10 Cholesteatoma

Cholesteatoma is a collection of ‘bad skin’ (migrating keratinising squamous epithelium) trapped within the middle ear or mastoid. It is a common and potentially dangerous condition. The incidence is approximately 10 cases per 100,000 population per annum. Between 7 and 10% of people diagnosed with cholesteatoma will develop a cholesteatoma in the other ear.

10.1 Pathophysiology

The single most important fact about the skin of the eardrum is that it migrates from the centre of the drum outward along the external ear canal, carrying keratin and wax debris with it. Therefore, the ear canal is self-cleaning. The skin of the ear canal is the only squamous epithelium that migrates in health. In disease, this skin can migrate into the middle ear and form a progressively enlarging ‘cyst of skin’ that destroys the tissue it comes up against. This may arise from problems in childhood when the eustachian tube fails to function normally and results in negative pressures behind the eardrum. The normal atmospheric pressure in the ear canal then pushes the eardrum to retract into the middle ear as a ‘retraction pocket’. This is usually in the more flaccid, pars flacida, in the attic of the eardrum and made easier if middle ear infections have damaged and thinned the membrane so that it loses its resilience. At first the eardrum skin is able to migrate out of the shallow pocket, but if the pocket becomes too deep, then the skin is unable to flow around the edge of the pocket and the surface layers of dead skin begin to accumulate and a cholesteatoma forms. Published evidence not only suggests that 16% of retraction pockets develop into a cholesteatoma, but also that surgery (either with ventilating tubes, fascial tympanoplasty or cartilage tympanoplasty) does not alter the progression of those pockets that will become cholesteatoma.

Skin can also be implanted or can migrate around the rim of a perforation or pocket in the thicker more ridgid pars tensa and cause a cholesteatoma. Skin may also be implanted at surgery, for example, grommet insertion. It is also thought possible that little feet of skin can migrate inward through the layers of the tympanic membrane and even that middle ear mucosa can metaplase to become squamous. Cholesteatoma can also be congenital, arising from epithelial cell rests in the forming middle ear that usually disappeares at 17 weeks of gestation. Congenital cholesteatomas obstruct the eustachian tube or surround the ossicles, causing a conductive hearing loss. They can be seen as a pearly white mass medial to a normal tympanic membrane. They usually present between the ages of 6 months and 5 years, behind an intact tympanic membrane, but they can sometimes present in adulthood.

Stay updated, free articles. Join our Telegram channel

Join