Cholesteatoma

A cholesteatoma is a benign mass that consists of keratinizing squamous cell epithelium that grows in the middle ear. Keratinized squamous epithelium is a type of skin cell that contains keratin, a protein that helps form hair, skin, and nails. Cholesteatomas primarily affect children and may be congenital or acquired. The most common type is acquired, which can then be further divided into primary or secondary.

Cholesteatomas are composed of several layers, including a cystic, matrix, and perimatrix layer. The cystic layer is composed of necrotic debris, sebum, and keratin. The matrix comprises squamous epithelium, while the perimatrix comprises inflammatory cells such as lymphocytes, neutrophils, plasma cells, histiocytes, and fibrocytes.  Essentially, skin and inflammatory cells build up, forming a cholesteatoma. 

The cause of cholesteatomas depends on whether it is congenital or acquired. Congenital cholesteatomas develop after remnants of keratinized squamous epithelium are confined behind the tympanic membrane. The middle ear is typically composed of non-keratinized squamous epithelium, a layer of skin cells that does not contain keratin. Debris can accumulate and form the cholesteatoma, a white keratinous mass located behind the tympanic membrane (i.e., ear drum).

The cause of primary acquired cholesteatoma is largely unknown. However, four theories exist as to the cause. The most accepted theory states that a pocket can form on the pars flaccida (i.e., flaccid, triangular part of the tympanic membrane) allowing debris to accumulate. The second theory states cholesteatomas may be caused by the hyperproliferation (i.e., excess production) of squamous epithelium in the middle ear. The third proposes a migration of keratinized squamous epithelium from the ear canal, where it is normally found, to the middle ear through a perforated tympanic membrane. The final theory hypothesizes that there is basal cell (i.e., a cell found at the bottom of the epidermis that is responsible for creating new cells) hyperplasia from the tympanic membrane that protrudes into the middle ear allowing for excess skin cell production. 

Secondary acquired cholesteatomas can be caused by trauma, ear infection (e.g., chronic otitis media), or surgical damage causing a perforation of the tympanic membrane.

The signs and symptoms of cholesteatomas depend on the severity and location. Initially, a person may experience otorrhea (i.e., ear drainage) with or without pain and ear fullness. Congenital cholesteatomas may present in infancy with poor hearing due to obstruction of the eustachian tube (i.e., the canal that connects the middle ear to the sinuses) during development. Dizziness can occur if the semicircular canal (i.e., a structure in the internal ear responsible for balance) is compressed. Facial paralysis may also occur if there is compression of the facial nerve, which is responsible for facial movement. Infection of a cholesteatoma may result in foul-smelling discharge from the external ear.

In severe cases, a cholesteatoma may erode the middle ear bones (e.g., stapes, incus, malleus), temporal bone, or mastoid bone, affecting the central nervous system, which can cause meningitis (i.e., infection of the meninges), abscesses, fistulas (i.e., abnormal openings), and permanent hearing loss.

Cholesteatomas may be diagnosed with a thorough physical examination by a healthcare professional. A complete physical exam of the head, neck, cranial nerves, and ear may be necessary. The cholesteatoma, a white keratinous mass, may be visible when a healthcare professional looks inside the ear with an otoscope. An audiogram, Weber, or Rinne tests may also determine the severity and type of any associated hearing loss. An audiogram measures the different frequencies and intensity that an individual can hear; while Weber and Rinne tests can assess whether there is sensorineural (i.e., inner ear damage) or conductive (i.e., outer ear damage) hearing loss. These tests can also determine which ear is affected. 

If additional neurologic symptoms are present, a brain computed tomography scan (CT scan) or magnetic resonance imaging (MRI) may be required to investigate the possibility of bone erosion, brain abscesses, or a fistula.

Treatment of a cholesteatoma depends on the size, surgical candidacy, and symptoms. The primary method of cholesteatoma removal is a mastoidectomy (i.e., removal of mastoid bone to access middle ear space). Surgical removal can prevent further complications from compression and infection. Nonetheless, cholesteatomas may reoccur between 5 to 50% of the time after surgical removal. 

An infected cholesteatoma can be challenging to treat without completely removing the cholesteatoma. Systemic antibiotics are usually ineffective as there is no blood supply to the keratin mass. Additionally, topical antibiotics often do not penetrate deep enough into the mass to completely resolve the infection. This leaves surgical removal as the best option to remove the source of infection. 

In cases of very small cholesteatomas, suction may be sometimes used to remove them. 

Even with cholesteatoma surgery, hearing loss may be permanent. Reconstructive surgeries like myringoplasty or tympanoplasty are types of surgeries that may be able to reestablish hearing. 

Cholesteatomas are middle ear masses that develop from accumulated skin cell debris consisting of keratinized squamous epithelial, sebum, necrotic debris, and inflammatory cells. Cholesteatomas may be caused by congenital epithelial remnants or may be acquired. Individuals with cholesteatomas may experience conductive hearing loss, dizziness, and facial nerve palsy. Brain abscesses, meningitis, and fistulas may develop from bone erosion, in severe cases. A complete physical examination of the head, neck, and ear is required to make a diagnosis. If there is concern for more severe neurologic symptoms and fever, a brain CT or MRI may be necessary. Treatment relies primarily on surgical removal of the cholesteatoma.