Bi-hemispheric tDCS as an adjuvant in the treatment of people who stutter: a randomized, double-blind preliminary trial

Introduction: Stuttering is a disorder of unknown origin, defined by repetition of sounds or syllables, prolongation of sounds and interruptions in speech flow, which might be due to impairments in motor planning. Transcranial direct current stimulation is a non-invasive brain modulation technique successfully used in rehabilitation and research. Methods: We examined the effect of bi-hemispheric tDCS over the inferior frontal cortices paired with speech exercises in improving the fluency of people who stutter. Eight participants were randomly assigned to real or sham stimulation groups in a parallel, double-blind trial. They performed fluency exercises under stimulation for five consecutive days and performances before and after intervention were compared. Results: Real stimulation significantly reduced the stutter duration up to six weeks after intervention and improved SSI-3 scores after one week. Although results showed a robust fluency time improvement, real stimulation did not significantly reduce the number of stuttered syllables. No psychosocial effects were observed after the intervention. Conclusions: These results support the efficacy of bi-hemispheric stimulation in improving speech flow and warrant further investigation of tDCS use in speech therapy.