What is your doctor's protocol to treat dysphagia(swallowing problems)?
Clinical effectiveness of the sequential 4-channel NMES compared with that of the conventional 2-channel NMES for the treatment of dysphagia in a prospective double-blind randomized controlled study
Journal of NeuroEngineering and Rehabilitation volume 18, Article number: 90 (2021)
Abstract
Background
To date, conventional swallowing therapies and 2-channel neuromuscular electrical stimulation (NMES) are standard treatments for dysphagia. The precise mechanism of 2-channel NMES treatment has not been determined, and there are controversies regarding the efficacy of this therapy. The sequential 4-channel NMES was recently developed and its action is based on the normal contractile sequence of swallowing-related muscles.
Objective
To evaluate and compare the rehabilitative effectiveness of the sequential 4-channel NMES with that of conventional 2-channel NMES.
Methods
In this prospective randomized case–control study, 26 subjects with dysphagia were enrolled. All participants received 2- or 4-channel NMES for 2–3 weeks (minimal session: 7 times, treatment duration: 300–800 min). Twelve subjects in the 4-channel NMES group and eleven subjects in the 2-channel NMES group completed the intervention. Initial and follow-up evaluations were performed using the videofluoroscopic dysphagia scale (VDS), the penetration-aspiration scale (PAS), the MD Anderson dysphagia inventory (MDADI), the functional oral intake scale (FOIS), and the Likert scale.
Results
The sequential 4-channel NMES group experienced significant improvement in their VDS (oral, pharyngeal, and total), PAS, FOIS, and MDADI (emotional, functional, and physical subsets) scores, based on their pretreatment data. VDS (oral, pharyngeal, and total) and MDADI (emotional and physical subsets) scores, but not PAS and FOIS scores, significantly improved in the 2-channel NMES group posttreatment. When the two groups were directly compared, the 4-channel NMES group showed significant improvement in oral and total VDS scores.
Conclusions
The sequential 4-channel NMES, through its activation of the suprahyoid and thyrohyoid muscles, and other infrahyoid muscles mimicking physiological activation, may be a new effective treatment for dysphagia.
Trial registration: clinicaltrial.gov, registration number: NCT03670498, registered 13 September 2018, https://clinicaltrials.gov/ct2/show/NCT03670498?term=NCT03670498&draw=2&rank=1.
Introduction
Dysphagia is a common and serious problem in patients with stroke and its prevalence ranges from 37 to 78% [1]. Decreased laryngeal elevation caused by pharyngeal muscle weakness is the main cause of dysphagia in patients with stroke, and this can result in aspiration and pharyngeal residue during swallowing [2, 3]. To date, diverse methods, such as oropharyngeal exercises, compensatory maneuvers, neuromuscular electrical stimulation (NMES), and diet control, are used for dysphagia treatment.
Most clinical studies regarding NMES evaluated the rehabilitative effects of this therapy, and 2-channel NMES is gaining attention owing to its muscle strengthening effect through motor stimulation and the facilitation of the swallowing reflex by sensory stimulation [4]. Freed et al. and Blumenfeld et al. indicated that transcutaneous electrical stimulation is superior to conventional dysphagia management probably due to the stimulation of the sensory cortex of the cerebrum, the recruitment of more motor units rather than volitional contractions, and increased local blood flow [5, 6]. In a previous study, a 2-channel NMES showed better outcomes than submental stimulation in submental and throat stimulations [7]. However, the precise mechanism of 2-channel NMES treatment has not been determined, and there are controversies regarding the efficacy of this therapy and the method of stimulation [8]. No previous study has provided the basis for the effectiveness of the co-stimulation of the suprahyoid and infrahyoid muscles, and a recent randomized controlled trial failed to prove the efficacy of 2-channel NMES in patients with stroke [7, 9]. Moreover, conventional 2-channel NMES does not stimulate muscles similar to the physiological sequence of muscle activation during swallowing [8, 10].
In our previous study, the suprahyoid muscles are activated about 150–350 ms earlier than the infrahyoid muscles [10]. These sequential contractions of the suprahyoid and infrahyoid muscles induce a circular motion of the hyoid bone during the normal swallowing process, which initially moves forward-upwardly and then moves backward-downwardly [11]. This suggests that simultaneous stimulation of the suprahyoid and infrahyoid muscles could result in the cancellation of positive effects [12,13,14]. However, the 2-channel NMES stimulates swallowing-related muscles simultaneously, which is different from the physiologic process. The stimulation of these muscles via 4-channel NMES may lead to a correction of the abnormal hyoid and laryngeal motion in patients with dysphagia [15].
Therefore, we hypothesized that the sequential 4-channel NMES, which is based on normal physiology, would improve the swallowing function in general. The primary purpose of this study was to compare the rehabilitative effects of the sequential 4-channel NMES to 2-channel NMES and confirm the superiority of the sequential 4-channel NMES over conventional 2-channel NMES using a randomized double-blind clinical trial. The secondary purpose of the study was to calculate the number of subjects required to confirm the superiority of the 4-channel NMES in a future clinical trial.
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