Transcranial Direct Current Stimulation for Treating Parkinson´s Disease-related Pain in OFF State

The Starstim tCS® equipment will be used, with 35 cm2 sponge electrodes. The tDCS over M1 will be performed by placing the active anode on the C3 point (10/20 EEG system) and the cathode on the contralateral supraorbital area (Fp2). Regarding the stimulated hemisphere, in cases of asymmetric pain, it will be applied to the contralateral M1, and in cases of bilateral pain, it will be applied to the M1 of the dominant hemisphere. A constant current of 2 mA (subthreshold intensity) will be applied for 20 minutes, with the first 30 seconds used as a ramp-up and the last 30 seconds as a ramp-down. Number of sessions: 1.

The Starstim tCS® equipment (Neuroelectrics Inc, Barcelona, Spain) will be used with 35 cm2 sponge electrodes. The tDCS sham over M1 will be performed by placing the electrodes in the same position as in the active tDCS protocol. However, the stimulator will automatically turn off after 30 seconds of stimulation, making it a reliable sham stimulation method. Therefore, subjects will feel the same tingling sensation but will not receive current for the remainder of the stimulation time.

After tDCS, the participant will take their regular dopaminergic medication in order to go from OFF state to ON state.