Etiology and pathogenesis of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is defined as inflammation of the nose and the paranasal sinuses characterised by two or more symptoms, one of which should be either nasal blockage/obstruction/congestion or nasal discharge (anterior, posterior nasal drip) + facial pain/pressure + reduction or loss of smell sensation of smell and either endoscopic signs of polyps and/or mucopurulent discharge primarily from the middle meatus and/or edema/mucosal obstruction primarily in middle meatus, and/or computerized tomography (CT) changes showing mucosal changes within the ostiomeatal complex and/or sinuses from more than 12 weeks . It is an increasingly common cause of patients visits to physicians and the principal diagnosis in nearly 2% of them . The prevalence of rhinosinusitis is estimated to be 14% of the global population . The location and extent of different rhinosinusitis pathological conditions imply a detailed knowledge of anatomic organization of paranasal sinuses, and the first and foremost of ethmoid sinuses. The structures of the lateral nasal wall and paranasal sinuses fall into two anatomically and physiologically distinct categories: the anterior and posterior ethmoid complex. The basal lamella of the middle turbinate is the distinct separation between the two ethmoid complexes. The ostiomeatal complex (OMC) is a functional entity of the anterior ethmoidal complex that represents the final common pathway for drainage and ventilation of the frontal, maxillary and anterior ethmoid cells. The sphenoethmoidal recess is a functional entity of the posterior ethmoid complex that represents the final common pathway for drainage and ventilation of the sphenoid and posterior ethmoid cells. Three clinical entities of CRS may be defined: chronic rhinitis, localized sinusitis and diffuse rhinosinusitis . Chronic rhinosinusitis is a multifactorial disease. Predisposing factors can be divided into: local host factors, general host factors and environmental or non-host factors 1, . Local host factors