Retraction pockets and attic cholesteatomas.

An attic cholesteatoma is defined as an epidermoid cyst found in the attic. This is differentiated from an infected retraction pocket of the pars tensa or a retraction pocket cholesteatoma. Stratified squamous epithelium may also be present in the middle ear as other clinical or pathological entities, such as metaplastic islands of the mucosa in chronic ears with central perforations. Histological examination of 22 temporal bones with attic cholesteatomas has shown them to reside mainly medial to the ossicular chain. This explains the difficulty they have in self-cleansing, as well as the ensuing secondary infection. When a similar process occurs lateral to the ossicles, a self-cleansing nature's atticotomy may be formed. The aetiology of an attic epidermoid cyst, i.e., an attic cholesteatoma, is usually considered to be an invasive retraction from the external ear. However, it is difficult to accept invasion of external canal skin into the upper medial attic. This is especially so in the face of such biological phenomena as epithelial contact inhibition, or the invariable outward migration of stratified squamous epithelium from the edges of retraction pockets as well as from cholesteatoma perforations. Also, large cholesteatomas usually present themselves from the "beginning" simultaneously with their perforations; no documentation of an evolving process from a pre-existing perforation exists at present. Marginal perforations, which have later evolved into attic cholesteatomas have so far not been documented. On the other hand, retraction pockets of the pars tensa or pars flaccida associated with some middle ear negative pressure do occur, however, it is yet to be shown that such retractions can reach the medial part of the ossicular chain and form epidermoid-like cysts there. Therefore, the possibility that an attic cholesteatoma often arises primarily in the attic and presents itself secondarily in the external canal as a "perforated" epidermoid cyst, is to be considered. The possibility that a congenital rest is responsible for such an epidermoid cyst has often been put forward, but evidence that such rests actually exist has not yet been presented. The frequency with which cholesteatoma sacs found in the attic show mucosal cells as part of their lining, suggests a metaplastic phenomenon. This means that the epithelial cells of the middle ear lining may have changed from mucosal into keratinizing cells (or even vice versa). Metaplastic changes of mucosas into keratinizing epithelium occur very frequently in the bronchi, nose, ears and genitourinary system. Attic epidermoid cysts may, therefore, be seen as an analogous formation to glandular cysts in the attic -- the latter being very frequently seen in there in chronically infected ears. Such "organ" formations (glands or epidermoid cysts) may arise when their respective cells (forming mucus or keratin) grow in the midst of connective tissue rather than on the surface...