Conclusions: Mucoid effusion can undergo a process of organization related to the inflammatory process and hypoventilation; organized effusion in the presence of epithelial breaks is a potential source for formation of granulation tissue and cholesterol granuloma within 3 months of evolution.
Objectives: The aim of this study was to investigate the evolution of mucoid otitis media and its relationship with the organized effusion within a time-span of 3 months.
Materials and methods: Two groups of animals were selected. In group I, 15 chinchillas had a chemically modified bovine collagen type 2 gelatin membrane placed through a mechanically induced tympanic membrane perforation, bridging the external auditory canal and the promontory. In group II, 75 cats underwent eustachian tube obstruction with soft grade silastic sponges. Experimental phases and animal sacrifices were performed under general anesthesia. After sacrifice, temporal bones were prepared, stained with hematoxylin and eosin and evaluated under light microscopy.
Results: The experimental ears in both groups were observed to undergo gradual pathological changes with increasing survival times. The acute inflammatory phase turned into chronic irreversible changes, which correlated directly with the initial amount of effusion and the areas of epithelial breaks, granulation tissue, cholesterol granuloma, and epithelial migration.