Implantable hearing aid

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Various device systems are designated as implantable hearing aids , which are intended to improve impaired hearing in certain indications and which are permanently implanted for use. Depending on the system, the entire device or parts of the system are implanted. Even with full implants, however, an external device is required with which a battery that is also implanted can be recharged.

Skull implants

Indications

A hearing aid with a cranial bone implant is used for ear malformations with atretic external auditory canal or residuals after chronic otitis media , where surgical measures cannot permanently improve hearing performance, or when conventional hearing aids cannot be worn. In addition, the following requirements are mentioned: a functioning inner ear and a functioning auditory nerve , the exclusion of a bone metabolic disease ( osteoporosis or reduced bone density ), cooperation in terms of hygiene and a minimum age of 5 years.

Risks and consequences of implantation

Poor hygiene can cause the wound to become infected. This in turn can lead to rejection and even meningitis . The probability of this occurring, however, is described as "extremely low".

BAHA system

Implanted titanium screw behind the ear

The device called BAHA® (“Bone Anchored Hearing Aid”) is a “partially implanted” hearing aid. The implant is a titanium screw that is anchored through the skin in the skull bone . An external hearing amplifier is attached to it with a snap coupling. The sound , converted into vibrations , is transmitted to the inner ear via the skull bone and the lower temporal bone . There are four different models of the hearing amplifier. The cost is around € 3000–5000, depending on the device variant. Over 30,000 patients worldwide have been treated with such a system.

The alpha M bone conduction hearing system is also available on the market. It is a non-open system with a holding magnet under the skin. There is no need for a screw penetrating the skin to connect the hearing amplifier. Since it works with electrical signal processing, it is, in contrast to the BAHA, an "active implantable medical device" according to the AIMG directive 90/385 / EEC.

Middle ear implants

The implants that are approved and used in Europe as of 2008 are listed below. The representations contain no statements about details of the surgical intervention and no statements about the extent of the (individually different) "hearing success". Middle ear implants with electrical signal processing are subject to the directive on active implantable medical devices (AIMG directive 90/385 / EEC).

Passive middle ear implants , with which a regular state of the ossicles is surgically established, have a purely physiological effect . These implants are not considered a hearing aid.

Indications

Active middle ear implants are used in adults when conventional hearing aids cannot be used due to medical problems such as outer ear malformations or allergies to hearing aid materials. The range of indications ranges from pure sensorineural hearing loss to combined hearing loss.

Most middle ear implants are not approved for children because the bones surrounding the middle ear are still growing. The Vibrant Soundbridge, which received approval for children in Europe in 2009, is an exception. The inner hair cells have to be largely intact, as for a normal hearing aid. In addition, in most cases the middle ear must function normally.

(Indications are given here with the reservation of the need for individual examination, necessary requirements and any contraindications to be observed.)

Risks and consequences of implantation

On the part of the provider, the surgical procedure is often described as low-risk and comparable to that of a simple middle ear operation ( tympanoplasty ).

However, as with any other operation, there is a risk of anesthesia complications (e.g. circulatory problems) and infection. More specific risks are damage to the taste buds, the chorda tympani , and the facial nerve (nervus facialis), which manifests itself in facial paralysis. As with other operations on the auditory ossicles , the greatest risk is the possible deafness of the operated ear.

If the implant contains a magnet to hold parts of the device that are externally attached to the skin, the patient may only be subjected to magnetic resonance imaging if the implanted magnet has been removed beforehand.

The performance of the rechargeable batteries will deteriorate after several years of operation and must be replaced with another surgical procedure. Since generally only the battery needs to be changed, the second surgical procedure can be less than the first implantation. The maximum operating time specified is 9 (Esteem system) to 13 (Carina system) years.

costs

The costs of an implantable hearing aid are currently (2007) around € 10,000 (Vibrant Soundbridge system) to € 30,000 (Esteem system) per device including the costs of the surgical procedure. The costs are only covered by the statutory health insurance companies for implantations for medical reasons that exclude the use of conventional hearing aids .

Vibrant Soundbridge system

The device called Vibrant Soundbridge ® System (from MED-EL ) is the most commonly used active middle ear implant. It consists of the externally worn audio processor and the implant that sits under the skin. The audio processor is held in place by a magnet that is positioned on the outside of the skin opposite a magnet located in the implant. The implant contains a receiver and the vibrating body FMT (Floating Mass Transducer) developed by Geoffrey R. Ball . Possible coupling points of the FMT in the middle ear are the anvil , the stapes , the round window or additional passive middle ear implants such as TORP and PORP. Various mechanical elements (couplers) are available to implement these coupling options. The microphone of the external audio processor picks up the sound and transmits it as an electromagnetic signal through the skin to the implant, which converts it into vibrations with the help of the FMT oscillating body. These vibrations are introduced as a mechanical sound signal via the coupling point and thus stimulate the hearing organ. The single-point fixation of the FMT on a middle ear structure means that the system is also suitable for treating children.

System Carina

In the device called “Carina ™”, the implant consists of three interrelated parts: a capsule that contains the control electronics, the microphone and a transducer called the “Middle Ear Transducer ™”. The electronics capsule contains the battery , magnet, sound processor and a connector for the transducer. The device components are inserted completely under the skin behind the auricle . The sound is picked up by the microphone under the skin, suitably processed into electrical signals by the electronics and transmitted to the transducer in the middle ear. The transducer has a tip that contacts the ossicles . From this point on, the sound vibrations transmitted there are processed as with normal hearing. Because of this sound processing, users of this hearing system report a more natural sound quality. The battery is charged with an external charger that is attached from the outside via the holding magnet contained in the implant. The implant can also be controlled without charging using a remote control device held by the magnet above the implant. The fully implantable hearing system is suitable for moderate to severe sound conduction , sound sensation and combined hearing loss . Possible indications for the fully implantable hearing system are, for example:

System Esteem

With the device called the "Esteem System", the implant behind the auricle under the skin consists of an audio processor and two transducers, the sensor and the driver. The sensor is connected to the ossicular chain and thus uses the eardrum as a natural microphone. The horn effect of the auricle is thus also used. The recorded sound vibrations are converted piezoelectrically and passed on to the audio processor. This filters and amplifies the electrical signals and forwards them to the driver, which converts them back into amplified mechanical vibrations and transmits them to the stapes and then to the cochlea . To avoid feedback , the ossicular chain must be interrupted; this leads to extreme conductive hearing loss when the device is switched off. During an explantation , the ossicular chain must also be reconstructed . The individually programmed audio processor also contains the battery. The device can be switched on or off and the volume changed with an external remote control.

System TICA

Scientists from the University of Tübingen developed the middle ear implant TICA, in which a conventional airborne sound microphone was also implanted. However, this caused problems with the implant growing in, and users might also have to reckon with quality losses due to the location of the microphone under the skin. This system has not been used since around 2004.

Inner ear implants / cochlear implants

The cochlear implant system consists of an external digital speech processor with microphone and a transmitter coil with magnet, and the actual implant, which is composed of another magnet, a receiver coil, the stimulator and the electrode carrier with the stimulation electrodes. The electrodes are inserted into the cochlea (cochlea). The receiving coil is placed under the skin behind the ear. The transmitter coil of the processor is attached to the scalp with the help of the magnets above the receiver coil of the implant. The voltage is supplied to the implant through the scalp by means of electromagnetic induction .

From a purely medical point of view, a cochlear implant can be used if the reason for the hearing impairment is a significant impairment of the function of the inner ear, in particular the hair cells . In Germany, however, the patient's career prior to deafness is also used when deciding on implantation. A CI fitting is not recommended for deaf adults who have become deaf before or during language acquisition, since verbal understanding is generally not to be expected.

Brain stem implant

A brainstem implant is an electronic device that directly stimulates the auditory pathways in the brainstem . It is a modified cochlear implant (CI) that does not electrically stimulate the inner ear ( cochlea ), but the first auditory nucleus in the brain stem. For this purpose, the implant is implanted in the skull behind the auricle; the stimulation electrode is positioned on the first auditory nucleus, the nucleus cochlearis. This electrode consists of a total of 21 "button electrodes".

The ABI has been designed and developed primarily for adult NF2 patients ( neurofibromatosis type 2). Among other things, NF2 means that tumors can develop primarily on the auditory nerve, which conducts acoustic signals from the cochlea to the brain. One consequence of this is that the tumor presses against the auditory nerves, but it can also damage other nerves in the same region. Therefore, there is usually no other option than to remove the tumor - the auditory nerves are often severed or damaged in such a way that acoustic signals can no longer be passed on. There is no longer any connection between the cochlea and the brain. To remedy this, the brain stem implant variant was developed.

literature

  • Pierre Federspil, Philipp A. Federspil: Middle ear hearing loss: Bone-anchored active hearing implants Dtsch Arztebl 2000; 97 (10): A-609 / B-528 / C-482
  • R. Leuwer: Disturbed Hearing - The supply of equipment for the hearing impairment: Conventional and implantable hearing aids. In: Laryngo-Rhino-Otology. 84, 2005, p. 51, doi : 10.1055 / s-2005-861131 .
  • Hans-Werner Bothe, Michael Engel: Evolution releases the human spirit, Neurobionics - A medical discipline in becoming Frankfurt am Main, Umschau, 1993

Web links

Individual evidence

  1. ↑ http://www.schwerhoerigenforum.de/faq/kapitel20.html#ci
  2. ↑ http://www.schwerhoerigenforum.de/faq/kapitel20.html
  3. ↑ http://www.hoerzentrum-marburg.de/hoerrehabilitation/implantbaren-hoergeraete.html
  4. ↑ http://www.schwerhoerigen-netz.de/MAIN/ratg.asp?inhalt=TECHNIK/300
  5. ↑ http://www.schwerhoerigenforum.de/viscacha/showtopic.php?id=2298
  6. ↑ Floating Mass Transducer (picture) ( Memento from December 7, 2010 in the Internet Archive )
  7. ^ Esteem system
  8. ↑ Image representation Esteem
  9. ↑ Report in Spiegel Online
  10. ↑ Discussion by users