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Cochlear Implants: What They Are, How They Work, and Who Should Get One

Megan Bilodeau, Au.D., CCC-A

Clinical Audiologist

Massachusetts Eye and Ear

Within the human ear is a snail-shaped organ about the size of a pea. This is the cochlea,

the organ of hearing. For humans to hear, sound is first collected by the outer ear and directed

through the ear canal to the eardrum. The sound waves vibrate the eardrum, and those vibrations

travel down three small bones – the smallest bones in the body. These bones push on the side of

the cochlea, which is fluid-filled, and the fluid moves from the vibration to stimulate cells that

look like hair. These hair cells send the signal up nerve fibers to our brain, where we perceive the

sound. This process makes up our normal, acoustic hearing. When people have hearing loss, they

may wear hearing aids that make the sound louder so it can better stimulate hair cells that may

not be functioning as well as they used to. For some people, hearing aids are not enough. These

people may need a cochlear implant.

A cochlear implant system is a surgical hearing device that contains two components: 1)

an external sound processor, and 2) a cochlear implant. The external sound processor is worn on

the ear or on the head. The sound processor contains microphones that detect sound and a

computer chip that processes the sound. The sound processor uses a magnet to connect to the

internal cochlear implant to deliver the processed signal. The cochlear implant uses electrodes

within the cochlea to stimulate nerve fibers directly. The cochlea is arranged by pitch, and the

electrodes stimulate different areas to match up with different pitches. This allows users to hear

low bass sounds, higher treble sounds, and everything in between. staff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436 staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436

A cochlear implant differs from a hearing aid in the way it delivers sound. A cochlear

implant bypasses the damaged areas of the cochlea, and the sound is delivered through small

electrical pulses directly to the nerve fibers. It can take time to adjust to hearing electrically

instead of acoustically. A new cochlear implant user will complete listening exercises to help

build up their brain’s ability to understand these new signals. The sound quality of a cochlear

implant also takes time to become more normal. Many people feel that the sound is robotic in the

beginning, or that people’s voices sound like cartoon characters. This is very normal at first and

typically improves over time.

Cochlear implants are intended for people who are not able to benefit from a hearing aid.

If someone has appropriately programmed hearing aids and still has difficulty understanding

speech, they may be a candidate for a cochlear implant. It is also important for potential

candidates to have a good support system of people who can help them complete listening

practice activities and adapt to their new way of hearing.

A cochlear implant evaluation is the first step in determining candidacy for a cochlear

implant. This appointment may include a traditional hearing test, as well as testing while wearing

hearing aids. This helps the audiologist determine whether a person is receiving good benefit

from hearing aids or not. A prospective cochlear implant recipient will also need to meet with an

otologist, a surgeon who specializes in ears. They will look at medical history and order imaging,

like a CT scan or an MRI, to determine if someone is a good surgical candidate.

Once someone is determined to be a candidate, they will have to choose which

manufacturer they would like to be implanted with. There are currently 3 FDA-approved

cochlear implant manufacturers: Advanced Bionics, Cochlear, and MED-EL. At this point in the

process, the candidate will meet with their audiologist again. The audiologist will help them

figure out which manufacturer might fit their lifestyle and needs the best.

Cochlear implant surgery is typically an outpatient procedure, meaning you would go

home the same day without spending the night in the hospital. The activation appointment comes

a few weeks after the surgery to ensure any swelling has gone down. This is when the external

sound processor is programmed and turned on for the first time. Many people have seen videos

of cochlear implants being turned on for the first time. It is important to keep in mind that the

implant may not sound pleasant at first. Speech is often not understandable on the first day.

Remember – it takes time and practice to learn how to hear through a cochlear implant. There are

many programming sessions that occur over the first year. Most patients continue to improve and

hear better at each appointment. While the cochlear implant process can seem long, it is worth it

for many people to regain the ability to understand speech. If you believe you or a loved one may

be a candidate for a cochlear implant, you can find your nearest cochlear implant center to

schedule an evaluation.

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