Which of the following bones is primarily affected in otosclerosis?

Explanation

## Pathology of Otosclerosis **Key Point:** Otosclerosis is characterized by abnormal bone remodeling in the otic capsule, with the **stapes footplate** being the most commonly affected ossicle. ### Anatomical Site of Involvement The stapes footplate, particularly at the **oval window**, is the primary site of otosclerotic bone formation. This occurs in approximately 90% of otosclerosis cases. ### Why the Stapes is Affected The stapes footplate is part of the otic capsule, which is composed of specialized bone derived from the otic capsule mesenchyme. This bone is uniquely susceptible to the abnormal remodeling process that characterizes otosclerosis. ### Clinical Consequence Fixation of the stapes footplate at the oval window leads to: - Loss of stapes mobility - Conductive hearing loss (early stages) - Mixed or sensorineural hearing loss (advanced stages with cochlear involvement) **High-Yield:** The **stapes fixation** is the hallmark finding in otosclerosis, distinguishing it from other causes of conductive hearing loss. This is why stapedectomy or stapedotomy is the definitive surgical treatment. ### Other Ossicles The malleus and incus are NOT primarily affected in otosclerosis. The temporal bone as a whole is not the primary site—only the otic capsule region is involved. [cite:Dhingra 8e Ch 8]