Otosclerosis is a condition characterized by abnormal bone growth within the middle and inner ear. This condition manifests as microscopic bone erosions followed by new bone formation. The resulting new bone structures typically lead to conductive hearing loss. In the normal hearing process, sound vibrations are transmitted from the outer ear to the eardrum. The eardrum then transfers these vibrations to the hammer (malleus), anvil (incus), and stirrup (stapes) bones in the middle ear. Movement of the stirrup bone causes the fluid in the inner ear to move, stimulating the inner ear cells. These cells convert sound vibrations into electrical signals that are sent to the brain. Damage to any part of this complex process can result in hearing loss. In otosclerosis, the abnormal bone foci forming within the ear commonly affect the hammer, anvil, or stirrup bones. It primarily leads to hearing loss by impeding the vibration of the stirrup bone.