Cholesteatoma

This lesion is somewhat inappropriately named as it is not exactly a tumour nor is it made of cholesterol but rather it is a 3-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. This (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.

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.

Primary acquired cholesteatoma

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. 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 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, lateral semicircular canal, middle and posterior cranial fossa.

Secondary acquired cholesteatoma

This arises as a result of insult to the tympanic membrane, such as perforation secondary to acute otitis media 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.

The epidemiological data regarding this condition is somewhat scant.² There has been a suggestion of an incidence of 9.2 per 100,000³ with congenital cholesteatomas accounting for 7% of cases and a male:female ratio of 4:1.⁴ However, these figures are based on single studies and accurate data is not available on account of non-presentation, undiagnosed cases and paucity of relevant studies. Suffice it to say that this is an uncommon problem.

• 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.
• Rarely, associated infection can manifest itself within the central nervous system (sigmoid sinus thrombosis, epidural abscess, meningitis) or as an abscess in the neck.
• There have been infrequent case reports of the cholesteatoma growing in the external⁶ and internal⁷ 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

• Usually presents in childhood (6 months - 5 years) but may present much later, in adulthood.⁴
• There is often no history of recurrent suppurative ear disease, previous ear surgery or tympanic membrane perforation.
• May be incidental finding up on routine otoscopy of an asymptomatic child⁸ - 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 (discharge) which may be foul-smelling.
• Recurrent otitis, poorly responsive to antibiotic treatment.
• Progressive, unilateral conductive hearing loss.
• Tympanic membrane perforation (~90% of cases) or retracted tympanum.
• Only finding may be pus-filled canal with granulation tissue.

Risk factors

• Congenital - cleft palate³
• Acquired - ear trauma (accidental or surgical) including insertion of grommets

• Myringosclerosis: thickening and calcification of the tympanic membrane secondary to inflammation.
• Myospherulosis (spherulocytosis):^9,10 an iatrogenic, chronic granulomatous reaction of red blood cells with petrolatum, lanolin or traumatised human adipose tissue in the nose and paranasal sinuses. This lipogranuloma forms after haemostatic packing with petroleum-based ointment and gauze.

Following physical examination, these patients will undergo a spectrum of audiological tests. Subsequently, if the borders of a small lesion can be fully visualised, no further investigation is needed.⁸

• 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. 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.¹
• Where there is concern about soft tissue involvement in addition to the bony erosion (e.g. herniated brain, epidural abscess and sigmoid sinus thrombosis), an MRI may also be performed.

Medical treatment

Medical therapy is reserved for those patients who refuse surgery or for whom a general anaesthetic would be too dangerous owing to co-morbidity. 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 (see below).

Surgical treatment

Overview

The aim of surgery is to remove the cholesteatoma. 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 individual surgeons' techniques and preferences. There will be a need for topical antibiotics in the first instance and possibly topical steroids later on if the granulation tissue gets out of hand.

Techniques

There are two methods used: the open and the closed techniques; there is ongoing debate over which is ideal. Ultimately, it depends on individual patient circumstances and sometimes, a decision cannot made until the operation has started.

• Open technique (tympanomastoidectomy): this is a longer and more involved procedure that entails removal of a number of structures post-operatively. 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 it 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. Recently, there have been promising developments in the role of specialised MRI imaging replacing the traditional second-look surgery.¹¹

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.

Conservative management

A cholesteatoma left in situ will inevitably grow. The complications of this depends on where it grows and erodes into. Thus, the patient develops a progressive conductive hearing deafness and then may go on to have problems with dizziness, facial nerve palsy, central nervous system problems (through a mass effect or as a consequence of abscess formation) and so on.

Surgical intervention

All but the first of the complications listed below are rare (of the order of about 1% or less)

• 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

Surgical removal of a cholesteatomas is usually complete although this may take more than one procedure (in no more than 5% of the patients who have had the open technique used and in 20-40% of those who have had the closed technique).¹ Life-long follow-up is required as cholesteatomas may recur, especially congenital ones.