Which of the following is the most common type of hearing loss pattern seen in otosclerosis?

Explanation

## Hearing Loss Patterns in Otosclerosis ### Natural History of Hearing Loss **Key Point:** Otosclerosis typically presents with **conductive hearing loss** due to stapes fixation, but may progress to **mixed hearing loss** as cochlear involvement develops. ### Progression Timeline | Stage | Mechanism | Hearing Loss Type | Audiometric Finding | |-------|-----------|-------------------|---------------------| | Early | Stapes footplate fixation | Conductive | Air-bone gap present | | Intermediate | Continued stapes fixation + early cochlear involvement | Mixed | Air-bone gap + bone conduction loss | | Advanced | Cochlear otosclerosis (cochlear involvement) | Mixed or SNHL | Bone conduction threshold drops | ### Carhart Sign **High-Yield:** The **Carhart sign** (a bone conduction notch at 2 kHz) is a characteristic audiometric finding in early otosclerosis and indicates stapes fixation with intact cochlear function. ### Cochlear Otosclerosis As the disease progresses, otosclerotic bone can extend into the cochlea, causing: - Sensorineural hearing loss superimposed on conductive loss - **Mixed hearing loss** pattern - Bone conduction thresholds worsen - Carhart sign may disappear in advanced disease **Clinical Pearl:** Not all patients with otosclerosis develop cochlear involvement. Some remain with pure conductive loss, while others progress to mixed loss. The presence of bone conduction loss suggests cochlear involvement. **Mnemonic:** **CONDUCTIVE → MIXED** — Otosclerosis typically starts with conductive loss (stapes fixation) and may progress to mixed loss (cochlear involvement).