Within the umbrella term of Genito-Pelvic Pain/Penetration Disorder, lifelong vaginismus is a condition in which difficulty and/or pain has limited or precluded initial and ongoing attempts at vaginal coitus/intercourse or insertion of objects such as a tampon or speculum, reportedly affecting between 6%-17% of cis-gender women. Agreed-upon treatments do not exist, though vaginal trainers (VT, commonly known as dilators) are often used to treat this condition. Transcranial direct current stimulation (tDCS) is a type of neuromodulation used to treat muscle dystonia, spasm, and pain [1]. Vaginismus involves the pelvic floor muscles (PFM) and is similar in its clinical presentation to dystonias (involving unwanted muscle contractions or spasm) and to chronic pain, both of which can be successfully treated with brain stimulation. Evidence for PFM primary motor cortex representation (voluntary control) appears to be located at the superomedial precentral gyrus near that of the lower limb, which has been shown to be successfully targeted with an M1SO montage (using saline electrodes) of anodal tDCS at 2mA for 20 minutes followed by a lower extremity behavioral task [2]. 

The AIMS of this original research study were to compare the effect of using sham and active tDCS on the following:

1) PFM surface electromyography (sEMG) (using PathwayTM NMR400 Synergy 3D software, per Glazer protocol of 1-minute resting baseline, 10 repetitions of rapid contractions, 10 repetitions of 10-second isometric endurance contractions, one repetition of a 60-second contraction, and a final 1-minute resting baseline).

2) Secondary measures of pain (measured with discrete numerical rating scale (0-10) during vulvar cotton swab mapping), muscle tone (rated with digital palpation on a discrete -5 to +5 scale, with -5 to -1 indicating decreased tone; 0="normal" tone; and +1 to +5 indicating increased tone), vaginal trainer (VT) accommodation (volumetric measurements in mm3 calculated based on VT length and circumference insertion) and questionnaires, including the Female Sexual Function Index (FSFI), Pain Catastrophizing Scale (PCS), and Beck Depression Inventory (BDI)).

This original research project was a parallel randomized controlled trial and used a double-blinded, mixed model design. Participants were randomized to two parallel groups of sham or active tDCS groups, both receiving the same behavioral intervention of VT insertion (with clinician guidance for breathing and pelvic floor muscle contract-relax techniques to promote pelvic floor muscle relaxation [3] and control) three times a week for four weeks (12 visits total). Participants and the clinician administering vaginal trainer behavioral treatment and outcomes measures were both blinded to randomization, which was computer generated with allocation maintained by a research assistant who also ran the tDCS equipment. Data was collected between November 2018 and March 2020 at an outpatient pelvic health-focused physiotherapy/physical therapy clinic. Participants were recruited from a convenience sample of patients seeking treatment for lifelong vaginismus, and included women ages 18-40 years who completed informed consent, not in menopause, not pregnant, self-report of vaginismus for 6 months or longer, currently attempting to be sexually active, having an FSFI score of 26.55/36 or less, and having intact scalp skin for electrode placement. Participants were excluded if they were pregnant, had scalp skin abrasions, seizure disorder, not attempting to be sexually active at the time of the study, had an active pelvic or urinary tract infection, had a personal history of urogenital or colon cancer, had a history of radiation treatment in the pelvis or abdomen, or did not meet all of the inclusion criteria. Comparisons between and within subjects were made before and after treatment, over time and from baseline to a one-month follow up depending on the study measure. Analyses were performed by a blinded biostatistician using SAS v9.4. Continuous variables (demographic data) were analyzed by t-test or by the Wilcoxon Rank Sum Test. Categorical variables were analyzed by the Fischer Exact Test when cell counts were lower than expected. Additional models were used to explore the interactions of group, time, and session.

The study was completed by 17 cis-gender women (22 qualified; 19 enrolled; 2 dropped out due to illness/scheduling issues, including 1 from both the active and the sham tDCS groups), with 9 completing the study who were randomized to the active tDCS + VT group, and 8 completing the study who were randomized to the sham tDCS + VT group. No adverse events were reported with active or sham tDCS or vaginal trainer use. There was no significant difference between groups in terms of age, time since symptom onset, race, ethnicity, or relationship status (all being married or in committed partnerships). Sham was also shown to be effective in this study. For the primary measure of pelvic sEMG, within the active tDCS group, there was a significant improvement in the ability to match a square wave with 10-second isometric contractions (p=.0457 at 9th visit, p=.0023 at 12th visit, p=.0141 at follow up). There were no other significant findings between or within groups for any other EMG findings. With active tDCS, there were significantly decreased cotton swab mapping pain reports at the end of sessions compared with the beginning of sessions (p=.0038), which was not seen with sham; however, there were overall low frequencies of pain report with cotton swab mapping amongst all participants. Over time (comparing 1st and 12th visits), both groups reported decreased pain at the beginning and end of sessions (p=.0303). Muscle tone significantly improved within sessions in active versus sham tDCS (p=.0118). Over time, muscle tone improved in both groups between earlier and later visits (p<.0258). Both groups improved significantly and equally in terms of VT accommodation over time (comparing between 1st and later visits/follow up, p<.0312). Both groups also had significant improvements in self-report measures between the 1st visit and follow up of sexual function (FSFI, p<.0001), pain (FSFI pain domain, p<.0001; and PCS, p<.0001), and affect (BDI, p=.0016).

The results of this study indicate that the pelvic floor muscle insertional/receptive difficulty and pain related to vaginismus may involve dysfunction at a supraspinal/cortical level, as demonstrated by the significant improvement in pelvic floor muscle control with a 10-second isometric contraction (demonstrated by surface EMG of the PFM) in the active tDCS group. This study demonstrates that vaginal trainers can be effective as treatment when combined with contract-relax behavioral intervention, and that tDCS can further augment these results.

Active tDCS appears to have augmented VT by improving muscle control and reducing pain. The behavioral VT treatment protocol (with breathing coordination and pelvic floor muscle contract-relax techniques) also proved to be effective as a stand-alone treatment for pain, muscle tone, VT accommodation, and outcomes questionnaires related to sexual functioning, depressive symptoms, and pain catastrophizing.

Rosset-Llobet, J., Fabregas-Molas, S., & Pascual-Leone, A. (2015). Effect of Transcranial Direct Current Stimulation on Neurorehabilitation of Task-Specific Dystonia: A Double-Blind, Randomized Clinical Trial. Med Probl Perform Art, 30(3), 178-184. doi:10.21091/mppa.2015.3033
Floyd JT, Lairamore C, Garrison MK, et al. Transcranial Direct Current Stimulation (tDCS) Can Alter Cortical Excitability of the Lower Extremity in Healthy Participants: A Review and Methodological Study. Front Neurol Neurosci. 2020;1: 1-12.
Kay AD, Dods S, Blazevich AJ. Acute effects of contract-relax (CR) stretch versus a modified CR technique. Eur J Appl Physiol. 2016;116(3): 611-621. doi:10.1007/s00421-015-3320-8.

Continence 7S1 (2023) 100820
DOI: 10.1016/j.cont.2023.100820