A 32-year-old man from rural India presents with a 6-month history of foul-smelling otorrhoea from the left ear and progressive conductive hearing loss. On examination, there is a perforation in the posterosuperior quadrant of the tympanic membrane with granulation tissue visible. High-resolution CT temporal bone shows erosion of the ossicular chain and scalloping of the lateral semicircular canal. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis of Cholesteatoma ### Key Clinical Features Present **Key Point:** The combination of posterosuperior perforation, foul-smelling discharge, ossicular erosion, and lateral semicircular canal scalloping on imaging is pathognomonic for cholesteatoma. ### Diagnostic Criteria | Feature | Cholesteatoma | CSOM | Acute Mastoiditis | |---------|---------------|------|-------------------| | Perforation site | Posterosuperior (marginal) | Central | May be absent | | Discharge character | Foul-smelling, scanty | Mucopurulent, profuse | Purulent, fever | | Ossicular erosion | Common (malleus, incus) | Possible but less specific | Rare | | Bone erosion pattern | Scalloped, smooth margins | Irregular | Acute lysis | | Lateral SCC involvement | Characteristic | Rare | Rare | | Granulation tissue | Present | Absent | Absent | ### Pathophysiology 1. **Retraction pocket formation** → negative middle ear pressure → invagination of posterosuperior tympanic membrane 2. **Epithelial ingrowth** → keratinous debris accumulation → chronic inflammation 3. **Osteoclastic activity** → bone erosion (ossicles, canal walls, tegmen) 4. **Foul odor** → anaerobic bacterial colonization of desquamated keratin **High-Yield:** Posterosuperior marginal perforation + foul discharge = cholesteatoma until proven otherwise. ### Imaging Findings in This Case - **Ossicular chain erosion** (especially malleus and incus) — due to pressure necrosis and osteoclastic resorption - **Lateral semicircular canal scalloping** — indicates bone erosion from chronic pressure; risk of labyrinthitis - **Granulation tissue** on otoscopy — represents chronic inflammatory response **Clinical Pearl:** Lateral SCC erosion is a red flag for potential vertigo and sensorineural hearing loss if surgery is delayed. ### Why This Is Cholesteatoma and Not CSOM - **CSOM** presents with central perforations, profuse mucopurulent discharge, and does NOT typically erode the lateral SCC or produce foul odor - **Cholesteatoma** is an aggressive lesion with bone-eroding potential; CSOM is primarily mucosal inflammation **Mnemonic: FOES** — **F**oul discharge, **O**ssicular erosion, **E**rosion of canal walls, **S**uperior perforation = Cholesteatoma. ### Management Implications **Key Point:** Imaging confirmation (HRCT ± MRI) is mandatory before surgery. Canal wall-down (CWD) or canal wall-up (CWU) mastoidectomy is the definitive treatment. **Warning:** Untreated cholesteatoma can lead to: - Facial nerve paralysis - Labyrinthitis and vertigo - Intracranial complications (meningitis, brain abscess, lateral sinus thrombosis) - Sensorineural hearing loss