Otosclerosis - A guide to Hearing Loss

This is the name given to an abnormal growth and development cycle of a tiny bone (‘stapes’) within the middle ear which obstructs the normal passage of sound waves through the ear and so results in hearing loss.

The ‘Stapes’

The stapes or to give it its colloquial name ‘the stirrup’is one of three bones in the middle ear which are collectively known as the ‘ossicles’.

These bones are the smallest ones found in the body and act as a type of connection system which transmits sounds from the outer ear into the cochlea (inner ear). Sounds are detected by the ear drum which pass through this to the first ossicle – ‘the hammer’ (malleous), then to the second ossicle – ‘the anvil’ (incus) before reaching the third ossicle – ‘the stirrup’ (stapes). The stapes then transmits these sounds into the inner ear via the cochlea. In normal circumstances these bones move easily in response to these sounds which enables a person to hear.

Abnormal stapes

But with otosclerosis the stapes bone follows an abnormal growth pattern which can spread to the opening to the cochlea. This then affects the amount of sound waves being transmitted to the cochlea. And a reduction in sound waves means a reduction in hearing.

This is a gradual process but the less flexible the stapes the greater the degree of hearing loss. Eventually the stapes becomes completely fixed which results in severe hearing loss.

This type of hearing impairment is called conductive hearing loss.

Sound is usually passed freely through the ear due to the plasticity of the individual components. But this unchecked growth around the stapes causes it to lose its flexibility and become rigid which then disrupts normal hearing.

This is usually confined to the stapes but in some situations it can spread to the cochlea and affect the nerve cells within. If this occurs then the transmission of signals to the brain will be affected which also affects the hearing. But this is a different type of hearing problem called sensorineural hearing loss.

Otosclerosis can affect one ear but it usually affects both.

Women are likely to be affected than men. And these are usually middle aged as well.

Causes of otosclerosis

Genetics seems to be largely to blame. You can inherit the gene for otosclerosis so if a family member suffered from this disease then you have a high chance of doing the same.

In fact, two out of three people with otosclerosis are from families with this condition. A viral infection such as measles can cause otosclerosis although this is not yet proven. Research findings suggest a link between the two but more work is needed to confirm (or reject) this.

There has been a decrease in the number of people developing otosclerosis after receiving the measles vaccination. It seems to be the case that a virus such as measles will trigger this condition in those people with a genetic predisposition to otosclerosis. But this is theoretical only.

Symptoms of otosclerosis

If you find that low pitched or soft sounds are difficult to hear or are experiencing dizziness, ringing/buzzing sounds in your ears and problems with your balance then you may have otosclerosis.

The most noticeable symptom will be hearing loss but whichever presents itself first you will need to see your GP. He or she will examine your ear and ask you about your medical history before referring you to an ear specialist. The specialist will carry out a series of hearing tests as well as a CT scan.

Treatment for otosclerosis

Your specialist and/or GP will decide upon the best course of treatment for you. Treatment options are:

• Hearing aid
• Fluoride tablets (these are rarely used)
• Surgery

Surgery involves removing the affected stapes and replacing it with a substitute made from either plastic or metal. This is called a ‘stapedectomy’and it may prevent the risk of the disease spreading into the inner ear. However this is an extremely delicate procedure which does have risks such as damaging the nerves within the ear which can affect taste or balance; causing tinnitus or failing to correct the disorder which can result in permanent hearing loss.

These are all things to consider before deciding upon surgery. You have the option of undergoing surgery now or using a hearing aid until your hearing reaches the point where this doesn’t seem to help and then opting for surgery

Surgery is performed upon the ear with the most damage. If this is successful then it is carried out on the other. But if surgery fails then you still have the one good remaining ear. Note: a point of interest for women: if you have been diagnosed with otosclerosis and are thinking of taking an oral contraceptive or hormone replacement therapy (HRT) then discuss this with your GP first.

The reason for this is that there some arguments that suggest that hormone treatment can worsen otosclerosis but seek your GP’s advice.