Botox may relieve persistent pelvic pain caused by endometriosis

A small study shows the toxin can lessen women’s pelvic spasms for months

Botox injection

PAIN POINT  Chronic pain in the pelvic floor from endometriosis, a disorder that affects an estimated 176 million women worldwide, may be relieved by Botox injections.

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For some women with endometriosis, the pain doesn’t stop after surgical and hormonal treatments. It can persist, triggered by muscle spasms that ripple through the pelvic floor. Now, a small study suggests that Botox, best known for smoothing wrinkles, could quell those spasms and relieve that pain.

Thirteen women diagnosed with the disorder, in which tissue similar to what lines the uterus grows elsewhere in the body, had the botulinum toxin injected into their pelvic floor, which supports the pelvic organs. The shots targeted areas of muscle spasm that were sites of pain. The women, ages 21 to 51, had been in pain for at least two years.

All reported a reduction in pain four to eight weeks after treatment. Eleven of the 13 rated their post-Botox pain as mild or completely gone, researchers reported online July 8 in Regional Anesthesia & Pain Medicine. Relief lasted from five to 11 months in seven of the 11 women followed for up to a year post injection.

Women in the study “had benefit beyond relief of pain. Some were able to resume having sex without pain. Some were able to function better,” says Barbara Karp, a neurologist at the National Institute of Neurological Disorders and Stroke (NINDS) in Bethesda, Md.

Eight of the 13 women had experienced moderate to very severe disability, according to a questionnaire designed to measure how the pain interferes with day-to-day activities such as walking, standing, sleeping, personal care and sex life. Six of these women’s scores indicated their disability had lessened after the injection.

Endometriosis affects an estimated 5 to 10 percent of reproductive-age women, or 176 million worldwide. Compounding the pain and infertility that accompanies the disorder is the lack of awareness of the condition; past studies have found that women face treatment delays and skepticism that they have a medical issue at all.

Standard treatments include hormone therapies and the surgical removal of tissue lesions located outside of the uterus. But there is no cure. Women who continue to have pain might be reassessed for surgery, change their hormone therapy, try physical therapy or take pain medications like opioids, says gynecologist Pamela Stratton, also at NINDS.

The participants in the study had had surgery and hormone treatments, but their pain persisted. All of the women also had pelvic floor muscle spasms.

Botulinum toxin is produced by the microbe that causes the food poisoning illness botulism. As Botox, it paralyzes certain muscles or blocks nerves. The toxin has been used to smooth wrinkles and to calm overactive muscles in neck spasms and bladder conditions (SN: 4/5/08, p. 213). Karp had experience using botulinum toxin to treat neurological disorders involving overactive muscles. So she, Stratton and their colleagues suspected Botox injections might also diminish the pelvic floor spasms and associated pain.

The results suggest that Botox may be “a promising tool” to treat these spasms, says obstetrician and gynecologist Andrea Rapkin of UCLA’s David Geffen School of Medicine, who was not involved in the study. But she notes the treatment is expensive, and the study size was very small.

Larger studies that compare the treatment to a placebo will be necessary to evaluate how safe and effective the botulinum toxin treatment is for this disorder. Whatever the outcome of those trials, the study “brings to light the fact that there are many aspects to endometriosis pain that have to be evaluated,” Rapkin says, not just that caused by tissue lesions.

Aimee Cunningham is the biomedical writer. She has a master’s degree in science journalism from New York University.

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