Pathogenesis of Attic Cholesteatomas

Abstract

An attic cholesteatoma is defined as an epidermoid cyst found in the attic. 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 or as a collapse of an atelectatic drum. 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 ofan 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 ofexternal canal skin into the upper medial attic (often through the scutum). This is especially so in the face ofsucb 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 cvolved into attic cholesteatomas have so far not been documented. 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 the 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 (including the congenital type) show mucosal cells as part of their lining, suggests a metaplastic phenomenon, This means that the epithelial cells in question may have changed from mucosal into keratinizing cells or vice versa. Metaplastic changes of mucosas into keratinizing epithelium occur very frequently in the bronchi, nose, ears and genitourinary system. Epidermoid cysts may, therefore, be seen as an analogous formation to glandular cysts in the attic - the latter being very frequently found in the attic 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 ofconnective tissue rather than on the surface. Budding of cells, giving rise to epidermoid cysts, is occasionally found in chronically-infected ears adjacent to cholesteatomas.