Pennsylvania Ear Institute

All Things Cochlear Implant: Q&A with an Audiologist

25 February 2024

Child with a cochlear implant February 25th marks International Cochlear Implant Day, making it a great time to spread awareness about the hearing assistance these incredible devices can provide. We talked to the lead audiologist at the Pennsylvania Ear Institute, Rebecca Blaha, AuD, about everything cochlear implant-related, including how they work and whether they might be a good fit for someone with hearing loss.

What are cochlear implants? How do they work?

A cochlear implant uses electrical stimulation to pulse at a rate that will, essentially, give access to sound to someone who has significant hearing impairment. As hearing loss develops, we lose sensory receptors in the inner ear, which are referred to as the hair cells (also called the cochlea). A hearing aid uses sound as pressure (called an acoustic hearing aid), which is what most people recognize as a hearing aid. It’s trying to push sound into the inner ear to activate these hair cells, but over time as the hair cells get damaged, we may lose the ability to activate them, so we have to figure out a more efficient way of getting sound stimulation into the inner ear. At some point, if we don’t have enough hair cells present, we have to bypass them and go to the nerve directly [by way of cochlear implant]. So, [for a cochlear implant], an electrode will be fed into the inner ear and curl around the cochlear structures and then when we pulse the electrodes using an electrical current, it will pulse right along the nerve fibers so we can activate them directly. This will send a signal of sound up to the brain, and with training, the brain will learn to understand that message (or sound) as speech.

What are the benefits of cochlear implants?

Cochlear implants will give patients more access to sound. Eventually, when a traditional hearing aid becomes less efficient, it can only produce so much sound pressure. That means that we will have only limited areas of sound getting into the inner ear. This can result in a limited perception of sound or speech. With a cochlear implant, we can give an individual more frequency-specific information, so they can hear and register lower and high-frequency sounds.

Are there any drawbacks to having an implant?

An implant does not restore any aspect of normal hearing anatomy. As such, [cochlear implants] do not sound natural in the beginning until your brain has been given enough time to adapt. Some patients are surprised at how mechanical it seems in the beginning - the sound quality seems unnatural until they’re adapted. For some, the transition process can be tricky in the beginning until each individual starts to practice more and get used to it.

Who are the best candidates for cochlear implants?

We usually consider how long you’ve had hearing loss. Generally, a person who has tried a hearing aid and does not perform well with it would be a good candidate. Someone who has continually been giving the brain some sound stimulation is a better candidate than someone who may be part of the Deaf community, did not wear a hearing aid, and used manual communication like sign language—their auditory system has not been stimulated so to implant them they will take longer to rehab and regain access to usable sound. For someone who's continually been using some form of amplification, those structures are a little bit more exercised so they will be more prepared for being stimulated [by a cochlear implant].
If it's a child, they can provide an implant as young as six months of age because their system is still new. They will adapt to that as their only sensation of sound and the brain will be coded to that message from the beginning. If you are very young and have not learned any speech and language, you’re a good candidate. If you’re an adult who has developed speech and language and has been able to use some form of amplification, you’re also a candidate.

What should someone expect when starting the cochlear implant process?

We would evaluate your hearing first to see the severity of your hearing loss because there is a guideline—it's called the 60/60 rule—that most implant manufacturers and experts have agreed upon. We’re looking at your sensitivity, we’re presenting a tone to you and we’re waiting for a response and looking at the lowest level that you were able to respond to.

If your hearing level is around 60 decibels or worse, then we’re going to start saying you have a severity that may not be optimally assisted with a traditional acoustic hearing aid. Then we will start looking at the severity of your hearing thresholds—we’re going to present speech to you and see how much of that speech you can repeat back. We’re looking to see if you are getting 60% or more accurate responses.

If you’re less than 60%, we will conduct some assessments with a hearing device. Most clinical facilities have some device, a hearing aid, that they can fit to you during the appointment. We’re looking at the percent of accuracy using the amplification—if the device is appropriately fit to your hearing needs, do you show a significant improvement or do you still struggle to understand any sound that it provides? We’re looking at the percentage of full words that you can repeat or how many sounds of the individual words were accurately repeated. We’re also giving you sentence tests, where we’re asking you to repeat the sentence and see how many words you get correct. Then we add a little background noise to see if you’re in a more typical listening environment and there’s something to distract you, how well do you have the ability to find the voice in the presence of that distraction? We’re looking at all these different factors to see if you’re doing fairly well on these tests with a traditional hearing aid, maybe you are a good candidate to continue with a traditional hearing aid—a nonsurgical intervention. But, if you still have significant difficulties doing any of the tasks, the traditional method of amplification is not really going to assist you. Then, we’re going to consider that the [cochlear] implant would be more efficient and we would refer you for a surgical consult.

Even if you are qualified auditorily by our testing, you still have to meet the criteria physically. A physician determines if you would be a good candidate to go through a surgical procedure. They consider if you have the appropriate ear anatomy. If you have all of the complete turns of the cochlea so that the electrodes would fit, nerve survival, if you would heal properly from surgery, etc. They will go over that and if you are approved, then they’ll do the surgery. It’s usually a fairly short surgery, I think around two hours, if not less. After maybe two to three weeks of healing, your processor would be activated and we would start stimulating.

What do patients want to know when they come in for cochlear implants?

Generally, they want to know what amount of improvement they should expect after they’re implanted, and that's hard to quantify. When you are evaluated, it should be a team approach, so your audiologist would qualify you based on your hearing level, but there should also be a discussion of what your expectations and motivations are and the level of familial support.

Do you have a good core network in place to help you go through this process of adaptation and training?
You may find that you need speech assistance to help train you to utilize the information, so a speech pathologist might be someone you might want to consult with to develop your auditory skills.

It’s more involved than just receiving the device. There's a whole process and we want to be sure each person fully understands what they are undertaking before they make the decision. A lot of times patients, thinking it's an implant, assume that it's completely internal. So, the minute I bring out my processor demonstrator and they see how large it is—because its magnetically attached and then you have an earpiece—when they see the size of it a lot of times they’re like ‘uh, oh I didn’t know what I was asking for, that's not what I wanted.'

What level of hearing restoration should a patient expect from the device?

It’s something we don’t make a lot of guarantees about. Studies have shown when somebody fails to respond effectively to a traditional hearing aid and they choose to move forward with a cochlear implant, 95% of the patients are happy with the decision. So, the subjective happiness or improvement is quite high, but when we look at studies that look at overall performance—looking at the ability of a patient to hear speech in quiet and then repeat words back on different tasks—sometimes the level of improvement doesn't look quite as stellar as people would hope. Maybe people are getting 65% understanding but with the hearing aid they were only getting 30% understanding, so the improvement is significant, but it's not 100%. Sometimes that's tricky because it will depend on a variety of factors.

How long is the adjustment period after getting a cochlear implant?

Within the first three months we see the biggest improvement in overall hearing abilities. So in the first three months you’ll go back with your provider for mapping, as we would call it, to figure out how we want to stimulate along the electrode array and to get the current levels optimized. The biggest improvement that most people get is in the first three months, and then by six months you’re pretty solidly established with the routine of use. The sound quality seems to be normalizing and your ability to repeat speech has been optimized for the majority of patients.

Will insurance cover the cost of an implant?

It really is variable across insurance plans. Different criteria are used to qualify you as an implant candidate. Medicare for older adults has a particular qualification standard where they’re looking for a very low percentage of speech understanding. As a provider, when you submit your documentation after the test results are collected you have to know the insurance guidelines to know whether your patient truly qualifies. The guidelines are usually based on the insurance plan. Depending on the plan, a lot of insurance plans support the patient for about 80% of the cost and then maybe 20% is due from the patient, but again it really depends. I can’t speak for Medicaid and other state-funded insurance, they have different qualifications.

How long do the devices last? Do they need to be updated regularly?

Internally that device should be there for the rest of your life. Internal failures of equipment are very rare. The internal device is just waiting for a signal from the external processor. The external processor is what gets updated about every five years, so when the patient receives their external processor it will operate under certain parameters based on the computer chip that is in it. Because it's outside, it's very similar to a hearing aid and that'll be updated as the technology improves. All it's doing is telling the internal electrodes how to stimulate, so you would upgrade your external processor every couple of years but [the internal portion] should stay there indefinitely.