Transcranial electrical stimulation (tES) in chronic pain patients: effects on daily-reported symptoms.

Background: Transcranial electrical stimulation has yielded positive results for relieving pain in patients with chronic pain (CP), but the existing evidence is insufficient. In order to address some gaps in the literature, we conducted a randomized, double blind, sham-controlled clinical trial aimed at evaluating the feasibility and efficacy of home-based neurostimulation in a sample of 120 patients.

Methods: The patients completed 15 self-administered home-based sessions of either transcranial direct current stimulation (tDCS, n = 48), transcranial alternate current stimulation (tACS, n = 48), or sham stimulation (n = 24). The primary outcome variable, i.e., pain intensity, and related variables were assessed online (using numerical rating scales from 0 to 10) throughout 45 days (pre-treatment, treatment, and post-treatment periods each of 15 days).

Results: ANOVA (classical and Bayesian frameworks) and time series analysis consistently showed that both tDCS and tACS decreased the patients' daily reported pain intensity (tDCS: tau = -0.553; p < 0.001; tACS: tau = -0.563; p < 0.001), pain unpleasantness (tDCS: tau = -0.489; p < 0.001; tACS: tau = -0.537; p < 0.001), interference due to pain (tDCS: tau = -0.368; p < 0.001; tACS: tau = -0.424; p < 0.001), and other symptoms such as fatigue (tDCS: tau = -0.255; p = 0.02; tACS: tau = -0.556; p < 0.001) and stress/anxiety (tDCS: tau = -0.245; p = 0.02; tACS: tau = -0.685; p < 0.001). No such improvement was observed in the group receiving the sham stimulation. The home-based treatment was associated with low drop-out rates (6.66%) and moderate satisfaction with the procedure (around 5 out of 10 in all groups), and minimal adverse effects of transcranial electrical stimulation were reported.

Conclusions: tDCS and tACS significantly reduced daily-reported pain in chronic pain patients. Home-based intervention could significantly reduce the high economic burden associated with chronic pain management in healthcare systems. Inclusion of daily reports assessed by time series analysis can improve clinical trials in the field of chronic pain.

Study registration: ClinicalTrials.gov ID number: NCT05099406 (https://clinicaltrials.gov/study/NCT05099406?term=NCT05099406%20&rank=1).