On pure tone audiogram, a patient shows air-bone gap of 40 dB at all frequencies with normal bone conduction thresholds. Tympanometry shows a flat (type B) curve with normal ear canal volume. What is the most likely diagnosis?

• A Otosclerosis
• B Ossicular discontinuity
• C External canal obstruction (wax)
• D Otitis media with effusion (secretory otitis media / glue ear) ✓

Explanation

Type B tympanogram (flat, no peak) with normal ear canal volume indicates middle ear effusion — the fluid prevents normal tympanic membrane movement. The air-bone gap up to 40 dB with normal bone conduction confirms conductive hearing loss. If ear canal volume were increased with a type B curve, perforation of TM would be the diagnosis. Ossicular discontinuity gives maximum air-bone gap (~60 dB) with a high compliance (type Ad) tympanogram. Otosclerosis shows type As (reduced compliance/stiff) tympanogram due to footplate fixation.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.