Dysphagia and Recovery After Vagal or Laryngeal Nerve Injury

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DESCRIPTION (provided by applicant): Swallowing is a critical human activity; failure seriously compromises health and well-being. Normal swallowing function depends on the bilateral integrity of the peripheral neural pathways for safe and efficient transport of the bolus through the mouth and pharynx. Due to its extensive anatomic course and vulnerability to disease and trauma, injury to the vagus and its laryngeal branches is not an uncommon medical finding across the lifespan. The specific impact of these injuries and the mechanisms causing the associated dysphagia are debated, while the contralateral effects of these nerve injuries are unknown. The overarching objective of this project is to understand the changes in patterns of EMG activity and in oropharyngeal kinematics during pathophysiologic swallowing following nerve injury. The specific aims include determination of the impact of three independent, unilateral nerve injuries, superior laryngeal nerve (SA1), recurrent laryngeal nerve (SA2) and proximal vagus (SA3), on swallowing in an infant pig model. The response variables include synchronous measurements of the kinematics of oropharyngeal and laryngeal structures and of bolus transit, as well as the EMG activity patterns in the hyoid, soft palate and pharyngeal musculature. We predict that the oro-pharyngeal behavior after these sensory and motor lesions will be disordered in specific ways so that these results can be used to predict specific dysfunctions which, for ethical reasons, can only be incompletely measured in humans. An understanding of the effect of isolated experimental nerve lesions on swallowing is critical to the assessment of naturally occurring dysfunction. This is especially so in this complex system, where one compromised structure can significantly disrupt other components that are interlinked both in terms of mechanics and control systems. The results from this study can ultimately serve as a basis for the design of clinical rehabilitative strategies. PUBLIC HEALTH RELEVANCE: Due to its extensive anatomic course and vulnerability to disease and trauma, injury to the vagus and its laryngeal branches is not an uncommon medical finding across the lifespan. Determination of the functional consequences of such injuries will elucidate how disruption of the biomechanical integrity of the oropharyngeal system produces dysphagia. Establishing the pathophysiologic basis for dysphagia is the first step towards developing an effective rehabilitative strategy for this condition.