Impact of recurrent laryngeal nerve lesion on oropharyngeal muscle activity and sensorimotor integration in an infant pig model

Abstract

The successful performance of a swallow requires dynamic integration between a wide range of sensory inputs and muscle activities to produce the coordinated kinematics of oropharyngeal structures. Damage to the recurrent laryngeal nerve (RLN) produces dysphagia in infants, with food or liquid entering the airway despite this nerve having minimal direct sensory or motor connections to the act of swallowing, apart from vocal fold closure. Previous results have demonstrated that a complete RLN lesion disrupts both performance and kinematics before initiation of the pharyngeal swallow in infants. We tested the hypothesis that a RLN lesion produces changes in the normal activity of oral floor, tongue, and infrahyoid muscles during a swallow. We recorded swallowing in our validated infant pig model, with synchronous high-speed imaging and fine-wire, chronic electromyography. We found changes in the timing, duration, and amplitude of the motor pattern in an array of muscles that are supplied by several different cranial and cervical nerves. Some of these changes in muscle activity are associated with the preparatory aspects of bolus aggregation or movement and so occur before the pharyngeal swallow. Taken with previous biomechanical results, these patterns suggest an intricate brain stem sensorimotor integration that occurs as part of a swallow. In particular, the execution of oral motor function is changed as a result of this simple lesion. NEW & NOTEWORTHY Damage to the recurrent laryngeal nerve compromises swallowing despite an absent or minimal contribution to either the motor or sensory aspects of this function. This study documents EMG changes, following RLN lesion, to non-RLN innervated muscles that are active during swallowing in an infant model. Some of these muscles fire before the pharyngeal swallow and are associated with the preparatory aspects of bolus aggregation and movement, suggesting important sensorimotor integration at a brain stem level.

The contractile patterns, anatomy and physiology of the hyoid musculature change longitudinally through infancy

“…R. Soc. B 288: 20210052 sides, as previous work examining muscle firing patterns has demonstrated (electronic supplementary material, figure S1) [34].…”

Specific Vagus Nerve Lesion Have Distinctive Physiologic Mechanisms of Dysphagia

“…Because these changes are related to airway protection outcomes, it seems more likely that the mechanism of aspiration is related to kinematics and bolus formation early in the swallow. Indeed, work on the effects of RLN lesion on patterns of muscle activation, both duration and timing, in swallowing has shown changes in the timing of muscle contraction for muscles located in the floor of the mouth, and which are active early in the swallow sequence before bolus formation (30). However, a complete comparison requires similar data for the SLN lesion animals.…”

Prevalence, incidence, and characteristics of dysphagia in those with unilateral vocal fold paralysis

“…Theoretically, individuals with isolated injury to the RLN are capable of achieving airway safety due to the compensatory contributions of the supraglottic larynx, the unimpaired side of the larynx, normal hyolaryngeal excursion, and pharyngeal constriction and shortening . Support for this compensation theory was found in a piglet model in which dynamic reorganization of the pharyngeal swallow and adequate airway protection were demonstrated subsequent to isolated RLN damage . In addition, Dworkin and Treadway found that 70% of a retrospective cohort of adults diagnosed with idiopathic UVP (N = 30) did not report any form of dysphagia .…”