Botulinum toxin injections were found to relieve chronic pelvic pain in women with endometriosis, suggesting that pelvic floor spasms may significantly contribute to endometriosis-linked pelvic pain, according to study results published in Regional Anesthesia & Pain Medicine.

In an open-label, proof-of-concept case series ( Identifier, NCT01553201), investigators aimed to determine whether botulinum toxin injections reduce pain and muscle spasm in women with surgically recorded endometriosis who experience chronic pelvic pain despite hormonal and surgical interventions.

Following administration of up to 10 mg oral diazepam and 4% lidocaine cream to the vaginal mucosa above the spasms, participants underwent transvaginal injection of onabotulinumtoxinA into pelvic floor muscle spasms; 100-unit vials were suspended in saline and administered to 3 or 4 preidentified areas of spasm. Measures of pain, muscle spasm, disability, and pain medication use were recorded at patient visits up to 1 year postinjection.

Of the 13 women included in the study, 11 experienced moderate pain and muscle spasms in more than 4 of 6 monitored pelvic muscles. All participants reported complete or significantly reduced spasms by 4 to 8 weeks following injection; 11 women reported absent or mild pain, 7 women reduced pain medication use, and 6 women experienced a decrease in disability.

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After treatment, 7 of the 11 women who experienced muscle spasms were followed for up to 1 year and reported 5 to 11 months of lasting relief.

“This study provides preliminary evidence that in women with evidence of pain arising from pelvic floor muscles, this approach might best be considered after the visceral aspects driving their pain have been managed, possibly with suppression of menses, and optimization of bowel and bladder function,” the investigators noted. “Importantly, this procedure may offer an opportunity to reduce opioid use. This intervention may then be incorporated into the chronic pain model of care, enabling a precision medicine approach with individualized, multifaceted treatment.”

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Tandon HK, Stratton P, Sinaii N, Shah J, Karp BI. Botulinum toxin for chronic pelvic pain in women with endometriosis: a cohort study of a pain-focused treatment [published online July 8, 2019]. Reg Anesth Pain Med. doi:10.136/rapm-2019-100529