Pathogenesis and pathophysiology of middle ear effusions.

The intention of this study was to gain insight into the pathogenesis, pathophysiology and course of middle ear effusions by means of an animal experiment. Simultaneously the clinical relevance of an electro-acoustical, non-invasive diagnostic procedure should be evaluated. Furthermore a method which permits prognostic statements had to be established using viscosimetry, in order to plan therapy for this most common childhood disease. The questions asked initially can be answered along the following lines: 1. The pathogenesis of middle ear effusions caused by a tubal dysfunction is submitted to a staged course. The Initial Stage is based on the condition of negative pressure. It presents with the onset of an inflammatory process including the forming of an inflammatory edema in the lamina propria with capillary proliferation, vascular dilatation and infiltrating round cells. An epithelial-mesenchymal interaction induces hyperplasia and differentiation of epithelial cells. An exudate of low viscosity develops inside the tympanum. In the course of the Secretory Stage, between the 30th and 80th day, an actively secreting respiratory epithelium is formed out of metaplasia. The viscosity of the mucus produced thereby increases by an exponential function between the 30th and 80th day, with statistic significance. The pathological process comes to a halt after the 80th day. The Steady State of chronic mucoid otitis media is found. The effusion's viscosity has increased extremely, due to active absorption of the middle ear mucosa. Toxic impairment of the secreting epithelium causes arrest of the mucociliary transport mechanism. A partial recovery with adhesive alterations results. 2. The alterations in the lamina mucosa found in the initial and secretory stage are reversible, once a regular tubal function is restored. 3. The osseous appositions, brought about by each relapse, are only partially reversible and lead to a reduction in pneumatized cavities. 4. Scheduled tympanometry; i.e. measuring impedance, is directly correlated with the acute pathophysiological condition and its course. Thus it permits statements concerning the progress and prognosis of the disorder. 5. The method of viscosimetry developed proved to be successful in determining the stage of the dynamic pathological process of middle ear effusion. 6. Presupposing the transferability of animal experimental findings to human conditions, a clinical conclusion can be drawn from our evaluations. An effusion resisting conservative therapy should be treated surgically by insertion of a ventilation tube after 3 months at the latest.