A Randomized, Double-Blind, Controlled Trial Shows that Onabotulinum Toxin A Nerve Blocks do Not Provide Improved Pain Control in Men with Chronic Scrotal Pain

Abstract

Purpose: The use of onabotulinum toxin A to chemically denervate the testis has been studied as a minimally invasive therapy to treat chronic scrotal pain. To our knowledge no randomized, controlled trials of onabotulinum toxin A for chronic scrotal pain management have been reported to date.

Materials and methods: In this double-blind, randomized, controlled trial men with chronic scrotal pain who achieved at least temporary pain relief following a cord block with local anesthesia were randomly assigned to a block using local anesthesia alone vs local anesthesia plus 200 IU onabotulinum toxin A. Standardized assessments of pain levels using a visual analogue score, disease impact, quality of life and mood were performed 1, 2, 3, 4, 12 and 18 weeks after injection. The study primary outcome was the change in the visual analogue score at 1 month. After study completion the men in the control group were given the option to receive onabotulinum toxin A as part of an open label trial.

Results: Of 64 men with a mean ± SD age of 45.9 ± 11 years and a mean 5.7 ± 5.7-year history of pain 32 received local anesthesia plus onabotulinum toxin A and 32 received local anesthesia alone. There was no statistically significant difference in any measured outcome when comparing those who received onabotulinum toxin A to controls. Nine of the 13 men (69.2%) in the open label trial achieved an improvement in the visual analogue score (mean group score 6.1 ± 1.66 to 4.5 ± 2.36, Student t-test p=0.022) with a reduction in persistent pain at 3 months in 6 of the 9 (66.7%).

Conclusions: This randomized, double-blind, controlled trial showed no superiority of onabotulinum toxin A plus local anesthesia over local anesthesia alone for pain control in men with chronic scrotal pain. Interestingly, significant pain improvement was noted in our open label onabotulinum toxin A trial, suggesting a potential placebo effect.

Keywords: botulinum toxins; nerve block; pelvic pain; scrotum; testis; type A.