Specific Vagus Nerve Lesion Have Distinctive Physiologic Mechanisms of Dysphagia

Abstract

Swallowing is complex at anatomical, functional, and neurological levels. The connections among these levels are poorly understood, yet they underpin mechanisms of swallowing pathology. The complexity of swallowing physiology means that multiple failure points may exist that lead to the same clinical diagnosis (e.g., aspiration). The superior laryngeal nerve (SLN) and the recurrent laryngeal nerve (RLN) are branches of the vagus that innervate different structures involved in swallowing. Although they have distinct sensory fields, lesion of either nerve is associated clinically with increased aspiration. We tested the hypothesis that despite increased aspiration in both case, oropharyngeal kinematic changes and their relationship to aspiration would be different in RLN and SLN lesioned infant pigs. We compared movements of the tongue and epiglottis in swallows before and after either RLN or SLN lesion. We rated swallows for airway protection. Posterior tongue ratio of safe swallows changed in RLN (p = 0.01) but not SLN lesioned animals. Unsafe swallows post lesion had different posterior tongue ratios in RLN and SLN lesioned animals. Duration of epiglottal inversion shortened after lesion in SLN animals (p = 0.02) but remained unchanged in RLN animals. Thus, although SLN and RLN lesion lead to the same clinical outcome (increased aspiration), the mechanisms of failure of airway protection are different, which suggests that effective therapies may be different with each injury. Understanding the specific pathophysiology of swallowing associated with specific neural insults will help develop targeted, disease appropriate treatments.

Innate immune suppression by SARS-CoV-2 mRNA vaccinations: The role of G-quadruplexes, exosomes, and MicroRNAs

“…The superior and recurrent laryngeal nerves are branches of the vagus that innervate structures involved in swallowing and speaking. Lesions in these nerves cause vocal cord paralysis associated with difficulty swallowing (dysphagia) difficulty speaking (dysphonia) and/or shortness of breath (dyspnea) ( Gould et al, 2019 ; Erman et al, 2009 ). We will return to these specific pathologies in our review of VAERS data below.…”

Innate Immune Suppression by SARS-CoV-2 mRNA Vaccinations: The role of G-quadruplexes, exosomes and microRNAs

“…The superior and recurrent laryngeal nerves are branches of the vagus that innervate structures involved in swallowing and speaking. Lesions in these nerves cause vocal cord paralysis associated with difficulty swallowing (dysphagia) difficulty speaking (dysphonia) and/or shortness of breath (dyspnea) [131,132]. We will return to these specific pathologies in our review of VAERS data below.…”

Advances in Swallowing Neurophysiology Across Pediatric Development: Current Evidence and Insights

“…SLN damage is more common after orofacial surgery/injury and may impact swallow initiation and also lead to dysphagia. Although both types of injuries may temporarily compromise airway safety in term infant pigs, the underlying physiological mechanisms of this compromise differ [45]. More specifically, RLN lesions have been shown to affect hyoid and tongue kinematics [46], volume consumed [47], the neuromuscular control of swallowing [46], and airway safety in infant pigs, and some of these changes can be pervasive.…”

“…More specifically, RLN lesions have been shown to affect hyoid and tongue kinematics [46], volume consumed [47], the neuromuscular control of swallowing [46], and airway safety in infant pigs, and some of these changes can be pervasive. SLN lesions have been associated with higher rates of reduced airway safety as well [48]; however, these changes are mostly explained by temporal dysfunctions in the coordination between suck and swallow cycles [48] or in epiglottic inversion timing [45].…”