Pathogenesis of attic retraction pocket and cholesteatoma as studied by computed tomography.

It is hypothesized that blockade of the tympanic isthmus causes isolation of the attic and the adjacent middle ear spaces and that subsequent building up of the negative pressure in these spaces results in retraction of the pars flaccida, leading to formation of attic retraction pockets and cholesteatomas. To examine this theory, computerized tomographic (CT) findings of these conditions were evaluated in a series of 53 ears with retractions of the pars flaccida (attic retractions of Tos type II or deeper), including both retraction pockets and cholesteatomas. In 26 of 28 ears with attic retraction pockets, at least a portion of attic was aerated, and in 22 of these 26 ears, the mastoid antrum was also aerated. In contrast, in the 25 cases with attic cholesteatomas, these numbers decreased to 10 and 5, respectively, and the lack of aeration of the attic was demonstrated in 15 of 25 (60%) of the cases. In three cases of cholesteatoma, follow-up CT revealed either growth of a cholesteatoma from a retraction pocket or development of a small cholesteatoma into a large one. In these ears it was seen that the well-pneumatized attic and mastoid antrum seen in the initial CT was depleted by the growth of cholesteatoma that took place over a period of 4 months to 2 years. These results, showing good patency of the aditus and a pneumatized antrum in early stages of most cases of retraction pockets and cholesteatomas, are not in agreement with the hypothesis that the blockade of the tympanic isthmus is responsible for the pathogenesis of retraction pockets and cholesteatomas originating in the pars flaccida.