Immediate Effects of Electrical Stimulation on Oropharyngeal Structure and Laryngeal Vestibular Closure: A Pilot Study in Healthy Subjects

Abstract

Objectives: This study examined the immediate effects of neuromuscular electrical stimulation (NMES) on the dynamics of oropharyngeal structure and laryngeal vestibular closure (LVC) in healthy subjects. Methods: Ten healthy male volunteers participated in this controlled, before-and-after, videofluoroscopic swallowing pilot study. The study was conducted in four phases (each performed twice): (1) saliva swallow (SS) before evaluation (BEFORE), (2) NMES while at rest with no SS (NMES AT REST), (3) SS during NMES (DURING NMES), and (4) SS to examine the aftereffects of NMES (AFTER). We measured distances that oropharyngeal structures moved in the NMES AT REST phase, and we analyzed the kinematics of saliva swallowing primarily in the BEFORE and AFTER phases. Results: Four changes in the morphology of the oropharyngeal structure caused by NMES AT REST were statistically significant: anterior–upward displacement of the hyoid bone and larynx, stretch of the laryngeal vestibule, and posterior ridge of the tongue root. Regarding the kinematics measured during SS, although there was no significant change in LVC reaction times, LVC duration in the AFTER phase was significantly longer than BEFORE. Regarding maximal displacement of the hyoid bone, there was significantly greater movement AFTER than BEFORE. As additional exploratory outcomes, the velocity of hyoid bone movement was significantly slower, and the hyoid-to-larynx approximation was significantly smaller, DURING NMES than AFTER. Conclusions: Longer duration of LVC might be caused by adaptive learning with NMES-induced structural changes in the oropharynx. Further clinical studies are warranted to determine whether this approach improves dysphagia, which impairs LVC.

Electrical Stimulation for Treatment of Dysphagia Post Head Neck Cancer: A Systematic Review and Meta-Analysis

“…In addition, there is evidence that NMES can promote neural adaptations through afferent feedback to the spinal cord during contractions triggered by stimulation, increased isometric strength and modification of the type of muscle fiber. 43 …”

“…42 Exercise is one of the most effective strategies for maintaining and recovering muscle function; coupled with this, there is evidence that NMES is a method that improves performance and muscle structure as a whole. 43 The mechanism of NMES on swallowing is still unclear, but there are some theories, one of which is the possibility of the electric current promoting greater resistance to swallowing when the infrahyoid muscle is stimulated, with which the individual should make a greater effort to overcome the NMES barrier and thus improve its range of motion during the hyolaryngeal excursion. In addition, there is evidence that NMES can promote neural adaptations through afferent feedback to the spinal cord during contractions triggered by stimulation, increased isometric strength and modification of the type of muscle fiber.…”

“…In addition, there is evidence that NMES can promote neural adaptations through afferent feedback to the spinal cord during contractions triggered by stimulation, increased isometric strength and modification of the type of muscle fiber. 43 Another aspect that has not been tested in this population is the associated use of NMES with resistance exercises. The literature has shown gains in hyolaryngeal excursion and movement speed during swallowing 43 , aspects that are altered in radio-induced dysphagia.…”

“…43 Another aspect that has not been tested in this population is the associated use of NMES with resistance exercises. The literature has shown gains in hyolaryngeal excursion and movement speed during swallowing 43 , aspects that are altered in radio-induced dysphagia. The surveys included do not specify the exercises used and generally approach the exercises or involved Supersupraglottic, Mendelsohn, Swallows Effortful 18 , but with null results or with a reduced effect size both in the NMES group and in the group that performed only the exercises.…”