Effects of Neuromuscular Electrical Stimulation for Masseter Muscle on Oral Dysfunction After Stroke

Abstract

ObjectiveTo determine positive effect of neuromuscular electrical stimulation (NMES) in conventional dysphagia therapy on masseter muscle oral dysfunction of patients after subacute stroke.MethodsAmong subacute stroke patients who were diagnosed as oropharyngeal dysphagia by videofluoroscopy swallowing study (VFSS), those with oral dysfunction were enrolled. They were randomly assigned to a study group or a control group. The study group received NMES on masseter muscle and suprahyoid muscle simultaneously, while the control group received NMES only on suprahyoid muscle. NMES therapy session as applied 30 minutes each time, two times per day for a total of 20 sessions. Both groups received conventional dysphagia therapy for 2 weeks. All enrolled patients were evaluated by VFSS after 2 weeks. Oropharyngeal swallowing function was evaluated by Penetration-Aspiration Scale, Functional Dysphagia Scale (FDS), and American Speech-Language-Hearing Association National Outcome Measurement System swallowing scale based on results of VFSS.ResultsPatients were randomly assigned to the study group (n=20) or the control group (n=20). There were no significant differences in baseline characteristics or initial values between the two groups. After 2 weeks of NMES, both groups showed improvement in scores of total FDS and pharyngeal phase FDS. Additionally, the study group showed improvement in oral phase FDS. Changes in all measurements were similar between the two groups.ConclusionIn this preliminary study, NMES for masseter muscle has a therapeutic effect on oral dysfunction of patients after subacute stroke.

<p>Effectiveness of Neuromuscular Electrical Stimulation on Post-Stroke Dysphagia: A Systematic Review of Randomized Controlled Trials</p>

“…48,49 The possible explanation might be electrical stimulation can increase pharyngeal and laryngeal activities by increasing the contraction force of hyoid bone muscle. 50 A study done by Zeng et al (2018) 31 reported that NMES and swallowing rehabilitation training together may significantly improve swallowing function which was consistent with the results of two similar studies conducted by Park et al, 41 and Lim et al 51 A study done by Lee et al (2019) 38 suggested that the application of NMES on masseter muscle had a therapeutic effect on oral dysfunction of patients after sub acute stroke. This might be due to chewing functional activities of this muscle might play an important role in stimulating the initiation of the swallowing process.…”

“…Out of 11 studies, 10 of them (n=748) confirmed that NMES had increased swallowing function of post-stroke dysphagia patients compared to the control groups in all outcome measures. 30,[33][34][35][37][38][39][40] However, one study (n=36) indicated that the NMES had no observed differences between the experimental and control groups. 36…”

“…The treatment duration ranged from 10-60 minutes for each session, 35,36 2-5 times per week 33,34,37 for a 2-6 week period. 30,38…”

“…Of all included studies, 6 studies evaluated swallowing function by using PAS. 30,[34][35][36]38,39 Four studies evaluated swallowing function by using VFDS, 30,32,38,40 and only three studies used FDS. 34,35,38…”

Effects of Neuromuscular Electrical Stimulation Synchronized with Chewing Exercises on Bite Force and Masseter Muscle Thickness in Community-Dwelling Older Adults in South Korea: A Randomized Controlled Trial

“…It is used in facilitation techniques to increase muscle strength and sensory awareness and to prevent muscle atrophy, thereby improving motor function [ 14 , 15 ]. Recently, several studies have demonstrated that NMES does not only induce the activation of the masticatory muscle [ 16 , 17 ] but is also effective for improving oral functions, including masticatory functions in the oral phase of the swallowing process [ 18 , 19 ], which might be due to cortical excitability and physiological changes induced by NMES.…”