Kinematic effects of hyolaryngeal electrical stimulation therapy on hyoid excursion and laryngeal elevation

The purpose of this study was to assess the effect of repeated sessions of electrical stimulation therapy (EST) on the neck muscles with respect to the stimulation site by using quantitative kinematic analysis of videofluoroscopic swallowing studies (VFSS) in dysphagia patients with acquired brain injury. We analyzed 50 patients in a tertiary hospital who were randomly assigned into two different treatment groups. One group received EST on the suprahyoid muscle only (SM), and the other group received stimulation with one pair of electrodes on the suprahyoid muscle and the other pair on the infrahyoid muscle (SI). All patients received 10-15 sessions of EST over 2-3 weeks. The VFSS was carried out before and after the treatment. Temporal and spatial parameters of the hyoid excursion and laryngeal elevation during swallowing were analyzed by two-dimensional motion analysis. The SM group (n = 25) revealed a significant increase in maximal anterior hyoid excursion distance (mean ± SEM = 1.56 ± 0.52 mm, p = 0.008) and velocity (8.76 ± 3.42 mm/s, p = 0.017), but there was no significant increase laryngeal elevation. The SI group (n = 25), however, showed a significant increase in maximal superior excursion distance (2.09 ± 0.78 mm, p = 0.013) and maximal absolute excursion distance (2.20 ± 0.82 mm, p = 0.013) of laryngeal elevation, but no significant increase in hyoid excursion. There were no significant differences between the two groups with respect to changes in maximal anterior hyoid excursion distance (p = 0.130) and velocity (p = 0.254), and maximal distance of superior laryngeal elevation (p = 0.525). EST on the suprahyoid muscle induced an increase in anterior hyoid excursion, and infrahyoid stimulation caused an increase in superior laryngeal elevation. Hyolaryngeal structural movements were increased in different aspects according to the stimulation sites. Targeted electrical stimulation based on pathophysiology is necessary.