Otosclerosis is a disease of the ear characterized by the formation of bone tissue between the stirrup and cochlea.
This results in the fixation of the stirrup in the inner ear, whereby the sound waves can no longer be transmitted to the snail to the full extent.
Hearing and ossicles – what are they and what are they for?
The sound is based on a mechanical wave and is bound to a medium, where it continues through pressure and density fluctuations. Air is compressed/bumped every time someone speaks, and this air reaches the ear.
If there is no air vibration, then no acoustic energy reaches the eardrum and not a single sound is heard. However, the more energy is transmitted, the louder the sound in the ear.
The sound pressure waves must reach the auditory nerve, where the mechanical wave is converted into nerve signals.
The sound waves cause the eardrum to vibrate.
All ossicles vibrate because the eardrum is connected to the hammer handle.
The tympanic cavity (part of the middle ear) allows the transmission of vibrations from an air medium to a liquid medium (because the inner ear contains perilymph).
The ossicle chain – hammer, anvil and stirrup – transmits sound from eardrum to cochlea.
What is the purpose of such a complex structure?
It is essential to amplify the sound in the ear.
The middle ear uses two physical laws to increase sound wave intensity:
- The surface area of the eardrum is much larger than that of the oval window, so the pressure per unit surface area of the oval window is much higher.
- The ossicle chain forms an advantageous leverage.
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Treatment of otosclerosis
Medication is of no use to treat this disorder, but there are no effective natural remedies.
Among the primary treatments used for this disease are hearing aids worn in only one ear: they help the patient to perceive the sounds and, above all, the voices more clearly.
When to operate?
Surgical treatment is indicated if the hearing loss is in an advanced phase, in which case this is the only possible treatment to recover.
If, on the other hand, the disease does not improve with the use of hearing aids or surgery, a CT scan is used to look for other causes that can explain this condition.
Studies show that complete deafness occurs over time if the disease is left untreated.
Surgical Stapedectomy
In the case of conductive hearing loss, this intervention is indicated.
Stapedectomy consists of removing the stirrup (stapes) from the middle ear, which is replaced by a tiny metal or plastic prosthesis, and is one of the surgical techniques used for otosclerosis. This is a difficult and delicate procedure and can fail for several reasons:
- The prosthesis may slip out of position.
- The oval window may close again.
- The anvil can erode.
If the prosthesis:
- migrates inwards, the tympanic vibrations directly stimulate the utriculus and sacculus with corresponding consequences for balance.
- migrates outwards, a fistula can form on the oval window.
Surgical stapedotomy
The most surgically practiced therapy for otosclerosis is stapedotomy:
- A small opening is attached to the foot plate of the stirrup.
- A pin is anchored in this opening, on which the prosthesis is attached.
This surgical technique does not provide for removal of the entire foot plate of the stirrup and avoids some complications associated with the larger incisions of stapedectomy.
The results obtained for restoring hearing are approximately equivalent in both surgical procedures.
For otosclerosis:
- in just one ear, this operation helps the patient to better perceive the sounds and to distinguish them more clearly in a noisy environment.
- in both ears, the operation is performed on the more severely affected ear, while a hearing aid is inserted in the opposite ear.
The operation takes about an hour.
Stapedotomy can be performed under general anesthesia, but it is usually preferred to anesthetize only one ear.
The first incision is made over the external auditory opening or inside the ear canal. In addition, very fine instruments are inserted to remove the upper part of the stirrup.
After that, a small opening is placed in the foot plate of the stirrup in the inner ear to insert a metal or plastic prosthesis into this area, which should transmit the sound to the remaining ossicles in the bone chain.
This procedure is also carried out by laser. Studies showed similar results, but with fewer side effects (cf. Keck et al 2002, Matkovic et al 2003, Vincent et al 2006).
In addition, you can also remove a small vein from the back of the hand to make a graft for the ear.
Surgical windowing
Windowing is a surgical procedure for the treatment of otosclerosis, but nowadays it is practically no longer performed.
One pierces part of the temporal bone (mastoid) and creates an artificial opening of the lateral semicircular passage instead of the oval window, which is closed by otosclerosis.
This is a surgical procedure that has many side effects.
Cochlear implant systems
Cochlear implants can help patients suffering from sensorineural hearing loss.
If the hearingis better before surgery, the greater the chance of hearing recovery.
Cochlear implants are more difficult to place in patients with this disorder because of the excessive bone tissue in the inner ear.
Surgical revision surgery
Despite surgical therapy, otosclerosis continues to progress.
Usually, neurosensory hearing loss progresses by 1 dB/year after surgery (Sakihara and Parving, 1999).
The success rate of the second operation (revision) is about 75%. However, the results do not correspond to those of the first operation (Lippy et al.).
Postoperative recovery period for otosclerosis
After surgical stapedectomy, many patients are able to go home the same evening or the following morning.
In any case, the patient should carefully lie down on the non-operated ear in the evening after the operation.
In the first days after surgery, dizziness may occur.
During the operation, a tampon is inserted into the ear canal.
Until the removal of the tampon one week after the surgical procedure, no improvement in hearing is noticed.
In the first week after surgery, patients only complain of a “feeling of emptiness” in their ears, as if the sounds were heard from a barrel or in a cave.
The sounds seem unpleasant, can be very loud, but gradually they normalize.
Provisions
As directed by the doctor (usually within 2-3 months):
- do not wet the ear canal,
- do not travel by air.
Prognosis for otosclerosis
The success rate of stapedectomy is approximately 90%.
The patient’s hearing improves significantly in the first 4-6 weeks after surgery. A further improvement may also be noticeable in the following months.
Due to a small taste nerve that passes through the ear (the chorda tympani), changes in taste sensation may occur over a few weeks or months after stapedectomy. Often patients perceive a metallic taste. In the course of a few weeks of convalescence, however, the sense of taste returns to normal.
- Otosclerosis: symptoms and causes
- fistula, causes, symptoms, surgery and prognosis
- Tympanic membrane perforation: surgery and healing time
