Cholesteatoma

What is cholesteatoma?

This lesion is inappropriately named, as it is not exactly a tumour, nor is it made of cholesterol. It is a three-dimensional collection of epidermal and connective tissues within the middle ear.

Its significance lies in the fact that it grows independently and can be locally invasive and destructive, particularly affecting the bones of the middle ear.

Bone erosion occurs mainly by pressure but release of osteolytic enzymes has been detected at the peripheral margins of the lesion. Osteolytic activity appears to be enhanced by the presence of infection.

The (usually) unilateral lesion can give rise to a spectrum of problems, ranging from painless otorrhoea (discharge from the ear) through to serious central nervous system complications.

Types of cholesteatoma

Congenital cholesteatoma

This occurs when squamous epithelium becomes trapped within the temporal bone during embryogenesis. It expands, resulting in conductive hearing loss either through obstruction of the Eustachian tube or by surrounding the ossicular chain. They account for only 2% of all cases of cholesteatoma.¹

Primary acquired cholesteatoma

These account for around 80% of all cases.¹ The precise pathophysiology of these lesions is not absolutely certain but it is thought that chronic negative middle-ear pressure due to a dysfunction of the Eustachian tube causes the tympanic membrane to be 'sucked back' and retract.²

As this process continues, there is erosion of the lateral wall of the epitympanum (the upper portion of the tympanic cavity which contains the head of the malleus and the body of the incus), producing a slowly expanding defect.

A 'retraction pocket' lined by squamous, non-keratinising epithelium is thus formed. The erosion often goes on, as the ball of epithelium grows, to surround the ossicles and may extend into the mastoid bone, the lateral semicircular canal, the middle cranial fossa and the posterior cranial fossa.

Secondary acquired cholesteatoma

These account for about 18% of all cholesteatomas.¹ This arises as a result of insult to the tympanic membrane, such as perforation secondary to acute otitis media (AOM) or trauma, or due to surgical manipulation of the drum.

Squamous epithelium may be inadvertently implanted by the insult so triggering the process of cellular growth resulting in cholesteatoma formation.

Spectrum of otitis media

Otitis media (OM) is an umbrella term for a group of complex infective and inflammatory conditions affecting the middle ear.

All OM involves pathology of the middle ear and middle ear mucosa. OM is a leading cause of healthcare visits worldwide and its complications are important causes of preventable hearing loss, particularly in the developing world.

There are various subtypes of OM. These include AOM, otitis media with effusion (OME), chronic suppurative otitis media (CSOM), mastoiditis and cholesteatoma. They are generally described as discrete diseases but in reality there is a great degree of overlap between the different types. OM can be seen as a continuum/spectrum of diseases:

• AOM is acute inflammation of the middle ear and may be caused by bacteria or viruses.³ A subtype of AOM is acute suppurative OM, characterised by the presence of pus in the middle ear. The eardrum may perforate.

• OME is a chronic inflammatory condition without acute inflammation, which often follows a slowly resolving AOM.⁴ There is an effusion of glue-like fluid behind an intact tympanic membrane in the absence of signs and symptoms of acute inflammation.

• CSOM is long-standing suppurative middle ear inflammation, usually with a persistently perforated tympanic membrane.⁵

• Mastoiditis is acute inflammation of the mastoid periosteum and air cells occurring when AOM infection spreads out from the middle ear.

• Cholesteatoma occurs when keratinising squamous epithelium (skin) is present in the middle ear as a result of tympanic membrane retraction.

How common is cholesteatoma? (Epidemiology)

The epidemiological data regarding this condition are somewhat scant, although it is one of the most common indications for otological surgery. In the USA, one study reported six cholesteatomas per 100,000 people but in Europe it is thought to be closer to 9 per 100,000.^{6 7}

Acquired cholesteatomas are about 1.4 times more likely to occur in men compared to women and their incidence is higher among low-income patients.

Cholesteatoma symptoms (presentation)

• The typical symptom of a cholesteatoma is chronic painless otorrhoea (discharge from the ear).

• Symptoms and signs vary according to the size of the cholesteatoma. Small lesions are associated with a progressive conductive hearing loss but, as the lesion grows and erodes into adjacent structures, there may be additional features such as vertigo, headache and facial nerve palsy.²

• Associated infection can (rarely) manifest itself within the central nervous system (sigmoid sinus thrombosis, epidural abscess, meningitis) or as an abscess in the neck.

• Case reports indicate cholesteatoma growing in the external and internal auditory canal.

• The former most commonly presents with otorrhoea and hearing impairment. The latter may result in total deafness of the affected ear and impaired facial movement.

Congenital cholesteatoma

• This usually presents in childhood (6 months to 5 years) but may occasionally present much later, in adulthood.

• There is often no history of recurrent suppurative ear disease, previous ear surgery or tympanic membrane perforation.

• It may be an incidental finding on routine otoscopy of an asymptomatic child - a pearly white mass is seen behind an intact tympanic membrane.

• Larger lesions lead to conductive hearing loss.

Acquired cholesteatoma

• Frequent or unremitting painless otorrhoea which may be foul-smelling.

• Recurrent otitis, poorly responsive to antibiotic treatment.

• Progressive, unilateral conductive hearing loss.

• Tympanic membrane perforation (approximately 90% of cases) or retracted tympanum.

• The only finding may be a pus-filled canal with granulation tissue.

Risk factors

• Congenital - cleft palate.

• Acquired - ear trauma (accidental or surgical), including insertion of grommets.

Differential diagnosis

• Otitis media with effusion.

• Otitis externa.

• Tympanosclerosis - the white appearance of fibrotic scarring of the tympanic membrane, commonly seen after grommet insertion, can give the impression of a cholesteatoma deeper within the middle ear.

• Osteonecrosis of the external auditory canal.

Investigations

Following physical examination, these patients will undergo a spectrum of audiological tests:

• CT imaging is the investigation of choice if there is a need for assessment of the extent of the lesion and to assess subtle bony defects.⁶ This will guide the surgeon as to how to go ahead with surgery and to help in establishing how successful surgery is likely to be. However, patients should be advised that CT cannot always accurately predict what the operative findings will be and intraoperative 'surprises' are relatively common with this condition.

• Where there is concern about soft tissue involvement in addition to the bony erosion (eg, herniated brain, epidural abscess and sigmoid sinus thrombosis), an MRI scan may also be performed.

Cholesteatoma treatment

Medical treatment

Medical therapy is reserved for those patients who refuse surgery or for whom a general anaesthetic would be too dangerous owing to comorbidity.

In these patients, regular ear cleaning with treatment of infections (topical ± systemic antibiotics) is advised but, ultimately, this will not prevent cholesteatoma growth with its consequences.

Surgical treatment

Overview
Surgery is the mainstay of treatment and the aim is to remove the cholesteatoma and leave a safe, dry ear.

Surgery involves a general anaesthetic and an incision behind the ear and in the auditory meatus. There will be a dressing applied which, depending on local practice, may be removed by the patient or the team - patients will be advised.

Follow-up is any time between a day and three weeks after surgery depending on each individual surgeon's techniques and preferences.

There will be a need for topical antibiotics in the first instance and possibly topical steroids later on if excessive granulation tissue forms.

Techniques
There are two methods used: the open and the closed techniques; there is ongoing debate over which is ideal. Ultimately, it depends on the type and location of the cholesteatoma and, sometimes, a decision cannot made until the operation has started.⁶

• Open technique (tympanomastoidectomy): this is a longer and more involved procedure that entails removal of a number of structures postoperatively. This is the more successful of the two types of procedure in terms of cholesteatoma removal and therefore a single procedure is usually sufficient. Its drawbacks are that there is a resultant enlarged auditory meatus (at least to twice its normal size) making hearing aids difficult to fit and occasionally resulting in dizziness on exposure to cold water or air. There is a need for annual or biannual auditory canal cleaning too.

• Closed technique (tympanoplasty): this method is associated with a better end result with regards to cosmetic appearance but, as it is associated with a higher risk of persistent or recurrent cholesteatomas, a second-look operation 6-12 months down the line is mandatory. MRI imaging may replace the traditional second-look surgery.

• The use of otoendoscopy is being investigated.

Outcomes
The aims of surgery are:

• To eliminate the cholesteatoma and its associated complications.

• To enable all the usual activities of daily living, including swimming.

• To conserve residual hearing ± improve hearing if possible.

• To reconstruct the ear in a manner that reduces the chances of recurrence.

Complications

If managed conservatively a cholesteatoma left in situ will inevitably grow. The complications depend on which structures it grows and erodes into.

Thus, the patient develops a progressive conductive deafness and then may go on to have problems with dizziness, facial nerve palsy, to central nervous system problems (through a mass effect or as a consequence of abscess formation).⁷

When a cholesteatoma is managed surgically, all but the first of the complications listed below are rare.

• Temporary (few months) alteration of taste.

• Perichondritis.

• Chondritis.

• Ear canal stenosis.

• Facial nerve injury.

• Formation of a fistula into one of the semicircular canals.

• Labyrinthine or middle-ear injury leading to long-term dizziness.

• Acquired cholesteatoma following surgery for congenital cholesteatoma has been reported.⁸

Prognosis

Surgical removal of a cholesteatoma is usually complete, but the risk of residual disease after corrective surgery varies from 5% to 30%.⁷ Between 7% and 10% of people diagnosed with cholesteatoma will develop a cholesteatoma in the other ear.