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.