Pure tone audiometry shows an air-bone gap of 35 dB at 250 Hz, 2000 Hz, and 4000 Hz bilaterally. Tympanometry shows a type As curve (reduced compliance, normal peak pressure). Stapedial reflexes are absent. What is the most likely diagnosis?

• A Ossicular discontinuity
• B Secretory otitis media
• C Eustachian tube dysfunction
• D Otosclerosis (stapedial fixation) ✓

Explanation

Otosclerosis produces a conductive hearing loss (typically maximal at low frequencies, with a characteristic Carhart's notch at 2000 Hz), a type As tympanogram (shallow, with reduced peak compliance due to stiffening of the stapedofootplate complex), and absent stapedial reflexes (stapes cannot vibrate). The air-bone gap is largest at low frequencies. Ossicular discontinuity would give a type Ad tympanogram (increased compliance, very high peak). Secretory otitis gives a flat type B tympanogram with absent reflexes. This pattern with type As and absent reflexes is classic for otosclerosis.

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

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Written and medically reviewed by the StethoPrep medical team.