Oropharyngeal and laryngeal sensory innervation in the pathophysiology of swallowing disorders and sensory stimulation treatments

Abstract

Oropharyngeal dysphagia (OD) affects older and neurological patients, causing malnutrition and dehydration and increasing the risk for aspiration pneumonia. There is evidence that sensory deficits in those populations are closely related to swallowing disorders, and several research groups are developing new therapies based on sensory stimulation of this area. More information on the sensory innervation participating in the swallow response is needed to better understand the pathophysiology of OD and to develop new treatments. This review focuses on the sensory innervation of the human oropharynx and larynx in healthy people compared with patients with swallowing disorders in order to unravel the abnormalities that may lead to the loss of sensitivity in patients with OD. We also hypothesize the pathway through which active sensory-enhancement treatments may elicit their therapeutic effect on patients with swallowing dysfunctions. As far as we know, this is the first time a review covers the anatomy, histology, ultrastructure, and molecular biology of the sensory innervation of the swallowing function.

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

“…The literature is ripe with studies exploring the influence of mechanoreceptors, taste receptors, and even thermal receptors on swallowing. Two reviews are dedicated to describing these mechanisms and their evidence . Intuitively, although not obviously, sensory feedback via cranial nerves V, VII, IX, and X is an apt mechanism for the body to know how to best guide a bolus through the digestive tract (Figure , Table ).…”

A comparative study on the therapeutic effect of TRPV1, TRPA1, and TRPM8 agonists on swallowing dysfunction associated with aging and neurological diseases

“…Older people and patients with neurological diseases suffering from OD present decreased oropharyngeal sensitivity . Reduced sensory input contributes to impaired motor response . Thus, sensory impairment is a potential target for treatment of swallowing dysfunction in older patients.…”

“…We have recently found that this impaired pharyngeal sensory function is due to disturbances in the pharyngo‐cortical connection together with a disrupted pattern of cortical activation . Studies have also found a close relationship between sensory deficits and impaired swallow response, which might imply that reduced sensory input contributes to impaired motor response . This sensory impairment might be a critical pathophysiological element and a potential target for treatment of swallowing dysfunction in older patients.…”

Increase of Substance P Concentration in Saliva after Pharyngeal Electrical Stimulation in Severely Dysphagic Stroke Patients – an Indicator of Decannulation Success?

“…More importantly, however, the close relation of SP increase and successful PES treatment alludes to a causal role of SP in the underlying physiological mechanism. SP occurs ubiquitary in the peripheral nervous system, is found in particular in C and Aδ fiber terminals in the pharyngeal mucosa and colocalizes there with TRPV1 channels which have been suggested to play an important role in the perception of noxious stimuli and prevention of aspiration [35, 36]. Thus, it is conceivable that PES triggered release of SP produces peripheral sensitization of sensory neurons, which then facilitates the motor swallow response in the upstream swallowing network.…”