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

Efficacy of Home-delivered Transcranial Direct Current Stimulation (tDCS) of the Motor Cortex in Patients With Chronic Pain Transiently Relieved by Motor Cortex rTMS : a Pragmatic Randomized Double Blind Sham Controlled Trial

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.

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.

Inclusion Criteria:

Chronic pain for at least 6 months Pain intensity ≥ 4/10 on 0-10 NRS Pain present every day or nearly every day Neuropathic pain (DN4 score ≥ 4/10) or nociplastic pain (Kosek et al Pain 2021) Patients previously treated with rTMS of the motor cortex in routine in our pain center but with only transient efficacy (ie, efficacy for less than one month, defined as pain intensity improved by at least 30 %) Affilitated to social security

Exclusion Criteria:

Contraindications to tDCS as stated in the manufacturer brochure (ie, implantable device , severe cognitive disorders, epilepsia, skin problems where will placed the electrodes, arterial or venous thrombosis, thrombophlebitis, metallic intracranial implant, cranioth-omy, incracranial aneuvrysm, cerebral tumor, severel sleep disorders such as narcolepsia) Conciomitant treatment which might increase the risk of epilepsia such as high doses opioids (≥ 140 mg morphine equivalent) or high. doses tricyclic antidepressants (≥ 150 mg per day) Pregnancy or lactation Age below 18 or > 80 years Pending litigation related to pain Pain more severe than neuropathic or nociplastic pain requiring treatment Severe disease such as cancer Severe psychiatric condition (psychosis) Impossible to be followed for up to 3 months Participation in a recent protocol (less than 3 months) Psychoactive drug abuse