Feasibility of using high-definition transcranial direct current stimulation (HD-tDCS) to enhance treatment outcomes in persons with aphasia

Abstract

Background: Transcranial direct current stimulation (tDCS) enhances treatment outcomes post-stroke. Feasibility and tolerability of high-definition (HD) tDCS (a technique that increases current focality and intensity) for consecutive weekdays as an adjuvant to behavioral treatment in a clinical population has not been demonstrated.

Objective: To determine HD-tDCS feasibility outcomes: 1) ability to implement study as designed, 2) acceptability of repeated HD-tDCS administration to patients, and 3) preliminary efficacy.

Methods: Eight patients with chronic post-stroke aphasia participated in a randomized crossover trial with two arms: conventional sponge-based (CS) tDCS and HD-tDCS. Computerized anomia treatment was administered for five consecutive days during each treatment arm.

Results: Individualized modeling/targeting procedures and an 8-channel HD-tDCS device were developed. CS-tDCS and HD-tDCS were comparable in terms of implementation, acceptability, and outcomes. Naming accuracy and response time improved for both stimulation conditions. Change in accuracy of trained items was numerically higher (but not statistically significant) for HD-tDCS compared to CS-tDCS for most patients.

Conclusions: Regarding feasibility, HD-tDCS treatment studies can be implemented when designed similarly to documented CS-tDCS studies. HD-tDCS is likely to be acceptable to patients and clinicians. Preliminary efficacy data suggest that HD-tDCS effects, using only 4 electrodes, are at least comparable to CS-tDCS.

Keywords: Aphasia; feasibility; high-definition tDCS; stroke; tDCS; treatment outcomes.

Figures

Fig. 1

Flow diagram of the study design.

Fig. 2

Electric field solutions for conventional sponge (CS-tDCS) versus high-definition (HD-tDCS) for four sample subjects in the study. Patient-specific head models were built based on individual MRI, FEM modeled, and optimized to focus currents to an fMRI-determined target (open circle). HD-tDCS results in higher electrical field intensities at target compared to CS-tDCS.

Fig. 3

A: High-definition tDCS (HD-tDCS) was applied using EEG sized electrodes held in plastic insets in an EEG cap. B: 8-channel HD-tDCS prototype device used in the study.