Temporal bone histology has been studied in chinchillas following middle ear deflation in the presence of nasopharyngeal colonization with S pneumoniae. All animals sacrificed within one hour following deflation had similar middle ear hsitology regardless of whether or not the animals had been colonized with S pneumoniae. All animals with negative nasopharyngeal culture for S pneumoniae sacrificed from 3–24 days following − 30 mm Hg negative middle ear pressure had negative middle ear cultures and normal morphology. During the same time period, however, nearly 60% of animals colonized with S pneumoniae developed acute otitis media with positive middle ear cultures for S pneumoniae. Histologic changes in the middle ear included the presence of effusion, leukocytes, granulation tissue, osteoneogenesis, mucosal metaplasia, and hemorrhage. Changes in the inner ear were much less frequent and included some leukocyte infiltration with hyperemia in the scala tympani and endolymphatic hydrops.
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