Otosclerosis

What is Otosclerosis?

Otosclerosis is a disorder of part of the inner ear bone called the "otic capsule" which is the hardest bone in the human body. It occurs in approximately 6% of the population. In some people with otosclerosis, abnormally growing otosclerotic bone spreads across the base of the stapes bone (the smallest bone in the human body). This reduces the ability of the of the stapes to vibrate and to transmit sound from the outside world through into the inner ear. Often with progression of the disorder, "inner ear" hearing loss will occur also.

 

Sometimes there may be a strong family history of Otosclerosis or hearing loss. For half of people affected by otosclerosis, there is no previous family history of otosclerosis at all.

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One current theory is that an inherited tendency to develop this disorder is activated by the measles virus,(often earlier in life) leading to development of symptoms in some. Several genes contributing to otosclerosis have also been identified.

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How may it affect me?

Otosclerosis causes hearing loss. Usually the hearing loss is called "conductive" because the stapes hearing bone becomes stiffer and fails to "conduct" normal sound through to the inner ear. The inner ear may hear normally, or may also have some hearing loss also.

This disorder gets worse at times of hormonal change and is a little more common in women. Thus following pregnancy symptoms may become worse.

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After many years of this condition, inner ear hearing loss may occur also, in addition to the conductive loss caused by stiffness of the stapes bone. Inner ear hearing loss is generally not correctable by surgery , whereas conductive hearing loss often is correctable by surgery.

Some experience tinnitus (ringing or a rushing sound in the ear), and a small number of people may experience dizziness

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What can be done about it?

Unfortunately there is no known cure for Otosclerosis yet. In past decades it was thought that fluoride therapy may be very promising in reducing inner ear hearing loss associated with otosclerosis, but it appears now in most cases that fluoride is ineffective, and may have some unwelcome side effects. The treatment offered currently is a "work around" with management of the hearing loss.

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The most frequent management options include:

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1. Hearing Aids are ideally suited to the treatment of Otosclerosis. They can be very effective and produce good quality sound. There are many excellent and cosmetically acceptable hearing aids these days, and technology continues to rapidly improve in this area. An example of this is the Cochlear Ltd "Osia" device, designed for those with a predominantly conductive hearing loss ( as occurs in Otosclerosis). There is no risk with hearing aid use, although there are a few downsides, including cost and the inability to wear the aids during water exposure, in some physical activities and in sleep.

2. Stapes/Stapedectomy/Stapedotomy Surgery: Usually results in a substantial improvement in hearing. The operation is performed under a general anaesthetic ( asleep). Local anaesthetic is inserted into the ear. The ear drum is gently lifted and the hearing bones in the middle ear carefully inspected. The movement of the stapes hearing bone is checked and the diagnosis is confirmed. A tiny hole 0.6 mm in diameter is drilled through the base of the stapes bone (the footplate) into the inner ear.  The bony arch of the stapes is removed using a laser. A platinum/titanium  or "Nitinol" piston, 0.5 mm in diameter is then inserted through the micro perforation in the footplate, and then is crimped onto the incus bone. There is some evidence that the hearing results may be better with the Nitinol type of prosthesis, which is " self crimping", and gives a very nice contact seal on the incus bone. The ear drum is then returned to its normal position. Ointment and a light dressing are inserted into the ear canal

 

An overnight stay is required. Physical exercise against resistance is not recommended for one month after surgery, but plenty of walking is fine, and probably it is OK to do light exercise on a cross trainer or exercycle after a fortnight. After a month, all activities can resume.

 

Scuba diving and bungy jumping should not ever be attempted after this procedure, because of the large pressure changes involved which could affect the inner ear, and subsequently the hearing.

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The prostheses are  3T MRI scan compatible-- which means that you are able to have the currently most powerful MRI scans done in the future.

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Most people who have hearing loss with otosclerosis, even those who have had surgery, will eventually will need hearing aids. It may be helpful to think of stapedectomy surgery as deferring the need for hearing aids-sometimes by 10-20 years.

 

How do we measure success?

Success of surgery is determined by whomever has had the surgery done for them!

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Success correlates with the reduction in the " air/bone gap" as measured by an audiologist pre and post operatively. The idea is that surgery will correct the mechanical part of the hearing loss, such that without a mechanical loss, the measuresments of the inner ear hearing, and the middle ear " air conduction" hearing will be close, or the same as each other. The closeness is referred to as the "air/bone gap". About 70% of the time, the gap will be quite small, within 10 dB of the inner ear, 20% of the time the gaps will be within 20 dB of the inner ear and 9-10% of the time there might be no improvement at all.

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Are there Complications of Stapedectomy Surgery?

Fortunately in experienced hands, complications are few. However they do include:

• Failure of the surgery to produce the desired result. The risk of this is between 5-10 %. This could result in a feeling of blockage of the ear and /or ringing in the ear.

• Permanent and total or partial hearing loss in the ear: The risk of this is approximately 1%. If this occurred, a cochlear implant may well be recommended to restore some hearing.

• Reduction or loss of taste sensation along the border of the tongue. This can occur temporarily for some weeks, months, or in rare cases permanently after the surgery.

• Dizziness - Some people experience some mild dizziness or unsteadiness for up to a week or so following the surgery.

• Tinnitus - ringing in the ear is an unusual complication of successful surgery but may occur in 1-3% ( usually successful surgery reduces tinnitus).

• Facial nerve damage or weakness. This is very rare- I have only seen one patient with this condition which developed several weeks after successful and which ultimately resolved after several months- this was suspected as being secondary to reactivation of a virus in the nerve.

 

If you would like further information about your own hearing condition please contact my team: 64-9-631 1965 or "office@ear.co.nz" for an individual consultation.