Recovery of aphasia: a case study with “dual” tdcs.

Abstract

Objectives. In the present study we used a “dual” tDCS (Vines et al., 2008; Giglia et al., 2011) training on inferior frontal gyrus’s (IFG) areas in order to improve the linguistic performance of EBE, an Italian female, left-handed, presenting a global aphasia following a stroke of right middle cerebral artery. Materials. For the picture naming task, 20 object and 20 action images, selected from a set of picture standardized for frequency, were presented on a paper sheet one at time. Method. Stimulation was used at 1mA for 15 minutes. Dual tDCS was given over both IFGs, cathode in the right (damaged areas) and anode in the left (preserved areas) daily for two weeks (weekend-free). The position of the electrodes was based on a previous pilot study on EBE, in which tDCS efficacy was greater when the cathode was positioned over the right Broca’s area and the anode over the left Broca’s area, compared to the opposite placement. One week after the end of the treatment, sham tDCS was delivered for another week. EBE performed the naming of the complete set of 40 pictures at the following times: before real tDCS (T0), immediately after the end of real tDCS (T1), before sham tDCS (T2) and after sham tDCS (T3). Since EBE was able to name no picture without a phonological cue (the first or the two first letters of the stimulus), the images in the picture naming task was first presented without cue, then with a first letter and, if no response was obtained, with the two first letters. The following scores were used: 0= incorrect response; 0.5= correct response with two letters of phonological cue; 1= correct response with one letter; 2= correct response without cue. Thus, a higher score means a better performance. These scores obtained at the four different times (conditions) of examination were compared by means of repeated measures one-way ANOVA. Results. ANOVA showed a statistically significant main effect of conditions. As showed by Duncan's post hoc analysis EBE made significantly less errors after real tDCS (T1) with respect to baseline (T0) (p<0.05), while no significant changes in performance were observed after sham tDCS (T3 vs T0). Discussion. Our study is the first in which dual stimulation is used in order to improve the linguistic performance of an aphasic patient. In our patient, considering left-handedness and aphasia following a right lesion, a right hemisphere dominance for language can be presumed. So, anodic stimulation of the left frontal areas could favor the recruitment of this area to compensate the function of the damaged language area; while cathodic stimulation of the right damaged area could have played its effect reducing transcallosal inhibitory drive to the homologue area. Conclusion. Dual tDCS could be a promising tool for aphasic recovery. This study shows that an intense training (at least ten days) improves linguistic performance also for severe nonfluent chronic aphasia.