Meeting Abstract
Mammalian swallowing requires the complex coordination of over 50 muscles innervated by multiple cranial and cervical spinal nerves for successful bolus transit. The oropharyngeal and airway sensory signals are critical to airway protection during the swallow, but exact sensorimotor interactions are poorly understood. Six infant pigs were implanted with radio opaque oropharyngeal markers and chronic indwelling electrodes in infra and supra hyoid muscles. Pigs were recorded feeding on milk mixed with barium using high speed videofluoroscopy and simultaneous EMG before and after surgical lesion of the right recurrent laryngeal nerve. Measurements included (1) assessment of swallow performance as airway protection (2) tongue, hyoid, and epiglottal kinematics, and (3) duration and relative timing of EMG signals. We tested the hypothesis that the relationship among kinematics, EMG, and airway protection changed as a function of RLN lesion. Following lesion, the relationship between tongue kinematics and airway protection changed for safe swallows only (p<0.001). Unsafe swallows did not change. Duration of firing of the thyrohyoid muscle in safe swallows also changed post lesion (p<0.001), with no changes in unsafe swallows (p=0.05). The generation of the motor patterns that produce the kinematics that result in safe swallows is compromised by lesion of nerves supplying the larynx, but unsafe swallows are similar pre and post lesion. Sensory signals from the upper airway are necessary for the brainstem generation of appropriate swallowing motor patterns.
