Proposed Methods for Sham-Controlled Transcranial Magnetic Stimulation Trial in Surgical Facial Pain Patients

Abstract

Abstract Introduction: Although several studies have investigated the efficacy and safety of transcranial magnetic stimulation (TMS) for pain relief in chronic orofacial pain disorders (COFP), significant variability in stimulation methodology and a lack of sham-controlled, double-blinded studies limit the conclusions which can be drawn from this literature. Objective To review the current literature on the use of TMS for COFP and propose an optimal, sham-controlled, double blinded randomized trial. Additionally, this study design is novel in its application of this treatment to a population of COFP patients whose pain can not be controlled pharmacologically during the vulnerable pre-surgical period. Proposed Methods: 34 COFP patients with poor pain control who are awaiting neurosurgical intervention will be randomized evenly into either the sham or true TMS condition and receive 5 consecutive days of treatment. Each stimulation session will be a train of 100 20-Hz pulses once per minute for 10 minutes focused on the contra-lateral M1 Hand area, a protocol and target which showed the most promise in prior studies. The sham condition will be achieved by using a sham-capable TMS coil and replicating the scalp sensation of stimulation using transcutaneous electrical nerve stimulation electrodes toggled on or off by a single unblinded study coordinator. The primary outcome measure will be change in reported pain on the Short Form McGill Pain Questionnaire (SFMPQ), completed by participants at several timepoints. Change in SFMPQ composite scores over time between groups may be analyzed with a repeated ANOVA among other exploratory analyses. Conclusion These proposed methods represent the most rigorous investigation of TMS for COFP-related pain that the authors are aware of. By combining the use of a sham condition, double-blinding, and the most promising stimulation protocol according to current literature, the results of this study would yield near-definitive evidence of TMS efficacy. Additionally, such a study could inform whether the adoption of TMS as a pre-surgical intervention might provide pain relief in this especially vulnerable setting.