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 demonstrates bone conduction better than air conduction bilaterally. Otoscopy is normal. A small bony prominence is noted anterior to the oval window on high-resolution CT temporal bone. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Otosclerosis ### Key Diagnostic Features **Key Point:** Otosclerosis is an autosomal dominant disorder of bone remodeling affecting the otic capsule, classically presenting with progressive conductive or mixed hearing loss in young women. ### Clinical Presentation This patient exhibits the classic triad of otosclerosis: 1. **Progressive bilateral hearing loss** — typically begins in the 20s–40s; accelerated by pregnancy (hormonal influence) 2. **Tinnitus** — present in ~75% of cases 3. **Vertigo** — occurs in ~25% of cases (cochlear involvement) ### Audiological Findings | Finding | Interpretation | | --- | --- | | **Weber lateralizes to affected ear** | Bone conduction better than air conduction on that side (conductive component) | | **Rinne: BC > AC bilaterally** | Conductive hearing loss pattern | | **Carhart notch** | Characteristic bone conduction peak at 2 kHz (pathognomonic but not always present) | **High-Yield:** The **Carhart notch** (bone conduction better than air at 2 kHz) is a classic finding in otosclerosis but is neither sensitive nor specific; its absence does not exclude the diagnosis. ### Imaging Findings **Clinical Pearl:** High-resolution CT temporal bone shows: - **Fenestral otosclerosis** (90%): bony proliferation anterior to the oval window (stapes footplate fixation) - **Cochlear otosclerosis** (10%): bone remodeling around cochlear capsule - Bilateral involvement in ~70% of cases The imaging description in this stem—"small bony prominence anterior to the oval window"—is pathognomonic for fenestral otosclerosis. ### Pathophysiology ```mermaid flowchart TD A[Genetic predisposition<br/>Autosomal dominant]:::outcome --> B[Abnormal bone remodeling<br/>in otic capsule]:::action B --> C[Stapes footplate fixation<br/>Fenestral otosclerosis]:::action C --> D[Reduced stapes mobility]:::action D --> E[Conductive hearing loss]:::outcome B --> F[Cochlear bone remodeling<br/>Cochlear otosclerosis]:::action F --> G[Sensorineural component]:::action G --> H[Mixed hearing loss]:::outcome ``` **Key Point:** The pathology is **stapes footplate fixation** due to abnormal bone remodeling, converting a mobile ossicle into a fixed mass and preventing sound transmission. ### Why Otosclerosis and Not Other Diagnoses - **Normal otoscopy** rules out external canal pathology or visible ossicular disease - **Bilateral involvement** is typical of otosclerosis (not unilateral trauma or ossicular discontinuity) - **Young woman** fits the epidemiology (female:male = 2:1; peak onset 20–40 years) - **Progressive nature** over years is characteristic (not sudden, as in ossicular discontinuity) - **CT finding of bony prominence at oval window** is diagnostic ### Management Overview **Tip:** Hearing aids are first-line for mild–moderate loss; **stapedectomy/stapedotomy** (surgical removal of fixed stapes and replacement with prosthesis) is definitive and highly successful (>90% closure of air-bone gap). **Warning:** Sodium fluoride therapy has been investigated but is not standard of care and has fallen out of favor due to limited efficacy and side effects.