Cholesteatoma

Definition and epidemiology

Cholesteatoma is a lesion of the middle ear cleft and mastoid air cells made up of keratinising stratified squamous epithelium, the underlying connective tissue and accumulated keratin debris. The joint consensus of the European Academy of Otology and Neurotology (EAONO) and the Japanese Otological Society (JOS) adopts this definition and divides middle ear cholesteatoma into congenital, acquired and unclassifiable forms (Yung et al., 2017). Histologically the lesion is benign, but because it expands by eroding bone its clinical course can be destructive (Castle, 2018). It is also referred to as chronic otitis media with cholesteatoma.

Acquired cholesteatoma has traditionally been divided into primary and secondary types. Primary acquired cholesteatoma arises when keratin collects in a retraction pocket, usually of the pars flaccida, and can no longer be cleared. Secondary acquired cholesteatoma develops when epithelium migrates into the middle ear from the edge of a perforation, or when it is implanted there by surgery or trauma. The EAONO/JOS classification expresses the same distinction as ‘retraction pocket cholesteatoma’ (pars flaccida, pars tensa or combined) and ‘non-retraction pocket cholesteatoma’ (perforation-related, iatrogenic or traumatic) (Yung et al., 2017). Congenital cholesteatoma is a white mass behind a normal, intact eardrum in a child with no history of perforation, otorrhoea or ear surgery (Levenson et al., 1989).

A population-based Finnish study covering 1982-1991 found a mean annual incidence of middle ear cholesteatoma of 9.2 per 100,000, with higher rates in men under 50 (Kemppainen et al., 1999). Cholesteatoma of the external ear canal is a separate entity and is covered in Keratosis Obturans and External Auditory Canal Cholesteatoma.

Symptoms and signs

The hallmark of acquired cholesteatoma is foul-smelling ear discharge (otorrhoea) that fails to respond to treatment or keeps recurring. Ear pain (otalgia) is usually not prominent. Hearing loss progresses slowly and is generally conductive, reflecting erosion of the ossicular chain. In some patients the cholesteatoma itself bridges the eroded ossicles and keeps transmitting sound, so hearing can be better than expected. Aural fullness and tinnitus may also be present.

On otoscopy there may be a deep, keratin-filled pars flaccida retraction pocket, erosion of the scutum, white keratin at the margin of a perforation, granulation tissue or an aural polyp. Congenital cholesteatoma typically appears as a white, pearly mass behind the anterosuperior quadrant of an intact eardrum. Most of these children have no discharge, and the lesion is found during a routine examination or when hearing loss is investigated (Levenson et al., 1989).

As the disease advances, complications can develop. A labyrinthine fistula caused by erosion of the bony labyrinth can produce vertigo and sensorineural hearing loss, and erosion of the facial canal can lead to facial palsy. Mastoid abscess, lateral sinus thrombosis, meningitis and brain abscess are potentially life-threatening; these features are red flags. In a Turkish series of 4630 patients with chronic suppurative otitis media, 18.4% of the 511 operated patients with cholesteatoma developed a complication; among all complications, mastoid abscess was the commonest extracranial one (28.3%) and lateral sinus thrombophlebitis the commonest intracranial one (19.5%) (Yorgancilar et al., 2013).

Causes and risk factors

The most widely accepted explanation for primary acquired cholesteatoma is the retraction (invagination) theory. Poor Eustachian tube function causes prolonged negative middle ear pressure, the flaccid part of the eardrum is drawn inwards, and keratin can no longer be shed from the resulting pocket. Epithelial migration through a perforation, metaplasia of the middle ear mucosa and basal cell hyperplasia are the other proposed mechanisms; no single theory explains every case, and several may act together (Castle, 2018). Bone erosion is driven by enzymes and cytokines released from the inflamed tissue beneath the cholesteatoma matrix, which increase osteoclast activity.

Risk factors include prolonged otitis media with effusion in childhood, Eustachian tube dysfunction, previous grommets or ear surgery, eardrum perforation, and adhesive otitis media and retraction pockets. Cleft palate and craniofacial anomalies raise the risk because Eustachian tube function is impaired. Congenital cholesteatoma is thought to arise from epithelial rests left in the middle ear during embryonic development (Levenson et al., 1989).

Audiological and clinical assessment

The diagnosis is made by otomicroscopy or endoscopy; audiological assessment and imaging are needed to define the extent of disease and plan surgery. The EAONO/JOS system describes the sites involved with the acronym STAM: difficult-access sites (S1, supratubal recess; S2, sinus tympani), tympanic cavity (T), attic (A) and mastoid (M). The stage depends on the number of sites involved and on the presence of complications (Yung et al., 2017).

• Pure-tone audiometry: usually a conductive hearing loss; the size of the air-bone gap depends on the degree of ossicular erosion. Elevated bone conduction thresholds point to labyrinthine involvement and a mixed hearing loss. Bone conduction thresholds should be documented with appropriate masking before surgery.
• Speech audiometry: word recognition scores usually match the bone conduction thresholds and provide a baseline for comparing pre- and postoperative hearing.
• Tympanometry and acoustic reflexes: a perforation gives a flat (type B) trace with a large ear canal volume; with an intact drum, a retraction or mass gives a negative-pressure (type C) or flat trace. Acoustic reflexes are usually absent in the affected ear.
• Fistula test and vestibular testing: in a dizzy patient, nystagmus or vertigo provoked by pressure changes on pneumatic otoscopy suggests a labyrinthine fistula; videonystagmography and the video head impulse test (vHIT) are added when needed.
• Computed tomography (CT): high-resolution temporal bone CT shows bone erosion, the state of the ossicles and the integrity of the tegmen, facial canal and horizontal semicircular canal. It cannot, however, tell whether a soft-tissue density is cholesteatoma, inflammatory tissue or fluid.
• Diffusion-weighted magnetic resonance imaging (MRI): on non-echoplanar diffusion-weighted imaging (non-EPI DWI) keratin shows restricted diffusion, so the sequence is used to distinguish cholesteatoma from other soft tissue and to follow patients after surgery.

A meta-analysis of non-EPI DWI showed high sensitivity and specificity for detecting cholesteatoma (Lingam and Bassett, 2017). In a Turkish study of 54 patients, diffusion-weighted MRI had a sensitivity of 97.7%, a specificity of 77.8% and a diagnostic accuracy of 94.4% (Kayalı Dinç et al., 2018). Very small lesions can be missed, so the result is interpreted alongside the clinical findings.

The differential diagnosis includes chronic otitis media without cholesteatoma, granulation tissue, cholesterol granuloma, middle ear tumours and external canal cholesteatoma. For the audiologist, the key task is to document preoperative air and bone conduction hearing completely and to report any shift in bone conduction thresholds, which may signal labyrinthine involvement.

Treatment and audiological rehabilitation

There is no medical cure for cholesteatoma; treatment is surgical and the choice of operation rests with the surgeon. Before surgery, aural toilet and ear drops can reduce discharge temporarily. The priorities of surgery are complete removal of disease and a dry, safe ear; hearing is preserved or improved where possible. Canal wall up and canal wall down mastoidectomy are the main options, and endoscopic ear surgery and mastoid obliteration have become more widely used in recent years.

After surgery, disease may be left behind (residual) or may form again (recurrent). A meta-analysis of 84 studies and 12,819 patients found a pooled recurrence rate of 11%: 13% in children and 10% in adults, 16% after canal wall up and 7% after canal wall down techniques, with lower rates in obliterated ears. Cumulative recurrence rose from 7% at 12 months to 18% at 60 months and up to 39% at 15 years (Massoud et al., 2025). Follow-up is therefore long, relying on planned second-look surgery or imaging with non-EPI DWI.

Hearing rehabilitation is part of the surgical plan. The ossicular chain can be reconstructed at the same operation or at a second stage using autologous ossicles, cartilage or a prosthesis (ossiculoplasty). A systematic review, based on low-level evidence, found that a preserved malleus predicted better postoperative hearing independently of stapes status (Blom et al., 2015). Persistent conductive or mixed loss is managed with an air conduction hearing aid. If discharge or earmould problems in an open mastoid cavity prevent its use, bone conduction implants are considered. In children, regular audiological follow-up after surgery matters for language development and school performance, and the other ear should also be monitored.

Impact on quality of life and advice

Recurrent discharge, odour and hearing loss can make people withdraw in social settings and cause communication difficulties at school or work. Long-term follow-up and the prospect of a second operation can be a source of anxiety. Discussing the expected course, the follow-up schedule and the options for hearing rehabilitation openly from the outset helps to reduce it. When hearing does not improve after surgery, a hearing handicap questionnaire can track everyday difficulties and guide rehabilitation.

Keep water out of an unoperated or recently operated ear, and use the ear protection your surgeon recommends for showering and swimming. If you have an open mastoid cavity, it needs regular cleaning by your doctor; do not use cotton buds. Keep your follow-up appointments and any recommended MRI scans even if you have no symptoms, because the disease can recur silently. A child with hearing loss in one ear should sit where they can see the teacher, with the better ear towards the lesson, and a remote microphone system helps in noisy classrooms. If ossicular reconstruction is planned, repeating hearing tests at the same centre with the same methods allows changes to be judged reliably.