A 35-year-old woman presents with progressive bilateral hearing loss over 5 years, worse in the left ear. Otoscopy is normal except for a faint pink hue behind the left tympanum. Audiometry shows air-conduction thresholds at 50 dB and bone-conduction thresholds at 0–10 dB bilaterally, with the gap marked **C** in the diagram measuring >30 dB on the left. Tuning fork testing shows the Weber test lateralizing to the left ear. Which of the following is the most likely diagnosis?

Explanation

## Why Otosclerosis with stapes footplate fixation is right The clinical presentation is pathognomonic for otosclerosis: progressive bilateral asymmetric conductive hearing loss in a young to middle-aged woman, normal otoscopy with Schwartze sign (pink hue indicating active vascular disease), and a large air-bone gap **C** (>30 dB) with normal bone conduction thresholds. The Weber lateralizing to the affected (left) ear confirms conductive loss—bone conduction is "louder" in the blocked ear, masking ambient noise. Otosclerosis causes abnormal bone remodeling at the fissula ante fenestram, leading to stapes footplate fixation and conductive hearing loss. The audiometric pattern with air-conduction elevated and bone-conduction normal is the hallmark of conductive pathology, and the air-bone gap **C** is the diagnostic hallmark that confirms the conductive component (Dhingra ENT 7e, Ch 14–16). ## Why each distractor is wrong - **Chronic otitis media with central perforation**: Would show a central TM perforation on otoscopy; this patient has normal otoscopy. Central perforation causes conductive loss but is not progressive and does not present with Schwartze sign. The clinical picture does not fit. - **Sensorineural hearing loss from noise exposure**: Would show bone-conduction thresholds elevated (cochlear damage), not normal at 0–10 dB. The air-bone gap **C** would be absent or minimal. Weber would lateralize away from the affected ear, not toward it. - **Eustachian tube dysfunction with middle ear effusion**: Typically presents acutely or subacutely post-URTI, especially in children. The progressive 5-year course, Schwartze sign, and normal otoscopy (effusion would show fluid level or air-fluid interface) make this unlikely. OME does not cause Schwartze sign. **High-Yield:** Air-bone gap **C** >30 dB with normal bone conduction = conductive loss; otosclerosis is the classic progressive cause in young women; Schwartze sign + Weber lateralization to affected ear confirms diagnosis. [cite: Dhingra ENT 7e, Ch 14–16; Otosclerosis section]