THE ROLE OF MIDDLE-EAR EFFUSIONS AND EPIDERMAL GROWTH-FACTOR IN CHOLESTEATOMA FORMATION IN THE GERBILLINE TEMPORAL BONE

To study the process of aural cholesteatoma formation, we used gerbill ine temporal bones to examine histologically the early stages of spont aneous cholesteatomas associated with experimentally induced otitis me dia with effusion (OME) following electric cauterizations of the eusta chian tube. Epidermal growth factor (EGF) was then localized immunohis tochemically in the pars flaccida of normal ears and the forming spont aneous cholesteatomas. Findings in the ears with the early spontaneous cholesteatomas were effusion inside the pars flaccida and hypertrophy and hyperkeratosis of the pars flaccida. Findings in the ears with ex perimental OME involved an effusion in the whole middle ear cavity as well as hypertrophy and hyperkeratosis in both the pars flaccida and p ars tensa. The incidence of ear drum changes was higher in the experim ental OME group than in control animals without cauterization. EGF was localized in the mucous layer of normal drums, the mucous layer and l amina propria of drums with hypertrophy alone, and all layers in drums with hypertrophy and hyperkeratosis. EGF was especially positive in t he cytoplasms of transformed cuboidal cells. These findings suggest th at EGF within the transformed mucous layer may play an important role as a biochemical factor in developing cholesteatomas.