Novel neuromuscular electrical stimulation system for treatment of dysphagia after brain injury

Abstract

The purpose of this study was to compare the effects of a novel neuromuscular electrical stimulation (NMES) to the effects of conventional treatment in patients with dysphagia after brain injury. In total, 26 patients were non-randomly divided into an experimental group (n = 12) and a control group (n = 14). The experimental group received NMES intervention followed by conventional treatment, including thermaltactile stimulation with intensive repetition of a dry-swallow task. The control group received conventional treatment without NMES. NMES at a fixed pulse duration of 50 μs and a frequency of 50 Hz was delivered over the skin areas above the motor point of the target muscles, i.e., the bilateral geniohyoid, mylohyoid/anterior belly of the digastric, and thyrohyoid muscles, using a high-voltage pulsed-current device. The two groups received 40-min treatments once a day, 5 days per week, for 8 weeks. Outcome, assessed before and 8 weeks after treatment, was evaluated with regard to the videofluoroscopic dysphagia scale (VDS), the anterior and superior displacement of the hyoid bone and larynx, and the functional oral intake scale. Both groups exhibited improvement, but the experimental group exhibited more significant improvement in the displacement of the hyoid bone and larynx, VDS-total score, and VDS-pharyngeal score than the control group did. The results suggest that NMES combined with conventional treatment is superior to conventional treatment alone in patients with dysphagia following treatment for brain injury. Further investigations are necessary to examine the effects of NMES in patients with more varied types of diseases.

Fig. 1.

Electrical stimulation was delivered using an high-voltage pulsed current (HVPC) device with a direct monophasic pulsed current and twin-peak pulse. A: HVPC device composite of active electrodes (8-mm diameter metal sphere electrode) and dispersive electrodes (gel pad), B: Active electrode.

Fig. 2.

Schematic diagram of high-voltage pulsed current (HVPC). Output waveforms from Universal Stimulation Current Unit ES-530 showing twin-peak pulse monophasic waveform, generating high voltage and a low total current, with very short duration and longer inter-pulse intervals.

Fig. 3.

Schematic of the stimulation region of the surface electrodes. The active electrodes were delivered bilaterally over the motor points of the target muscles, and the dispersive electrodes were placed over the cervical spine. A: mylohyoid/anterior belly of digastric muscles, B: geniohyoid muscles, C: thyrohyoid muscles.

Fig. 4.

Comparison of hyoid bone and larynx displacement and videofluoroscopic dysphagia scale (VDS) score changes between the experimental and control groups. Changes for VDS and hyoid bone and larynx displacement following the two interventions are shown. A: VDS, B: hyoid bone and larynx displacement. Graph depicts means ± standard deviation. Significant differences between the experimental group and the control group are indicated at **p < 0.01. p < 0.01 (Mann-Whitney U test between the experimental and control groups).