Development of tympanosclerosis: can predicting factors be identified?

The etiological hypothesis is that there might be factors triggering an immunological chain reaction that eventually leads to tympanosclerosis formation.

Tympanosclerosis is a condition leading to a calcification process in the middle ear and, occasionally, also to the lining of the inner ear. This sometimes leads to hearing loss due to fixation of the middle ear ossicles. In severe cases. deafness may occur as a result of the inner ear impairment. Surgery is the treatment offered, often with poor long-term results, and, alternatively, prescription of hearing aids. Some patients develop tympanosclerosis after mild inflammatory otitis media processes whereas some heal without tympanosclerosis after more aggressive infections. This difference may be due to individual variations in the inflammatory response. The biological mechanism of calcification in tympanosclerosis is probably similar to that occurring in other calcifying tissues due to diseases.

The present investigation was performed to develop methods for immunohistochemical analyses of this delicate tissue consisting of both hard bone and the very thin tympanic membrane. Sprague-Dawley rats were inoculated with a suspension of Streptococcus pneumoniae, type 3, into the middle ear and sacrificed after 1 week up to 6 months. A new technique was elaborated where the whole specimen was prefixed briefly and then en bloc incubated with the primary antibodies and after that decalcified in edetic acid (EDTA). Primary antibodies against macrophages were used for the immunohistochemical staining.

Acute otitis media was successfully induced in the rats and myringosclerosis was seen in 30% of the animals, often localized close to the bony frame where macrophages could also be detected.

Acute otitis media and myringosclerosis were introduced in the animals. Conventional immunological techniques were tested on this delicate tissue. A new method for immunohistochemical staining was elaborated in which specimens were stained en bloc before decalcification and sectioning were performed. Expression of macrophages was demonstrated in the tympanic membrane.