Effects of Transcranial Direct Current Stimulation on Apraxia of Speech and Cortical Activation in Patients With Stroke: A Randomized Sham-Controlled Study

Abstract

Purpose The study aims to investigate, using anodal transcranial direct current stimulation (A-tDCS), over which site, the left lip region of primary motor cortex (M1) or the Broca's area, there would be better recovery from apraxia of speech (AoS) in patients with poststroke aphasia and to examine for altered activation in speech-related areas after tDCS with nonlinear electroencephalography (EEG). Method Fifty-two patients with AoS were randomized into A-tDCS over the left M1 (A-tDCS-M1), Broca's area, and sham tDCS groups who underwent 10 sessions of tDCS and speech treatment for 5 days. The EEG nonlinear index of approximate entropy was calculated for 6 subjects in each group before and after treatment. Results After treatment, the change in speech-language performance improved more significantly in the A-tDCS-M1 group than the other 2 groups ( p < .05). EEG approximate entropy indicated that both A-tDCS groups could activate the stimulated sites; the improvement in the A-tDCS-M1 group was correlated with high activation in the dorsal lateral prefrontal cortex and Broca's areas of the left hemisphere in addition to the stimulated site. Conclusion A-tDCS over the left M1 can improve the speech function in patients with poststroke aphasia and severe AoS and excite and recruit more areas in the motor speech network.