Healthy Volunteers Immediately Adapt to Submental Stimulation During Swallowing.

Area of Science:

• Biomechanics of swallowing
• Neuromuscular electrical stimulation

Background:

• Transcutaneous electrical stimulation is used for dysphagia, with suprahyoid and infrahyoid approaches yielding different effects on hyolaryngeal movement.
• Recent dysphagia therapy utilizes large submental electrodes, often with resistance exercises, necessitating an understanding of their impact on swallowing biomechanics.

Purpose of the Study:

• To investigate the effects of submental electrical stimulation on hyolaryngeal movement and swallowing kinematics in healthy volunteers.
• To test the hypothesis that submental stimulation might elevate the hyoid, increase vestibular opening, and potentially compromise swallowing safety.

Main Methods:

• Seven healthy volunteers underwent videofluoroscopy (VF) while swallowing 5 mL of liquid barium.
• Swallowing trials were conducted under three conditions: stimulation at rest, swallowing without stimulation, and swallowing with submental stimulation.

Main Results:

• At rest, stimulation caused significant anterior movement of the hyoid and larynx and increased the hyoid-larynx distance.
• During swallowing with stimulation, volunteers significantly reduced anterior hyoid motion and increased hyoid elevation compared to un-stimulated swallowing.
• No significant changes in laryngeal movement or hyoid-larynx distance were observed during stimulated swallowing.

Conclusions:

• Healthy volunteers demonstrated immediate compensatory adjustments to submental electrical stimulation during swallowing.
• These adjustments involved reducing anterior hyoid motion and increasing superior hyoid motion, without altering laryngeal kinematics.
• Findings suggest an innate motor control schema for swallowing with feedforward correction capabilities to mitigate potential negative effects of stimulation.