Finding the Right Words: Transcranial Magnetic Stimulation Improves Discourse Productivity in Non-fluent Aphasia After Stroke

Abstract

BACKGROUND: Loss of fluency is a significant source of functional impairment in many individuals with aphasia. Repetitive transcranial magnetic stimulation (rTMS) administered to the right inferior frontal gyrus (IFG) has been shown to facilitate naming in persons with chronic left hemisphere stroke and non-fluent aphasia. However, changes in fluency in aphasic subjects receiving rTMS have not been adequately explored. AIMS: To determine whether rTMS improves fluency in individuals with chronic nonfluent aphasia, and to identify aspects of fluency that are modulated in persons who respond to rTMS. METHODS #ENTITYSTARTX00026; PROCEDURES: Ten individuals with left hemisphere MCA strokes and mild to moderate non-fluent aphasia participated in the study. Before treatment, subjects were asked to describe the Cookie Theft picture in three separate sessions. During treatment, all subjects received 1200 pulses of 1 Hz rTMS daily in 10 sessions over two weeks at a site that had previously been shown to improve naming. Subjects repeated the Cookie Theft description two months after treatment. Five subjects initially received sham stimulation instead of real TMS. Two months after sham treatment, these individuals received real rTMS. Performance both at baseline and after stimulation was coded using Quantitative Production Analysis (Saffran, Berndt & Schwartz, 1989) and Correct Information Unit (Nicholas & Brookshire, 1993) analysis. OUTCOMES #ENTITYSTARTX00026; RESULTS: Across all subjects (n=10), real rTMS treatment resulted in a significant increase in multiple measures of discourse productivity compared to baseline performance. There was no significant increase in measures of sentence productivity or grammatical accuracy. There was no significant increase from baseline in the sham condition (n=5) on any study measures. CONCLUSIONS: Stimulation of the right IFG in patients with chronic non-fluent aphasia facilitates discourse production. We posit that this effect may be attributable to improved lexical-semantic access.

Figures

Figure 1

Map depicts lesion overlap for all 10 left MCA stroke subjects mapped onto the Colin27 MNI template. The location of maximal overlap (bright orange) includes the left Insula, Heschl’s gyrus, and Rolandic operculum.

Figure 2

Outline of study events.

Figure 3

Right hemisphere overlay of optimal real TMS sites for the 10 subjects in the study mapped onto the Colin27 MNI template. Subjects are labeled as Real or Sham subjects 1–5 (based on which type of treatment they received first, although the sites shown all correspond to their real TMS sites), and correspond with subject labels in Table 1. Shading indicates gyral anatomy: Green=pars opercularis, Red=pars triangularis, Yellow=pars orbitalis.

Figure 4

Performance on measures of discourse productivity before and 2 months after receiving real rTMS (N=10). Vertical lines represent standard error. Significant improvement (p=

Figure 5

Performance on measures of (A) sentence productivity, (B) grammatical accuracy, and (C) lexical selection (N=10) before and 2 months after real TMS stimulation (N=10). Vertical lines represent the standard error. NW=Narrative Words; CCW= Closed-class Words; OCW= Open-class Words; CIU= Correct Information Units; SL= Sentence Length; UL= Utterance Length; EI = Elaboration Index; WF = Well-formed; VI= Verbs Inflected; Prop= Proportion.