Botulinum toxin injection for chronic pelvic pain: A systematic review

Botulinum toxin has proven therapeutic effects in alleviating pain in several myofascial disorders, with an expanding potential in chronic pelvic pain. The objective of this systematic review is to evaluate the efficacy and safety of botulinum toxin injection as an off-label treatment for female chronic pelvic pain.

Using PRISMA guidelines, MEDLINE, EBM Reviews, PubMed, CINAHL, TRIP Database, EMBASE, Web of Science and gray literature were searched. Studies assessing the efficacy of botulinum toxin for chronic pelvic pain in adult females, with 10 or more women, published in English up to 13 January 2020, were included. All eligible studies were reviewed and data were extracted by two independent reviewers using a standardized form. Quality of evidence was graded using the Cochrane Risk of Bias 2 tool for randomized controlled trials and the Ottawa-Newcastle scale for observational studies.

In all, 491 records were screened. Seventeen articles were included in the final review: 5 randomized controlled trials and 12 observational studies. The quality of evidence ranged from low to high. There was a large degree of heterogeneity in study designs, and thus a meta-analysis was not feasible. All observational studies concluded that botulinum toxin was an effective treatment for chronic pelvic pain, with the greatest change in visual analog scale from 8.69 at baseline to 3.07 at 24 months post-injection. However, only one of the five randomized controlled trials found statistical significant differences favoring botulinum toxin in the reporting of the EQ-5D (botulinum 0.78 [0.69-1.00], control 0.69 [0.25-0.81], P = .03) and frequency of intercourse (botulinum 1 [1-1.75], placebo 1 [0-1], P = .025). The most common adverse effect was transient localized pain at injection site (6%-88%). No serious adverse events were reported.

Although observational studies were encouraging, there is insufficient high quality evidence to recommend botulinum toxin injection for chronic pelvic pain. However, it appears to be safe to use. Future studies of higher quality in its treatment efficacy are indicated.