Cochlear implant

Valeria Dahm is a freelance writer in the medical department. She studied medicine at the Technical University of Munich. It is particularly important to her to give the curious reader an insight into the exciting subject area of medicine and at the same time to maintain the content.

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A cochlear implant, or CI for short, is an electronic inner ear prosthesis that enables hearing impaired and deaf people to hear. This is achieved through electrical stimulation of the auditory nerve. However, the treatment is only promising in children and in adults whose hearing loss has not existed for too long. Read all about the surgical procedure, when it is performed, and the risks involved.

What is a cochlear implant?

A cochlear implant consists of an external speech processor that is worn behind the ear like a hearing aid and the implant itself, which is surgically inserted into the cochlea. The speech processor, which consists of a microphone, cable and coil, converts sound vibrations into electrical signals. From these he encodes pulse patterns that are sent to the implant by radio waves or induction. The recipient of the implant decodes the signals and forwards them to the cochlea via an electrode. There the electrical impulses stimulate the auditory nerve. It forwards the signals to the brain, which processes the information like a natural acoustic event.

The normal hearing process

The healthy ear picks up sound waves, passes them on to the eardrum via the ear canal and sets it in mechanical vibration. The three ossicles in the middle ear - hammer, anvil and stapes - are transferred to the so-called oval window. Immediately behind it is the inner ear with the fluid-filled cochlea: a spiral-shaped bone cavity. This is where the actual sensory organ is located, a coiled, fluid-filled tube system made of fine membranes. Sensory cells are embedded in these and are equipped with fine hairs that protrude into the fluid. If these vibrate due to sound waves, they pass the stimulus on to the brain via the auditory nerve. Here the signals are converted into acoustic information.

If there is a serious disruption of this process within the inner ear, a cochlear implant may help. According to the German Cochlear Implant Society, around 30,000 people in Germany wear such an inner ear prosthesis.

When do you perform cochlear implant surgery?

An intact auditory nerve and an intact central auditory pathway are the basic requirements for a cochlear implant. If the auditory nerve is destroyed, a so-called auditory brain stem implant can partially restore the hearing ability instead.

Cochlear implants are used for:

Damage to the hair cells in the cochlea (known as cochlear deafness)
Post-lingual deafness - this means that deafness only occurs after learning the language
Prelingual or inherited deafness in children - this means that deafness occurs before language learning
Hearing impairment that makes it impossible to understand speech even with a hearing aid

In contrast to children, adults who were born deaf are usually no longer given a cochlear implant. Your brain has never learned to recognize and interpret acoustic stimuli. Since it is already mature, it is not to be expected that it will be able to develop the appropriate skills for a spoken language understanding.

What do you do with a cochlear implant operation?

In addition to the general preoperative diagnosis, preparation for the operation also includes a more detailed examination of the ear, nose and throat area, various hearing tests, magnetic resonance imaging (MRI) or computed tomography (CT) to assess the internal head structures. In addition, there is detailed personal advice and information from the attending doctor.

The operation is always performed under general anesthesia. In a first step, the surgeon opens the skin behind the ear in order to mill a recess in the now exposed skull bone. The external speech processor will also be attached here later.From there he drills a canal into the middle ear, from which he creates an opening in the inner ear through another hole. He uses this access to push the electrode into the cochlea. He anchors the actual implant in a separate bone bed behind the ear. The cochlear implant is tested during the operation and the function of the auditory nerve is checked.

Normally, the patient can then leave the hospital immediately. The postoperative controls include a CT or MRI, which can be used to check the position of the implant, and careful monitoring of wound healing. In this way, any complications can be identified at an early stage. The conclusion is the individual setting of the speech processor after the wound has completely healed.

What are the risks of cochlear implant surgery?

In addition to the general risks, such as infection, that can be associated with any operation, in some cases specific complications also arise in the course of a cochlear implant operation:

dizziness
Damage to nerves
Unwanted stimulation of other nerves (especially the facial and taste nerves)
Middle ear infections
Tinnitus (ringing in the ears)
Loss of any residual hearing
Technical complications, implant defects and misalignments
Material incompatibility

Cochlear Implant: Limitations

Cochlear implants open up many possibilities for those affected: They can communicate more easily with their fellow human beings and thus (again) have a greater share in social encounters. The quality of life increases significantly after receiving a cochlear implant. However, disadvantages and limitations should always be kept in mind before an operation.

The implant must be removed both when sleeping and when doing certain sports such as swimming or martial arts.
In rare cases, strong magnetic fields, electrostatics or high-frequency signals can lead to unintentional irritation of the auditory nerve.
External, additional microphones may be necessary in order to perceive TV and audio devices as realistically as possible.
Since this is a complex device, technical complications can arise.
Care and maintenance both at home and in the clinic in charge can take up a lot of time.
Despite intensive training, there is seldom a complete restoration of speech understanding because the linguistic information for the brain remains incomplete.
Last but not least, some people find the cochlear implant to be visually unattractive.

What do I have to consider after a cochlear implant operation?

Both the postoperative basic therapy and the follow-up therapy as well as lifelong follow-up care are decisive factors for the success of the procedure.

Basic therapy

In addition to general medical follow-up care, the basic therapy includes the initial setting and step-by-step optimization of the speech processor. A special focus is on hearing and language tests, controls and intensive listening and language training. In addition, there is training in the handling and use of additional devices.

Some patients do not get on well with their cochlear implant at first. They find it difficult to accept the technical device that has been implanted in them or they have problems processing the sensory pressures that are now storming on them. Both can significantly limit the success of the therapy. In such cases, additional psychological support may be necessary.

Follow-up therapy

The basic therapy is continued as part of the subsequent therapy. The brain first has to get used to the new artificial stimulation of the hearing and learn the necessary perception and processing processes. An intensive combination of training and recurring adjustments to the speech processor form the basis for the success of the treatment. Regular audiometric controls help.

Aftercare

A cochlear implant requires lifelong follow-up care by a clinic with appropriate experience. It is used for medical and technical control and advice. The doctors regularly check the patient's hearing, speech and language performance and document them. The aim is to optimize and stabilize the patient's individual communication skills.

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