Otolaryngologic clinics of North America
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Otolaryngol. Clin. North Am. · Feb 2010
ReviewAfferent nerves regulating the cough reflex: mechanisms and mediators of cough in disease.
Bronchopulmonary C fibers and acid-sensitive, capsaicin-insensitive mechanoreceptors innervating the larynx, trachea, and large bronchi regulate the cough reflex. These vagal afferent nerves may interact centrally with sensory input arising from afferent nerves innervating the intrapulmonary airways or even extrapulmonary afferents such as those innervating the nasal mucosa and esophagus to produce chronic cough or enhanced cough responsiveness. The mechanisms of cough initiation in health and in disease are briefly described.
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Otolaryngol. Clin. North Am. · Feb 2010
ReviewCough due to asthma, cough-variant asthma and non-asthmatic eosinophilic bronchitis.
Among the most common causes of chronic cough are asthma (25%) and nonasthmatic eosinophilic bronchitis (10%). In asthma, cough may present as an isolated symptom, in which case it is known as cough variant asthma. Variable airflow obstruction and airway hyper-responsiveness are cardinal features of asthma, which are absent in nonasthmatic eosinophilic bronchitis. ⋯ In most cases, the trigger that causes the cough is uncertain, but occasionally occupational exposure to a sensitizer is identified, and avoidance is recommended. In both conditions, there is improvement following treatment with inhaled corticosteroids, which is associated with the presence of an airway eosinophilia and increased exhaled nitric oxide. Generally, response to therapy in both conditions is very good, and the limited long-term data available suggest that both usually have a benign course, although in some cases fixed airflow obstruction may occur.
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Otolaryngol. Clin. North Am. · Feb 2010
ReviewEvidence for sensory neuropathy and pharmacologic management.
Recent literature points to postviral sensory neuropathy as a possible cause for refractory chronic cough. Vagal neuropathy may affect the sensory branches, inducing chronic cough or laryngospasm. Although the clinical presentation is fairly well described, there is little in the way of diagnostic criteria to establish this diagnosis. This article highlights the clinical picture of this disease and the efficacy, side-effect profiles of the currently used pharmacological interventions.
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Occupational and environmental irritants play a role in the pathogenesis of chronic cough. An irritant is a non-corrosive chemical, which causes a reversible inflammatory change on living tissue by chemical action at the site of contact. The clinical and pathologic spectrum of chemically induced respiratory tract irritation ranges from neurogenically mediated alterations in regional blood flow, mucus secretion, and airway caliber to the initiation of cough. ⋯ The chemosensory type evolved to protect against an injured lung from a respiratory tract infection or after inhaling high levels of irritant gases and particulates that accumulated in confined quarters of early times. For this latter type of cough reflex, normally quiescent transient receptor potential (TRP) cation channels TRPV1(vanilloid) and TRPA1 (ankyrin) become activated or hyperactivated after lung injury, with lung inflammation, or in response to chemicals. Although animal and laboratory investigations support the possibility of human TRPpathies, further investigations are essential for the further elucidation of the role of TRP cationic channels in instigating chronic cough in humans.