Transcranial Direct Current Stimulation in Parkinson's Disease Patients in the Off State : A Randomized Controlled Crossover Trial Examining the Effects on Pain With and Without the Influence of Dopaminergic Medication

Share

Abstract

Background: tDCS has demonstrated hypoalgesic effects on Parkinson's disease (PD)-related pain applied in the On state but not in the Off state. We aimed to determine the effect of tDCS in the Off state followed by dopaminergic medication on PD-related pain. Methods: This randomized controlled crossover trial included 15 patients (age range 39–81, 5 male) with PD-related pain in the Off state. All participants received both an active and sham tDCS sessions of 20 min over the M1 contralateral to pain at 2 mA intensity in two separate days while in Off state. Following tDCS they took its dopaminergic medication. Outcome measures were assessed at baseline, post-tDCS and post-medication intake. The Numeric Pain Rating Scale (NPRS), Global Rating Of Change (GROC), Conditioned Pain Modulation (CPM), Pain Pressure Thresholds (PPT) and Widespread Mechanical Hyperalgesia (WMH) were evaluated. Results: No significant differences were found after active tDCS in NPRS, GROC, CPM, PPT's or WMH when compared to sham at post-medication intake measure. However, examining exclusive effects of tDCS in the Off state for NPRS, active tDCS was superior to sham tDCS (p = 0.037). No meaningful changes between stimulation conditions were found in GROC, CPM, PPT's and WMH at post-tDCS measure. Conclusions: One session of tDCS over the M1 alleviates pain perception in PD patients in the Off state. However, tDCS followed by dopaminergic medication intake does not yield additional benefits in pain processing suggesting pathways different to dopaminergic ones in pain regulation in PD patients. These findings are exploratory and carry high risk of type-II error. Trial Registration: clinicaltrials.gov identifier: NCT06214377.