In most people with ADOA or ADOA-plus, the most noticeable symptom initially is the deterioration of their vision. In recent years, however, it has become increasingly clear that a portion of patients also develop hearing problems.
Scientific research shows that approximately 20% of people with ADOA will experience inner ear hearing loss (sensorineural hearing loss) during their lifetime. When this occurs, we refer to it as ADOA-plus or ADOA-plus syndrome.
Just like the deterioration of vision, this hearing loss usually progresses very slowly and gradually. This typically begins when a person is between 10 and 30 years old (the second or third decade of life). In rare cases, hearing even deteriorates before vision declines.
What is sensorineural hearing loss?
Sensorineural hearing loss (also called perceptive hearing loss) is a form of hearing impairment caused by a problem in the inner ear or the auditory nerve. The inner ear contains the cochlea, a small fluid-filled organ that picks up sound vibrations. Inside this cochlea are the hair cells. These are tiny sensory cells that convert sound vibrations into electrical signals, so that the auditory nerve can transmit them to the brain. With sensorineural hearing loss, these sounds are not properly converted or transmitted, resulting in impaired hearing. This form of hearing loss is usually permanent.
What is a cochlear implant?
A cochlear implant (CI) is an electronic hearing prosthesis for severely hearing-impaired or deaf individuals. Unlike a conventional hearing aid, which merely amplifies sound, a CI works differently. The device converts external sounds into electrical signals that directly stimulate the auditory nerve. In this way, the auditory nerve can still transmit the sound information to the brain. A CI is an effective solution when heavy, conventional hearing aids provide insufficient results.
In conversation with experts
To get answers to frequently asked questions about hearing loss and cochlear implants (CIs), we spoke with Prof. Dr. Christoph Arnoldner, a leading expert in the field of hearing implants. He works at the Medical University of Vienna and has been guiding people with severe hearing loss in regaining their hearing for many years. Thanks to his wealth of experience in both medical practice and scientific research, he is a competent discussion partner when it comes to cochlear implants at ADOA-plus.
In addition, Matthias, who now wears a cochlear implant himself, answered our practical questions about managing the implant in daily life and aftercare.
Interview with Prof. Dr. Arnoldner
1) Where is the hearing impairment located in ADOA-plus patients: in the cochlea, in the auditory nerve, or both? Does this vary from patient to patient?
In principle, the problem with ADOA-plus lies in the connection between the hair cells of the cochlea and the auditory nerve. This means that the hair cells are present in the cochlea and the auditory nerve is also present, but that in this condition, the stimulus from the hair cells is not transmitted to the auditory nerve and therefore not to the brain, causing the affected person to have hearing loss.
It is plausible that different variants of ADOA-plus lead to different degrees or types of hearing loss, but the mechanism mentioned above is the current, generally accepted medical view.
2) What are the first signs of hearing loss with ADOA-plus?
It usually starts with it becoming more difficult to follow conversations in challenging listening situations, such as in a busy room or with a lot of background noise.
3) What are the names of the tests that distinguish hearing loss at the cochlear level from hearing loss at the level of the auditory nerve?
Various specialized examinations exist for this. These involve hearing tests such as pure-tone audiograms and speech audiograms, but also more complex measurements such as otoacoustic emissions (OAE), electrocochleography (ECochG), and electrical brainstem audiometry (e-BERA). In addition, radiological scans are performed, such as a CT or MRI scan.
4) Why does a cochlear implant (CI) work with existing damage to the auditory nerve, even though the CI actually replaces the cochlea (or does the CI also replace the auditory nerve)?
A CI only works if the auditory nerve is still functional. If the nerve does not work at all, the CI does nothing either, and you would have to place a brainstem implant, for example. Fortunately, with ADOA-plus, only the very tips of the auditory nerve do not work—say, the connection to the hair cells. The parts of the nerve that lie deeper still function perfectly. The CI stimulates precisely those deeper parts, allowing these patients to hear again with a CI.
5) What are the exclusion criteria for a cochlear implant (focused on the hearing impairment, not on general suitability for surgery)?
This is a complex subject and often not black and white. A clear reason not to place a CI is if the auditory nerve is completely absent (aplasia) or is not properly developed (hypoplasia).”
6) How long does an average CI operation take?
On average about an hour and a half.
7) Which follow-up appointments are necessary (such as processor adjustment, routine checks, battery replacement, and speech therapy)?
That is different for everyone. Often, a patient still comes in every two weeks during the first three months. After that, it becomes monthly, then every three months, and from the second year onwards, it shifts to every six months and eventually once a year.
8) What should be considered when choosing a CI?
Choose a system that allows the doctor to perform the necessary tests during the operation, for example with a test electrode. It is also important that the system offers electrodes of different lengths, so that there is always one that fits the length of your cochlea exactly.
9) What should ADOA-plus patients look out for when choosing a clinic for the placement of a CI implant?
It really has to be a hospital that specializes in hearing implants, and that also has experience with brainstem implants, for example.
10) Are there alternatives to a CI for sensorineural hearing loss?
You can try regular hearing aids, but in this case, they usually do not help enough. If a CI unexpectedly does not work, a brainstem implant can be considered.
Interview with Matthias
Matthias, an ADOA-plus patient and CI wearer, adds the following practical points:
1) What can you tell us about replacing the batteries?
The implant receives power from the audio processor via induction. The audio processor contains two type 675 hearing aid batteries, but the system can also operate with a rechargeable battery. Whether you use standard batteries or a rechargeable battery, they must be replaced after every 24 hours of use.
This works very simply (even for the visually impaired) by sliding the flap back. When the battery is empty, you hear or see a clear warning signal. The batteries are readily available and cost from about 35 cents each. However, using a rechargeable battery is more economical.
2) What information can you give us about the speech therapy aftercare?
The duration of this varies from person to person and depends on how long you have been unable to understand speech, your age, and how well you can use the CI. This can range from a few weeks to several months. In Austria, health insurance covers these costs. Such a rehabilitation program is very beneficial and is best undertaken approximately six months after the surgery.
3) Is replacement of a CI necessary?
The implant itself is in principle intended to remain in place forever. The external audio processor can be replaced in Austria after 7 years via health insurance.
Prof. Dr. Arnoldner and Matthias, thank you very much for answering our questions, and we wish you much success and all the best!
With special thanks to Christina, Ulrike, Matthias, and Prof. Dr. Christoph Arnoldner for their valuable contribution to this interview.
