Pathology of otitis media.

Otitis media is characterized by inflammation of the middle ear. The pathologic changes seen in this condition tend to occur on a continuum, progressing from acute and subacute stages to the chronic phase, in which irreversible tissue damage is observed. The earliest morphological changes involve the lamina propria of the middle ear mucosa and include increased capillary permeability, edema, and leukocytic infiltration. During the late acute to subacute stages, the mucosa also tends to show a marked increase in numbers of ciliated and secretory epithelial cells. As the inflammatory process enters the chronic phase, there is a continuing shift in the population of infiltrating leukocytes toward increasing numbers of mononuclear cells that secrete substances that facilitate tissue destruction and fibrosis. There is also development and proliferation of granulation tissue, which is intimately involved in the process of bone erosion. As granulation tissue matures, it becomes denser and less vascular--a process that leads to permanent fibrosis and formation of adhesions that may significantly compromise middle ear function. Other pathologic entities occasionally associated with chronic otitis media include cholesteatoma, cholesterol cysts and granuloma, and tympanosclerosis, all of which may contribute to irreversible alterations of middle ear structure.