Description

• Cholesteatoma is a misnomer for a collection of pearly skin cells found in the mastoid, middle ear, or external auditory canal. These cells, once in place and growing, can lead to otorrhea (drainage), hearing loss, infection, bony erosions, labyrinthine fistulas, facial nerve paralysis, and can even invade into the intracranial space causing neurologic problems up to and including death (1,2,3,4).
• Cholesteatoma was originally named based on its fatty appearance in the middle ear (1,3). Cholesteatoma does not in fact contain any cholesterol. A more fitting name would be keratoma because it is comprised of differentiated keratinizing epithelial cells (1,3). However, traditions are difficult to break, and cholesteatoma remains the preferred terminology today (1).

Epidemiology

Cholesteatomas are found in all age groups. Congenital cholesteatomas are usually found only in pediatric patients, whereas acquired cholesteatomas can be found in any individual with middle ear disease (1,2,3). Acquired cholesteatomas are divided into primary acquired and secondary acquired.

Incidence
The average age for diagnosis of cholesteatoma is 9.7 years for acquired and 4.5 years for congenital (1). There exists a slight male preponderance for the disease. However, female patients are more likely to have bilateral disease and exhibit recurrence of disease in subsequent follow-up appointments (1). Overall, the incidence of acquired cholesteatoma is decreasing, secondary to the widely accepted and implemented early use of pressure equalization (PE) tubes for otitis media and other middle ear disease (1).

Prevalence
The prevalence of acquired cholesteatoma is approximately 15 cases per 100,000 children and 12 cases per 100,000 adults. By comparison, congenital cholesteatomas are rare only affecting approximately 0.12 per 100,000 children. Congenital cholesteatoma is becoming more commonly reported because recognition and screening of the disease has become more sensitive (1).

Etiology and Pathophysiology

• Congenital cholesteatoma can form by abnormal embryologic development in locations such as the tympanic membrane, middle ear, or petrous apex. During normal development, there are “rests” or pockets of epithelial cells that involute. Failure to involute leads to misplaced epithelial cells that can grow and congenital cholesteatoma. These were first defined as “an embryonic rest of epithelial tissue in the ear without tympanic membrane perforation and without a history of ear infection” (1).
• Primary acquired cholesteatomas are generally those that arise from a retraction pocket and are not directly related to repeated infections (1). Epidermal skin cells are erroneously introduced into the middle ear space in the retraction pocket and continue to grow in an uncontrolled fashion. Cleft palate patients, who are particularly prone to eustachian tube dysfunction (ETD) and retraction pocket formation, are at high risk for cholesteatoma formation.
• Secondary acquired cholesteatomas arise from epidermal skin cells that are introduced into the middle ear space via an existing perforation. These perforations can be attributed to trauma, surgeries (myringotomy, PE tubes, tympanic membrane repairs, etc.), blast injuries, or acute infections leading to perforation. Another cause is metaplasia of middle ear cells into keratinizing epidermal cells secondary to chronic infection (1). However, this last pathway does not represent the majority of secondary acquired cholesteatomas.

Genetics
As described above, cholesteatoma can arise in various clinical situations. Cholesteatoma can arise as part of a constellation of symptoms in syndromic children (e.g., branchio-oto-renal syndrome). It can also stem from a disease process like otitis media with effusion. To date, there is no specific gene correlated with acquired cholesteatoma (4). Discussion of specific genetic contributions to syndromic processes associated with cholesteatoma is beyond the scope of this article.

Risk Factors

As alluded above, acquired cholesteatoma is more prevalent in patients with long-standing middle ear disease. Chronic ETD causes negative pressure in the middle ear space leading to retraction of the tympanic membrane, accumulation of fluid in the middle ear space, predisposition for infection within accumulated fluid, and possible tympanic membrane perforation (1,2,3). Each of these disease states contributes in part to formation of an acquired cholesteatoma (either primary or secondary).

General Prevention

The primary treatment for ETD and hence cholesteatoma formation is primarily with PE tubes. Although perforation in the tympanic membrane is the primary mechanism of secondary acquired cholesteatoma, evidence supports placement of PE tubes for the treatment of ETD to prevent and potentially reverse the formation of retraction pockets in the tympanic membrane (1,2,3).

Commonly Associated Conditions

• ETD
• Tympanic membrane perforation
• Down syndrome
• Cleft lip/palate
• Apert syndrome
• Crouzon syndrome
• Pfeiffer syndrome
• Pierre Robin sequence
• Turner syndrome