Age and gender effects on submental motor-evoked potentials

Abstract

It is not known whether there are ageand/or gender-related differences in magnitude of motor-evoked potentials (MEPs) of the submental muscles. Knowledge of this is important in investigations of neurophysiological aspects of swallowing. Forty healthy participants (20 males, 20 females; 20 young [21-35 years], 20 old [53-88 years]) were recruited. Surface electromyography (EMG) electrodes were placed at midline underlying the submental muscle group. Age-and genderrelated differences were evaluated in two neurophysiologic measures of swallowing: MEPs stimulated by single-pulse transcranial magnetic stimulation (TMS) over the motor cortex and surface electromyography (sEMG) recorded from the same submental muscle group during non-stimulated swallows. The older participants had larger MEPs during saliva swallowing than the young participants (p = 0.04, d=0.86). Conversely, the older participants had lower amplitude submental EMG activity during nonstimulated swallows (p=0.045, d=0.67). Gender had no significant effect on MEP magnitude and on submental activity during saliva swallowing. There were no effects of age or gender on MEP latencies. These findings suggest deterioration in muscle function with age in a sample of healthy adults presenting with functional swallowing. We speculate that muscular decline is partially ameliorated by increased cortical activity-i.e., increased submental MEPs-so as to preserve swallowing function in healthy older subjects. These findings emphasize the need for different reference points for evaluation of submental MEPs of different age groups.

TMS brain mapping of the pharyngeal cortical representation in healthy subjects

“…In our study, the pharyngeal MEPs were harder to elicit compared to those of other muscles, such as those controlling the hand. While the amplitudes of MEPs from hand musculature have been reported to be mostly above 200mV [37,38], those from the pharyngeal muscles in our study were only around 35mV, which is consistent with previous studies [8,39,40]. Most of the PMEPs we observed were of a two-peak form, which is in line with N. Freundlieb et al This study pointed out that a two-peak conformation might be due to a higher threshold and a lower number of neurons being stimulated [13] that would thus result in smaller cortical representations, lower amplitudes and two-peak MEP shapes.…”

“…Despite our important observations, there were also some limitations in our study. It has been reported that the CoG for arm target is more anterior in elderly adults than in young persons [47] and that different MEP amplitudes are elicited across different age groups [39]. However, for convenience, the volunteers we recruited were all young healthy adults and thus the representations and locations that we report may be different than those of elderly adults and cannot be completely and directly translated to patients of all ages [48].…”

Comparison of EMG power during sleep from the submental and frontalis muscles

“…No significant differences in power were observed for either f EMG or s EMG when stratified by sleep stage, age, sex, and sleep disordered breathing, unlike what was reported for waking state EEG 17. As expected, muscle tone in the submentalis decreased on a continuum and was lowest during REM.…”

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

“…The muscles involved in swallowing consist of a greater number of type II muscle fibers than type I, and NMES is a strong stimulus for motor unit recruitment of type II fibers and evokes a contraction. 42 A study done by Sola et al (2017) 39 confirmed that NMES improved swallowing functions in sub acute stroke dysphagic patients, compared to standard swallow therapy, after 3-week intervention. But, no difference was observed at 3-month follow-up between the groups.…”