The theory of the trigger, the bridge and the transmigration in the pathogenesis of acquired cholesteatoma

The purpose of the study was to evaluate factors in the otitis media proces s that could play a role in the pathogenesis of acquired cholesteatoma. The study was divided in two parts. firstly the temporal bones of 75 cats and 15 chinchillas with induced otitis media, and 78 human bones with otitis me dia were evaluated. Special emphasis was placed on epithelial breaks. These breaks were commonly observed, leaving areas of connective tissue of the m ucoperiostium in direct contact with the middle ear effusion. As these chan ges progressed, the effusion became organized, serving as a bridge for gran ulation tissue. In later stages these areas became totally or partially cov ered with epithelium. Areas of epithelial breaks became connected to each o ther through the organized effusion. Cholesteatomas in humans seem to sprea d using the connective tissue as scaffolding. Secondly, we reviewed 15 chin chillas in which a chemically modified membrane was placed leading from the external auditory canal to the promontory, through a tympanic membrane per foration. Squamous epithelial migration with cholesteatoma formation occurr ed through the tympanic membrane perforation, collagen membrane, organized effusion and granulation tissue in 53.5% of the experimental animals. The a uthors propose the theory that for transmigration of squamous epithelium to occur, a trigger (inflammatory process) and a bridge (granulation tissue a nd organized effusion) are needed in a predisposed subject.