An onabotulinumtoxinA injection into the pelvic floor sites with muscle spasms may alleviate pain in women with endometriosis, according to study results published in Regional Anesthesia & Pain Medicine.

The study included 13 women with surgically diagnosed endometriosis who were injected with 100 units of onabotulinumtoxinA transvaginally under electromyography guidance into areas of the pelvic floor experiencing muscle spasms. Participants received topical anesthetic and were injected under conscious sedation. Changes in pain intensity, muscle spasm, disability, and pain medication use were assessed at periodic visits for up to 1 year after injection.

Before the injection, 11 participants had spasm in >4 of 6 assessed pelvic muscles and reported moderate pain (median visual analog scale [VAS] score of 5 on a 1 to 10 scale; VAS score range, 2 to 7).

At 4 to 8 weeks after the injection, all participants had absent/less widespread (≤3 muscles) spasm (P =.0005). Post-injection pain was rated as absent/mild by 11 participants (median VAS score, 2; range 0 to 5; P <.0001). Of all the patients, 7 decreased their consumption of pain medication.

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Of the 8 participants with at least moderate pre-injection disability, 6 reported reduced disability after injection (P =.0033). Of the 11 participants who were followed for 1 year, relief was found to have lasted between 5 and 11 months. Many participants reported an interest in receiving additional injections after the study was completed as they had experienced substantial and prolonged relief.

The most common adverse event related to the injection was temporary pain at the injection site, which lasted <24 hours.

Study limitations include participant self-selection, a small sample size, and the focus on only 3 paired pelvic floor muscles.

“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,” noted the researchers.

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Reference

Tandon HK, Stratton P, Sinaii N, et al. Botulinum toxin for chronic pelvic pain in women with endometriosis: a cohort study of a pain-focused treatment. Reg Anesth Pain Med. 2019;44:886-892.