This will be a randomised, double-blind, parallel-group, bi-centric study versus placebo stimulation. Patients undergoing previous treatment with rTMS of the motor cortex in routine in our pain center and with at least 30 % pain relief with rTMS (after 10 sessions) but only transient pain relief (less than one month) will stop their treatment for at least one month. They will then be randomised to receive one of the 2 treatments under study (active tDCS of the motor cortex, placebo tDCS of the motor cortex, TENS eco plus). The protocol will involve a 20-minute tDCS session (2 mA) at home, 5 days a week for 12 weeks. The treatment will continue for 12 weeks and the final evaluation will take place at 12 weeks.
TENS ECO PLUS is a portable transcranial direct current stimulation (tDCS) system (tDCS kit) supplied by the Monath Electronic laboratory, designed for use at home; this system will first be tested in hospital during a test session with explanations to the patient on how to use it. The stimulation intensity is blocked above a certain threshold by the system to avoid any risk of epileptic seizure. Sham or placebo stimulation uses the same medical device without active stimulation.
Given the exploratory nature of the trial and in order to reduce study participant's exposure to a potentially useless treatment, blinded interim analysis will be conducted dring the course of the trial in the first 40 enrolled patients and the study will be stopped early if this analysis suggests large differences between the two treatment groups or conversely shows obvious futility.