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 & 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 & 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.

Utilizing Repetitive Transcranial Magnetic Stimulation to Improve Language Function in Stroke Patients with Chronic Non-fluent Aphasia

“…Significant improvements in naming were observed, which persisted for at least eight months following completion of stimulation 8 . We subsequently replicated and extended these results, and have demonstrated that 1 Hz stimulation resulted in persistent improvements in both naming and spontaneous elicited speech in chronic non-fluent aphasic patients [9][10][11] . Encouragingly, the results of small studies such as these have been replicated in further investigations in patients with chronic stroke 12 , as well as in patients with subacute stroke and aphasia 13 .…”

“…Importantly, like a number of prior investigators 8,12,13,23 , we have observed that most patients undergoing site-finding respond optimally to stimulation of the pars triangularis. However, we have also found that patients vary with respect to optimal site within the pars triangularis, and that a minority exhibit an optimal response to a different site in the right inferior frontal gyrus 11 . This underscores the importance of correct site identification.…”

Transcranial Magnetic Stimulation as an Intervention Tool to Recover from Language, Swallowing and Attentional Deficits after Stroke: A Systematic Review

“…The most part of the analysed studies (20 out of 21) studied the unaffected (right) hemisphere in the inferior frontal gyrus as a stimulation target, the majority in pars triangularis (Brodmann area 45). Medina et al [15] found the right pars triangularis to be the optimal site of stimulation in 9 of the 10 patients and Naeser et al [14] claimed that suppression of right pars triangularis, but not of pars opercularis, improved naming in aphasia.…”

“…In fact, aphasia is only associated to a lesion on the right hemisphere in 4% of the aphasia cases with poststroke patients [13]. Nonfluent aphasia originates problems in speech output such as interrupted speech, word omission or statements with limited syntactic complexity [15]. As a consequence of stroke, it affects about 38% of the patients [3][4][5] and becomes chronic in 10-18% of survivors [3,5].…”

Neurostimulation for traumatic brain injury

“…Aphasic patients show increased metabolic activation of the nondominant inferior frontal and superior temporal areas as evaluated by PET. 113 Previous studies used low-frequency TMS to suppress the hypothetical overactivity of the contralesional inferior frontal gyrus in patients with chronic aphasia that resulted in a significant increase in discourse productivity 98 and improved picture naming. 108 Likewise, several studies show enhancement of specific aspects of cognitive function when tDCS is applied in the injured brain, such as with recovery of language function.…”