A pure tone audiogram shows a 40 dB air-bone gap with normal bone conduction thresholds. Tympanometry shows a flat (type B) pattern with abnormally LARGE canal volume. Ipsilateral and contralateral acoustic reflexes are absent. What is the most likely diagnosis?

• A Tympanic membrane perforation with intact ossicular chain ✓
• B Otosclerosis with stapes fixation
• C Secretory otitis media (glue ear)
• D Adhesive otitis media with type As tympanogram

Explanation

A flat type B tympanogram with LARGE static compliance volume indicates the probe microphone is measuring a large, open space — as occurs when the tympanic membrane is perforated, allowing the ear canal probe to communicate with the entire middle ear and mastoid air cell system. Normal type B (with normal or reduced volume) occurs in middle ear effusion. Acoustic reflexes are absent because the perforation prevents the required pressure seal for stapedial reflex testing. Otosclerosis produces type As (reduced compliance but intact TM), not type B with large volume.

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

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Written and medically reviewed by the StethoPrep medical team.