Individualized treatment with transcranial direct current stimulation in patients with chronic non-fluent aphasia due to stroke

Abstract

While evidence suggests that transcranial direct current stimulation (tDCS) may facilitate language recovery in chronic post-stroke aphasia, individual variability in patient response to different patterns of stimulation remains largely unexplored. We sought to characterize this variability among chronic aphasic individuals, and to explore whether repeated stimulation with an individualized optimal montage could lead to persistent reduction of aphasia severity. In a two-phase study, we first stimulated patients with four active montages (left hemispheric anode or cathode; right hemispheric anode or cathode) and one sham montage (Phase 1). We examined changes in picture naming ability to address (1) variability in response to different montages among our patients, and (2) whether individual patients responded optimally to at least one montage. During Phase 2, subjects who responded in Phase 1 were randomized to receive either real-tDCS or to receive sham stimulation (10 days); patients who were randomized to receive sham stimulation first were then crossed over to receive real-tDCS (10 days). In both phases, 2 mA tDCS was administered for 20 min per real-tDCS sessions and patients performed a picture naming task during stimulation. Patients' language ability was re-tested after 2-weeks and 2-months following real and sham tDCS in Phase 2. In Phase 1, despite considerable individual variability, the greatest average improvement was observed after left-cathodal stimulation. Seven out of 12 subjects responded optimally to at least one montage as demonstrated by transient improvement in picture-naming. In Phase 2, aphasia severity improved at 2-weeks and 2-months following real-tDCS but not sham. Despite individual variability with respect to optimal tDCS approach, certain montages result in consistent transient improvement in persons with chronic post-stroke aphasia. This preliminary study supports the notion that individualized tDCS treatment may enhance aphasia recovery in a persistent manner.

Keywords: aphasia; language disorders; neurorehabilitation; stroke; tDCS.

Figure 1

Flow chart indicating the number of study subjects who were screened and enrolled; subjects in shaded boxes were excluded from analyses.

Figure 2

Overview of study events.

Figure 3

Phase 1: Mean change in picture-naming in 12 subjects after stimulation with 1 sham and 4 active montages in box plots; box height represents the interquartile range, the black line within the box represents the median, the whiskers represent the upper and lower ranges. Each patients' mean change is superimposed on the box plots as solid gray circles. Asterisk indicates statistical significance (^*p < 0.05) between the sham and left-cathodal montages.

Figure 4

Phase 1: (A) Lesion overlap plots for different optimal montage-groups; (B) Lesion overlap between the cathodal montage groups; (C) Subtraction plot comparing left-anodal group to cathodal montage group.

Figure 5

Phase 2: Mean WAB-AQ scores in (A) real tDCS and (B) sham tDCS groups at pre-tDCS, 2 weeks and 2-months; vertical lines represent standard errors, and asterisks indicate statistical significance (^**p < 0.001, ^*p < 0.05).