Panel discussion: pathogenesis of otitis media. Pathology and microbiology of otitis media.

Otitis media (OM) can be subdivided into purulent, serous, mucoid, and chronic forms. It may occur in the absence of tympanic membrane changes and involve the inner ear. Purulent otitis media is characterized early by edema, hyperemia, and polymorphonuclear leukocyte infiltration in the subepithelial space (SES) and later by mucosal metaplasia, granulation tissue, and osteitis. S. pneumoniae and H. influenza are most commonly identified. Serous and mucoid OM frequently develop from eustachian tube dysfunction. Serous transudate from vessels in the SES passes to the middle ear (serous otitis media). Basal cells differentiate into goblet cells and subepithelial glandular formation occurs. This secretory activity, coupled with fluid reabsorption, results in a mucoid effusion. Bacteria can be cultured from about 30% of these effusions. Chronic otitis media denotes irreversible tissue pathology. It may be sterile although S. aureus and coliform bacteria are frequently isolated.