NIH scientists identify spasm in women with chronic pelvic pain associated with endometriosis

Press release

Thursday, July 11, 2019

A small study suggests that botulinum toxin could be a potential treatment.

Pelvic pain associated with endometriosis often becomes chronic and can persist (or recur) as a result of surgeries and hormonal interventions. According to the results published in Regional Anesthesia & Pain Medicine, treatment of pelvic floor muscle spasms with botulinum toxin could relieve pain and improve quality of life. The study was conducted by scientists from the National Institute of Neurological Disorders and Stroke (NINDS), which is part of the National Institutes of Health.

"Injections of botulinum toxin have been incredibly effective in reducing pain levels, as well as the use of pain medication by patients, including opioids," said Pamela Stratton, MD, a gynecologist and scientist at NINDS, who led the study with Barbara Karp, MD, neurologist and program director at NINDS. "Many women in our study reported that the pain had a profound effect on their quality of life and that this treatment could perhaps help them return to a normal life."

Endometriosis occurs when the uterine lining develops outside the uterus and is estimated to affect up to 176 million women worldwide. It is an inflammatory condition that can lead to infertility and cause chronic pain. The usual gynecological treatments include hormone therapy and surgery to remove growths. However, in many cases, the pain returns after the interventions.

In the study, women with endometriosis who underwent surgical treatment, usually taking hormones to suppress menses, but who continued to experience pain and pelvic floor spasms, initially received injections of botulinum toxin or saline in the setting of a clinical trial spasm areas. At least one month after the masked injection of the study, 13 participants opted to receive open injections of botulinum toxin in areas where spasm remained and were followed for at least four months. These patients have been described in the current study at the NIH Clinical Center.

In all participants, during follow up, no spasm of pelvic floor muscles was detected or occurred in fewer muscles. Within two months of receiving the injections, pain was reduced in all participants, with 11 out of 13 reporting that their pain was mild or had disappeared. In addition, the use of pain medication was reduced in more than half of the participants. Before receiving injections of toxins, eight participants reported moderate or severe disability and, after treatment, six of these patients reported improvement.

Participants experienced a decrease in muscle spasms and pain relief that resulted in fewer disabilities and less use of painkillers. These results suggest that women with endometriosis may experience pelvic floor muscle spasm and contribute to persistence of pain after standard treatment. Importantly, the beneficial effects have been long-lasting, with many patients reporting pain relief for at least six months.

Botulinum toxins, such as Botox, block the nerve signals of muscle contraction and have been used to treat migraines and certain movement disorders. Previous research has suggested that botulinum toxin may help women with other types of chronic pelvic pain, but this treatment has not been studied in women with endometriosis.

"We know that many doctors use botulinum toxin to help their patients, but each uses slightly different techniques and methods, including different brands of toxin and different doses. This study will begin to provide rigor to help set up standardized protocols and treatment for pelvic pain, "said Dr. Karp.

Larger clinical studies will need to confirm the current results. In addition, future research will focus on the mechanisms underlying chronic pelvic pain and a better understanding of how botulinum toxin might help treat these disorders.

NINDS is the largest funder of brain and nervous system research. NINDS 'mission is to research fundamental knowledge about the brain and the nervous system and to use it to reduce the burden of neurological diseases.

About the National Institutes of Health (NIH):
The NIH, the country's medical research agency, has 27 institutes and centers and is part of the US Department of Health and Human Services. NIH is the lead federal agency that leads and supports basic, clinical and translational medical research. She studies causes, treatments and cures for common and rare diseases. For more information on NIH and its programs, visit www.nih.gov.

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