Effects Of Repetitive Transcranial Magnetic Stimulation With Different Frequencies Over Contralesional Pharyngeal Motor Cortex On Patients With Post-stroke Dysphagia

Objective Dysphagia,one of the common complications after stroke,leads to increased mortality and poor long-term outcomes.The traditional swallowing rehabilitation strategies mainly include compensatory intervention such as posture intervention and swallowing training mainly based on muscle strength and sensory stimulation,but the effectiveness of these techniques has not been fully demonstrated.Repetitive transcranial magnetic stimulation(rTMS)is a technique used to modulate brain activity in specific cortical and subcortical areas.It has been widely applied to treat dysfunction after stroke.However,the stimulation parameters(such as stimulation site and stimulation frequency)that repetitive transcranial magnetic stimulation is used to treat dysphagia after stroke remain to be studied.The purpose of this study is to investigate the effect of high-frequency and low-frequency repetitive transcranial magnetic stimulation at the contralesional motor cortex over the cortical representation of suprahyoid muscles on post-stroke dysphagia and to explore the mechanism of repeated transcranial magnetic stimulation to improve dysphagia after stroke.Methods Forty-two stroke patients with dysphagia were enrolled.Patients were randomly divided into three groups: the high-frequency stimulation group(n=14),the low-frequency stimulation group(n=13),and the sham stimulation group(n=15).All patients received routine medicine and conventional swallowing training,including oral muscle training,pharynx sensory stimulation,tongue-pressure resistance training,respiratory training and Shaker training for 30 minutes a day,5 days a week.For the high-frequency stimulation group,250 pulses of 5Hz rTMS over the contralesional motor cortex over the cortical representation of the suprahyoid muscle were administered 10 min daily for 2 consecutive weeks.For the low-frequency stimulation group,250 pulses of 1Hz rTMS over the unaffected motor cortices over the cortical areas that project to the suprahyoid muscles were applied 10 min daily for 2 consecutive weeks.For the sham stimulation group,sham rTMS was applied at the contralesional hemisphere 10 min daily for 2 consecutive weeks.They all performed videofluoroscopic swallowing study(VFSS)and surface electromyography(sEMG)before and after treatment.The evaluation was performed using penetration aspiration scale(PAS),functional dysphagia scale(FDS),root mean square(RMS)and resting motor threshold(RMT).Results No significant differences between groups were observed in terms of clinical rating scales.After treatment,the scores of PAS and FDS were lower than those before treatment,the values of RMS were increased,the difference was statistically significant.Only high-frequency rTMS increased cortical excitability of the unaffected hemisphere.After treatment,there was a significant difference in the scores of PAS and FDS among the three groups.Mean changes in PAS and FDS score in the high-and low-frequency stimulation groups were significantly higher than those in the sham stimulation group.There was a significantly larger change in FDS scores in the high-frequency stimulation group than in two other groups.Compared with the low frequency group,the RMT value of the high frequency group was significantly reduced after treatment.Conclusions 5Hz rTMS and 1Hz rTMS at the contralesional motor cortex over the cortical representation of the suprahyoid muscle is effective as an additional treatment strategy to traditional dysphagia therapies.High-frequency rTMS may be more beneficial to patients than low-frequency rTMS in improving the effectiveness of swallowing in patients with dysphagia after stroke.