Chapter 50. Cholesteatoma

• Squamous epithelium in the middle ear or mastoid
• Otorrhea and conductive hearing loss
• Retraction of the tympanic membrane with a squamous debris collection or a whitish mass behind an intact tympanic membrane
• Testing includes computed tomography (CT) scanning, which can be useful in delineating disease extent but is not critical to making a diagnosis in most cases

Acquired Cholesteatoma

Cholesteatoma is the presence of squamous epithelium in the middle ear, mastoid, or epitympanum. The most common form of cholesteatoma is the acquired variety, which is classified as primary and secondary acquired cholesteatoma. Primary acquired cholesteatoma is the most common of these types and forms as a retraction of the tympanic membrane. In most cases, the retraction occurs in the pars flaccida, although pars tensa retractions can also occur (Figure 50–1). Secondary acquired cholesteatoma forms as a result of either squamous epithelial migration from the tympanic membrane or implantation of squamous epithelium into the middle ear during surgery, such as ventilation tube placement or tympanoplasty.

Congenital Cholesteatoma

Cholesteatomas that occur without tympanic membrane retraction or implantation of squamous epithelial material are considered to be congenital in origin. This comprises a minority of cholesteatoma cases. It is classically defined as an embryonic rest of epithelial tissue in the ear without tympanic membrane perforation and without a history of ear infection. This definition has been modified in recent years, but essentially it is a condition typically seen in young children without evidence of the acquired type of cholesteatoma.

The pathogenesis of primary acquired cholesteatoma remains unclear. Factors that appear to be associated with formation of cholesteatoma retractions of the tympanic membrane include poor eustachian tube function and chronic inflammation of the middle ear, as in chronic otitis media. In theory, chronic negative middle ear pressure leads to retractions of the structurally weakest area of the tympanic membrane, the pars flaccida. Once the retractions form, the normal migratory pattern of the squamous epithelium is disrupted, resulting in the accumulation of keratin debris in the cholesteatoma sac. Chronic infection and inflammation ensue, leading to biochemical changes in the local environment that foster the further growth and migration of the squamous epithelium and increased osteoclastic activity, resulting in bone resorption. The local inflammatory response further inhibits eustachian tube function, increases mucosal edema and mucous secretion, and disrupts the drainage pathways of the temporal bone. This environment also fosters the growth of bacteria, including Pseudomonas aeruginosa, Streptococcus, Staphylococcus, Proteus, Enterobacter, and anaerobes, which increase the host's inflammatory response and continue the cycle. It is ...