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

Dysphagia after stroke: research advances in treatment interventions

After a stroke, most patients have dysphagia, which can lead to aspiration pneumonia, malnutrition, and adverse functional outcomes. Protective interventions aimed at reducing these complications remain the cornerstone of treatment. Dietary adjustments and oral hygiene help mitigate the risk of aspiration pneumonia, and nutritional supplementation, including tube feeding, might be needed to prevent malnutrition. Rehabilitative interventions aim to enhance swallowing function, with different behavioural strategies showing promise in small studies. Investigations have explored the use of pharmaceutical agents such as capsaicin and other Transient-Receptor-Potential-Vanilloid-1 (TRPV-1) sensory receptor agonists, which alter sensory perception in the pharynx. Neurostimulation techniques, such as transcranial direct current stimulation, repetitive transcranial magnetic stimulation, and pharyngeal electrical stimulation, might promote neuroplasticity within the sensorimotor swallowing network. Further advancements in the understanding of central and peripheral sensorimotor mechanisms in patients with dysphagia after a stroke, and during their recovery, will contribute to optimising treatment protocols.

Effects of transcutaneous neuromuscular electrical stimulation on post-stroke dysphagia: a systematic review and meta-analysis

Background

Dysphagia is one of the common complications after stroke. It is closely related to lung infection and malnutrition. Neuromuscular electrical stimulation (NMES) is widely used in the treatment of post-stroke dysphagia, but the evidence-based medical evidence of NMES is limited. Therefore, this study aimed to evaluate the clinical efficacy of NMES in patients with post-stroke dysphagia by systematic review and meta-analysis.

Methods

We searched the CNKI, Wanfang, VIP, SinoMed, PubMed, Embase, Cochrane Library, and Web of Science databases for all randomized controlled trials (RCTs) of NMES in the treatment of post-stroke dysphagia from the establishment of the database to 9 June 2022. The risk of bias assessment tool recommended by Cochrane and the GRADE method was used to assess the risk of bias and the quality of evidence. RevMan 5.3 was used for statistical analysis. Sensitivity and subgroup analyses were performed to evaluate the intervention effect more specifically.

Results

A total of 46 RCTs and 3,346 patients with post-stroke dysphagia were included in this study. Our meta-analysis showed that NMES combined with routine swallowing therapy (ST) could effectively improve swallowing function in Penetration-Aspiration Scale (MD = -0.63, 95% CI [-1.15, -0.12], P = 0.01), Functional Oral Intake Scale (MD = 1.32, 95% CI [0.81, 1.83], P < 0.00001), Functional Dysphagia Scale (MD = - 8.81, 95% CI [-16.48, -1.15], P = 0.02), the Standardized Swallowing Assessment (MD = -6.39, 95% CI [-6.56, -6.22], P < 0.00001), the Videofluoroscopic Swallow Study (MD = 1.42, 95% CI [1.28, 1.57], P < 0.00001) and the Water swallow test (MD = -0.78, 95% CI [-0.84, -0.73], P < 0.00001). Furthermore, it could improve the quality of life (MD = 11.90, 95% CI [11.10, 12.70], P < 0.00001), increase the upward movement distance of hyoid bone (MD = 2.84, 95% CI [2.28, 3.40], P < 0.00001) and the forward movement distance of hyoid bone (MD = 4.28, 95% CI [3.93, 4.64], P < 0.00001), reduce the rate of complications (OR = 0.37, 95%CI [0.24, 0.57], P < 0.00001). Subgroup analyses showed that NMES+ST was more effective at 25 Hz, 7 mA or 0-15 mA, and at courses ( ≤ 4 weeks). Moreover, patients with an onset of fewer than 20 days and those older than 60 years appear to have more positive effects after treatment.

Conclusion

NMES combined with ST could effectively increase the forward and upward movement distance of the hyoid bone, improve the quality of life, reduce the rate of complications, and improve the swallowing function of patients with post-stroke dysphagia. However, its safety needs to be further confirmed.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO, identifier: CRD42022368416.

Statistical Power and Swallowing Rehabilitation Research: Current Landscape and Next Steps

Despite rapid growth in the number of treatments to rehabilitate dysphagia, studies often demonstrate mixed results with non-significant changes to functional outcomes. Given that power analyses are infrequently reported in dysphagia research, it remains unclear whether studies are adequately powered to detect a range of treatment effects. Therefore, this review sought to examine the current landscape of statistical power in swallowing rehabilitation research. Databases were searched for swallowing treatments using instrumental evaluations of swallowing and the penetration-aspiration scale as an outcome. Sensitivity power analyses based on each study's statistical test and sample size were performed to determine the minimum effect size detectable with 80% power. Eighty-nine studies with 94 treatment comparisons were included. Sixty-seven percent of treatment comparisons were unable to detect effects smaller than d = 0.80. The smallest detectable effect size was d = 0.29 for electrical stimulation, d = 0.49 for postural maneuvers, d = 0.52 for non-invasive brain stimulation, d = 0.61 for combined treatments, d = 0.63 for respiratory-based interventions, d = 0.70 for lingual strengthening, and d = 0.79 for oral sensory stimulation. Dysphagia treatments examining changes in penetration-aspiration scale scores were generally powered to reliably detect larger effect sizes and not smaller (but potentially clinically meaningful) effects. These findings suggest that non-significant results may be related to low statistical power, highlighting the need for collaborative, well-powered intervention studies that can detect smaller, clinically meaningful changes in swallowing function. To facilitate implementation, a tutorial on simulation-based power analyses for ordinal outcomes is provided ( https://osf.io/e6usd/ ).

The Facial Skin Blood Flow Change of Stroke Patients with Facial Paralysis after Peripheral Magnetic Stimulation: A Pilot Study

Background: Facial paralysis (FP) is a common symptom after stroke, which influences the quality of life and prognosis of patients. Recently, peripheral magnetic stimulation (PMS) shows potential effects on peripheral and central nervous system damage. However, the effect of PMS on FP after stroke is still unclear. Methods: In this study, we applied PMS on the facial nerve of nine stroke patients with FP. At the same time, laser speckle contrast imaging (LSCI) was used to explore the facial skin blood flow (SkBF) in 19 healthy subjects and nine stroke patients with FP before and after the PMS intervention. The whole face was divided into 14 regions to compare the SkBF in different sub-areas. Results: In baseline SkBF, we found that there were no significant differences in the SkBF between the left and right faces in the healthy subjects. However, there was a significant difference in the SkBF between the affected and unaffected faces in Region 7 (Chin area, p = 0.046). In the following five minutes after the PMS intervention (Pre_0–5 min), the SkBF increased in Region 5 (p = 0.014) and Region 7 (p = 0.046) and there was an increasing trend in Region 3 (p = 0.088) and Region 6 (p = 0.069). In the five to ten minutes after the intervention (Post_6–10 min), the SkBF increased in Region 5 (p = 0.009), Region 6 (p = 0.021) and Region 7 (p = 0.023) and there was an increasing trend in Region 3 (p = 0.080) and left and right whole face (p = 0.051). Conclusions: These pilot results indicate that PMS intervention could increase facial skin blood flow in stroke patients with FP. A further randomized controlled trial can be performed to explore its possible clinical efficacy.

The Effects of Neuromuscular Electrical Stimulation on Swallowing Functions in Post-stroke Dysphagia: A Randomized Controlled Trial

The study aimed to evaluate the effects of traditional dysphagia therapy (TDT) and neuromuscular electrical stimulation (NMES) combined with TDT on functionality of oral intake, dysphagia symptom severity, swallowing- and voice-related quality of life, leakage, penetration-aspiration, and residue levels in patients with post-stroke dysphagia (PSD). Thirty-four patients with PSD were included in our prospective, randomized, controlled, and single-blind study. The patients were divided into two groups: (1) TDT only (control group, n = 17) and (2) TDT with NMES (experimental group, n = 17). TDT was applied to both groups for three consecutive weeks, 5 days a week, 45 min a day. Sensory NMES was applied to the experimental group for 45 min per session. Patients were evaluated by the functional oral intake scale (FOIS), the eating assessment tool (EAT-10), the swallowing quality of life questionnaire (SWAL-QOL), and the voice-related quality of life questionnaire (VRQOL) at baseline, immediately post-intervention, and at the 3rd month post-intervention. Fiberoptic endoscopic evaluation of swallowing (FEES) with liquid and semi-solid food was performed pre- and post-intervention. A significant post-intervention improvement was observed on all scales in both groups, and these improvements were maintained 3 months post-intervention. Leakage and penetration-aspiration levels with semi-solid food declined only in the experimental group. In conclusion, TDT is a non-invasive and inexpensive method that leads to improvement in many swallowing-related features in stroke patients; however, NMES as an adjunct therapy is costly but can provide additional benefits for improving features, such as penetration-aspiration and residue levels.

Therapeutic Effect and Optimal Electrode Placement of Transcutaneous Neuromuscular Electrical Stimulation in Patients with Post-Stroke Dysphagia: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background: To date, there is no conclusive evidence that transcutaneous neuromuscular electrical stimulation (TNMES) benefits patients with post-stroke dysphagia (PSD). In addition, the optimal TNMES electrode placement has not been well-established. This systematic review and meta-analysis were conducted to investigate these two research gaps. Methods: Five major databases were systematically searched for randomized controlled trials (RCTs) through January 2022. Effect sizes were computed using Hedges’ g statistic, which were then entered into the random-effects model to obtain pooled effect estimates. Results: Twenty-four RCTs met the eligibility criteria. On the improvement of swallowing function, TNMES alone was not superior to conventional swallowing therapies (CSTs); combined therapy of TNMES and CSTs significantly surpassed CSTs alone (standardized mean difference (SMD) = 0.91, 95% confidence interval (95% CI): 0.68 to 1.14, p < 0.0001; I2 = 63%). Moreover, significant pooled effect sizes were observed in subgroups with horizontal electrode placement above the hyoid bone (SMD = 0.94, 95% CI: 0.72 to 1.16; I2 = 0%) and horizontal electrode placement just above and below the hyoid bone (SMD = 0.87, 95% CI: 0.59 to 1.14; I2 = 0%). The largest pooled effect size was observed in the subgroup that individualized electrode placement according to dysphagia evaluation (SMD = 1.65, 95% CI: 0.38 to 2.91; I2 = 90%). Conclusion: TNMES should be used in combination with CSTs for PSD. Horizontal electrode placement should target suprahyoid muscles or both suprahyoid and thyrohyoid muscles.

Quantification of the Masseter Muscle Hardness of Stroke Patients Using the MyotonPRO Apparatus: Intra- and Inter-Rater Reliability and Its Correlation with Masticatory Performance

BACKGROUND Chewing dysfunction is one of the most common serious complications after a stroke. It may be influenced by the hardness of the masseter muscle and masticatory performance; however, the association between these 2 factors is not explicit. Thus, it is meaningful to explore the functional status of the masseter muscle among stroke patients. The main objectives of this study were to examine the intra- and inter-rater reliability of the MyotonPRO apparatus in measuring masseter muscle hardness in stroke patients and to investigate the correlation between the bilateral masseter muscle hardness and masticatory performance in these patients. MATERIAL AND METHODS A total of 20 stroke patients participated in our study. The hardness of the masseter muscle was measured by 2 physiotherapists using the MyotonPRO apparatus. Overall, each patient masticated 2 pieces of red-blue bicolor chewing gum for 20 chewing cycles each. The chewing pieces were analyzed using ViewGum software for masticatory performance. RESULTS The intra- and inter-rater reliability of the MyotonPRO apparatus for measuring bilateral masseter hardness of stroke patients was excellent. The correlation analysis showed that the hardness index of the masseter muscle on the affected side was moderately correlated with the masticatory performance of the same side. CONCLUSIONS The MyotonPRO device can be used for measuring the masseter muscle hardness of stroke patients, with excellent reliability. This study established the construct validity between the stiffness of the masseter muscle and masticatory performance.

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

The purpose of this review was to summarize the latest best scientific evidence on the efficacy of neuromuscular electrical stimulation on swallowing function in dysphagic stroke patients. A comprehensive systematic search of literature published between November 2014 and May 2020 was performed using the following electronic databases: PubMed/Medline, CINAHL, PEDro, Science Direct, Google Scholar, EMBASE, and Scopus. Only randomized controlled trials (RCT) evaluating the effect of neuromuscular electrical stimulation on swallowing function in dysphagic stroke patients were included. Physiotherapy Evidence Database (PEDro) has been used to evaluate the risk of bias of included trials. This review was reported in accordance with PRISMA statement guideline. The methodological quality of the studies was determined using PEDro scale and GRADE approach. Evidence of overall quality was graded from moderate to high. Eleven RCTs involving 784 patients were analyzed. The primary outcome measures of this review were functional dysphagia scale (FDS) and standard swallowing assessment. This review found neuromuscular electrical stimulation (NMES) coupled with traditional swallowing therapy could be an optional intervention to improve swallowing function after stroke in rehabilitation department.

Effectiveness of Different Application Parameters of Neuromuscular Electrical Stimulation for the Treatment of Dysphagia after a Stroke: A Systematic Review

Background: Dysphagia causes severe complications among people with a stroke. Physiotherapy allows the cure of this pathology, and among the tools it offers is neuromuscular electrical stimulation. However, this is a technique that has not been protocolized. Therefore, it was considered necessary to carry out a systematic review on the efficacy of the various parameters of application of the neuromuscular electrical stimulation in dysphagia generated after a stroke. Methods: A systematic search for publications was conducted in March 2020 in the Pubmed, Cinahl, Medline, Web of Science and Scopus databases, using as search terms: Electric stimulation therapy, Deglutition disorders and Stroke. Results: 21 articles were obtained in which the application of neuromuscular electrical stimulation was applied in isolation (n = 7) or in combination with other techniques such as strengthening exercises and manual therapy techniques (n = 14), with this second modality of treatment having greater benefits for patients. Conclusion: The greatest efficacy of this technique is reached when applied at 60-80 Hz, 700 μs of pulse duration, at the motor intensity threshold and in sessions of 20–30 min.

Effects of Neuromuscular Electrical Stimulation (NMES) on salivary flow in healthy adults

Background

Neuromuscular electrical stimulation (NMES) is a method used for enhancing suprahyoid muscle activity and is widely applied as a treatment for dysphagia. Patients often complain of saliva pooling in the pharynx during NMES. Therefore, the purpose of this study was to investigate the changes in salivary flow during NMES.

Material and Methods

Twenty healthy adults participated in this study. Electrical stimulation was applied at constant strength for 60 minutes to the suprahyoid muscles using VitalStim®. Participants were examined under three conditions of NMES: sensory threshold plus 75% of the difference between sensory and pain thresholds (75% Stim), SensoryStim, and Sham. Saliva collections, using a 10-min spitting method, were performed seven times: before stimulation (S1), during stimulation (S2-S6), and 5 min after stimulation ended (S7).

Results

Significant differences were observed in saliva flow between S1 and S7, as well as S2 and S7 in 75% Stim.

Conclusions

This study indicates that an increase in saliva flow was promoted after NMES. Therefore, NMES may have effects on patients with xerostomia.

Key words:Neuromuscular electrical stimulation, suprahyoid muscle, sensory threshold, pain threshold, saliva flow.

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

This study is aimed at investigating the effects of synchronized neuromuscular electrical stimulation (NMES) and chewing exercises on bite force and the masseter muscle thickness in community-dwelling older adults. Material and methods: Forty older adults were enrolled in South Korea and randomly assigned to either an experimental or control group. The experimental group performed chewing exercises using the No-Sick Exerciser equipment synchronized with NMES applied to the bilateral masseter muscles, while the control group performed only chewing exercises. Both groups received interventions for 20 min/day, 5 days/week, for 6 weeks. Bite force was measured using the OCCLUZER device, and masseter muscle thickness was measured using a portable ultrasound. Results: Both groups showed a significant increase in bite force and masseter muscle thickness compared to baseline measurements (p < 0.05). The experimental group showed a significantly higher increase in bite force and masseter muscle thickness than the control group after combined intervention (p < 0.05). Conclusion: This study demonstrates that NMES synchronized with chewing exercises is more efficient in increasing bite force and masseter muscle thickness than chewing exercises alone in community-dwelling older adults.

Effect of Neuromuscular Electrical Stimulation on Masseter Muscle Thickness and Maximal Bite Force Among Healthy Community-Dwelling Persons Aged 65 Years and Older: A Randomized, Double Blind, Placebo-Controlled Study

Aim: This study investigated the effect of neuromuscular electrical stimulation (NMES) on masseter muscle thickness and maximal bite force among healthy community-dwelling elderly persons older than 65 years. Materials and methods: A total of 40 participants were randomly assigned to the experimental and placebo groups. In the experimental group, NMES was applied to both masseter muscles, and electrical signals were gradually increased until the participants felt a grabbing sensation (range 6.0–7.5 mA) in the masseter muscle. The placebo group, in contrast, underwent NMES in the same manner and procedure as the experimental group with less electrical intensity (0.5 mA). All interventions were administered five times a week for six weeks, 20 min per day. The outcomes were masseter muscle thickness assessed using ultrasound and maximal bite force using a bite force meter. The level of significance was set as p < 0.05. Results: The experimental group showed a significant increase in both masseter muscle thickness and maximal bite force as compared with the placebo group (p = 0.002 and 0.019, respectively). Moreover, the degree of change in the masseter muscle thickness and maximal bite force significantly increased in the experimental and placebo groups (p < 0.001, both). Conclusions: This study demonstrated that NMES could be an effective modality for increasing masseter muscle thickness and maximal bite force in healthy older adults.