Experimental retraction pocket cholesteatoma.

An animal model for retraction pocket (primary acquired) cholesteatoma is presented. Bilateral eustachian tube obstruction by electrocauterization of the nasopharyngeal portion was performed in 16 Mongolian gerbils. Animals were killed at 2, 4, 8, and 16 weeks. At 2 weeks all animals had bilateral serous effusions and retracted tympanic membranes. At 4 weeks, four of eight ears had middle ear fluid, retractions, and cholesteatomas. After 8 weeks, five of eight ears had middle ear effusions, and four of these had cholesteatomas; one ear had total atelectasis with a cholesteatoma filling the bulla. By 16 weeks, six of eight ears had developed cholesteatomas. Some animals did not develop effusion or retraction because of failure or recanalization of eustachian tube obstruction. This study provides experimental evidence that aural cholesteatomas may arise by retraction of the tympanic membrane.