Transcranial Direct Current Stimulation Paired With Verb Network Strengthening Treatment Improves Verb Naming in Primary Progressive Aphasia: A Case Series

Purpose: There are few evidence-based treatments for language deficits in primary progressive aphasia (PPA). PPA treatments are often adopted from the poststroke aphasia literature. The poststroke aphasia literature has shown promising results using Verb Network Strengthening Treatment (VNeST), a behavioral therapy that focuses on improving naming by producing verbs and their arguments in phrases and sentences. Emerging research in poststroke aphasia and PPA has shown promising results pairing behavioral language therapy with transcranial direct current stimulation (tDCS). Method: This study used a double-blind, within-subjects, sham-controlled crossover design to study the effect of anodal tDCS applied to left inferior frontal gyrus (IFG) plus VNeST versus VNeST plus sham stimulation in two individuals with nonfluent variant PPA and one individual with logopenic variant PPA. Participants received two phases of treatment, each with 15 1-hr sessions of VNeST. One phase paired VNeST with tDCS stimulation, and one with sham. For each phase, language testing was conducted at baseline, and at 1 week and 8 weeks posttreatment conclusion. For each participant, treatment efficacy was evaluated for each treatment phase by comparing the mean change in accuracy between baseline and the follow-up time points for naming trained verbs (primary outcome measure), untrained verbs, and nouns on the Object and Action Naming Battery. Mean change from baseline was also directly compared between tDCS and sham phases at each time point. Results: Results revealed a different pattern of outcomes for each of the participants. A tDCS advantage was not found for trained verbs for any participant. Two participants with nonfluent variant PPA had a tDCS advantage for generalization to naming of untrained verbs, which was apparent at 1 week and 8 weeks posttreatment. One participant with nonfluent variant also showed evidence of generalization to sentence production in the tDCS phase. Conclusion: VNeST plus anodal tDCS stimulation of left IFG shows promising results for improving naming in PPA.