Effectiveness of transcranial direct current stimulation for the management of neuropathic pain after spinal cord injury: a meta-analysis.

objectivesTo conduct a systematic review and meta-analysis to examine the effect of transcranial direct current stimulation (tDCS) on reducing neuropathic pain intensity in individuals with spinal cord injury (SCI).

methodsMedline, CINAHL, EMBASE and PsycINFO databases were searched for all relevant articles published from 1980 to November 2014. Trials were included if (i) tDCS intervention group and a placebo control group were present; (ii) at least 50% of participants in the study had an SCI and there were at least three participants; (iii) participants were aged 18 years or older; and (iv) persistent pain for at least 3 months. Studies were excluded if: (i) the tDCS intervention group was compared with an active treatment group; (ii) there was insufficient reporting detail to enable pooling of data; and (iii) it was a nonclinical trial (that is, reviews, epidemiology, basic sciences). A standardized mean difference (SMD) ± s.e. and 95% confidence interval (CI) was calculated for each outcome of interest and the results were pooled using a fixed or random effects model, as appropriate. Effect sizes were interpreted as: small > 0.2, moderate > 0.5, large > 0.8.

resultsFive studies met inclusion criteria of which four were randomized controlled trials and one was a prospective controlled trial. The pooled analysis found a significant effect of tDCS on reducing neuropathic pain after SCI post treatment (SMD = 0.510 ± 0.202; 95% CI, 0.114-0.906; P < 0.012); however, this effect was not maintained at follow-up (SMD = 0.353 ± 0.272; 95% CI, -0.179 to 0.886; P < 0.194). A reduction of 1.33 units on a 10-item scale was observed post treatment. No significant adverse events were reported.

conclusionMeta-analytic results indicate a moderate effect of tDCS in reducing neuropathic pain among individuals with SCI; however, the effect was not maintained at follow-up. A mean pooled decrease of 1.33 units on a 10-item scale was found post treatment. Several factors were implicated in the effectiveness of tDCS in reducing pain. Due to the limited number of studies and lack of follow-up, more evidence is required before treatment recommendations can be made.