Excitatory repetitive transcranial magnetic stimulation induces improvements in chronic post-stroke aphasia

Abstract

Background: Aphasia affects 1/3 of stroke patients with improvements noted only in some of them. The goal of this exploratory study was to provide preliminary evidence regarding safety and efficacy of fMRI-guided excitatory repetitive transcranial magnetic stimulation (rTMS) applied to the residual left-hemispheric Broca's area for chronic aphasia treatment.

Material/methods: We enrolled 8 patients with moderate or severe aphasia >1 year after LMCA stroke. Linguistic battery was administered pre-/post-rTMS; a semantic decision/tone decision (SDTD) fMRI task was used to localize left-hemispheric Broca's area. RTMS protocol consisted of 10 daily treatments of 200 seconds each using an excitatory stimulation protocol called intermittent theta burst stimulation (iTBS). Coil placement was targeted individually to the left Broca's.

Results: 6/8 patients showed significant pre-/post-rTMS improvements in semantic fluency (p=0.028); they were able to generate more appropriate words when prompted with a semantic category. Pre-/post-rTMS fMRI maps showed increases in left fronto-temporo-parietal language networks with a significant left-hemispheric shift in the left frontal (p=0.025), left temporo-parietal (p=0.038) regions and global language LI (p=0.018). Patients tended to report subjective improvement on Communicative Activities Log (mini-CAL; p=0.075). None of the subjects reported ill effects of rTMS.

Conclusions: FMRI-guided, excitatory rTMS applied to the affected Broca's area improved language skills in patients with chronic post-stroke aphasia; these improvements correlated with increased language lateralization to the left hemisphere. This rTMS protocol appears to be safe and should be further tested in blinded studies assessing its short- and long-term safety/efficacy for post-stroke aphasia rehabilitation.

Figures

Figure 1

Individual areas of fMRI activation that correspond to the nerTMS target (white circle) superimposed on individual T1-weighted anatomical images to illustrate the extent of the ischemic strokes and the location of the BOLD signal changes. Subjects 1, 3, 4 and 6 presented with anomic aphasias (1 and 3 had also dysarthria and 6 had conduction aphasia); other subjects presented with non-fluent aphasias, all Broca’s type. All images are in radiological convention (left on the picture corresponds to right in the brain).

Figure 2

Group z-score maps for the pre-rTMS (upper row) and post-rTMS (lower row) semantic decision and tone decision fMRI task. Brain regions showing BOLD signal increases for the tone decision > semantic decision contrast are shown in cyan/blue; regions showing BOLD signal increases for the semantic decision > tone decision are shown in yellow/red. BOLD signal changes are significant at an uncorrected p <0.05. Each z-score map is presented in radiological convention, with left on the picture corresponding to the right hemisphere, and are superimposed on an average T1-weighted image generated from all subjects (dilatation of the left lateral ventricle and area of encephalomalacia in the left MCA distribution is clearly seen). Talairach coordinates of the selected slices for each panel range from z=−21 mm (left) to z=+27 mm (right).

Figure 3

Pre-/post-rTMS group differences for the SDTD fMRI task shown as z-score maps. Brain regions showing post- > pre-rTMS BOLD signal are shown in yellow/red; regions showing pre- > post-rTMS BOLD signal are shown in cyan/blue. BOLD signal changes are significant at an uncorrected p <0.05. Each z-score map is presented in radiological convention, with left on the picture corresponding to the right hemisphere, and is superimposed on an average T1-weighted image generated from all subjects (dilatation of the left lateral ventricle and area of encephalomalacia in the left MCA distribution is clearly seen). Talairach coordinates of the selected slices range from z=−21 mm (top left) to z=+35 mm (bottom right). Locations of the centroids and the corresponding Brodmann’s areas are provided in Table 2.