The type of implant that is used depends on the type of hearing loss and how bad it is. Here are some of the most common types of hearing implants.
Bone-Anchored Hearing Systems
Bone converts sounds into vibrations that are sent directly into the inner ear via the bones in the head. Bone-anchored hearing systems bypass the outer ear and the middle ear. There are active and passive bone conduction devices. With an active device, the skin stays intact. The device has two parts: an external part (the processor) and a surgically implanted fixture placed in the bone behind the ear. There are two types of bone conduction implants. The first is a fixture that protrudes through the skin so that the processor can attach onto it. The second is fully implanted under the skin, with the processor attached using a small magnet inside the processor.
Bone-anchored hearing systems work best for people who have at least one inner ear that functions normally. They may have conductive hearing loss (their outer or middle ears do not transmit sound correctly) or complete hearing loss in one ear only.
Middle Ear Implant
A middle ear implant has two parts: an external part (the ‘processor’) and the surgically implanted internal part. The processor transmits sound to the internal part of the hearing implant. This consists of a receiver just below the skin to pick up the sound from the processor, together with the implant, which is attached to one of the bones in the middle ear, or attached near to the membrane window of the cochlea. It picks up sounds and converts them into vibrations which are sent to the middle ear and further into the inner ear.
Middle ear implants are suitable for those with a mild-moderate mixed or conductive hearing loss or a sensorineural hearing loss.
Cochlear Implant
A cochlear implant consists of an external portion that sits behind the ear and a second portion that is surgically placed under the skin. The implant has a microphone, which picks up sound from the environment. It also has a speech processor, which selects and arranges sounds picked up by the microphone. Next, it has a transmitter and receiver/stimulator, which receives signals from the speech processor and converts them into electric impulses. An electrode array collects the impulses from the stimulator and sends them to different regions of the auditory nerve. This allows sound vibrations to bypass damaged parts of the ear and go directly to the inner ear and the auditory nerve, and ultimately the brain.
Cochlear implants make it possible for people to hear and understand sounds even if they have damaged hair cells in the inner ear and have a severe or a profound sensorineural hearing loss.
Auditory Brainstem Implant
An auditory brainstem implant has two parts: an external part (the processor worn on the ear) and the surgically implanted internal part. A microphone on the processor picks up the sound around it, and turns it from a sound wave into an electrical signal. The processor then transmits the sound signal to the internal part of the hearing implant. This consists of a receiver just below the skin, together with the implant which is positioned within the brainstem. This means that the implant is bypassing both the cochlea and the hearing nerve, taking a short cut to the brainstem.
These are suitable for those with a severe sensorineural hearing loss, leading to near total loss of sound.
Advantages of Hearing Implants
- Improves ability to communicate with and enjoy the outside world
- Improved quality of life
- Lessened social isolation
- Decrease misunderstandings
- Decreased dropped conversations
Disadvantages (Considerations) of Hearing Implants
- Involves a surgical procedure.
- Most implants cannot fully restore hearing. They can only improve the ability to receive and process audio information.
- As with any mechanical device, there is ongoing maintenance that is involved.
- They may need to be removed for water and sports activities.
- Cosmetic implications
