Swallowing and sensation: evaluation of deglutition in the anesthetized larynx

To better characterize the role of laryngeal sensory systems in swallowing, we assessed 5 healthy adult volunteers via functional endoscopic evaluation of swallowing before and after bilateral superior laryngeal nerve block. The volunteers were tested multiple times with both liquid and puree consistencies. Laryngeal anesthesia resulted in a significantly higher (p < .05) incidence of premature spillage, pharyngeal residual, and laryngeal penetration with all consistencies, and a higher incidence of tracheal aspiration with liquid. Aspiration of puree was increased, but the difference did not achieve significance. These results contrast with those achieved by others with topical anesthesia, which caused little impairment. Other afferent modalities besides light touch, interrupted by superior laryngeal nerve block but not by topical anesthesia, may account for the difference. It is likely that this study underestimates the severity of clinical disability from afferent deficits, because of the short duration of the experimental deficit and the lack of associated comorbidities in the subjects. These findings have implications for clinical sensory testing and sensate flap reconstruction of pharyngeal defects.