The effectiveness of transcranial direct current stimulation as an add-on modality to graded motor imagery for treatment of complex regional pain syndrome: A randomized proof of concept study

BACKGROUND: The efficacy of graded motor imagery (GMI) for the management of complex regional pain syndrome (CRPS) is supported by evidence, but its treatment effect remains generally modest. Transcranial direct current stimulation (tDCS) has been advocated as an adjunct intervention to enhance the effect of motor imagery approaches in pain populations. OBJECTIVE: The purpose of this study was to investigate the effectiveness of GMI+active tDCS compared to the GMI+sham tDCS in the treatment of CRPS type I. METHODS: 22 patients (n=11/group) were randomly assigned to the experimental (GMI+tDCS) or placebo (GMI+sham tDCS) group. GMI treatments lasted 6 weeks; anodal tDCS was applied over the motor cortex for 5 consecutive days during the first 2 weeks and once a week thereafter. Changes in pain perception, quality of life, kinesiophobia, pain catastrophizing, anxiety and mood were monitored after 6 weeks of treatment (T1) and 1-month post treatment (T2). RESULTS: GMI+tDCS induced no statistically significant reduction in pain compared to GMI+sham tDCS. Although we observed significant group differences in kinesiophobia (P=0.012), pain catastrophizing (P=0.049) and anxiety (P=0.046) at T1, these improvements were not maintained at T2 and did not reached a clinically significant difference. DISCUSSION: We found no added value of tDCS combined with GMI treatments for reducing pain in patients with chronic CRPS. However, given that GMI+sham tDCS induced no significant change, further studies comparing GMI+tDCS and tDCS alone are needed to further document tDCS's effect in CRPS