Otosclerosis – gradual hearing loss

Otosclerosis - gradual hearing loss

Beethoven was undoubtedly one of the great European composers. He composed some of his best-known works when, due to his deafness, he could only communicate with “conversation books”. His progressive hearing loss began when he was 26 years old. Today, most researchers assume that its cause was otosclerosis of the inner ear.

What is otosclerosis?

Three tiny bones in the tympanic cavity are behind the eardrum: the malleus, anvil, and stirrup. They are flexibly connected like a chain, dampening the sound waves from outside and transmitting them further into the inner ear. The smallest bone in the body, the stapes, is attached to the membrane of the oval window that connects to the inner ear.

In otosclerosis, remodelling processes and increased new bone formation occur at various middle and inner ear points. Hence, the name for this disorder is derived from the Greek: “Oto” for ear and “sclerosis” for hardening. The oval window and the stapes are almost always affected, and in some cases, structures of the inner ear, such as the cochlea or vestibular system.

The new bone can grow around the insertion point of the stirrup and almost wall it in. As a result, this auditory ossicle increasingly loses its mobility (stapes fixation) and is less and less able to transmit the sound. Hearing disorders (conductive hearing loss) are the result. 

If the inner ear is also affected by the ossification, there can also be ringing in the ears ( tinnitus ) and – rarely – dizziness. There are cases where only the inner ear is affected (capsular otosclerosis); then, there is a pure sensorineural hearing loss, and the sound conduction is intact.

 

Who is affected, and what are the causes?

Otosclerosis almost always begins between the ages of 20 and 40. Studies show that women are about twice as likely to get the disease as men and white people are particularly susceptible. In almost two-thirds of cases, both ears are affected during the disease.

It is still not known precisely how new bone is formed. A genetic component has long been suspected. Studies indicate that specific genes are altered at a certain point in otosclerosis patients.

However, it cannot be ruled out that there are other triggers. In many affected women, the symptoms worsen during pregnancy or during menopause, which speaks for hormone involvement. Antibodies against measles were found in the inner ear fluid of some patients, which is why viruses are also discussed as triggers.

What are the symptoms of otosclerosis?

In most of those affected, hearing loss becomes noticeable after age 20, usually first in one ear, later often in both ears. This progresses slowly but steadily to the point of complete deafness. Many also suffer from ringing in the ears (tinnitus). If the inner ear is also affected, dizziness can also occur.

A common symptom is that sufferers hear better in ambient noise – this phenomenon is known as “Paracusis Willisii”. The cause is that, on the one hand, the other people automatically speak louder in such situations, and, on the other hand, the disturbing noises in the ears are then less noticeable. Those affected themselves speak rather quietly since their voice is transmitted via the bones, which works, of course.

 

How is the diagnosis made?

There is a whole range of ear examinations, but in the end, these only give more or less clear indications of otosclerosis or make it possible to rule out other diseases. The doctor puts the test results together like a jigsaw puzzle.

The following tests are used to diagnose otosclerosis:

  • Anamnesis interview:  In the interview, the doctor will clarify whether there are any previous illnesses and what your symptoms look like.
  • Otoscopy: The doctor uses a magnifying glass to examine the eardrum and ear canal to rule out inflammation. In most cases, otosclerosis is not visible on otoscopy.
  • Tuning fork test (Weber/Rinne test):  As part of the tuning fork test, one is struck and placed on different parts of the head or held in front of the ears. In doing so, tell the doctor whether and, if so, when you can no longer perceive the vibrations of the tuning fork.
  • Gellé experiment: A rubber ball is placed on the ear canal beside striking the tuning fork. This creates an overpressure that impedes air conduction with normal hearing. The tone of the tuning fork seems quieter. In the case of otosclerosis, on the other hand, the tone does not change for the person affected.
  • Speech audiogram:  Speech comprehension is measured with the help of a speech audiogram.

Magnetic resonance therapy or computed tomography can accurately picture the ear and skull region if otosclerosis is suspected.

What therapy is there for otosclerosis?

The most essential treatment method for otosclerosis when the inner ear is not or hardly affected is microsurgery. The stirrup is partially removed, a hole is drilled in its footplate, and a stamp-shaped prosthesis (so-called piston) made of Teflon, platinum, titanium or gold is inserted, and this is attached to the anvil with a small eyelet. This procedure (stapedotomy/septoplasty) restores the mobility of the ossicular chain and, thus, the transmission of sound to the inner ear.

In the past, the entire stirrup was often replaced with a prosthesis (stapedectomy). This procedure is only rarely used today due to the higher risk.

If there is also sensorineural hearing loss, the operation will not help. A hearing aid can be fitted in such cases (or if the patient does not want the surgery). This amplifies the sound but does not prevent the disease from progressing.

the course of the operation

The operation lasts at least 30 minutes and is usually performed under local anaesthetic – this has the advantage that the doctor can already check your hearing during the operation. Access is from the outside via the ear canal by cutting open the eardrum and folding it away. This is how you get into the tympanic cavity, and – after removing the upper stirrup – you can drill a hole in your “foot” with a needle or a laser beam. An improvement usually occurs within two weeks after the operation at the latest.

 

What do you have to watch out for after the operation?

For the first few days after surgery, the ear canal is stuffed with a sponge or gauze soaked in antibiotic ointment. The patient has to stay in the clinic for around two to three days and is usually on sick leave for two to three weeks. Water should not get into the ears for the first two weeks; therefore, a bathing cap, earmuffs or similar should be worn even when showering.

It takes about four to six weeks for it to heal completely. During this time, the affected person should not take any flights or dives, as the pressure fluctuations can damage the ear. Some experts even advise not to use it for three months. If you have a cold, decongestant nose drops should be taken for the same reason.

Cochlea-Implantat als Alternative

An alternative in treating otosclerosis, especially in sensorineural hearing loss, is the cochlear implant (CI). This is placed under the skin behind the auricle. The doctor inserts an electrode connected to the implant into the cochlea through a thin canal. The cochlear implant converts the sound waves into electrical impulses, which it transmits to the auditory nerve. 

After the operation, wound pain and slight bleeding may occur. The stitches are removed about seven days after the operation. It usually takes two to three weeks for the wounds to heal completely.

The implant is activated for the first time around four to six weeks after the operation. This requires a hospital stay of several days. As part of this, the person concerned receives instructions on using the cochlear implant and the first hearing tests are carried out. Hearing training is also given by a speech therapist in the following months.

Course and prognosis in otosclerosis

The difficulty in treating otosclerosis lies in deciding whether and when to operate. The earlier the intervention takes place, the easier it is to succeed and the higher the success rates (improvement in hearing by more than 90 per cent, and in many cases, the tinnitus also disappears).

However, as with any surgery, complications can occur, making the decision to have surgery difficult when hearing is not too severely impaired. For example, the hearing ability of those affected deteriorates after the operation in about one per cent of cases, and 0.5 per cent even become deaf.

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