Efficacy of Home-delivered Transcranial Direct Electrical Stimulation or Chronic Pain

This clinical investigation aims to evaluate the efficacy and safety of a home-based device providing electrical stimulation of the brain named transcranial direct current stimulation (tDCS ) , in patients with chronic pain who have been transiently relieved by repetitive transcranial magnetic stimulation delivered at hospital (less than one month benefit). The general objective is to show that these patients may best benefit from home based tDCS while rTMS performed in hospital has only limited and transient efficacy. Each participant will be randomized into one of two arms to receive during 3 months either active tDCS or sham tDCS. Neither the investigator nor the patient will be aware of the treatment. The efficacy will be assessed on pain intensity (primary outcome at 3 months) and several secondary outcomes (qualify of life, pain symptoms , global impression of change, pain relief, sleep, anxiety, depression) every month for up to 3 months. Safety will be assessed at each follow up visit for up to 3 months. The participants will be asked to self stimulate themselves with the device 5 days per week for about 20 minutes.