Clinical measurement of pharyngeal surface electromyography: exploratory research

Dysphagia diagnosis is limited by our inability to evaluate the underlying neuromuscular pathology of swallowing. A novel approach using pharyngeal surface electromyography (PsEMG) has been reported in the literature.

Three exploratory projects were undertaken to provide data toward the validation of PsEMG as a clinical measure of pharyngeal physiology. The first evaluates laterality of electrode placement in the pharynx. The second and third evaluate PsEMG using a circumferential and unidirectional electrode, respectively, during swallowing maneuvers.

In experiment 1, a catheter housing 3 manometric sensors and 1 bipolar PsEMG electrode was randomly inserted in each nares of 10 participants. Moving jaw radiographs were taken, and the PsEMG electrode was measured in millimeters from midline. In experiments 2 and 3, the catheter was placed in 22 and 40 research participants, respectively. Waveform characteristics were collected during swallowing maneuvers. The 2 experiments differed by type of electrode (circumferential, unidirectional) and swallowing maneuver (noneffortful and effortful swallow; noneffortful, effortful, and tongue-hold swallow).

Midline electrode placement occurred on 20% of trials with deviation of up to 14.7 mm on all other trials. Maneuver-specific differences in amplitude were not detected with PsEMG; unacceptable levels of intrasubject and intersubject variability were identified. Temporal relationships of PsEMG and pharyngeal manometric pressure appeared appropriate. The unidirectional electrode revealed a unique bimodal PsEMG pattern that may reflect sequential contraction of muscles of the posterior pharyngeal wall.

The current PsEMG design and procedures do not validly measure pharyngeal muscle activity. Recommendations for improved methods are provided.