Background and objectives Many women with endometriosis continue to have pelvic pain despite optimal surgical and hormonal treatment; some also have palpable pelvic floor muscle spasm. We describe changes in pain, spasm, and disability after pelvic muscle onabotulinumtoxinA injection in women with endometriosis-associated pelvic pain, a specific population not addressed in prior pelvic pain studies on botulinum toxin.
Methods We present an open-label proof-of-concept case series of women with surgically diagnosed endometriosis. Under conscious sedation and with topical anesthetic, 100 units of onabotulinumtoxinA was injected transvaginally into pelvic floor muscle spasm areas under electromyography guidance. Changes in pain intensity, muscle spasm, disability, and pain medication use were assessed at periodic visits for up to 1 year after injection.
Results Thirteen women underwent botulinum toxin injection and were followed for at least 4 months. Before injection, 11 of the 13 women had spasm in >4/6 assessed pelvic muscles and reported moderate pain (median visual analog scale (VAS): 5/10; range: 2–7). By 4–8 weeks after injection, spasm was absent/less widespread (≤3 muscles) in all (p=0.0005). Eleven rated their postinjection pain as absent/mild (median VAS: 2; range: 0–5; p<0.0001); 7/13 reduced pain medication. Disability decreased in 6/8 women with at least moderate preinjection disability (p=0.0033). Relief lasted 5–11 months in 7 of the 11 patients followed for up to 1 year. Adverse events were mild and transient.
Conclusions These findings suggest pelvic floor spasm may be a major contributor to endometriosis-associated pelvic pain. Botulinum toxin injection may provide meaningful relief of pain and associated disability.
Trial registration number NCT01553201
- botulinum toxin
- chronic pelvic pain
- pelvic floor
- muscle spasm
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Funding Botulinum toxin and funds for study monitoring were provided by Allergan through a Clinical Trials Agreement with the National Institutes of Health. This work is supported by the Intramural Research Programs of the Clinical Center, the National Institute of Neurological Disorders and Stroke, and the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
Competing interests BIK is also an investigator on one study for which the NIH has received a grant from Allergan and another study for which the NIH has received a grant from Merz.
Patient consent for publication Not required.
Ethics approval The clinical trial (NCT identifier: NCT01553201) was approved by the Institutional Review Board of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.
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