ESSENTIALS OF DIAGNOSIS
Squamous epithelium in the middle ear or mastoid.
Otorrhea and conductive hearing loss.
Retraction of the tympanic membrane (TM) with a squamous debris collection or a whitish mass behind an intact TM or perforation.
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, and magnetic resonance imaging (MRI) with nonechoplanar diffusion-weighted imaging, which can differentiate cholesteatoma from other tissues and fluid.
A. 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 or secondary acquired cholesteatoma. Primary acquired cholesteatoma is the more common of these types and forms as a retraction of the TM. In most cases, the retraction occurs in the pars flaccida, although pars tensa retractions can also occur (Figure 52–1). Secondary acquired cholesteatoma forms as a result of either squamous epithelial migration from a TM perforation or implantation of squamous epithelium into the middle ear during surgery, such as ventilation tube placement or tympanoplasty.
Formation of primary acquired cholesteatoma in the pars flaccida portion of the tympanic membrane. (Illustration © 2018 Chris Gralapp, CMI.)
B. Congenital Cholesteatoma
Cholesteatomas that occur without TM 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 TM 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.
JD. Congenital cholesteatoma of the middle ear and mastoid. Ann Otol Rhinol Laryngol.
. (Classic definition of congenital cholesteatoma.)
The pathogenesis of primary acquired cholesteatoma remains unclear. Factors that appear to be associated with formation of cholesteatoma retractions of the TM include history of poor eustachian tube function and chronic inflammation of the middle ear, as in chronic otitis media or recurrent acute otitis media. In theory, chronic negative middle ear pressure and/or other poorly understood factors lead to retractions of the structurally weakest area of the TM, 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. ...