis elbow, known medically as lateral epicondylitis, is an overuse injury to tendons in the outer side of the elbow. As the name implies, it often arises in racquet-sport enthusiasts, but it can also result from other repetitive arm motions, such as using a screwdriver, hammering or painting.

There are many options for treating tennis elbow, including rest, anti-inflammatory pain medications, braces and injections of corticosteroids. But in studies, only anti-inflammatory lotions or ointments have proven effective, Dr. Shiu Man Wong told Reuters Health.

For their study, Wong and colleagues at the Chinese University of Hong Kong and Prince of Wales Hospital recruited 60 adults who'd suffered tennis elbow pain for at least three months. Half received a single injection of botulinum toxin type A in the affected area, and half were injected with saline.

One month and three months later, patients who'd received the toxin showed greater improvements in their pain than placebo patients did, the researchers found. In the botulinum toxin group, the average score on a standard pain-rating scale fell from 65.5 to 23.5 over three months. Among placebo patients, the average score dipped from 66.2 to 43.5.

For a few patients, though, the toxin did cause muscle weakness in the fingers; muscle weakness is a typical side effect of Botox in general.

More studies are needed to confirm the toxin's effectiveness for tennis elbow, Wong said. It's not clear why it may aid the condition, but direct analgesic effects may be at work, according to the researcher.

In tests of grip strength, Wong noted, there were no overall differences between the two study groups - suggesting that the pain relief was not just a product of reduced muscle tension around the elbow.

Botulinum toxin may eventually prove useful for painful conditions like chronic headache and tennis elbow, according to Dr. Seth L. Pullman of Columbia University in New York City. But for now, doctors should reserve it for conditions marked by abnormal muscle spasms, he writes in an accompanying editorial.

SOURCE: Annals of Internal Medicine, December 6, 2005.