Experimental production of cholesteatoma in rabbits by using non-irritants (skin tolerants).

The application of various skin tolerant substances to the postero-superior and antero-inferior aspects of the external auditory canal of the rabbit, with an intact ear drum and middle ear, produced cholesteatomas in the skin of the auditory canal and in the tympanic membrane, particularly in the pars flaccida. At the antero-inferior insertion of the tympanic membrane, however, cholesteatoma growth could not be induced in these animal experiments. In severe diffuse otitis externa, secondary to the operative closure of the external auditory canal, cholesteatomas also develop preferentially in the pars flaccida. The relatively thick, loose intermediate layer of connective tissue allows a rapid expansion of epithelial ridges, thus favouring the formation of cholesteatoma in this region.