Cholesteatoma

What Is a Cholesteatoma?

A cholesteatoma is an abnormal, non-cancerous growth of skin cells — specifically keratinising squamous epithelium — that develops in the middle ear, usually behind or within a retraction pocket of the eardrum. Despite its name, a cholesteatoma is not a tumour and not a cancer. It is essentially a cyst-like collection of dead skin cells that forms a pearl-white mass. However, cholesteatomas are locally destructive: as they grow, they can erode the delicate structures of the middle ear and surrounding bone, and in advanced cases can damage the inner ear, facial nerve, or structures of the skull base.

In the United Kingdom, cholesteatomas are estimated to affect approximately 9 to 12 per 100,000 people each year, according to data from the British Society of Audiology (BSA) and NHS audiology services. While this makes it a relatively uncommon condition compared to simple ear infections, the potential for serious complications means that early diagnosis and treatment are essential. If you have been told you may have a cholesteatoma, or if you have symptoms such as a persistent foul-smelling ear discharge, understanding the condition fully can help you feel informed and prepared for the steps ahead.

Congenital vs Acquired Cholesteatoma

Cholesteatomas are classified into two broad types, each with different origins:

Congenital Cholesteatoma

Congenital cholesteatomas are rare, accounting for roughly 2 to 5% of all cholesteatoma cases. They are present from birth, caused by skin cells becoming trapped behind an intact eardrum during foetal development. They are typically discovered incidentally during routine examinations in childhood, appearing as a whitish mass behind a normal-looking eardrum. Because there is usually no history of ear infections or eardrum perforations, congenital cholesteatomas can go undetected for years.

Acquired Cholesteatoma

Acquired cholesteatomas are far more common and develop during a person's lifetime. They most often arise in association with chronic Eustachian tube dysfunction, which creates persistent negative pressure in the middle ear. This negative pressure draws the eardrum inwards, forming a retraction pocket — a weakened area of the eardrum that gradually deepens over time. Dead skin cells, which normally migrate outwards along the ear canal, become trapped within this pocket and accumulate, eventually forming a cholesteatoma.

Other risk factors for acquired cholesteatoma include recurrent middle ear infections, previous eardrum perforation (particularly marginal perforations near the edge of the eardrum), and previous ear surgery or grommet insertion.

How a Cholesteatoma Develops

Understanding the mechanism behind cholesteatoma formation helps explain why the condition is progressive and why surgery is almost always necessary. The process typically follows these stages:

• Eustachian tube dysfunction — The Eustachian tube fails to equalise pressure properly, creating negative pressure in the middle ear space. This can result from chronic allergies, recurrent colds, sinusitis, or anatomical factors.
• Eardrum retraction — The persistent negative pressure pulls part of the eardrum inwards, creating a retraction pocket, most commonly in the upper (attic) region of the eardrum known as the pars flaccida.
• Skin cell accumulation — The ear canal is lined with skin that naturally sheds and migrates outwards. In a retraction pocket, this self-cleaning process fails, and dead skin cells — keratin debris — accumulate within the pocket.
• Growth and expansion — The trapped skin debris continues to build up, forming an enlarging cholesteatoma sac. Enzymes released by the cholesteatoma erode surrounding bone, allowing the mass to expand into the mastoid bone, the ossicular chain, and potentially beyond.
• Secondary infection — Bacterial infection of the trapped debris produces the characteristic foul-smelling discharge and can accelerate bone erosion.

This progressive nature is why cholesteatomas do not resolve on their own and why a watch-and-wait approach is not appropriate — unlike many other ear conditions, surgical intervention is the definitive treatment.

Symptoms of Cholesteatoma

Cholesteatomas typically develop slowly, and early symptoms may be subtle or mistaken for a recurring ear infection. The most common symptoms include:

• Persistent, foul-smelling ear discharge — This is often the earliest and most characteristic symptom. Unlike the discharge from a simple ear infection, the smell from a cholesteatoma is distinctively offensive due to the breakdown of accumulated keratin debris and secondary bacterial infection. The discharge is typically scanty but persistent, recurring over weeks or months rather than clearing with a course of antibiotics.
• Progressive hearing loss — Hearing loss is usually conductive, caused by erosion of the ossicles (the three tiny bones of hearing — the malleus, incus, and stapes) or by the cholesteatoma mass physically blocking sound transmission. The hearing loss typically worsens gradually over months or years as the cholesteatoma enlarges. A hearing test and bone conduction test can help determine the type and severity of the loss.
• A feeling of fullness or pressure in the affected ear.
• Earache or discomfort — Though pain is not always present, and its development may indicate complications.

In more advanced cases, symptoms may include dizziness or vertigo (indicating erosion into the inner ear or formation of a labyrinthine fistula), facial weakness (if the facial nerve, which runs through the middle ear, is affected), or severe headache and fever (suggesting intracranial complications). These are warning signs that require urgent medical attention.

Diagnosis and Investigations

Cholesteatoma is diagnosed through a combination of clinical examination and imaging. If your GP suspects a cholesteatoma, you will be referred to an ENT (ear, nose, and throat) specialist for further assessment.

Otoscopy

The first step is a careful visual examination of the ear canal and eardrum using an otoscope or microscope. The ENT specialist may see a retraction pocket filled with white, pearly debris — the characteristic appearance of a cholesteatoma. In some cases, a polyp (fleshy growth) may be visible in the ear canal, or the eardrum may show signs of chronic perforation or retraction. Aural toilet — careful cleaning of the ear under microscope guidance — is often performed to allow a clear view.

Audiometry

A comprehensive hearing assessment is essential to document the type and degree of hearing loss. Bone conduction testing helps distinguish between conductive hearing loss (from ossicle damage) and sensorineural loss (from inner ear involvement). Tympanometry can provide additional information about middle ear function. These results form an important baseline against which post-surgical hearing can later be compared.

CT Scanning

A high-resolution CT scan of the temporal bone is the standard imaging investigation. It shows the extent of the cholesteatoma, any bony erosion of the ossicles, the mastoid bone, or the tegmen (the thin bone separating the middle ear from the brain), and helps the surgeon plan the operation. CT scanning is particularly important for identifying potential complications and guiding surgical approach.

MRI Scanning

Diffusion-weighted MRI is increasingly used both before surgery (to help characterise the lesion) and after surgery (to monitor for recurrence). MRI can distinguish cholesteatoma from other soft tissue, making it valuable for surveillance without the need for second-look surgery in many cases.

Complications if Left Untreated

While cholesteatomas grow slowly, they are relentlessly progressive. Without surgical treatment, a cholesteatoma can cause increasingly serious complications as it erodes through surrounding structures:

• Ossicle erosion and hearing loss — The incus (anvil) is most commonly affected, followed by the stapes and malleus. Progressive destruction of the ossicular chain leads to worsening conductive hearing loss.
• Labyrinthine fistula — Erosion into the lateral semicircular canal of the inner ear creates an abnormal opening, causing episodes of vertigo triggered by pressure changes in the ear canal. This is found in approximately 5 to 10% of cholesteatoma cases at surgery.
• Sensorineural hearing loss — If the cholesteatoma erodes into the cochlea (inner ear), permanent sensorineural hearing loss can result, which cannot be restored by surgery or hearing aids alone.
• Facial nerve palsy — The facial nerve passes through the middle ear in a thin bony canal. Erosion of this canal can damage the nerve, causing weakness or paralysis on the affected side of the face. This is a serious complication requiring urgent surgical intervention.
• Mastoiditis — Spread of infection into the mastoid bone behind the ear can cause swelling, pain, and redness behind the ear.
• Intracranial complications — In rare but life-threatening cases, cholesteatoma can erode through the tegmen into the middle cranial fossa, leading to meningitis (infection of the brain lining), epidural or subdural abscess, or brain abscess. These require emergency neurosurgical intervention.

These serious complications are uncommon with modern medical care, as most cholesteatomas are detected and treated before they reach this stage. However, they underscore why early diagnosis and surgical management are so important.

Surgical Treatment

Treatment for cholesteatoma is almost always surgical. Unlike ear infections that can be treated with antibiotics, a cholesteatoma will not resolve with medication — it must be physically removed. The goals of surgery are to completely remove the cholesteatoma, eradicate any infection, create a safe, dry ear, and where possible, preserve or reconstruct hearing.

Mastoidectomy

The main operation is called a mastoidectomy, often combined with tympanoplasty (repair of the eardrum). There are two principal surgical approaches:

• Canal Wall Up (CWU) — The posterior wall of the ear canal is preserved, maintaining normal ear canal anatomy. This approach leaves a more natural-looking ear canal and avoids the need for regular cleaning of a cavity. However, it carries a higher risk of cholesteatoma recurrence (approximately 20 to 30%) because it is harder to visualise and completely remove disease behind an intact canal wall. Second-look surgery or MRI surveillance is often planned 9 to 12 months after the initial operation.
• Canal Wall Down (CWD) — The posterior canal wall is removed, creating an open mastoid cavity. This gives the surgeon excellent visibility and access, resulting in a lower recurrence rate (approximately 5 to 10%). However, the resulting cavity requires lifelong care — periodic cleaning by an ENT specialist, careful water precautions when bathing or swimming, and hearing aids may sit less comfortably.

The choice between CWU and CWD depends on the extent and location of the cholesteatoma, the condition of the ossicles, the patient's anatomy, and the surgeon's experience. Your ENT surgeon will discuss the advantages and disadvantages of each approach with you before surgery.

Hearing Reconstruction (Ossiculoplasty)

If the ossicles have been eroded by the cholesteatoma, the surgeon may reconstruct the hearing mechanism using prosthetic ossicles (titanium or hydroxyapatite implants) or by repositioning remaining bone. This is called ossiculoplasty and can be performed during the initial surgery or as a staged procedure. Hearing outcomes vary depending on the extent of damage — some patients achieve excellent hearing restoration, while others may need hearing aids for ongoing support.

Recurrence and Long-Term Follow-Up

One of the most important aspects of cholesteatoma management is the risk of recurrence. Cholesteatomas can recur in two ways:

• Residual disease — Small fragments of cholesteatoma left behind during surgery that continue to grow. This is more common with canal wall up procedures.
• Recurrent disease — A new cholesteatoma developing from a new retraction pocket, particularly if the underlying Eustachian tube dysfunction has not resolved.

Overall recurrence rates are approximately 10 to 30%, depending on the surgical approach, the extent of the original disease, and patient factors. This is why long-term follow-up is essential after cholesteatoma surgery — in most UK NHS departments, lifelong monitoring is recommended.

MRI surveillance with diffusion-weighted imaging has transformed post-operative monitoring. Previously, second-look surgery was routinely performed 9 to 12 months after initial surgery to check for residual or recurrent disease. Now, non-echo planar diffusion-weighted MRI can reliably detect cholesteatoma recurrence as small as 2 to 3 millimetres, reducing the need for re-operation in many patients. NICE and the BSA support the use of MRI surveillance as an alternative to routine second-look surgery.

When to Seek Urgent Help

See your GP promptly if you experience any of the following symptoms, as they may indicate a cholesteatoma or a complication requiring urgent attention:

• Persistent or recurrent foul-smelling discharge from one ear that does not respond to antibiotic ear drops
• Progressive hearing loss in one ear
• Dizziness or vertigo alongside ear symptoms
• Weakness or drooping on one side of the face
• Severe headache, high fever, or neck stiffness with ear symptoms
• Swelling, redness, or tenderness behind the ear

Your GP will examine your ears and, if a cholesteatoma is suspected, will refer you urgently to an ENT specialist. In the UK, cholesteatoma is managed within NHS ENT departments, and surgery is available at no cost to the patient. Early referral and treatment significantly reduce the risk of serious complications and give the best chance of preserving or restoring hearing.

If you have concerns about hearing changes or ear symptoms, a professional hearing assessment is a good first step. You can book an appointment with audiologists near you, including Boots Hearingcare, Specsavers Audiology, or Hidden Hearing, or search for your nearest clinic.