No effects of anodal transcranial direct stimulation on language abilities in early rehabilitation of post-stroke aphasic patients

Abstract

Background and purpose

Recent research suggests that an increased level of stroke-affected left hemisphere cortical (especially frontal) excitability is associated with better language improvement in aphasic patients. Anodal transcranial direct current stimulation (A-tDCS), increasing cortical activity, may facilitate perilesional left hemisphere recruitment to subserve language processing and enhance effects of behavioural therapy. The aim of the study (randomized, double-blind, sham-controlled) was to evaluate the effectiveness of repeated A-tDCS over Broca area as a strategy to enhance aphasia recovery during early post-stroke rehabilitation.

Material and methods

Thirty-seven participants with moderate or severe aphasia were randomized to receive 15 consecutive daily sessions of A-tDCS (1 mA, 10 min; experimental group, n = 18) or sham stimulation (1 mA, 25 s; control group, n = 19) followed by language therapy. Effects of tDCS were assessed using the Boston Diagnostic Aphasia Examination, performed before and after the rehabilitation, and three months later.

Results

The results did not confirm a positive impact of repeated A-tDCS, preceding language therapy, on language abilities in our patients. Although both groups improved after the therapy, there were no statistically significant differences between groups in either short-term or long-term tDCS effects. Effect sizes for the experimental group, at post-treatment and the 3-month follow-up, were slightly higher than in controls but insufficient to infer any beneficial influence of the applied intervention.

Conclusions

The findings do not support A-tDCS functional benefits during early rehabilitation of post-stroke aphasia. Further research is needed to explore the effectiveness of this kind of neuromodulation.