A 28-year-old woman presents with progressive bilateral hearing loss over the past 2 years. She reports tinnitus and occasional vertigo. On examination, Weber test shows lateralization to the right ear, and Rinne test shows bone conduction better than air conduction bilaterally. Otoscopy reveals a normal tympanic membrane. Pure tone audiometry shows a low-frequency conductive hearing loss with a characteristic 2 kHz bone conduction dip. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Otosclerosis ### Key Clinical Features **Key Point:** Otosclerosis is a primary bone disease of the middle ear characterized by abnormal bone remodeling at the oval window, leading to stapes fixation and conductive hearing loss. ### Diagnostic Criteria Met in This Case | Feature | Finding | Significance | |---------|---------|---------------| | **Age & Sex** | 28-year-old woman | Typical onset 20–40 years; female predominance (2:1) | | **Hearing Loss Pattern** | Bilateral, progressive, low-frequency | Characteristic of otosclerosis; often starts unilaterally | | **Weber Test** | Lateralization to right | Indicates conductive loss on right (better bone conduction) | | **Rinne Test** | Bone > Air bilaterally | Confirms conductive hearing loss | | **Carhart Notch** | 2 kHz dip on bone conduction | Pathognomonic finding in otosclerosis | | **Otoscopy** | Normal tympanic membrane | Rules out middle ear pathology | | **Tinnitus & Vertigo** | Present | Common associated symptoms | ### Pathophysiology 1. **Abnormal bone remodeling** at the oval window (stapes footplate) 2. **Stapes fixation** → loss of ossicular chain mobility 3. **Conductive hearing loss** → air-bone gap 4. Progressive involvement may lead to **mixed or sensorineural component** (cochlear otosclerosis) **High-Yield:** The **Carhart notch** (bone conduction dip at 2 kHz) is virtually pathognomonic for otosclerosis and distinguishes it from other causes of conductive hearing loss. ### Imaging Findings - **High-resolution CT temporal bone:** Lucency around stapes footplate ("halo sign"), demineralization of otic capsule - **Diagnosis is primarily clinical + audiometric** (CT confirms but not required for diagnosis) ### Management Overview ```mermaid flowchart TD A[Otosclerosis Diagnosed]:::outcome --> B{Hearing Loss Severity?}:::decision B -->|Mild-Moderate| C[Hearing Aids]:::action B -->|Moderate-Severe| D{Patient Desires Surgery?}:::decision D -->|Yes| E[Stapes Surgery/Stapedectomy]:::action D -->|No| F[Hearing Aids]:::action C --> G[Sodium Fluoride Trial] F --> G E --> H[Success Rate 90%]:::outcome G --> I[May slow progression]:::outcome ``` **Clinical Pearl:** Sodium fluoride may slow progression of otosclerosis by stabilizing bone metabolism, though evidence is mixed. Stapedectomy (replacement of stapes with prosthesis) has >90% success rate for hearing restoration. **Warning:** Do not confuse otosclerosis with ossicular discontinuity or sensorineural loss — the normal tympanic membrane, bilateral presentation, and Carhart notch are key discriminators.