BACKGROUND AND PURPOSE:

• Up to 23% of chronic pelvic pain may be atributable to myofascial pain
  • Sensitive pelvic floor muscles with trigger points | Associated with other significant pain disorders such as dyspareunia and interstitial cystitis
• Onabotulinumtoxin A has been used to treat pain disorders, but data is limited regarding myofascial pelvic pain
• Dessie et al. (AJOG, 2019) compared the effects of onabotulinumtoxin A versus placebo injections to the pelvic flood muscles of women with myofascial pain

METHODS:

• Double-blind, randomized, placebo-controlled trial (RCT)
• Participants
  • ≥18 years
  • Myofascial pelvic pain including reporting both of the following
    • Pain ≥6 on a 10-point visual analog scale (VAS) ≥50% of the time
    • Pain on palpation ≥6 on the VAS in ≥1 of 6 pelvic floor muscle groups
• Groups randomized to the following
  • Pelvic floor injection of 200 units of onabotulinumtoxin A
  • Pelvic floor injection of 20 mL of saline
• Physical therapy
  • Begun 4 weeks after injection for 8 weeks duration
• Validated questionnaires
  • Baseline and then 2, 4, and 12 weeks after injection
• Urogynecologist (blinded to treatment) examined patient with palpation of pelvic floor muscle groups
• Primary outcome
  • Change in participant-reported pain on palpation of the most painful pelvic floor muscle from baseline to 2 weeks
• Secondary outcomes: Changes in the following
  • Pain at 4 and 12 weeks | Overall self-assessment based on VAS | Quality-of-life questionnaires | Medication use | Physiotherapy compliance | Adverse events
• Statistical analysis
  • 24 participants per arm required to have 80% power to detect primary outcome effect (additional patients recruited to account for participant drop out)

RESULTS:

• 59 women were randomized
  • 30 participants in intervention group | 29 participants in placebo group
• No significant differences between the onabotulinumtoxin A and placebo groups were found for the following
  • Change in participant-reported pain at 2 weeks
  • Participant-reported pain on palpation for any muscle group at 4 or 12 weeks
• Participants in the intervention group were more likely to report their symptoms were improved at 4 weeks (p=0.03; based on the Patient Global Impression of Improvement index)
• Adverse events at 2 weeks
  • Most common: Constipation in both arms, with 10.1% reporting de novo constipation with no statistical difference between groups
  • 22% of the intervention group reported urinary incontinence (4 in the intervention group and 1 in placebo group)
  • Other complications occurred in <4 participants

CONCLUSION:

• Onabotulinumtoxin A injections to the pelvic floor did not result in improved pelvic pain outcomes on clinical exam, although some women did report improved symptoms

Learn More – Primary Sources:

A randomized, double-blind, placebo-controlled trial of onabotulinumtoxinA trigger point injections for myofascial pelvic pain

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