A 28-year-old man from rural Rajasthan presents with a 6-month history of foul-smelling otorrhoea from the left ear following a head injury. On otoscopy, there is a perforation in the postero-superior quadrant of the tympanic membrane with granulation tissue visible. Pure tone audiometry shows conductive hearing loss. High-resolution CT temporal bone reveals a soft-tissue density in the epitympanic recess with erosion of the ossicles and lateral semicircular canal. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Cholesteatoma ### Key Clinical Features in This Case **Key Point:** The combination of postero-superior perforation, foul-smelling discharge, ossicular erosion, and lateral semicircular canal erosion on imaging is pathognomonic for cholesteatoma. ### Diagnostic Criteria Met | Feature | Finding in Case | Significance | |---------|-----------------|---------------| | **Perforation site** | Postero-superior quadrant | Typical location for cholesteatoma (Shrapnell's membrane) | | **Otorrhoea character** | Foul-smelling | Indicates keratinous debris and secondary infection | | **Imaging findings** | Ossicular erosion + SCC erosion | Bone-eroding property of cholesteatoma | | **Conductive hearing loss** | Present | Due to ossicular disruption | | **Granulation tissue** | Visible on otoscopy | Cholesteatoma matrix with inflammatory response | ### Pathophysiology of Bone Erosion 1. **Pressure necrosis** — expanding keratinous mass compresses bone 2. **Enzymatic erosion** — collagenase and proteases from inflammatory cells 3. **Osteoclastic activation** — bone-resorbing cells recruited by inflammatory mediators 4. **Loss of blood supply** — ischemic necrosis of bone ### High-Yield: Cholesteatoma vs. CSOM without Cholesteatoma | Feature | Cholesteatoma | CSOM (non-cholesteatoma) | |---------|---------------|------------------------| | **Perforation site** | Postero-superior, marginal | Central, safe | | **Bone erosion** | YES (ossicles, SCC, facial canal) | NO | | **Foul odour** | Marked | Mild | | **Granulation tissue** | YES | May be present | | **CT findings** | Soft-tissue density with bone erosion | No bone erosion | **Clinical Pearl:** Postero-superior perforation with bone erosion on imaging is the single most discriminating feature between cholesteatoma and simple CSOM. ### Why Imaging Confirms the Diagnosis **High-Yield:** HRCT temporal bone is the gold standard for diagnosis and preoperative planning. The presence of: - Soft-tissue density in epitympanic recess - Ossicular erosion (malleus, incus, stapes) - Lateral semicircular canal erosion (risk of vertigo/sensorineural hearing loss) - Possible facial canal dehiscence All point definitively to cholesteatoma rather than simple CSOM. ### Management Implications **Warning:** Lateral SCC erosion indicates advanced disease with risk of: - Labyrinthitis ossificans - Sensorineural hearing loss - Vertigo (if labyrinthine fistula develops) - Meningitis (if erosion extends to dura) **Key Point:** Surgical intervention (canal wall-up or canal wall-down mastoidectomy) is indicated to prevent intracranial complications.