How do we hear?
The ear consists of the outer, middle and inner ear. Sound travels through the outer ear and reach the eardrum, causing it to vibrate. The vibration is then transmitted through three tiny bones in the middle ear called the ossicles. These three ossicles are called malleus, incus and stapes, sometimes known as hammer, anvil and stirrup. The vibration then enters the inner ear which is a snail-shaped bony structure filled with fluid. The nerve cells within the inner ear are stimulated to produce nerve signals.
These nerve signals are carried to the brain, where they are interpreted as sound.
What is otosclerosis?
Otosclerosis is a disease of the bone surrounding the inner ear. It can cause hearing loss when abnormal bone forms around the stapes, reducing the sound that reaches the inner ear. This is called conductive hearing loss. Less frequently, otosclerosis can interfere with the inner ear nerve cells and affect the production of the nerve signal. This is called sensorineural hearing loss.
Who gets otosclerosis?
The cause of otosclerosis is not fully understood, although it tends to run in families and can be hereditary. People who have a family history of otosclerosis are more likely to develop the disorder.
Otosclerosis affects the ears only and not other parts of the body. Both ears are usually involved in some extent. However, in some individuals, only one ear is affected. It usually begins in the teens or early twenties. Some research suggests a relationship between otosclerosis and the hormonal changes associated with pregnancy.
What are the symptoms?
The commonest symptom is hearing loss that may take many years to become obvious. The degree of hearing loss may range from slight to severe. It can be conductive, sensorineural or both.
In addition to hearing loss, some people with otosclerosis may experience tinnitus or noise in the ear. The intensity of the tinnitus is not necessarily related to the degree or type of hearing loss. Very rarely, otosclerosis may also cause dizziness.
How is otosclerosis diagnosed?
An examination by an otolaryngologist is needed to rule out other diseases or health problems that may cause these same symptoms. The amount of hearing loss and whether it is conductive or sensorineural can be determined only by careful hearing tests.
How can otosclerosis be treated?
There is no known cure for otosclerosis. The individual with otosclerosis has several options: do nothing, be fitted with hearing aids, or surgery. No treatment is needed if the hearing impairment is mild.
Hearing aids amplify sounds so that the user can hear better. The advantage of hearing aids is that they carry no risk to the patient. An audiologist can discuss the various types of hearing aids available and make a recommendation based on the specific needs of an individual.
Aims of the operation
If one ear is affected, the operation may help to locate the direction of sound and hear better in noisy background.
The operation is called a stapedotomy. If both ears are affected, the operation is usually done on the poorer ear. The patient may still need a hearing aid in the opposite ear.