When sound-amplifying, conventional hearing aids are no longer sufficient to compensate for a hearing loss, the insertion of a hearing aid implant can provide relief. One option is the cochlear implant (CI), which is an inner ear implant that serves as an electronic hearing replacement. For this purpose, it bypasses the function of damaged hair cells, provides direct stimulation of the auditory nerve, and thus bypasses the impaired part of the hearing. Consequently, the implant is suitable for severe to profound sensorineural hearing loss.
Application areas - For whom is a cochlear implant useful?
Basically, the insertion of a cochlear implant (CI) should be considered in cases of all damage to the inner ear, in cases of increasing hearing loss (hypacusis), as well as when conventional hearing aids do not provide sufficient care. The latter occurs as soon as an excessive number of hair cells of the inner ear is destroyed. Contrary to the long-standing belief that cochlear implants are only applicable in case of loss of residual hearing, nowadays residual hearing can be preserved and used together with the advantages of the CI. Also possible is a hybrid fitting of hearing aid and implant. This form is suitable in cases of varying degrees of hearing impairment of the ears as well as for the fitting of unilaterally deafened persons. However, the presence of a cochlea or auditory nerve is an indispensable prerequisite.
The main target group of cochlear implants are, on the one hand, adults who have poor speech perception due to severe bilateral deafness. Here, it must be differentiated whether the deafness occurred before, during or after language acquisition. In cases of deafness before or during language acquisition, the auditory nerve is often already too degraded in adulthood due to the lack of stimuli. Thus, the earlier a CI fitting is sought after hearing loss, the higher the chance of success.
On the other hand, children who have had profound hearing loss since birth or acquired it during childhood can also be fitted with a cochlear implant. The timing of the procedure is also crucial here: the chances of success are particularly high if the implant is placed before the child reaches the age of two. After the age of eight, children who are deafened at an early age or from birth have only a limited ability to acquire spoken language and the chance of success of the implantation is therefore limited.
Construction - How is a cochlear implant constructed?
Cochlear implants are made up of two components: An outer part, which contains the microphone, speech processor, transmitting coil and a magnet, and an inner part - the actual implant - with the receiving coil, magnets and electrode array. The former is attached externally behind the pinna, while the implant sits in the temporal bone, close to the pinna under the skin.
hearing aid on head
The connection between the battery-powered outer part and the inner part is wireless, with the power supply realized with the help of the magnets via electromagnetic induction through the scalp. In addition, the inside and outside magnets allow the transmitting coil to be stably fixed to the head. Furthermore, there is a direct point of contact between the implant and the cochlea in the inner ear due to the placement of the electrode array in the cochlea itself.
How it works - How does a cochlear implant work?
The hearing process with the cochlear implant is initiated by the recording of sound waves through the external component, which transmits the audio information to the sound processor. In the processor, the main signals are converted into digital information and sent to the internal implant by means of the transmitting coil.
Here, conversion takes place again - into electrical impulses, which reach the electrode array in the cochlea by being passed on. With the help of the electrodes, electrical stimulation of the auditory nerve is now triggered to transmit the impulses to the brain. In the brain, the electrical signals are finally identified as sounds and the auditory impression is created.
Surgery - What is the process of inserting a cochlear implant?
Before surgery, it is important to consider several parameters: the duration of the critical hearing loss, speech competence, the condition of the auditory nerve, the presence of other perceptual and processing disorders, and the motivation to train to hear with CI significantly influence the implantation success prognosis. In addition, extensive hearing tests with and without hearing aids, hearing performance, and quality of life are recorded in advance to weigh whether a CI is the appropriate hearing solution for the particular patient. After suitability has been verified, there is ultimately the preparatory question of how to organize rehabilitation and aftercare.
During the procedure, a 5-8 cm incision is made behind the ear. Shaving away hair is hardly necessary for this - contrary to common belief. Once the site is exposed, a depression is milled into the skull bone. This allows the creation of a canal in the petrous bone that extends to the middle ear and provides access to the round window. A small drill can now be inserted through the channel to drill a hole in the cochlea near the round window. The surgeon then inserts the implant through the drilled hole, and its wires are attached to the temporal bone. While the surgery is still in progress, the implant is tested to verify the arrival of evoked stimuli at the brainstem. Finally, depending on the method chosen, the canal is either filled with bone material or left open, and the opening of the head is sutured.
The following day after implantation an x-ray is taken to check the fit of the implant. Inpatient treatment usually takes place for the first five to seven days, with stitches usually being removed after seven days. Once the wound is completely healed, the first activation of the cochlear implant is performed approximately one to two weeks after surgery. Fine-tuning and optimization of hearing settings provide increasing refinement of hearing over the following months. Regular checking and maintenance of the cochlear implant should not be limited to this period, however, but should become a lifelong, periodic routine to correct or prevent disorders early.
The first fitting also marks the beginning of intensive auditory training to practice interpreting the sound signals received with the CI. The learning process can be compared to learning a new foreign language and is highly individual. However, all CI users have one thing in common: motivation and effort are prerequisites for training, but - regardless of the intensity - will not lead to a hearing quality comparable to natural hearing.
Risks - What are the risks of implanting a cochlear implant?
While the insertion of the inner ear implant is a routine procedure, it is not without risks. There is a risk of middle ear infection, mastoiditis, and possible damage to the eardrum. Postoperatively, temporary restrictions of the facial and gustatory nerves, which are at risk because of their proximity to the milling, are possible. In addition, dizziness or loss of balance - usually temporary - may occur. Also present is the risk of anesthesia and postoperative infection typical of surgical procedures.
Pros and cons: What are the pros and cons of a cochlear implant?
Determining the advantages and disadvantages of the cochlear implant is only feasible to a limited extent, because success is highly dependent on personal prerequisites and training motivation. Accordingly, the decision for or against a cochlear implant can only be made on the basis of individually defined advantages and disadvantages. While the CI improves participation in everyday life and work environment, enhances ambient noise as well as voice perception, and thus can lead to a safe experience, its disadvantages are not to be disregarded.
The idea of having optimal speech understanding without further effort after implantation is unfortunately utopian. In addition to the need for intensive training in the use of the cochlear implant and the fact that perfect hearing is not feasible even with CI, there is also the risk of identification conflict. Depending on the environment and the time of implantation, wearers may feel at home neither in the hearing world nor in the hearing impaired world. Especially for children of hearing impaired parents, this can be a major conflict of interest. But even for adults who have identified with their hearing impairment for years, it is a massively impactful experience.
Cochlear implant costs
The cost of a cochlear implant is approximately €40,000, with ongoing follow-up costs. However, public health insurers usually cover all costs for surgery, rehabilitation and aftercare. If you or your child are privately insured, it is necessary to consult with the health insurance company to find out about cost coverage.
Cochlea implant manufacturer
Cochlear implants are currently produced by four manufacturers: Cochlear, Oticon Medical, Advanced Bionics, and Med-El.