Chronic Neuropathic Pain in MS Reduced by Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) reduced chronic neuropathic pain in patients with multiple sclerosis (MS), according to findings from a randomized controlled single-blinded study published in Pain Medicine.

Patients with MS (N=30) were recruited in Melbourne, Australia, and randomly assigned to receive a 5-day course of tDCS (n=15) or sham treatment (n=15). The tDCS consisted of a 2 mA constant current that was applied for 10 minutes followed by no stimulation for 25 minutes and another 10-minute stimulation period. The sham treatment had the same setup but current stimulation was only applied for 30 seconds. All participants were assessed for pain using the visual analog scale (VAS), Neuropathic Pain Scale, Depression Anxiety Stress Score, Short Form McGill Pain Questionnaire, and MS Quality of Life 54 measure.

The baseline characteristics of the study groups were similar. Overall, in both the sham and treatment groups, participants were mostly women (86% vs 73.3%, respectively), a majority had their MS diagnosis for >10 years prior (60% vs 80%, respectively), and the most common site for reported pain was in the lower extremities (bilateral: 33.3% vs 46.7%, respectively; unilateral: 40% vs 26%, respectively).

After the first 4 days of treatment, VAS scores had declined significantly among participants in the treatment group (P =.01) and remained significantly lower up to 2 weeks after treatment (P =.01). The mean VAS score at baseline for the treatment group was 6.3 (standard deviation [SD], 2), which decreased to 3.7 (SD, 3) at 4 weeks after the intervention (P =.001).

There were no significant differences in either the sham or treatment groups between baseline and 4 weeks after treatment for any of the other neuropathy pain measures.

At the conclusion of the study, patients were asked which study group they thought they were assigned to, and 56% correctly guessed their treatment group.

In addition to the small sample sizes, a limitation of this study was the large percentage of participants with pain in their lower extremities. Current research on the effect of tDCS has been focused on pain in the upper extremities. However, the investigators still observed a reduction in lower limb pain.

The study authors concluded that repeated tDCS over 5 days was able to reduce pain intensity for patients with chronic neuropathic pain due to MS, and that tDCS therapy had long-lasting effects.

Reference

Young J, Zoghi M, Kahn F, Galea MP. The effect of transcranial direct current stimulation on chronic neuropathic pain in patients with multiple sclerosis: randomized controlled trial [published online June 28, 2020]. Pain Med. doi:10.1093/pm/pnaa128