Applications of Transcranial Magnetic Stimulation in Post-Stroke Dysphagia
Keywords:transcranial magnetic stimulation, deglutition, dysphagia, stroke
Objectives: To summarize the main findings of using transcranial magnetic stimulation (TMS) and repetitive TMS (rTMS) in physio-logic swallowing response and to review the parameters related to rTMS protocols in post-stroke dysphagia (PSD) treatment.
Study design: English-language literatures published from 1st January 1999 to 20th August 2020 were sought using PUBMED, MEDLINE, and Web of Science; and MeSH terms of transcranial magnetic stimulation, swallowing, deglutition, dysphagia, and stroke. Nineteen randomized control trials (RCT), six non-RCT, and one systematic review article were included.
Setting: Rehabilitation centers and university hospitals in Europe or Asia.
Subjects: Normal population and post-stroke dysphagia patients.
Methods: A narrative review of all the relevant papers related to TMS or rTMS was conducted.
Results: TMS is used to investigate swallowing physiology and to treat dysphagia. Several experiments have shown positive outcomes of swallowing functions without any serious complications. Two parameters: frequency and stimulation side, have different effects. Low-frequency stimulation has an inhibitory effect by decreasing the cortical excitability while high-frequency stimulation has the opposite effect by increasing the excitability. Low-frequency stimulation applied over the unaffected hemisphere inhibits interhemispheric interaction. High-frequency stimulation applied over the unaffected or the affected hemisphere might facilitate the recovery. Bilateral hemispheric stimulation by using high-frequency was shown to improve outcomes. To alter the cortical signal in swallowing, rTMS can be applied on both pharyn-geal cortical hemisphere and the cerebellum.
Conclusion: rTMS is one intervention which may facilitate neurological recovery after dysphagic stroke. Although there was weak evidence to support dysphagia treatment, the recent studies showed positive effects. rTMS may be beneficial adjunctive therapy in post-stroke dysphagia treatment if a strong evidence protocol is addressed.
Keywords: transcranial magnetic stimulation, deglutition, dysphagia, stroke
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