Bone Conduction Implant Center

How hearing works

There are three parts to the ear: the external ear, the middle ear, and the inner ear. Each part plays a role. Normally, sound waves pass through the ear canal (external ear) and cause the ear drum to vibrate. Vibration of the ear drum causes movement of the hearing bones (the malleus or hammer, incus or anvil, and stapes or stirrup) which are in the middle ear. The stapes interfaces with the fluid that fills the inner ear (or cochlea), and its movement causes a fluid wave to pass through the inner ear. This fluid wave causes movement of tiny hair cells within the cochlea. When those hair cells are displaced they generate an electrical signal that is transmitted by the hearing nerve to the brain where it processed.

Types Of Hearing Loss

Since the external and middle ear conduct sound. If there is a mechanical problem with external or middle ear it will cause a conductive (or mechanical) hearing loss. The inner ear creates the electrical signal and transmits it through the nerve. If there is a problem in the inner ear, a sensorineural hearing loss results. When the problem effects both systems it creates a mixed hearing loss.

When is a bone conduction device used

Conductive hearing loss

Often, we can surgically correct conductive hearing losses. If surgical correction has failed, or there is some other reason that the conductive loss can’t be corrected, you may be a candidate for a bone conduction implant. A bone conduction implant bypasses the normal conductive pathway (ear canal to ear drum to ossicles to cochlea) and directly sends the sound wave to the cochlea.

Bone conduction implants are an excellent way to correct a conductive hearing loss.

Single sided deafness

If one ear has lost its ability to hear, but the other ear has good hearing, a bone conduction implant may be a good option. The bone conduction device, in this instance, transmits the sound wave through the skull to the normal hearing ear.

If the “good” ear has hearing loss, a bone conduction device may not be your best option. It has only a limited ability to increase the volume (or the “gain”) in the good ear.

Types of bone conduction implants

Bone conduction implants consist of two parts:

External processor
- - The external processor functions much like a hearing aid. It has a microphone which picks up sound.
Internal implant
- - There are two different types of internal implant: active and passive. Passive implants are essentially a screw which osteointegrates into the skull. Active implants have an “oscillator” which creates a sound wave that is transmitted to the cochlea.

Percutaneous

The first bone conduction implants, known as Bone Anchored Hearing Aids, connected an external processor to a passive implant. The processor connected directly to an abutment that passed through the skin to the implant. All the sound waves are generated by the external processor. This type of implant is still available and may be recommend in certain situations. However, the percutaneous type of implant has limitations and complications that have made it a much less popular choice. Also, the skin attenuates the sound wave and limits the range of frequencies that are passed.

Transcutaneous

Newer bone conduction devices use an external processor which attaches to the internal implant by transducing the signal through the skin. The external processor attaches magnetically. The implant itself is active – it generates a sound wave that is sent to the cochlea. Because these implants are near the skull the signal is much clearer. They have a broader range of frequencies that they transmit which creates a more natural and clearer sound. Since there is no portion passing through the skin, there are fewer skin related complications.

Placement of the device

Bone conduction implants are placed surgically. The procedure is performed as an outpatient, or same day, surgery. It is generally done under a general anesthetic and takes less than an hour. The device is activated 2-3 weeks after surgery.

Bone conduction implant devices

Active:

Med El Bonebridge

Cochlear Americas Osia

Oticon Sentio

Passive:

Oticon Ponto

Cochlear Americas BAHA

Bone Conduction Implant Center

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