Cholesteatoma (Squamous Epithelial Disease)
High-Yield Revision Notes for NEET PG / NEXT
A cholesteatoma is a misnomer—it contains neither cholesterol nor lipids, and it is not a neoplastic tumor. It is histologically defined as a sac of keratinizing stratified squamous epithelium located pathologically within the middle ear cleft or mastoid cavity that expands progressively and destroys surrounding bone.
Clinical Correlations: White keratin debris seen superiorly in the attic on otoscopy matches bone erosion visible on coronal cuts of an HRCT scan.
Pathogenesis & Classification
Bone destruction is primarily mediated by local osteoclastic activity driven by inflammatory cytokines (e.g., TNF-alpha, IL-1, IL-6) and acid proteases, rather than raw mechanical pressure alone.
1. Congenital Cholesteatoma
- Criteria (Levenson’s): White, pearly mass medial to an intact tympanic membrane in a patient with no history of ear discharge, TM perforation, or prior otic surgery.
- Embryologic Origin: Trapped embryonic epithelial rests within the middle ear space during development (specifically the epitympanic medial ring). Most commonly found in the anterosuperior quadrant of the tympanic cavity.
2. Acquired Cholesteatoma
- Primary Acquired: Develops secondary to chronic invagination of a localized retraction pocket in the Pars Flaccida (Shrapnell’s Membrane). Driven by long-standing Eustachian tube dysfunction (Wittmaack’s Theory).
- Secondary Acquired: Squamous epithelial migration through a pre-existing marginal or attic perforation of the Pars Tensa following acute or chronic suppurative otitis media (Habermann’s Theory).
Clinical Manifestations
- Otorrhea: Scant, continuous, or intermittent ear discharge characterized by a **profoundly foul, putrid odor**. The fetid odor is caused by bone necrosis and secondary infection with anaerobic organisms.
- Hearing Loss: Conductive hearing loss (CHL) due to ossicular erosion. SURGICAL TRAP: If the expanding mass bridges a gap left by an eroded incus, the patient’s audiometric air-bone gap may remain deceptively normal (the “cholesteatoma-hearer”).
Diagnostic Workup
- Otoscopy: Visualizes a retraction pocket, a marginal/attic perforation, or a pearly-white mass. Granulation tissue or an isolated “attic polyp” presenting in the external auditory canal is highly suspicious for hidden squamous pathology.
- High-Resolution CT (HRCT) of the Temporal Bone: The imaging modality of choice. Key radiological findings include a soft-tissue mass in the attic/Prussak’s space, accompanied by blunting of the scutum and erosion of the ossicular chain (most commonly involving the long process of the incus).
- Diffusion-Weighted MRI (Non-EPI DWI): Highly specific for distinguishing recurrent or residual postoperative cholesteatoma (which demonstrates hyperintense signal diffusion restriction) from simple inflammatory granulation tissue or fluid collections.
Complications (High-Yield Board Targets)
Due to enzymatic bone absorption, cholesteatomas breach anatomic boundaries systematically:
| Complication Type | Anatomic Target & Presentation |
|---|---|
| Labyrinthine Fistula | Erosion of the lateral (horizontal) semicircular canal bone. Presents with vertigo triggered by pressure changes—positive Fistula Test (tragal compression induces vertigo and nystagmus). |
| Facial Nerve Palsy | Erosion of the bony fallopian canal covering the facial nerve, most commonly at its tympanic (horizontal) segment just superior to the oval window. |
| Intracranial Spread | Erosion through the tegmen tympani or tegmen mastoideum leading to extradural abscess, subdural empyema, sigmoid sinus thrombophlebitis, or meningitis. Temporal lobe or cerebellar abscesses are common. |
Management Protocol
The primary goal of intervention is to create a “safe ear” by completely eradicating the disease tissue; restoring or preserving hearing remains secondary. Medical therapy is strictly limited to managing active secondary infections.
- Canal Wall Down (CWD) Mastoidectomy: The posterior bony canal wall is surgically removed, turning the external auditory canal and the mastoid cavity into one single, widely exteriorized common space. Classic example: **Radical or Modified Radical Mastoidectomy**.
Consequence: The patient requires periodic, lifelong master cavity cleanings in the outpatient clinic.
- Canal Wall Up (CWU) Mastoidectomy: Disease is cleared via combined transcanal and transmastoid approaches while **preserving the posterior bony ear canal wall**. Lower rate of post-surgical cavity problems but carries a significantly **higher risk of hidden, recurrent, or residual cholesteatoma**.