Effectiveness of transcranial direct current stimulation and visual illusion on neuropathic pain in spinal cord injury

Abstract

The aim of this study was to evaluate the analgesic effect of transcranial direct current stimulation of the motor cortex and techniques of visual illusion, applied isolated or combined, in patients with neuropathic pain following spinal cord injury. In a sham controlled, double-blind, parallel group design, 39 patients were randomized into four groups receiving transcranial direct current stimulation with walking visual illusion or with control illusion and sham stimulation with visual illusion or with control illusion. For transcranial direct current stimulation, the anode was placed over the primary motor cortex. Each patient received ten treatment sessions during two consecutive weeks. Clinical assessment was performed before, after the last day of treatment, after 2 and 4 weeks follow-up and after 12 weeks. Clinical assessment included overall pain intensity perception, Neuropathic Pain Symptom Inventory and Brief Pain Inventory. The combination of transcranial direct current stimulation and visual illusion reduced the intensity of neuropathic pain significantly more than any of the single interventions. Patients receiving transcranial direct current stimulation and visual illusion experienced a significant improvement in all pain subtypes, while patients in the transcranial direct current stimulation group showed improvement in continuous and paroxysmal pain, and those in the visual illusion group improved only in continuous pain and dysaesthesias. At 12 weeks after treatment, the combined treatment group still presented significant improvement on the overall pain intensity perception, whereas no improvements were reported in the other three groups. Our results demonstrate that transcranial direct current stimulation and visual illusion can be effective in the management of neuropathic pain following spinal cord injury, with minimal side effects and with good tolerability.

Figure 1

Schematic drawing of the setting (as described by Moseley et al., 2007) used for the virtual reality procedure to induce walking visual illusion during transcranial DCS in the patients with SCI.

Figure 2

(A) Mean values (±standard deviation) of the intensity of pain rated in the NRS at baseline in the four groups of patients. (B) Percentage of improvement for the overall pain intensity perception in each group at the different times of evaluation following treatment. Data are shown as mean ± standard error. *P < 0.005 (Mann–Whitney U) transcranial DCS + visual illusion (VI) versus visual illusion and versus placebo. **P ≤ 0.05 (Mann–Whitney U) transcranial DCS + visual illusion versus transcranial DCS, versus visual illusion and versus placebo. ***P ≤ 0.05 (Mann–Whitney U) transcranial DCS + visual illusion versus transcranial DCS, versus visual illusion. (C) Percentage of improvement for the general pain perception in each patient and mean of the group (black circle) at the last day of the treatment. Grey line, mean value of percentage improvement and confidence interval (95% CI) in the placebo group (mean 5.59; CI range, from 15.5 to −4.3).

Figure 3

Patient global impression of change after the last day of treatment. Rated on a seven-point scale of overall change experienced by patients at the last day of treatment. VI = visual illusion.