Effect of Repetitive Transcranial Magnetic Stimulation According to the Stimulation Site in Stroke Patients With Dysphagia

Abstract

Objective: To investigate the effect of repetitive transcranial magnetic stimulation (rTMS) according to the stimulation site in subacute stroke patients with dysphagia.

Methods: This study was designed as a matched comparative study. Twenty-four patients who had dysphagia after ischemic stroke were recruited, and they were divided into two groups after matching for age and stroke lesion. The patients in group A received rTMS over the brain cortex where motor evoked potential (MEP) was obtained from the suprahyoid muscle. Group B received rTMS over the brain cortex where MEP was obtained from the abductor pollicis brevis muscle. rTMS was performed at 110% of MEP threshold, 10 Hz frequency for 10 seconds, and then repeated every minute for 10 minutes. Dysphagia status was measured by the Functional Dysphagia Scale (FDS), the Penetration-Aspiration Scale (PAS), and the Dysphagia Outcome and Severity Scale (DOSS) using the results of a videofluoroscopic swallowing study. These evaluations were measured before, immediately, and 4 weeks after rTMS.

Results: Group A showed significant improvement compared to group B in the DOSS score immediately and 4 weeks after rTMS. There were no significant differences in the changes of FDS and PAS scores between groups A and B immediately and 4 weeks after rTMS.

Conclusion: rTMS over a hot spot for the suprahyoid muscle caused more improvement in swallowing function when compared to that over the interconnected site.

Keywords: Deglutition Disorders; Stroke; Transcranial Magnetic Stimulation.

Fig. 1. Stimulation sites included the following: for group A, to stimulate a specific dysphagia site, a hot spot was obtained from motor evoked potentials (MEP) of the suprahyoid muscle (A); for group B, to stimulate an interconnected remote site related to dysphagia, a hot spot was obtained from MEP of the abductor pollicis brevis muscle (B).

Fig. 2. In repeated measures analysis of variance test, all dysphagia scores were improved over time up to 4 weeks after rTMS in group A and only FDS score was improved in group B. There was no significant group-time interaction in all dysphagia scores. FDS, Functional Dysphagia Scale; PAS, Penetration-Aspiration Scale; DOSS, Dysphagia Outcome and Severity Scale; rTMS, repetitive transcranial magnetic stimulation; group A, rTMS over the cortex representing the suprahyoid muscle; group B, rTMS over the cortex representing the abductor pollicis brevis. ^*p<0.05.

Fig. 3. In repeated measures analysis of variance test, MMSE score was not significantly improved over time up to 4 weeks after rTMS, and there was no significant group-time interaction (A). K-MBI was improved over time up to 4 weeks after rTMS, while there was no significant group-time interaction (B). MMSE, Mini-Mental Status Examination; K-MBI, Korean version of the Modified Barthel Index; rTMS, repetitive transcranial magnetic stimulation; group A, rTMS over the cortex representing the suprahyoid muscle; group B, rTMS over the cortex representing the abductor pollicis brevis. ^*p<0.05.

Fig. 4. Treatment effects in (A) FDS, (B) PAS, and (C) DOSS scores. Group A showed significantly bigger increase in DOSS scores than group B both immediately after and 4 weeks after rTMS. ΔFDS, ΔPAS, ΔDOSS, amounts of changes from before rTMS. FDS, Functional Dysphagia Scale; PAS, Penetration-Aspiration Scale; DOSS, Dysphagia Outcome and Severity Scale; rTMS, repetitive transcranial magnetic stimulation; group A, rTMS over the cortex representing the suprahyoid muscle; group B, rTMS over the cortex representing the abductor pollicis brevis. ^*p<0.05.

Fig. 5. When the treatment effects from baseline to immediately and 4 weeks after rTMS were compared between the two groups, no difference in improvement of the MMSE and K-MBI scores was observed (A, B). ΔMMSE, ΔK-MBI, amount of change from before rTMS. rTMS, repetitive transcranial magnetic stimulation; Group A, rTMS over the cortex representing the suprahyoid muscle; Group B, rTMS over the cortex representing the abductor pollicis brevis; MMSE, Mini-Mental Status Examination; K-MBI, Korean version of the Modified Barthel Index.