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

OBJECTIVES:

To 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).

METHODS:

Medline, 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.

RESULTS:

Five 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.

CONCLUSION:

Meta-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.