Role of IgE-mediated hypersensitivity in otitis media with effusion: pathophysiologic considerations.

A pathophysiologic model of otitis media with effusion secondary to IgE-mediated hypersensitivity is described. Specific mediators of inflammation are released by mucosal mast cells in the nasal mucosa following the interaction of antigen and specific IgE antibody. These mediators increase vascular permeability, mucosal blood flow, and, most important, mucus production. Furthermore, accessory cell types are recruited by colony-stimulating factors that in turn provide an autocrine-positive feedback for the influx of further inflammatory cells. The eustachian tube is then effectively obstructed by both intrinsic venous engorgement and extrinsic mucus plugs, isolating the middle ear space from the ambient environment. The net result is the increased exchange of nitrogen into the middle ear mucosa from the middle ear cavity. This causes the development of a significant middle ear underpressure that disrupts tight junctions and allows for transudation of fluids into the middle ear space. The prolonged obstruction of the eustachian tube with mucus results in middle ear inflammation, mucosal metaplasia, and increased glandular activities, all of which are hallmarks of chronic otitis media with effusion.