Bayesian analysis of the effect of transcranial direct current stimulation on experimental pain sensitivity in older adults with knee osteoarthritis: randomized sham-controlled pilot clinical study.

Purpose: Previous studies have indicated that transcranial direct current stimulation (tDCS) with the anode over the motor cortex and the cathode over the contralateral supraorbital region is effective in reducing clinical pain in patients with chronic pain, but these studies have not focused on experimental pain sensitivity. Therefore, the aim of this study was to examine the effect of tDCS on experimental pain sensitivity in older adults with knee osteoarthritis (OA).

Patients and methods: Forty community-dwelling participants aged 50-70 years with knee OA pain were randomly assigned to receive five daily sessions of 2 mA tDCS for 20 minutes (n = 20) or sham tDCS (n = 20) using a parallel group design. A multimodal quantitative sensory testing battery was completed, including heat pain, pressure pain threshold (PPT), punctate mechanical pain, and conditioned pain modulation (CPM).

Results: The active tDCS group showed greater increases in heat pain thresholds and tolerances, PPTs, and CPM, and reductions in punctate pain. In addition, beneficial changes in experimental pain measures were associated with reductions in clinical pain. Future studies are needed to extend these findings to better understand the underlying mechanisms of tDCS as well as to optimize treatment parameters including number and duration of stimulation sessions.

Conclusion: Our findings demonstrate that tDCS reduces experimental pain sensitivity, and these beneficial changes in experimental pain measures were associated with reductions in clinical pain.