A meta-analysis of site-specific effects of cathodal transcranial direct current stimulation on sensory perception and pain.

Bita Vaseghi,Shapour Jaberzadeh,Maryam Zoghi,Alessio Avenanti

doi:10.1371/journal.pone.0123873

Bita Vaseghi, Shapour Jaberzadeh + Show 2 more

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https://doi.org/10.1371/journal.pone.0123873

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Abstract

The primary aim of our meta-analysis was to evaluate the effects of cathodal transcranial direct current stimulation (c-tDCS) on sensory and pain thresholds (STh and PTh) in healthy individuals and pain level (PL) in patients with chronic pain. Electronic databases were searched for c-tDCS studies. Methodological quality was evaluated using the PEDro and Downs and Black (D&B) assessment tools. C-tDCS of the primary motor cortex (S1) increases both STh (P<0.001, effect size of 26.84%) and PTh (P<0.001, effect size of 11.62%). In addition, c-tDCS over M1 led to STh increase (P<0.005, effect size of 30.44%). Likewise, PL decreased significantly in the patient group following application of c-tDCS. The small number of studies precluded subgroup analysis. Nevertheless, meta-analysis showed that in all groups (except c-tDCS of S1) active c-tDCS and sham stimulation produced significant differences in STh/PTh in healthy and PL in patient group. This review provides evidence for the site-specific effectiveness of c-tDCS in increasing STh/PTh in healthy individuals and decreasing PL in patients with chronic pain. However, due to small sample sizes in the included studies, our results should be interpreted with caution. Given that the level of blinding was not considered in the inclusion criteria, the results of the current study should be interpreted with caution.

Highlights

Cathodal transcranial direct current stimulation (c-tDCS) is one of the non-invasive brain stimulation techniques which depends on the parameters of the applied current, may induce decreased or increased corticospinal excitability [1, 2]
We aimed to investigate the sitespecific effects of c-tDCS on sensory threshold (STh)/pain threshold (PTh) in healthy individuals and pain level (PL) in patients with chronic pain
The results indicated that the overall effect size of meta-analysis compared the effects of M1 c-tDCS and sham on PTh did not change after exclusion of each

Summary

Introduction

Cathodal transcranial direct current stimulation (c-tDCS) is one of the non-invasive brain stimulation techniques which depends on the parameters of the applied current, may induce decreased or increased corticospinal excitability [1, 2]. The inhibitory effect of c-tDCS has been recently utilized for treatment of different clinical conditions including pain management [3,4,5]. To understand how c-tDCS modulates pain, it should be noted that a large distributed network of brain sites are activated during pain processing [6] which collectively is called pain neuromatrix [7, 8]. Some parts of the pain neuromatrix are superficial, including the primary sensory cortex (S1), primary motor cortex (M1), and dorsolateral prefrontal cortex (DLPFC).

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