title: Afferent nerve ending density in the human laryngeal mucosa: potential implications on endoscopic evaluation of laryngeal sensitivity.
abstract: Laryngeal sensitivity is crucial for maintaining safe swallowing, thus avoiding silent aspiration. The sensitivity test, carried out by fiberoptic endoscopic examination of swallowing, plays an important role in the assessment of dysphagic patients. The ventricular folds appear to be more sensitive than the epiglottis during the sensitivity test. Therefore, this study aimed to investigate the mechanical sensitivity of the supraglottic larynx. In seven healthy adults undergoing microlaryngoscopy to remove vocal cord polyps, we excised mucosal samples from the epiglottis and ventricular folds. We measured afferent nerve fiber density by immunoelectron microscopy. All of the subjects underwent an endoscopic sensitivity test based on lightly touching the laryngeal surface of the epiglottis and ventricular folds. The discomfort level was self-rated by the subjects on the visual analog scale. Samples were fixed and stored in cryoprotectant solution at 4 °C. Sections were stained with the protein gene product 9.5, a pan-neuronal selective marker. Nerve fiber density was calculated as the number of fibers per millimeter length of section. The mean nerve fiber density was higher in ventricular samples than in epiglottis samples (2.96 ± 2.05 vs 0.83 ± 0.51; two-sided p = 0.018). The mean visual analog scale scores were significantly higher for touching the ventricular folds than for touching the epiglottis (8.28 ± 1.11 vs 4.14 ± 1.21; two-sided p = 0.017). The higher sensitivity of the ventricular region should be considered for further refining clinical endoscopic evaluation of laryngeal sensitivity.
authors.affiliation: Otorhinolaryngology Section, Department of Sensorial Organs, Sapienza University, Viale del Policlinico, 155, 00161, Rome, Italy, giovanni.ruoppolo@uniroma1.it.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Ruoppolo
authors.forename: Ilenia
authors.initials: I
authors.lastname: Schettino
authors.forename: Antonella
authors.initials: A
authors.lastname: Biasiotta
authors.forename: Rocco
authors.initials: R
authors.lastname: Roma
authors.forename: Antonio
authors.initials: A
authors.lastname: Greco
authors.forename: Pietro
authors.initials: P
authors.lastname: Soldo
authors.forename: Dario
authors.initials: D
authors.lastname: Marcotullio
authors.forename: Alessandro
authors.initials: A
authors.lastname: Patella
authors.forename: Emanuela
authors.initials: E
authors.lastname: Onesti
authors.forename: Marco
authors.initials: M
authors.lastname: Ceccanti
authors.forename: Francesca
authors.initials: F
authors.lastname: Albino
authors.forename: Carla
authors.initials: C
authors.lastname: Giordano
authors.forename: Andrea
authors.initials: A
authors.lastname: Truini
authors.forename: Marco
authors.initials: M
authors.lastname: De Vincentiis
authors.forename: Maurizio
authors.initials: M
authors.lastname: Inghilleri
mesh_terms: D000328:Adult; D000368:Aged; D003679:Deglutition / Q000502:physiology*; D004825:Epiglottis / Q000294:innervation / Q000473:pathology / Q000502:physiology; D006801:Humans; D007820:Laryngeal Mucosa / Q000294:innervation* / Q000473:pathology / Q000502:physiology; D007828:Laryngoscopy / Q000379:methods*; D016253:Microscopy, Immunoelectron; D008875:Middle Aged; D009411:Nerve Endings / Q000648:ultrastructure*; D009475:Neurons, Afferent / Q000502:physiology*; D055100:Optical Fibers; D012018:Reflex; D012684:Sensory Thresholds