OnabotulinumtoxinA Injections for the Treatment of Myofascial Pelvic Pain: 12-year Experience at a Tertiary Care Academic Center

OBJECTIVE: The aim of this study was to highlight the safety of OnabotulinumtoxinA (BTA) injections, with or without concurrent pudendal nerve block, in treating women with myofascial pelvic pain (MFPP). DESIGN: This was a retrospective cohort study. SETTING: Tertiary care academic center PARTICIPANTS/MATERIALS: We conducted a chart review of patients who were diagnosed with MFPP and treated with BTA with or without pudendal nerve block between January 2010 and February 2022. METHODS: BTA was injected transvaginally into the pelvic floor muscle group. The primary outcomes were adverse events after BTA injections, and the secondary outcome was the effect of concomitant pudendal nerve block at the time of BTA injections. RESULTS: The cohort included 182 patients; 103 (56.6%) received BTA injections with pudendal nerve block, and 79 (43.4%) received BTA alone. There were no significant demographic differences between the two groups. Post-treatment complications of BTA administration included worsening of pelvic pain (11.5%), constipation (6.6%), urinary tract infection (2.7%), urinary retention (3.8%) and fecal incontinence (2.7%). No statistical difference was noted in the number of phone calls, patient-initiated electronic messages, emergency room visits, or clinic visits for both groups within 30 days post-treatment. The mean number of total injections was 1.6 in the BTA-only group and 1.7 in the BTA with pudendal block group (p=0.421). Median time to re-intervention with a second BTA injection was 6.0 months; 5.6 months in the BTA with pudendal block group and 6.8 months in the BTA-only group; p=0.46. There were 63 re-intervention events after BTA injections. LIMITATIONS: Limitations of our study include the retrospective design making it vulnerable to missing or incomplete data available for review CONCLUSION: OnabotulinumtoxinA is beneficial in treating women with MFPP; with a duration of therapeutic effect of approximately 6 months. The use of a concurrent pudendal nerve block did not impact clinical outcomes.