Description
Cholesteatoma is a keratinising squamous epithelium-lined cystic lesion, which can exhibit aggressive behaviour similar to neoplastic growth. Though benign, these lesions can cause significant local destruction. The development can occur within the middle ear, the petrous apex or the external auditory canal. This entity can be categorised into congenital and acquired cholesteatomas.
Pathogenesis
- The exact cause of cholesteatoma is not completely understood, but it’s generally thought to occur due to a dysfunction in the Eustachian tube leading to negative pressure and retraction of the tympanic membrane (most common).
- Another theory proposes migration of epithelial tissue through a perforation in the tympanic membrane.
- Most commonly, cholesteatomas are associated with poor Eustachian tube function as well as chronic ear infection.
- Congenital cholesteatomas are thought to arise from embryonic remnants of epithelial tissue.
Subtypes
- Acquired cholesteatoma (98%): Chronic middle ear infection is common. Arises in the attic/Prussak space
- Primary acquired cholesteatoma: Usually in region of the pars flaccida
- Secondary acquired cholesteatoma: Usually develop through a defect of the lower two-thirds of the tympanic membrane (pars tensa).
- Congenital (2%): Effectively an epidermoid cyst. Arises from epithelial nests in middle ear, mastoid or petrous bone.
Epidemiology, Risk Factors & Associations
- Cholesteatoma is relatively rare, with a reported incidence of 9.2 cases per 100,000 population.
- Cholesteatoma is most commonly seen in adults, but can occur at any age (30-40 years is most common, 60%).
- Risk factors include chronic otitis media, childhood ear infections, Eustachian tube dysfunction, tympanic membrane retraction or perforation, and previous ear surgery.
- There’s an association with certain conditions such as Turner syndrome and cleft palate.
Clinical Features
- Progressive hearing loss (most common symptom, 95%)
- Tinnitus, ear-fullness
- Otalgia
- Otorrhoea
- Dizziness or vertigo may occur if the inner ear or balance nerves are affected.
- Facial nerve palsy may occur in severe cases due to erosion of the facial canal.
Complications
If left untreated, cholesteatomas can lead to complications:
- The destructive nature of the cholesteatoma can lead to ossicular destruction and consequently conductive hearing loss.
- Other complications can include labyrinthine fistula (dehiscence of semicircular canal – usually lateral), labyrinthitis, mastoiditis and automastoidectomy, petrous apicitis, meningitis, cerebral abscess, and facial nerve palsy (involvement of facial canal).
Pathological Features
Histopathology
- A cholesteatoma cyst is lined by stratified squamous epithelium and filled with layers of keratin debris.
- The matrix can erode and destroy the adjacent bone due to the production of bone resorptive cytokines.
Radiological Features
General Features
- The lesion often presents as a soft tissue mass within the middle ear, mastoid air cells, or petrous apex.
- Most commonly occurs in the middle ear but may be seen in the petrous apex, geniculate fossa, cerebellopontine angle, or external canal.
- Most common location of congenital cholesteatoma is the anterosuperior portion of the middle ear, near the eustachian tube or stapes.
- Can cause bony erosion, including that of ossicles and temporal bone (tegmen tympani, petrous apex or sigmoid plate)
- Acquired cholesteatomas;
- Tend to erode the head of malleus and long process of incus
- Displace the ossicles medially
- Congenital cholesteatomas;
- Tend to erode short process of incus and stapes.
- Displace the ossicles laterally
CT
- Shows soft tissue mass and extent of bony erosion.
- Erosion of the ossicles, scutum, tegmen tympani, facial canal or mastoid bone, is a key feature suggestive of cholesteatoma.
- May see soft tissue density in the middle ear or mastoid region.
- Underpneumatisation and sclerosis of mastoid air cells may represents chronic infection
- Normal mastoid pneumatisation in a young patient without history of chronic ear infection suggests congenital cholesteatoma
MRI
- Cholesteatomas typically appear as soft-tissue masses in the middle ear, mastoid, or petrous apex.
- T2: High signal intensity.
- DWI: Restricted diffusion – differentiates cholesteatoma (restricted diffusion) from chronic middle infection with inflammatory and granulation tissue (no restricted diffusion).
- T1 Gd+: No enhancement.
Grading and Staging
Sade Staging System for Middle Ear Cholesteatoma
This is a relatively straightforward staging system that focuses on the presence or absence of cholesteatoma, the level of destruction in the middle ear, and the status of the ossicular chain.
- Stage I: Limited to the middle ear without ossicular destruction.
- Stage II: Limited to the middle ear with ossicular destruction.
- Stage III: Extends into the mastoid without affecting the external ear.
- Stage IV: Invades the external ear or has caused complications such as facial nerve palsy, labyrinthitis, intracranial abscess, or meningitis.
Differential Diagnosis
- Otitis media with effusion: Commonly presents with ear pain, hearing loss and sometimes fever. CT may show opacification of the middle ear, but no bony erosion.
- Malignant, necrotising external otitis: Severe life-threatening Pseudomonas aeruginosa infection of older adults with diabetes.
- Otosclerosis: Presents with progressive conductive hearing loss. CT shows sclerosis around the ossicles, particularly the stapes.
- Glomus tumour: Presents with pulsatile tinnitus, hearing loss. On imaging, shows a well-defined enhancing mass in the region of the jugular bulb or middle ear.
Management
Management typically involves surgical removal of the cholesteatoma. Surveillance with imaging and clinical examinations are crucial due to the risk of recurrence. Audiological support and rehabilitation are also important aspects of management.