Otoscopy of a 20-year-old man reveals a dark blue, bulging tympanic membrane. Myringotomy aspirates thick brownish fluid described as 'chocolate' coloured, containing shining crystals on microscopy. The underlying lesion is:

• A Cholesteatoma
• B Cholesterol granuloma ✓
• C Glomus tympanicum tumour
• D Haemotympanum

Explanation

Cholesterol granuloma results from impaired middle ear ventilation causing mucosal congestion, haemorrhage, and breakdown of blood with deposition of cholesterol crystals. Foreign body giant cells surround the crystals, producing the characteristic 'blue drum' with chocolate-brown middle ear fluid. Glomus tumour shows a reddish blush through the drum with pulsation, haemotympanum follows trauma and is red, and cholesteatoma presents as a pearly white keratin mass rather than dark fluid.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.