Sensory dysphagia: A case series and proposed classification of an under recognized swallowing disorder

Abstract

Background Although sensory feedback is a vital regulator of deglutition, it is not comprehensively considered in the standard dysphagia evaluation. Difficulty swallowing secondary to sensory loss may be termed “sensory dysphagia” and may account for cases receiving diagnoses of exclusion, like functional or idiopathic dysphagia. Methods and Results Three cases of idiopathic dysphagia were suspected to have sensory dysphagia. The patients had (1) effortful swallowing, (2) globus sensation, and (3) aspiration. Endoscopic sensory mapping revealed laryngopharyngeal sensory loss. Despite normal laryngeal motor function during voluntary maneuvers, laryngeal closure was incomplete during swallowing. The causes of sensory loss were identified: cranial neuropathy from Chiari malformation, immune‐mediated neuronopathy, and nerve damage from prior traumatic intubation. Conclusions Sensory loss may cause dysphagia without primary motor dysfunction. Sensory dysphagia should be classified as a distinct form of swallowing motility disorder to improve diagnosis. Increasing awareness and developing appropriate assessment tools may advance dysphagia care.

The Internal Superior Laryngeal Nerve in Humans: Evidence for Pure Sensory Function

“…By uniquely studying patients undergoing elective laryngectomy, our study is the first to measure the interarytenoid response from stimulation of the fully dissected iSLN and RLN in humans. Because the iSLN is critical for normal swallowing and protecting the airway from aspiration, our findings further support the importance of iSLN afferent regulation of swallowing, and the existence of iSLN deafferentation syndromes causing dysphagia and aspiration 1,24 …”

“…Because the iSLN is critical for normal swallowing and protecting the airway from aspiration, our findings further support the importance of iSLN afferent regulation of swallowing, and the existence of iSLN deafferentation syndromes causing dysphagia and aspiration. 1,24 The long motor response latencies when the iSLN was supramaximally stimulated support the classic understanding that the iSLN only induces motor activity by serving as the afferent limb of a brainstem-mediated response. Even when all iSLN nerve fibers were recruited by applying stimulation multiple times the threshold level, no short latency motor response was recorded.…”

“…42 Clinically, the pure sensory function of the iSLN supports the pathophysiological mechanism that dysphagia and aspiration can occur exclusively from sensory loss, without primary motor dysfunction. 24 Previously, blockade of the iSLN in healthy adults was found to result in effortful swallowing, globus sensation, and aspiration secondary to incomplete closure of the larynx during swallowing. 1 Because the iSLN has no efferent function, we deduce that these three clinically significant symptoms of failed motor coordination can result from sensory blockade alone.…”

An Airway Protection Program Revealed by Sweeping Genetic Control of Vagal Afferents

“…One of the most fundamental functions of the vagus nerve is to provide the first line of defense that protects the airways from injury. Defects in vagally mediated reflexes in the upper airways cause some of the most pervasive and severe clinical problems associated with aging including dysphagia (difficulty swallowing), weight loss, choking, speech impairment, and respiratory tract infections such as aspiration pneumonia (Jadcherla et al, 2010;Ludlow, 2015;Santoso et al, 2019). Furthermore, hyperactivity or sensitization of upper airway neurons may contribute to asthma, chronic cough, and sudden infant death syndrome (SIDS).…”

“…RLN afferents instead predominate below the vocal folds, with dense innervation of the trachea and lung. Loss of SLN function by nerve injury or transient application of local anesthetic causes dysphagia, incomplete laryngeal closure, and risk of airway aspiration (Jadcherla et al, 2010;Jafari et al, 2003;Santoso et al, 2019). Electrically stimulating the SLN evokes hallmarks of airway protection including cough, apnea (breathing pause), vocal fold adduction, and fictive swallowing (Bolser, 1991;Doty, 1951).…”