A 28-year-old woman presents with progressive bilateral hearing loss over the past 2 years. She reports tinnitus and occasional vertigo. On otoscopy, the tympanic membranes appear normal. Audiometry shows a conductive hearing loss with a characteristic dip at 2 kHz (Carhart bone conduction notch). Tympanometry is normal. CT temporal bone shows bilateral stapes fixation with no ossicular erosion. What is the most likely diagnosis?

## Diagnosis: Otosclerosis ### Clinical Presentation **Key Point:** Otosclerosis is a primary disorder of bone metabolism affecting the otic capsule, characterized by abnormal bone remodeling and stapes fixation. This patient presents with the classic triad: - Progressive **conductive hearing loss** (bilateral in this case) - **Tinnitus** and vertigo - **Normal tympanic membrane** on otoscopy ### Diagnostic Features | Feature | Finding | Significance | |---------|---------|---------------| | **Audiometry** | Carhart notch (2 kHz dip) | Pathognomonic for otosclerosis | | **Bone conduction** | Initially normal, then affected | Indicates stapes fixation | | **Tympanometry** | Type A (normal) | Rules out middle ear effusion | | **CT findings** | Bilateral stapes fixation | Confirms otic capsule involvement | | **Ossicular chain** | Intact | Excludes ossicular erosion/discontinuity | ### Pathophysiology **High-Yield:** Otosclerosis involves abnormal bone remodeling at the oval window, leading to: 1. Stapes footplate fixation → conductive hearing loss 2. Cochlear involvement (spongiotic bone) → sensorineural component (mixed hearing loss) 3. Cochlear blood flow compromise → tinnitus and vertigo ### Epidemiology & Risk Factors **Clinical Pearl:** - **Female predominance** (2:1 ratio; this patient is female) - **Age of onset:** 20–40 years (this patient is 28) - **Bilateral in 70–80% of cases** (present in this case) - **Genetic:** Autosomal dominant with incomplete penetrance - **Hormonal:** Pregnancy accelerates progression **Mnemonic — Risk Factors for Otosclerosis: FOHNS** - **F**emale - **O**tosclerosis (family history) - **H**ormonal (pregnancy, estrogen) - **N**oise exposure (controversial) - **S**tress ### Management Algorithm ```mermaid flowchart TD A[Otosclerosis diagnosed]:::outcome --> B{Hearing loss severity?}:::decision B -->|Mild/Moderate, no functional impact| C[Observation + hearing aid]:::action B -->|Moderate-Severe, functional impact| D[Surgical candidacy?]:::decision D -->|Yes| E[Stapedectomy/Stapedotomy]:::action D -->|No| F[Hearing aid + Sodium fluoride trial]:::action E --> G[Ossicular replacement prosthesis]:::action G --> H[Hearing restoration]:::outcome C --> I[Monitor audiometry annually]:::action ``` ### Treatment Options **Medical:** - Sodium fluoride (controversial; may slow progression in early disease) - Hearing aids (first-line for mild-moderate loss) **Surgical:** - **Stapedectomy** (gold standard): Removal of fixed stapes footplate + insertion of prosthesis - **Stapedotomy** (preferred): Small fenestra in footplate + piston prosthesis (lower risk of perilymphatic fistula) - Success rate: 90% restoration of air-bone gap - Risks: Sensorineural hearing loss (1–2%), facial nerve injury, perilymphatic fistula **Key Point:** This patient with bilateral stapes fixation and progressive hearing loss is an ideal candidate for stapedotomy if she has functional hearing loss and desires improvement.