Repetitive Peripheral Magnetic Stimulation for Strengthening of the Suprahyoid Muscles: A Randomized Controlled Trial

The mouth-opening muscular performance in adults and elderlies with and without dysphagia: A systematic review and meta-analysis

OBJECTIVES

To characterize mouth-opening muscular performance (MOMP) in adults and elderly individuals with dysphagia and healthy controls.

METHODS

We searched the PubMed, EMBASE, CINAHL, Cochrane, Scopus, and Web of Science databases from inception to Jan. 26, 2023. Two independent researchers considered the titles, abstracts, and full texts of potentially eligible papers from 1451 search results. Twenty-five studies that evaluated mouth-opening maximal strength (MOMS) in healthy adults, elderly individuals, and patients with dysphagia met the inclusion criteria.

RESULTS

We found comparable, reliable values with significant sex differences in maximal mouth opening strength (MMOS) in the meta-analysis for healthy elderly patients (females 5.31 ± 0.47 kg vs. males 7.04 ± 0.70 kg; mean difference of 0.84 kg). Age has also emerged as an essential factor in reducing strength. There was a significant reduction in the MMOS score in the only study that compared dysphagic individuals to healthy elderly individuals. In another study, the MMOS score was comparable to the meta-analysis of healthy elderly individuals.

CONCLUSIONS

Both sex and age play significant roles in the MMOS. There is no reliable data on the normal mouth-opening strength and endurance of healthy adults, patients with dysphagia, or individuals with other relevant clinical problems.

Effects of different mylohyoid muscle stimulations on swallowing cortex excitability in healthy subjects

BACKGROUND

Dysphagia has been recognized by the World Health Organization as a medical disability. Improving mylohyoid muscle function plays an important role in pharyngeal dysphagia. The aim of this study was to evaluate the treatment of transcranial magnetic stimulation (TMS), peripheral magnetic stimulation (PMS), and electrical stimulation (ES) for dysphagia.

METHODS

Forty healthy subjects were randomly divided into four groups: TMS+PMS, TMS, PMS, and ES. TMS stimulated the cortical representative area of the mylohyoid muscle and the PMS was directly stimulating the mylohyoid muscle, both of them at a frequency of 10 Hz for a total of 1,800 pulses. The intensity of ES was based on the subject's tolerance level, usually 2-5 mA. Functional near infrared spectroscopy (fNIRS) and motor evoked potential (MEP) of the mylohyoid muscle were used to evaluate the immediate effects of stimulation on swallowing cortex excitability of healthy subjects before and after intervention.

RESULTS

The fNIRS results revealed notable activation across multiple channels in the four groups of healthy subjects both pre- and post- the intervention. Among these channels, the activation levels were most pronounced in the TMS+PMS group, followed by the TMS, PMS, and ES groups, respectively. Regarding the MEP results, post-intervention observations indicated a reduction in bilateral latency and an increase in bilateral amplitude in the TMS+PMS group. Additionally, the left amplitude exhibited an increase in the TMS group.

CONCLUSIONS

In fNIRS, all four stimulation methods significantly activated the swallowing cortex of healthy subjects, and the activation of TMS+PMS was the most obvious, followed by TMS, PMS, and ES.

Feasibility and Safety of an Eight-Week Exercise Program with the Additional Peripheral Magnetic Stimulation of the Abdominal Muscles

Peripheral magnetic stimulation has recently been introduced as a non-invasive but effective physical agent to improve muscle strength and everyday function. The aim of this study was to evaluate the feasibility and safety of an exercise program focusing on the abdominal muscles in combination with the peripheral magnetic stimulation of the abdominal muscles. Male and female overweight and obese adults (n = 19) participated in an eight-week exercise program with the additional peripheral magnetic stimulation of the abdominal muscles. Outcome measures included changes in abdominal subcutaneous fat thickness, trunk muscle strength, body composition, and self-reported body satisfaction. Subcutaneous fat thickness was significantly reduced after the intervention (p < 0.01-p < 0.001). Trunk flexion and left side flexion strength increased significantly after the intervention, although no significant changes were observed for trunk extension (p = 0.07) and right side flexion strength (p = 0.13). The body satisfaction self-assessment score significantly increased (p < 0.01), while body mass, body mass index, and fat mass significantly decreased after the intervention (p < 0.05). Our findings suggest that an exercise program with the additional peripheral magnetic stimulation is feasible and safe for overweight and obese participants. These results support the use of peripheral magnetic stimulation as a safe adjunct to the voluntary abdominal muscle contraction. Future studies are needed to evaluate the efficacy of the additional peripheral magnetic stimulation of the abdominal muscles compared to the voluntary contraction of the abdominal muscles alone.

Effect of Peripheral Magnetic Stimulation for Dysphagia Rehabilitation: A Systematic Review

Recently, a therapeutic method to stimulate the suprahyoid muscle using peripheral magnetic stimulation for dysphagia rehabilitation has been reported. However, clinical evidence, application protocol, and intervention method remain unclear. Therefore, a systematic review of the published literature is needed. The objective of this study was to systematically review clinical studies of peripheral magnetic stimulation applied for rehabilitation of dysphagia. Issues to be considered in future studies are also suggested. This systematic review performed a literature search of four databases (Medline, Embase, CINAHL, and Web of Science) to identify relevant studies published on the application of repetitive peripheral magnetic stimulation (rPMS) for swallowing-related muscles between 2010 and 2022. Seven studies were reviewed. Randomized controlled trials and one-group pre-post, case study designs were included. In the included studies, rPMS was applied to strengthen the submental suprahyoid muscles. The intervention regime varied. The rPMS was applied at a frequency of 30 Hz for 2 s. Rest time ranged from 8 s to 27-28 s. The number of intervention sessions ranged from 2-3 to 30. The intensity ranged from pain-inducing minimum intensity (90% of maximum stimulus output) to non-painful intensity (70-80% of maximum intensity). The rPMS on the suprahyoid muscles had positive effects on physiological changes in the swallowing function, such as displacement of the hyoid bone, muscle strength (cervical flexor, jaw-opening force), swallowing safety, swallowing performance, and swallowing-related quality of life. Participants also reported little pain and adverse reactions during rPMS. Although rPMS is a therapeutic option that can help improve the swallowing function as a non-invasive stimulation method in the rehabilitation of dysphagia, clinical evidence is needed for the development of clear stimulation protocols and guidelines.

Possible Rehabilitation Procedures to Treat Sarcopenic Dysphagia

Sarcopenic dysphagia requires the presence of both dysphagia and generalized sarcopenia. The causes of dysphagia, except for sarcopenia, are excluded. The treatment for sarcopenic dysphagia includes resistance training along with nutritional support; however, whether rehabilitation procedures are useful remains unclear. In this narrative review, we present possible rehabilitation procedures as a resistance training for managing sarcopenic dysphagia, including Shaker exercise, Mendelsohn maneuver, tongue-hold swallow exercise, jaw-opening exercise, swallow resistance exercise, lingual exercise, expiratory muscle strength training, neuromuscular electrical stimulation, and repetitive peripheral magnetic stimulation. We hope that some procedures mentioned in this article or new methods will be effective to treat sarcopenic dysphagia.

A Randomized Controlled Trial of Repetitive Peripheral Magnetic Stimulation applied in Early Subacute Stroke: Effects on Severe Upper-limb Impairment

OBJECTIVES

Repetitive peripheral magnetic stimulation (rPMS) is a non-invasive method that activates peripheral nerves and enhances muscle strength. This study aimed to investigate the effect of rPMS applied in early subacute stroke on severe upper extremity impairment.

DESIGN

Randomized controlled trial.

SETTING

Rehabilitation department of a university hospital.

SUBJECTS

People aged 30-80 years with no practical arm function within four weeks of a first stroke.

INTERVENTIONS

Participants were randomly assigned to either the rPMS group (n = 24, 20Hz and 2400 pulses of rPMS to triceps brachii and extensor digitorum muscles daily for two weeks in addition to conventional physiotherapy) or the control group (n = 20, conventional physiotherapy).

MAIN MEASURES

The primary outcome was the upper extremity motor section of Fugl-Meyer Assessment after treatment. Secondary outcomes included Barthel Index and root mean square of surface electromyography for muscle strength and stretch-induced spasticity of critical muscles of the upper extremity. Data presented: mean (SD) or median (IQR).

RESULTS

The rPMS group showed more significant improvements in the Fugl-Meyer Assessment (12.5 (2.5) vs. 7.0 (1.4), P < 0.001), Barthel Index (15 (5) vs. 10 (3.7), P < 0.001), and strength-root mean square (biceps brachii: 20.5 (4.8) vs. 6.2 (2.7), p < 0.001; triceps brachii: 14.9 (5.8) vs. 4.3 (1.2), p < 0.001; flexor digitorum: 5.1 (0.8) vs. 4.0 (1.1), p < 0.001) compared with the control group.

CONCLUSION

In patients with no functional arm movement, rPMS of upper limb extensors improves arm function and muscle strength for grip and elbow flexion and extension.

Effect of electromyography-triggered peripheral magnetic stimulation on voluntary swallow in healthy humans

BACKGROUND

Electrical stimulation therapy is effective for patients with dysphagia. However, because of the pain, strong stimulation cannot be applied. Although magnetic stimulation induces less pain, there are no reports on magnetic stimulation being synchronised with a swallowing reflex.

OBJECTIVE

This study aimed to determine whether it is possible to induce magnetic stimulation during a voluntary swallowing using electromyography (EMG)-triggered peripheral magnetic stimulation and to evaluate its effect on healthy individuals.

METHODS

A total of 20 healthy adults in seated position were instructed to swallow saliva and 10 ml of barium under videofluoroscopy. For concomitant use of magnetic stimulation, a magnetic stimulus for suprahyoid muscles at 30 Hz frequency was applied for 2 s when the EMG level in the sternohyoid muscle exceeded the threshold. During the voluntary swallowing, the movement of the hyoid bone and opening width of the upper oesophageal sphincter (UES) were measured. Furthermore, pressure topography was evaluated in 6 subjects using high-resolution manometry.

RESULTS

The magnetic stimulation significantly extended the movement time of the hyoid bone (p < 0.001). During liquid deglutition, significant increases were observed in the anterior maximum movement distance of the hyoid bone (p < 0.05), opening width of the UES (p < 0.001) and anterior movement distance of the hyoid bone at the maximum UES opening (p < 0.01). In the pressure topography, the maximum pressure immediately after UES closure significantly decreased with magnetic stimulation (p < 0.05).

CONCLUSION

EMG-triggered peripheral magnetic stimulation made it possible to apply magnetic stimulation during a voluntary swallowing.