Efficacy of transcranial direct-current stimulation in women with provoked vestibulodynia

Abstract

Abstract: Background: Provoked vestibulodynia (PVD) is a highly prevalent condition characterized by acute recurrent pain located at the vaginal entrance in response to pressure application or attempt of vaginal penetration. Despite a wide variety of treatments offered to women with PVD, a high proportion of women are refractory to conventional treatment. Transcranial direct-current stimulation (tDCS) is a non-invasive brain stimulation technique that has been shown effective for improving various chronic pain conditions. Growing evidence suggests that the central nervous system (CNS) could play a key role in PVD. Targeting the CNS could be a promising treatment avenue for women suffering from PVD. Objective: The purpose of this study was to evaluate and compare the efficacy of active and sham tDCS in reducing pain intensity during intercourse in women with PVD. Study design: We conducted a triple-blind, parallel group, randomized controlled trial (RCT). Women, aged between 17-45 years and diagnosed with PVD by a gynecologist using a validated protocol were randomized to 10 sessions of either active tDCS (intensity = 2mA) or 10 sessions of sham tDCS, over a 2-week period. Both active and sham tDCS were applied for 20 minutes, with the anode positioned over the primary motor cortex (M1), and the cathode, over the contralateral supraorbital area. Outcome measures were collected at baseline, 2 weeks after treatment and at 3-month follow-up by an evaluator blinded to group assignation. The primary objective was pain intensity during intercourse, as assessed with a numerical rating scale. Secondary outcomes focused on sexual function and distress, vestibular sensitivity, psychological distress, treatment ,satisfaction and patient impression of change. Statistical analyses were conducted on the intention-to-treat basis, and treatment effects were evaluated using a mixed linear model for repeated measures. Results: A total of 40 women were randomly assigned to received either active (n=20) or sham (n=20) tDCS treatments between November 2014 and February 2016. Baseline characteristics were similar between active and sham tDCS groups. Active tDCS did not significantly reduced pain during sexual intercourse compared to sham tDCS 2 weeks after treatment (p=0.84) and at follow-up (p=0.09). Mean [95% CI] baseline and 2-week assessment pain intensity were respectively 6.8 [5.9 - 7.7] and 5.6 [4.7 - 6.5] for active tDCS (p=0.03) versus 7.5 [6.6 - 8.4] and 5.7 [4.8 - 6.6] for sham tDCS (p=0.001). Non-significant differences between the two groups were also found in regards to sexual function and distress after treatment (p>0.20) and at follow-up (p>0.10). Overall, at 2-week assessment 68% women assigned to active tDCS reported being very much, much or slightly improved compared to 65% of women assigned to sham tDCS (p=0.82), and still comparable at follow-up 42% versus 65%, respectively (p=0.15). Conclusion: Findings suggest that active tDCS is not more effective than sham tDCS for reducing pain in women with PVD. Likewise, no significant effects were found on sexual function, vestibular sensitivity or psychological distress.