A 28-year-old woman presents with progressive bilateral hearing loss over the past 2 years. She reports tinnitus and occasional vertigo. Her mother had similar hearing problems starting in her 20s. Otoscopic examination is normal. Audiometry shows bone conduction thresholds better than air conduction thresholds (air-bone gap of 30 dB). Weber test shows lateralization to the right ear. What is the most likely diagnosis?

## Clinical Diagnosis: Otosclerosis ### Key Diagnostic Features **Key Point:** Otosclerosis is a primary osseous dysplasia of the otic capsule causing progressive conductive or mixed hearing loss, typically in young adults (20–40 years). ### Pathophysiology Otosclerosis involves abnormal bone remodeling at the oval window (stapes footplate), leading to: 1. Stapes fixation → conductive hearing loss 2. Cochlear involvement (cochlear otosclerosis) → sensorineural component 3. Progressive ossification of the stapes footplate ### Clinical Presentation in This Case | Feature | Finding | Significance | |---------|---------|---------------| | **Age & Sex** | 28-year-old woman | Peak incidence 20–40 years; 2:1 female predominance | | **Bilateral hearing loss** | Progressive over 2 years | Bilateral in ~70% of cases | | **Family history** | Mother affected | Autosomal dominant inheritance (60% of cases) | | **Otoscopy** | Normal | Hallmark feature—tympanum and ossicles appear normal | | **Air-bone gap** | 30 dB | Conductive component from stapes fixation | | **Weber lateralization** | Right ear | Indicates conductive loss on right (bone conduction better) | | **Tinnitus & vertigo** | Present | Cochlear involvement (cochlear otosclerosis) | ### Audiometric Pattern (Carhart Sign) **High-Yield:** The classic **Carhart notch** is a bone conduction dip at 2 kHz, pathognomonic for otosclerosis. It reflects cochlear involvement and is seen in ~50% of cases. ### Confirmatory Investigations - **High-resolution CT temporal bones:** Shows demineralization around the oval window ("fisheye" lesion), stapes fixation, cochlear involvement - **Tympanometry:** Type A (normal middle ear pressure and compliance) — rules out middle ear effusion - **Stapedial reflex:** Absent or reduced (stapes fixation) ### Management Overview ```mermaid flowchart TD A[Otosclerosis diagnosed]:::outcome --> B{Hearing loss severity?}:::decision B -->|Mild-moderate, conductive| C[Hearing aids]:::action B -->|Moderate-severe| D[Surgical candidacy?]:::decision D -->|Yes| E[Stapedectomy/Stapedotomy]:::action D -->|No/Refused| F[Hearing aids + Sodium fluoride trial]:::action E --> G[Ossiculoplasty if needed]:::action G --> H[Hearing restoration]:::outcome ``` **Clinical Pearl:** Stapedectomy (removal of fixed stapes and replacement with prosthesis) is the gold standard surgical treatment, with >90% success rate for air-bone gap closure. **Key Point:** Sodium fluoride may slow progression in early cochlear otosclerosis but is not curative. [cite:Dhingra's Otolaryngology 9e Ch 8]