In otosclerosis, the primary pathological process involves abnormal bone remodeling at which anatomical site?
A. Oval window (stapes footplate)
B. Round window niche
C. Malleal neck
D. Incudostapedial joint
Explanation
Pathological Site in Otosclerosis
Key Point
Otosclerosis is characterized by abnormal bone remodeling (osteoclasia followed by osteosclerosis) that occurs specifically at the oval window, most commonly at the anterior oval window margin.
Mechanism of Stapes Fixation
The disease process involves:
1.
Osteoclastic resorption of normal otic capsule bone
2.
Replacement with abnormal, hypervascular bone (otosclerotic focus)
3.
Gradual fixation of the stapes footplate within the oval window niche
4.
Loss of stapes mobility → conductive hearing loss
Why the Oval Window?
The oval window is the only mobile ossicle articulation in the middle ear. The stapes footplate normally vibrates freely within the oval window membrane. When otosclerotic bone encroaches on this space, the footplate becomes progressively fixed, preventing sound transmission to the inner ear.
Clinical Pearl
The anterior oval window margin is the most common site (>90% of cases), followed by the posterior margin. Rarely, otosclerosis can extend to involve the round window or cochlear capsule (cochlear otosclerosis).
High-YieldNEET PG
Stapes fixation at the oval window causes a progressive conductive hearing loss with a characteristic Carhart bone (bone conduction better than air conduction at 2 kHz).
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