Swallowing dysfunction, or dysphagia, is a common complication following stroke. Although spontaneous recovery of swallowing function was seen in most patients in a time course of a few weeks to 6 months after stroke, around 50% of patients recovered slowly and had chronic dysphagia clinically. It is worth noting that dysphagia has great impact on clinical outcome, in terms of not only quality of life but also risk of severe complication such as aspiration pneumonia, malnutrition, and even death.
After damage on swallowing ability, several cause would arise risk of aspiration and one of them was inadequate hyolaryngeal elevation. Suprahyoid muscle played an important role in hyolaryngeal movement so re-training on suprahyoid muscle might be an efficient method.
Conventional treatments of dysphagia focused on restore or improve swallowing functions through oropharyngeal muscle training, swallowing maneuvers, or compensation strategy. However, the effectiveness of traditional therapy was still limited and inconsistent.
Noninvasive brain stimulation (NIBS) has gained increasing attention as a promising neuromodulation therapy which could improve neurological deficit and functional level through inducing the cortical neuroplasticity. Among NIBS, repetitive transcranial magnetic stimulation (rTMS) is the most widely used and delved. It has been utilized in stroke patient for promoting functional reorganization and modulate neural connection in motor and language area. In a previous network meta-analysis, we also indicated that rTMS showed the best efficacy in improving the swallowing function in acute and subacute poststroke dysphagia, when compared with transcranial direct current stimulation, surface neuromuscular electrical stimulation, and pharyngeal electrical stimulation (PES). Despite of the positive results, there was still limited evidence on the effect of rTMS in chronic dysphagia and the mechanism by which rTMS improved dysphagia outcome is unclear. Specifically, whether the rTMS on a representation cortex directly increase functional gain, such as strength and contractility of the target area remained unclear. On the other hand, theta burst stimulation (TBS), consisting of continuous TBS (cTBS) and intermittent TBS (iTBS), is a new stimulation model of TMS and seemed to be helpful on motor recovery in chronic stroke. Furthermore, previous research had showed iTBS was not inferior to rTMS on the improvement of poststroke dysphagia using stimulation at suprahyoid motor cortex of affected hemisphere. In this study, we aim to investigate the therapeutic efficacy of both high frequency rTMS and iTBS applying on suprahyoid motor cortex in chronic poststroke dysphagia, and its effect on hyolaryngeal movement.
In each stage, patients with subcortical stroke will be randomized into three groups. The three experimental groups receive either bilateral or ipsilateral rTMS, or iTBS (with contralateral sham stimulation) at suprahyoid motor cortex, while the placebo group receive bilateral sham stimulation. Stimulation will be given at 5 hertz(Hz), 1000 pulses of rTMS or 600 pulses of iTBS per session, for a total of 10 sessions. The swallowing function, penetration-aspiration scale of video-fluoroscopic swallowing study, motor evoked potential of suprahyoid muscles, intraoral pressure, and ultrasound swallowing exam will be evaluated before therapy, and at 1, 3, 6 months post therapy.
