A 28-year-old woman presents with progressive bilateral hearing loss over 2 years. She reports tinnitus and occasional vertigo. Otoscopy is normal. Weber test shows bone conduction better than air conduction bilaterally. Audiometry reveals low-frequency conductive hearing loss with a characteristic Carhart notch at 2 kHz. She has no family history of deafness. What is the most likely diagnosis?

Explanation

## Diagnosis: Otosclerosis ### Clinical Presentation **Key Point:** Otosclerosis is a primary disease of the otic capsule characterized by abnormal bone remodeling, leading to fixation of the stapes footplate and conductive hearing loss. ### Diagnostic Features in This Case | Feature | Finding | Significance | |---------|---------|---------------| | Age at onset | 28 years (young adult) | Typical age of presentation (20–40 years) | | Sex | Female | 2:1 female predominance | | Hearing loss | Bilateral, progressive | Characteristic bilateral involvement | | Otoscopy | Normal | Excludes external/middle ear disease | | Weber test | Bone > air conduction | Conductive hearing loss pattern | | Carhart notch | 2 kHz dip | Pathognomonic finding in otosclerosis | | Tinnitus | Present | Common associated symptom | | Vertigo | Occasional | Occurs when cochlear involvement develops | ### Pathophysiology 1. Abnormal bone remodeling in the otic capsule (enchondral layer) 2. Stapes footplate fixation, typically at oval window 3. Loss of ossicular chain mobility → conductive hearing loss 4. Later: cochlear involvement → sensorineural component ### High-Yield Points **High-Yield:** The **Carhart notch** (bone conduction dip at 2 kHz with normal air conduction at other frequencies) is pathognomonic for otosclerosis and distinguishes it from other causes of conductive hearing loss. **Mnemonic: OTOSCLEROSIS** — **O**val window **T**hickening, **O**ssicular **S**tapes **C**onduction **L**oss, **E**arly **R**emodeling, **O**tic capsule **S**tiffness, **I**mpaired **S**ound transmission. **Clinical Pearl:** Otosclerosis may be accelerated by pregnancy due to hormonal influences on bone metabolism; some women report worsening hearing loss during pregnancy. ### Management Approach ```mermaid flowchart TD A[Suspected otosclerosis]:::outcome --> B{Confirm diagnosis}:::decision B -->|Audiometry + Carhart notch| C[Otosclerosis confirmed]:::outcome C --> D{Patient preference & hearing impact}:::decision D -->|Hearing aid trial| E[Amplification]:::action D -->|Surgical candidacy| F[Stapedectomy/Stapedotomy]:::action E --> G[Monitor progression]:::action F --> H[Ossicular chain reconstruction]:::action H --> I[Restore air-bone gap]:::outcome ``` **Key Point:** Diagnosis is clinical (history + audiometry) and confirmed by imaging (high-resolution CT shows demineralization around oval window, "double density" sign). Stapedectomy is the definitive surgical treatment with >90% success rate.