Antigen challenge induces a supraglottic but not a subglottic edema in the rat larynx

Toward an Understanding of the Pathophysiology of Chronic Laryngitis

Chronic laryngitis, characterized by inflammation of the laryngeal tissues, is the most commonly diagnosed organic voice disorder, yet treatments targeting suspected etiologic factors have demonstrated limited efficacy. A major barrier to the development of improved medical therapies for chronic laryngitis is a fundamental gap in knowledge related to the pathophysiology of laryngeal inflammation. This article provides a review of the literature specific to laryngeal immunity in health and disease.

Histological effects of inhaled corticosteroids and ß2-agonists on laryngeal mucosa in an allergic rat model

OBJECTIVE

To constitute an animal model of laryngeal allergy and evaluate the laryngeal effects of inhaled corticosteroids and ß2-agonists on the laryngeal mucosa in an allergic rat model.

STUDY DESIGN

Prospective randomized.

SETTING

The Experimental Medical Research Institute (DETAE) at Istanbul University.

SUBJECTS AND METHODS

Wistar Albino rats (n = 32) were sensitized with ovalbumin. Unsensitized rats (n = 8) served as controls. The rats were exposed to aerosolized ovalbumin (1%). On days 28 through 42, every 2 days preceeding ovalbumin exposure, rats were further exposed to aerosolized phosphate buffered saline (n = 8), fluticasone propionate (n = 8), salbutamol (n = 8), and combined salbutamol+fluticasone propionate (n = 8). Inflammatory cell infiltration was graded semi-quantitatively. The quantitative data included mast cell count and degranulation. Ultrathin sections were investigated under transmission electron microscope.

RESULTS

The simultaneous and pairwise comparison of groups (Kruskal-Wallis) revealed statistically significant difference among groups at supraglottic level (critical P < .05, <.01) and no difference at glottic level. In ovalbumin+phosphate buffered saline exposed rats, the light microscopy of supraglottic mucosa revealed regular epithelium with severe inflammatory cell infiltration and increased mast cell count. Electron microscopy revealed increased mast cell degranulation. Increased inflammatory cell infiltration was detected along with reduced mast cell count among fluticasone propionate treated rats. Mild inflammatory cell infiltration was encountered in combined salbutamol+fluticasone propionate treated rats.

CONCLUSION

This study supported the presence of localized allergic reaction in the supraglottic laryngeal mucosa through the observation of increased mast cell number and degranulation. It was also shown that inhaled corticosteroids increase inflammation whereas combined inhaled corticosteroids and ß2-agonists minimize allergic and inflammatory reactions in supraglottic laryngeal mucosa providing a safer therapeutic option.

Evidence for primary laryngeal inhalant allergy: a randomized, double-blinded crossover study

BACKGROUND

Despite anecdotal reports, no controlled studies to date link allergen exposure with a change in vocal function or dysphonia. The aim of this study was to determine whether allergen exposure in susceptible individuals impairs vocal function.

METHODS

The study was a prospective, double-blind, placebo-controlled study in which subjects serve as their own controls. The participants were 5 inhalant allergic adults with suspected dysphonia from allergies, without evidence of reactive lower airways based on methacholine challenge. All subjects were exposed to 2 experimental conditions in which they were challenged with (1) orally inhaled diluent placebo on 1 day, and (2) orally inhaled allergen on another day. Conditions were randomly ordered across subjects and separated by at least 48 hours. Phonatory threshold pressure (PTP) at the 80th percentile pitch was measured prior to diluent and allergen challenge, and 15 and 60 minutes postchallenge to assess potential change in vocal function after challenge testing.

RESULTS

A repeated measures ANOVA revealed a significant main effect for treatment (allergen vs placebo, p = 0.013) with greater PTP required post-allergen challenge compared to placebo and an effect size of 0.821.

CONCLUSION

A primary causal relationship between allergen exposure and impaired vocal function, as assessed by PTP, was observed in adults with documented allergy independent of asthma or nasal exposure. The current design establishes a safe model for laryngeal inhalant allergen challenge.

Laryngitis: types, causes, and treatments

Inflammatory processes that affect the unified airway can concurrently exert significant influence on the larynx and surrounding mucosal surfaces. Laryngeal inflammation can be present secondary to direct effects of irritants, toxins, and antigens, but can also involve mechanical and infectious effects as well as secondary inflammation from behavioral mechanisms. This review examines laryngeal inflammation in the context of the unified airway and discusses pathophysiologic mechanisms that are central to the development of acute and chronic laryngitis.