Electromyography as a Biofeedback Tool for Rehabilitating Swallowing Muscle Function

Abstract

Dysphagia (swallowing impairment) is a common and serious problem in individuals who have suffered neurological injuries (strokes, acquired brain injury) as well as individuals with neurodegenerative conditions or head and neck cancer. The effortful swallow and Mendelsohn maneuver are two therapy techniques, recommended to address specific muscle-function related abnormalities in dysphagia due to neurological injury. The process of swallowing is a complex neuromuscular sequence, involving contributions from approximately 25 pairs of muscles in the upper aerodigestive tract. Contraction of the floor- of-mouth muscles (particularly the mylohyoid and geniohyoid) facilitates upward and forward movement of the hyoid and larynx in swallowing (Burnett et al., 2003; Pearson et al., 2010). Hyolaryngeal movement has two important functional consequences: 1) closure of the entrance to the airway; and 2) opening of the sphincter between the pharynx and the esophagus, i.e., the upper esophageal sphincter (UES), via traction forces (Cook et al., 1989). Patients with reduced hyolaryngeal excursion in swallowing are at risk for aspiration (entry of foreign material into the airway) and post-swallow residues, particularly in the pyriform sinuses, which lie just above the UES. The structures involved in swallowing are illustrated in Figure 1, which is a still shot taken from a videofluoroscopic swallowing study (VFSS) showing aspiration of material into the trachea as well as residues in the valleculae and pyriform sinuses. Surface electromyography (sEMG) is useful for monitoring performance of the effortful swallow and Mendelsohn maneuver exercises, which are indicated as therapy techniques for patients with reduced hyolaryngeal movement in swallowing. SEMG can be used to collect and display information regarding performance of these maneuvers in treatment; such performance-contingent information can enhance motivation, compliance and task- performance. For the effortful swallow, sEMG can be used to measure the amplitude of muscle contraction used by a patient and to compare this to their regular swallowing. Amplitude targets can be used to guide a patient to work harder on this exercise, and sEMG information can be used to inform both the patient and the clinician of success in achieving these targets across the course of treatment. For the Mendelsohn maneuver, the goal is to maintain submental muscle contraction and excursion of the hyolaryngeal complex, thereby prolonging opening of the UES (Mendelsohn & McConnel, 1987); sEMG can be used to measure and display the duration of muscle contraction used in this task.