Otosclerosis is a common cause of hearing loss in young adults, which results from abnormal bone growth inside the ear.
There are three tiny bones (ossicles) deep inside the ear, which move back and forth when sound waves enter.
These three bones transmit sound waves to the cochlea (inner ear), which converts them into nerve signals that are sent to the brain.
In otosclerosis, the stapes ('stirrup' bone) begins to fuse with the surrounding bone, eventually becoming fixed so it cannot move. Sound waves can no longer be efficiently transmitted into the inner ear.
How do I know I have otosclerosis?
It can take years for the stapes to fuse with the surrounding bone and for hearing to become noticeably impaired.
The decline in hearing usually happens over months or a few years. Some sound can still be transmitted though, so it doesn't cause total deafness.
Most people with otosclerosis notice their hearing problem in their 20s or 30s. It can be in one or both ears. The condition is a little more common in females.
Hearing loss often results in the person speaking loudly and struggling with background noise, but otosclerosis is different. Someone with otosclerosis may speak quietly and background noise can be helpful – possibly because voices are raised in volume and pitch.
If you have any of these symptoms, see your doctor.
What's the cause?
In otosclerosis, abnormal bone forms in the area just in front of the stapes and over time, grows onto the stapes and stops it moving when sound waves enter the ear. The exact cause is unclear, but half of cases run in families and are thought to result from inheriting a faulty gene from a parent.
It is possible that in some patients, the measles virus may trigger otosclerosis in those who have inherited the faulty gene.
How serious can it be?
Rarely, otosclerosis can spread to the cochlea and the tiny hairs that turn sound waves into electrical signals can become damaged, resulting in greater hearing loss.
Unlike the hearing loss caused by a fused stapes, hearing loss caused by cochlear damage cannot be improved with surgery.
How is it diagnosed?
Your doctor will ask about your symptoms, examine your ear, take your medical history and test your hearing.
If you are found to have some hearing loss, you'll be referred to an ear, nose and throat (ENT) specialist or an audiologist (hearing specialist) at a nearby hospital, where you can expect to have further tests. Find out more about these hearing tests for adults.
How is it treated?
Otosclerosis can be treated with either a hearing aid or surgery.
A hearing aid is an electronic device consisting of a microphone, an amplifier, a loudspeaker and a battery. It increases the volume of sound entering your ear so you may be able to hear things more clearly.
An audiologist will discuss the different types of hearing aid available and advise which is best for you. Read about the different types of hearing aid.
An operation called a stapedotomy to restore your hearing may also be possible.
The operation can be done under either general or local anaesthetic. A cut is made inside the ear canal and the top part of the stapes is removed. A small opening is made at the base of the stapes and a plastic or metal implant put into the ear to conduct sound from the remaining ossicles into the inner ear.
This is a delicate operation that is usually very successful – but as with all operations, it carries a small risk of complications, including:
- losing more or all of your hearing
- a hole in the eardrum
- altered sensation of taste (usually temporary)
- new or worsened tinnitus
- facial weakness (rare, and usually only short-lived)
The surgeon should discuss with you the risks and benefits of both surgery and hearing aids.