Information on otosclerosis

What is otosclerosis?

The three smallest bones in the human body are located in the middle ear cavity: the hammer, anvil and stirrup. They are connected to one another and transmit the sound waves to the cochlea in the inner ear. The vibrations are transmitted from the middle ear to the inner ear via the stapes, which is connected to the inner ear via the eardrum.

Otosclerosis is a disturbed bone remodeling process that leads to ossification (sclerosing) in the ear. As a result of this ossification, the bones responsible for sound transmission lose their mobility and deafness occurs in the late stages of the disease. The ossification usually begins in the middle ear and can spread to the inner ear. The condition begins on one side and later spreads to the other ear.

The cause of the disease is usually a disorder of bone metabolism in the labyrinth capsule - a small bony part in the inner ear. Starting at the eardrum, it spreads from there to the stapes. As ossification progresses, the stapes loses its range of motion and thus continuously reduces its ability to transmit sound.

Otosclerosis usually manifests itself between the ages of 20 and 40. Women are more frequently affected than men. Of the almost 10 percent of the population who show changes in the middle and inner ear, only 1 percent are affected by otosclerosis.

What are the symptoms of otosclerosis?

The most important symptom of gradually progressing otosclerosis is increasing hearing loss. In 60 to 70 percent of cases, the disease also spreads to the second ear. In women, otosclerosis often begins during pregnancy. The accompanying symptoms of otosclerosis typically include tinnitus, where the affected person hears a buzzing and/or whistling sound.

Causes of otosclerosis
The exact causes of otosclerosis are still unclear. Viral infections (e.g. mumps, rubella, measles) are considered to be relevant factors that can lead to the outbreak of the disease.

Autoimmune diseases are also considered a possible cause. In an autoimmune disease, the body's defense cells react oversensitively to its own tissue, which it perceives as a foreign body, and attack it.

Genetic predispositions are also being discussed. A familial clustering has been identified and five genes (so-called OTSC genes 1-5) have so far been identified that are altered in otosclerosis patients. Due to the genetic abnormality, the defect can be inherited, so that if an affected parent has the disease, the disease often also occurs in the children.

Otosclerosis occurs very frequently in women during pregnancy, although cases have also been observed after menopause. Women who suffer from otosclerosis often report an increase in symptoms as soon as they start taking the pill. It is therefore suspected that hormones also play a role in the development of otosclerosis: increased hormone levels appear to accelerate the remodeling processes of ossification.

Diagnosis of otosclerosis

The ENT doctor is the first point of contact for patients who have problems in the ear, nose and throat area. In an initial consultation, the doctor determines the type and origin of the disease by asking various questions, such as:

Do these symptoms occur frequently in your family?

Have you had problems with your ears in the past?

Have you had a bacterial or viral infection recently?

Do you often hear a buzzing and humming in your ears?

After the detailed conversation, the doctor begins the physical examination. He uses a type of magnifying glass with light and inserts it into both ears (otoscopy). Here he can already observe changes: reddish swellings indicate inflammation, for example. Patients who have otosclerosis usually have neither swelling nor redness; the ear canal and eardrum look pretty normal at first glance. In some rare cases, however, a reddish spot can be seen shining through the eardrum (known as Schwartze's sign).

If the otoscopy does not provide any useful information, a hearing test is usually carried out. The Rinne and Weber tuning fork test is particularly important. The ENT doctor vibrates a tuning fork and holds it in front of the patient's ear or places it at various points on the head and asks the patient to tell him when he no longer hears the vibrations and whether he hears them. This test allows the doctor to narrow down whether the problem is a disturbance in the perception of sound or in the conduction of sound. If there is a conduction of sound, the sound waves are not properly transmitted to the inner ear. If the problem is in the perception of sound, a problem in the inner ear, in the auditory nerve, is to be suspected.

In otosclerosis, the ossification is usually in the middle ear (sound conduction is impaired), but there is also capsular otosclerosis, which also causes changes in the inner ear (sound perception is impaired). In addition, mixed forms often occur that affect both the inner and middle ear, making it difficult to clearly classify the condition. By examining both ears, it can be determined whether the symptoms occur in both ears or only in one. If both ears are affected, further tests must be carried out because the classification is not always easy.

The doctor also tests the mobility of the eardrum using tympanometry and the mobility of the stapes using a stapedius reflex test: if this is no longer mobile, the stapedius reflex also fails.

Further tests also concern speech comprehension: using an audiogram, the doctor can directly determine whether speech is harder to hear.

Finally, the ENT doctor also uses imaging procedures: MRIs, CTs and X-rays can show the extent to which otosclerosis has progressed and how the anatomical structures in the ear area have changed. Fractures and dislocations can also be ruled out in this way. As additional tests, the doctor can also carry out a TCS (tympano-cochlear scintigraphy) and a test of the sense of balance.
Only treatment option: Otosclerosis surgery
If left untreated, otosclerosis will continue to worsen. The progressive course cannot be stopped with medication. Cortisone therapy can be considered, which can slow down the hearing loss, but this will not improve hearing. Only surgery can help. Doctors differentiate between a stapedotomy and a stapedectomy.

Stapedectomy

During a stapedectomy, surgeons remove the sclerotic stapes in an operation, either manually with surgical instruments or with the help of a laser, and replace it with an artificial one. The stapesplasty is connected to the incus and the eardrum like the real stapes, so that sound transmission can proceed normally again.

Stapedotomy

In the past, the stapes was completely removed and replaced with a new artificial prosthesis (stapedectomy). Nowadays, stapedotomy is more common, in which not the entire stapes is removed, but only the long leg. The rest, which is connected to the oval window, is left. A small hole is drilled, the eardrum is lifted off on one side and the replacement is attached to the incus on one side and the stapes on the other. The operation itself is quite short, taking half an hour, and is carried out under local anesthesia. After the operation, the eardrum is folded back and attached to its original position. It is important that an ear bandage, also known as an ear tamponade, must be worn for two weeks after the operation.

Treatment for capsular otosclerosis

In capsular otosclerosis, the ossification has already spread to the inner ear. This means that not only sound conduction but also sound perception is impaired, because the nerve pathways important for hearing run along here. A stapedectomy or stapedotomy alone would not help, and on the other hand, the ossification worsens if surgery is not performed. The affected patients are therefore usually given a hearing aid, but this must be followed by an operation to reduce the sclerosis. If the capsular otosclerosis can no longer be compensated for by a simple hearing aid, the treatment of choice is the so-called cochlear implant, in which two small electronic components are attached, one on the outside of the ear and one directly in the inner ear, which can restore hearing.

After the operation, dizziness and nausea can occur, but these subside within a few days. Only occasionally does the dizziness last longer than usual and in very rare cases hearing deteriorates after surgery.

What is the prognosis for otosclerosis?

The prognosis can be divided into different categories depending on when the otosclerosis occurs and when it was diagnosed. It is certain that without treatment, all otosclerosis will lead to hearing loss and, in extreme cases, to complete deafness. The sooner patients begin treatment, the better the chances of a complete cure.

In general, it has been shown that more than 90 percent of patients can eliminate otosclerosis through surgery and experience a significant improvement in their hearing. Otosclerosis cannot be prevented. It is therefore all the more important that people with a family history of hearing problems have regular check-ups with specialist doctors.

Only a specialist doctor can detect a problem early and thus initiate a possible operation in order to reduce or, in the best case, prevent a serious course of otosclerosis.