Morphological changes in the middle ear due to chronic tubal obstruction. An experimental study of cholesterin granuloma.

Long-term tubal dysfunction may cause various lesions in the tympanic membrane and cavity in the middle ear. Typical sequelae of such lesions include adhesive otitis media, cholesterin granuloma, and cholesteatoma in the pars of tensa, but the pathogenesis of these diseases has not been clarified completely. This animal study was designed to clarify the pathogenesis of these diseases by investigating changes in the morphology of the tympanic cavity caused by experimentally induced long-term tubal dysfunction on the assumption that the diseases were the sequelae of chronic tubal dysfunction.<BR>Long-Term tubal obstruction was achieved by one of the following methods: electrocoagula-tion of the tympanic opening of auditory tube followed by insertion of a muscle autograft into the opening, insertion of a muscle autograft with tissue adhesive applied, or a combination of such an insertion with injection of dead cells of Influenza bacillus into the tympanic cavity for sustained stimulation of tympanic cavity.<BR>A total 56 ears were studied, and 43 of these were not-infected. Fourteen ears of the not-infected ears showed evidence of cholesterol clefts, and 3 of the 14 ears showed a formation of cholesterin granuloma. These findings suggested that a space which was more tightly closed for a longer duration was a proroquicito for the formation of cholesterol clefts. The process of the formation of such granulomas was also postulated as follows: appearance of cholesterol clefts in the liquid retained in the tympanic cavity, followed by infiltrarion and growth of foreign cells, primarily in the clefts, which may result in granulation. In 3 ears, granulation in the tympanic cavity precipitated an adhesion of the tense part of the tympanic membrane to the promontrium cavi tympani. These ears were thought to be in the early stage of adhesive otitis media. Such an adhesion of the tense part of the tympanic membrane seemed to require disappearance of the fibrous layer of the tympanic membrane, injury of the mucosa in the tympanic cavity, and accompanying granulation in the tympanic cavity and on the reverse side of tympanic membrane.<BR>In conclusion, the finding that long-term tubal obstruction resulted in a formation of cholesterin granuloma and adhesive otitis media in some cases suggested a significant relationship between these diseases and tubal dysfunction.