Understanding Otosclerosis

Hearing is a crucial sense for day to day life, and healthy hearing is dependent on the way sounds are conducted through the ear to the brain. A large part of the conduction depends on the ability of the middle ear and its structures to transmit the sounds from the outer ear to the inner ear through vibrations of the tympanic membrane and the ossicles. The ossicles (malleus, incus, and stapes) are three tiny bones in the middle ear that act like a chain connecting the outer and the inner ear. In a condition known as “otosclerosis”, bony tissue, or a sponge like growth develops around the foot of the stapes, rendering it immobile. The hinderance to proper vibration of the ossicular chain causes a hearing loss.

Otosclerosis is a common condition and is hormone dependent. It is most common in middle aged women, pregnancy aggravating the growth of the spongy bone. Research has shown that otosclerosis has a genetic predisposition and a family history of hearing loss is common. The most common symptoms include hearing loss and tinnitus. Occasionally individuals with otosclerosis may experience episodes of vertigo if the inner ear is involved. Onset of symptoms usually occur around the third decade of life and progressively involves both ears.

How is it diagnosed?

A basic aural examination with an otoscope may reveal a reddish blush on the promontory of the cochlea in severe cases. A pure tone audiogram is done to assess the severity of hearing loss. Individuals exhibit conductive hearing loss of varying degrees, with good bone conduction thresholds. A classic audiometric sign of otosclerosis is the “Carhart’s Notch” which is a dip in the bone conduction threshold at 2000Hz, which can be attributed to the resonant frequency of the middle ear. If left untreated, it may lead permanent hearing loss. Imaging studies like a CT scan is also used to rule out the presence of other conditions that can present with similar symptoms.

Treatment options

Treatment depends on various factors such as type and degree of hearing loss, age, and individual medical history. In case of purely conductive otosclerosis, the conditions should be treated surgically, treating the poorer ear first followed by the better ear. This surgical treatment option is known as stapedectomy, which includes removing the ossified or fixed stapes and replacing it with a micro-prosthesis. It is a small procedure that can be done under local or general anesthesia, and is almost always successful at restoring normal hearing thresholds. The aim of stapes surgery is to re-establish the passage of sounds to the inner ear via the ossicular chain, and improve the hearing thresholds enough to obviate the need for hearing aids. It is important to discuss surgical treatment and its limitations with each individual to clarify any potential risks or if a hearing loss can persist even after surgery.

In such conditions where there are contraindications to surgery, such as mixed hearing loss involving the inner ear structures or children less than pre-adolescent age, a hearing aid can be prescribed as an assistive management option to improve hearing.

Post – surgical management

During post-surgical recovery, follow up care is extremely important. Individuals who have undergone stapedectomy will be asked to avoid lifting heavy weights, swimming, travelling by airplane, and excessive straining. There are no dietary restrictions. Following all instructions and regular follow ups help ensure the success of the procedure.