ABSTRACT
A cholesteatoma is an expanding, destructive lesion of the temporal bone consisting of keratinising squamous epithelium. The condition is further classified aetiologically as either congenital or acquired and by anatomical location. Congenital cholesteatomas are thought to arise either from the presence of an ectopic epidermis rest or from metaplasia. The exact aetiology of primary cholesteatoma is debated but the most commonly accepted theory is that of progression of a retraction pocket of the tympanic membrane, usually either in the pars flaccida or in the posterior segment of the pars tensa. A tertiary cholesteatoma is considered to be caused by iatrogenic or traumatic implantation of squamous epithelium into the middle ear. The diagnosis of cholesteatoma is made clinically but Computed tomography scanning can aid surgical planning. It should be recognised that keratin is indistinguishable from mucosal inflammation or effusion within the middle ear or mastoid: disease extent is gauged by evidence of bone erosion.
