The Effect of Transcranial Direct Current Stimulation on Stuttering: A Preliminary Report

Abstract

<p>Stuttering is a neurodevelopmental speech fluency disorder that has life-long impacts on people who stutter. Behavioural treatments for adults who stutter (AWS) fails to maintain the benefits, resulting in participants re-presenting for treatment. While the precise cause of stuttering is unclear, multiple neuroimaging studies have suggested aberrant neural activation associated with stuttering in different brain regions, particularly the supplementary motor area (SMA). The study aims to investigate the safety and treatment add-on effects of High Definition Transcranial Direct Current Stimulation (tDCS) via a randomized controlled trial study with a double-blinded design.</p><p>Six AWS were randomized to a control group (sham tDCS) and an experimental group (anodal tDCS). Both groups received the speech prolongation technique as the behavioural treatment, for five sessions, with the experimental group receiving anodal tDCS (1 mA for 20 minutes), and the control group receiving sham tDCS, over the SMA. Stuttering severity were independently measured across three time points before treatment (i.e., two weeks, one week and immediately before treatment), and three time points after treatment (i.e., immediately after, one week and six weeks after treatment).</p><p>The preliminary results show that stuttering severity was reduced in anodal tDCS group with larger treatment effect size than sham group, but the group difference was not statistically significant. Nevertheless, the anodal tDCS significantly reduced percent of stuttered syllables after each treatment session, as compared with the sham condition.</p><p>The findings suggested that tDCS combined with behavioral treatment is a safe and promising add-on treatment for stuttering therapy when applied over SMA. Further research with larger sample size should be needed to apply different tDCS parameters to examine the treatment outcomes over the long terms.</p>