Cochlear implants: how are they different from hearing aids?What is hearing aid?

The ear has three parts: outer ear, middle ear and inner ear. When outer ear and middle ear parts are defective, the hearing aids use the same basic parts to carry sounds from the environment into your ear and make them louder. Most hearing aids are digital, and all are powered with a traditional hearing aid battery or a rechargeable battery.

Small microphones collect sounds from the environment. A computer chip with an amplifier converts the incoming sound into digital code. It analyses and adjusts the sound based on your hearing loss, listening needs and the level of the sounds around you. The amplified signals are then converted back into sound waves and delivered to your ears through speakers, sometimes called receivers.

How is cochlear implant different from other hearing aids?

Cochlear implants replace the function of damaged sensory hair cells inside the inner ear. Unlike hearing aids, which mostly make sounds louder, cochlear implants may further improve the clarity of sound and enhance your ability to understand conversations. A cochlear implant provides the sense of sound by stimulating the auditory nerve directly. Unlike hearing aids, they require surgical implantation.

Who is a candidate for cochlear implantation?

Children with loss of hearing as young as 6 months old may be eligible for a cochlear implant. It is beneficial to do implantation as early as possible to expose children to sounds during the critical period of language acquisition. After implantation, they must undergo intense speech and language therapy to achieve the best possible outcome from the device.

Children are considered viable candidates when they:

• Have profound hearing loss in both ears.

• Get little or no benefit through the use of hearing aids.

• Are healthy and any medical conditions would not compromise surgery.

• Understand(when able), along with their parents, their role in the successful use of cochlear implants.

• Have support from an educational program that will emphasize the development of auditory skills.

Adults

• Individuals 18 years of age or older.

• Moderate severe to profound sensorineural hearing loss in both ears.

• Limited benefit from amplification defined by preoperative test scores of ≤ 50% sentence recognition in the ear to be implanted and ≤60% in the opposite ear or binaurally.

• Get little or no benefit from hearing aids.

• Have no medical problems that could put them at risk during surgery.

• Have a strong desire to be part of the hearing world and communicate through listening, speaking and speech reading.

Important Considerations:

• Many individuals with residual low frequency hearing can be CI candidates and can benefit from CI.

• Cochlear implantation devices can be tailored based on: passion for music, work in noisy or reverberant environments, what are lifestyle demands?

• Determine motivation to experiment with hearing aids, in both the implanted and/or contralateral ears.

How do cochlear implants work?

These implants usually consist of 2 main components:

• The externally worn microphone, sound processor and transmitter system.

• The implanted receiver and electrode system, which contains the electronic circuits that receive signals from the external system and send electrical currents to the inner ear.

External component

The microphone and speech processor are housed in a small unit that looks like a behind-the-ear hearing aid. A small wire usually links them to the transmitter, which is positioned over the internal part of the device. The microphone picks up acoustic sounds and sends it to the speech processor. The processor analyses and digitizes the signal before sending it to the transmitter. The transmitter then codes the signals and sends them to the implanted receiver via the magnetic coupling.

Internal Component

The internal part of a cochlear implant includes a receiver, which is located under the skin on the temporal bone, and one or more electrode arrays. The receiver collects the signals from the transmitter and converts them to electrical pulses. It then dispatches the pulses to the electrodes that have been inserted deeply into the inner ear. These electrodes directly stimulate the auditory nerve throughout a portion of the cochlea and the brain then interprets these signals as sound.

Risks of cochlear implants

As with any surgical procedure involving an implanted medical device, there are risks. According to the FDA, they include:

• injury to the facial nerve

• infection

• dizziness or tinnitus

• numbness

• changes in taste

Manufacturers of cochlear implants

Cochlear Americas, Advanced Bionics and Med-El are the primary suppliers of cochlear implants. In the E.U., Oticon Medical also provides cochlear implants. Your ENT doctor and

audiologist will recommend the best cochlear implant for you, based on your hearing exam results and anatomical considerations.

One cochlear implant or two?

Cochlear implantation can be used if you suffer from hearing loss in one ear (single-sided) or both ears (bilateral). If you are deaf in both ears, having two implants improves the ability to locate sound and makes it easier to understand speech in noisy environments.

What are hybrid cochlear implants?

Cochlear now makes a hybrid design, which only stimulates the cochlea in the high frequencies for people who have high-frequency hearing loss. These devices work best for people with severe-to-profound hearing loss at high frequencies, yet who still have some residual, lower-frequency hearing abilities. The first hybrid cochlear implant was approved by the FDA in March 2014.

The acoustic component amplifies the natural low-frequency hearing you have, while the cochlear implant restores access to the high-frequency sounds you might not hear.

The implant has two parts: an external sound processor with an acoustic component and an internal implant.

1. Microphones on the sound processor pick up sounds and convert them to digital signals.

2. At the same time, the acoustic component amplifies the sounds you hear and sends them through the ear canal just like a standard hearing aid.

3. The digital signals from the sound processor are transferred through the coil to the cochlear implant just under the skin.

4. The cochlear implant sends electrical signals along the electrode into the inner ear.

5. Hearing nerve fibres in the inner ear pick up the signals, combine them with the amplified sounds and send them to the brain. This is then translated as sound.

What next?

Once the cochlear implant is activated, sound can be heard but the brain does not automatically make connections with meaning. Time and practice is needed to adapt and assign meaning to the new incoming sound provided by the cochlear implant, as understanding occurs in the brain. Children who have never heard before are in the process of developing a language system with the new auditory signal provided by the cochlear implant. Adults who have an established language system must also learn to attach meaning to the new signal. All recipients require immersion in an auditory-rich environment in order to reach their maximum potential. Aural rehabilitation aids the process of attaching meaning to sound.

Rehabilitation for children begins shortly after the implant is activated. The Cochlear Implant Centre requires families to commit to a minimum of one year of rehabilitation in order to maximize outcomes. One-hour rehabilitation sessions for children occur on a weekly basis. Rehabilitation for adults begins with an adult rehabilitation consultation. Individualized needs in the areas of auditory therapy, communication management and the adjustment to an auditory environment are determined. Based upon the results of this functional evaluation, the therapist will recommend a treatment plan for follow-up services, which may occur weekly or as needed.

Rehabilitation Goals and Objectives

Goals and objectives are tailored to meet the individualized needs of the pediatric and

adult patients. In our rehabilitation sessions, therapists empower patients (children and parents, adults and their support network) to understand and advocate for their personal

communication needs.

For more information

At Bangalore Cochlear Implant Institute, Dr. Sampath Chandra Prasad Rao supported by an excellent team of ENT surgeons and Audiologists provide client specific hearing rehabilitation solutions. For any information connect with us through info@bciinstitute.net.

Phone no: +91 6366888883.