What is otosclerosis? The pathology of this disease is due to the resorption of normal bone in the bony labyrinth of the inner ear near the oval window and its replacement by a new spongy bone rich in blood vessels. This spongy new bone foci gradually ossify and harden, hence the customary term “otosclerosis”. This pathological bone foci gradually spreads to the floor of the stapes, fixing it to the oval window. Sound is transmitted from the tympanic membrane and auditory bone to this area, and cannot be transmitted to the inner ear. If this pathological bone foci spreads inward to the inner ear, causing cochlear damage or degeneration of the vestibulocochlear nerve, it is called “cochlear otosclerosis”. The age of onset is more common in young and middle-aged people. The cause of otosclerosis has not yet been clarified. The disease mostly occurs in young people, and the lesions develop gradually, so hearing loss also occurs slowly. Most of the time, the disease begins in the early 20s. It starts on one side and gradually evolves into bilateral. As the duration of the disease increases, the hearing loss also gets progressively worse. However, the rate of progression of deafness varies greatly from patient to patient and even from one patient to another. As soon as the stapes are completely fixed, the deafness gradually stabilizes. If the lesion continues to progress to the inner ear, the deafness caused by the degenerative lesion of the cochlear nerve will continue to worsen and will not be terminated by the fixation of the stapes. In otosclerosis, if the lesion is limited to the stapes floor, sound conduction is blocked and it manifests as conductive deafness. If the lesion invades the cochlea, round window, or vestibular cochlear nerve endings, it adds a component of sensorineural inspiratory impairment and becomes mixed deafness. Approximately 80% of patients are often accompanied by significant tinnitus. Tinnitus may occur before or simultaneously with deafness. In advanced stages, the lesion invades the inner ear and both air-conduction and bone-conduction hearing will decline dramatically. Treatment principles for otosclerosis: (1) The cause of the disease is unknown, and the treatment aims only at restoring hearing and cannot be curative. (2) Surgical treatment is the most effective measure to improve hearing, and stapedectomy is commonly used. (3) Those who cannot be operated can be equipped with hearing aids.