Implantable Hearing Devices
Adults and children with a moderate – profound hearing loss in both ears can potentially benefit from cochlear implantation in one or both ears.
If communication is difficult, even with a well-fitted hearing aid, then you may benefit from a cochlear implant. Children who have been born profoundly deaf or who may acquire a hearing loss soon after birth will routinely be considered for a cochlear implant.
How does an implant work?
1. A sound processor worn behind the ear captures the sound and turns it into a digital code. The processor has a battery which powers the entire system.
2. The sound processor then transmits the digitally coded sound across the skin through a transmitting coil to the implant.
3. The implant converts the digitally coded sound into electrical impulses and sends these along the electrode array placed in the cochlea.
4. The implant’s electrodes stimulate the cochlear nerve, which then sends the impulses to the brain where they are interpreted as sound.
Age is not a factor in adult implant success. As long as an adult is fit for surgery and there are no indications of dementia, then implant surgery is possible. Many adults in their eighties and nineties have been very successfully implanted and report a greatly improved quality of life.
For congenitally deaf children, research indicates that receiving a cochlear implant by one year of age leads to the best speech and language outcomes.
What can people expect with a cochlear implant? There is a wide range of outcomes: many implantees hear well enough to understand a phone conversation; others hear many sounds but still may have difficulty understanding conversation.
A number of factors affect how much a person gains from a cochlear implant. These include the length of their deafness, the amount and type of residual hearing, as well as the ability to make sense of a degraded signal.
The sound from an implant is different from normal hearing and from hearing with a hearing aid. Adults, who have previously had normal hearing, tell us that voices and sounds are different to what they remember. In general, the longer the recipient has been without sound, the longer it will take to make sense of the new sounds.
Cochlear Implant Mapping
Following the initial surgery and recovery period, the sound processor is “turned on” and tuned (known as mapping). This is a computer-based procedure that goes hand-in-hand with rehabilitative counselling and monitoring of the recipient’s progress with the implant. Similar to adapting to a standard hearing aid, the recipient of a cochlear implant needs to learn to hear with the new device and a process of adaption will occur over weeks and months.
Medicare rebates are available for this service, provided the implantee has an appropriate referral from their Ear, Nose and Throat Specialist, who performed the surgery. A gap fee may be applicable for some of these rehabilitative appointments.
Bone Implanted Hearing Solutions
Implantable middle ear and bone conduction hearing solutions use the physical conduction of sound through the bones of the middle ear (the ossicles) and the skull to transmit sound waves to the inner ear and auditory nerve to be transformed into signals that the brain recognises.
Each of the implantable systems will have an external sound processor and a surgically implanted device, either under the skin of the mastoid area or within the middle ear. The system works by enhancing natural bone transmission as a pathway for sound to travel to the inner ear.
The implant is placed during a short surgical procedure and over time, naturally integrates with the skull bone or ossicles. The externally worn sound processor transmits sound vibrations through the external abutment to the titanium implant. The vibrating implant sends signals across the skull through the auditory pathway to the opposite inner ear which finally stimulates the nerve fibres, and this process allows the sensation of hearing.
Who is a candidate for Implantable Hearing Systems?
The bone conduction device can help people with conductive and mixed-loss hearing impairment. This includes people with chronic infections of the ear canal, people with absence of, or a very narrow ear canal as a result of a congenital ear malformation, infection, or surgery; also people with a single-sided hearing loss. Both children and adults can benefit from a bone conduction system.
For people with single sided deafness, the bone conduction system is placed on the side of the deaf ear (all other conditions would be fitted to the worse hearing ear). The bone conduction implant effectively transmits sounds from the worse hearing side to the normal ear and ultimately results in a sensation of hearing from the poorer ear. The user can hear sounds from both sides making communication in noisy situations easier. However, as the sound from the poor ear is heard in the good ear, localisation of sound will still be difficult.
Assessment and Rehabilitation
The Audiologists at EAS can assess a client’s audiological suitability and discuss possible benefits and limitations of the device. Arrangements would also be made for trialling a bone conducted sound processor on a headband. Although the benefit from using the headband is not as great as that gained from using the surgically implanted abutment, it does allow prospective candidates to experience what bone conduction could sound like. Generally, we find that if a patient enjoys the sound from the soft band, then they will benefit from the surgically implanted Bone conduction implant. However, if they do not enjoy the experience of a bone conduction speech processor on the soft band, then they are unlikely to benefit from surgery.
Following the initial assessment by the EAS audiologist, the implantation is done by an Ear, Nose and Throat Specialist locally or in Launceston. The recipient should not need to travel interstate for this surgery. There is a recovery period, following the implantation of the implant, which is reducing to a few weeks with improved surgical techniques. The sound processor is then fitted and “switched on” and then the process is similar to hearing aid fittings, with several review appointments needed to ensure that the sound of the device is satisfactory.