A 28-year-old woman presents with progressive bilateral hearing loss over 3 years. She reports that her hearing worsened during her recent pregnancy. Otoscopy is normal, and tuning fork tests show Rinne negative (bone conduction better than air conduction) and Weber lateralizing to the worse ear. Acoustic reflexes are absent. An audiogram is obtained showing a conductive hearing loss pattern with an air-bone gap. The structure marked **A** in the diagram shows a characteristic depression of bone conduction thresholds at 2 kHz. What is the most likely diagnosis?

Explanation

## Why Otosclerosis with stapes fixation is right The clinical presentation — young woman, progressive conductive hearing loss worsening during pregnancy, normal otoscopy, absent acoustic reflexes, and the pathognomonic Carhart notch (depression of bone conduction at 2 kHz marked as **A**) — is diagnostic of otosclerosis. The Carhart notch is a mechanical artifact reflecting loss of middle-ear resonance contribution to bone conduction at the cochlear resonant frequency (2 kHz), not true cochlear pathology. This finding is virtually pathognomonic for otosclerosis and resolves after successful stapedectomy. Otosclerosis is the most common cause of progressive conductive hearing loss in young adults with an intact tympanic membrane, with a 2:1 female predominance and typical onset age 20–40 years. Pregnancy accelerates progression due to estrogen-driven bone remodeling. (Cummings Otolaryngology 7e Ch 145; Glasscock-Shambaugh Surgery of the Ear 7e) ## Why each distractor is wrong - **Chronic suppurative otitis media with ossicular erosion**: CSOM typically presents with otorrhea, perforated tympanic membrane, and conductive loss from ossicular discontinuity or erosion. Otoscopy is abnormal (perforation, drainage). The Carhart notch is NOT a feature of CSOM; it is specific to otosclerosis. Pregnancy does not accelerate CSOM. - **Congenital stapes fixation (congenital stapes ankylosis)**: This is a rare congenital condition presenting in infancy or early childhood with congenital conductive hearing loss. It does not show progressive worsening with age or pregnancy. The Carhart notch is not characteristic of congenital stapes fixation. Onset in a 28-year-old with recent progression is incompatible with this diagnosis. - **Paget disease of bone with otic involvement**: Paget disease is a systemic bone disorder typically affecting older adults (>40 years), presenting with bone pain, deformity, and elevated alkaline phosphatase. While it can cause conductive hearing loss via otic capsule involvement, it does not typically present in a young woman with pregnancy-related worsening. The Carhart notch is not a recognized feature of Paget disease. HRCT would show characteristic "cotton-wool" bone lesions, not the focal otospongiotic lesions of otosclerosis. **High-Yield:** Carhart notch at 2 kHz in bone conduction + young woman + pregnancy-related worsening + absent reflexes + normal TM = otosclerosis until proven otherwise; stapedectomy is curative. [cite:Cummings Otolaryngology 7e Ch 145; Glasscock-Shambaugh Surgery of the Ear 7e]