Breaking Through: Cochlear Implant Advances - Part One

Presented by Tina Childress of Advanced Bionics

This is a report on Tina's presentation at ALDAcon 2006 held in October 2006. This is part one of two parts.

Here's more coverage of this great convention.

~~~~~

I lost my hearing at age 28 in eight months. Yet I've never attended an ALDAcon before.

Bilateral implantation

Localization Cues - now that I have bilateral CIs, I can localize well enough to know where my daughter is calling from. Our brain uses the signal from both sides to get information. A good analogy is the use of an eyepatch, like when you get your eyes checked. When you use only one eye, you don't have very good depth perception, so you're not allowed to drive.

Head Shadow Effect - The head blocks sound, so if you only hear out of one ear, it's hard to hear sound coming from the other side. But in a noisy environment, that can work to your advantage. The head can block the noise you don't want to hear, so you can hear better what you do want to hear.

Binaural Squelch - This refers to the ability to focus on and listen to one speaker in room full of noise. Being able to do this requires two ears.

I had a Hearing In Noise Test (HINT) three months after I got my second implant. This is a test of ability to hear sentences, and in my test, the sentences were 10 dB louder than the noise. I scored 74% in the ear that was implanted first, 52% in the second, and 92% using both.

Binaural summation - This refers to the fact that sound perceived from two ears is perceived as louder than sound perceived from a single ear.

Candidacy considerations

The decision to get a CI has always been an important one. Now people also have to decide if they should get two CIs at the same time.

Q. Does insurance cover a second implant?
A. Some do. Talk to your CI center, because they are familiar with which companies cover a second implant.

Q. I have never had bilateral hearing. Would bilateral CIs work for me?
A. That's a question for the CI center. They would have to evaluate you.

Bilateral CIs are a big advantage when a person is trying to hear in noise. The average binaural advantage is 5 dB, which usually equates to about 30% gain in HINT scores.

Localization is important for safety, hearing in groups and finding distant sounds. I lost my car in a mall parking lot after I had bilateral implants. I activated the horn and I was able to find my car. I never could have done that with a single implant.

Unlike other hearing aid and CI microphones, our T-Mic sits right in the ear. So it takes advantage of spectral intensity cues provided by the outer ear. The outer ear also helps shield against other unwanted sounds, and it allows people to use standards headphones.

Other considerations for bilateral implantation

If you have an implant now and get a second one, your first one will probably be your dominant one for a long time. And the longer the time between the two implantations, the longer the first will be dominant. If you get them closer together in time, the dominance isn't as great and won't last as long.

For those who do pretty well with the first one, the second one may not progress as fast as the first. The differences you see may be quality issues - things will just sound better.

A voice barely heard at 10 feet with one ear can be heard at 40 feet with two ears.

Listening with bilateral implants is less tiring and stressful.

Things sound more like what we remember as hearing people.

It's instructive to compare the situation with bilateral CIs now with the situation with hearing aids in the 1970s. That's when it became common for people to use two hearing aids. Now we're going through a similar thing with CIs.

If you have questions or want to talk to a bilateral user, come by our booth and we'll put you in touch with one.

Speech Processing Strategies

Sound can be characterized by three domains, and it's important to consider all of them in a processing strategy.
Intensity Domain - We give your brain as much information as possible and let your brain do the work. Our input dynamic range is 96 dB.
Temporal Domain - We use up to 5200 hz sampling rate and 83K pps.
Spectral Domain - The HiRes120 has 120 channels.

120 spectral bands via current steering

Because we can stimulate multiple electrodes simultaneously, we are able to effectively create virtual channels, which allows to provide more frequency information. This is especially important for music and listening in noise.

This 120 channel capability is available to people implanted since the spring of 2001, because the internal device supports the required technology.

It may help some people to understand the various domains by considering a digital camera analogy.
The Temporal rate can be compared to the camera resolution (pixels). The spectral resolution can be compared to the number of colors. And the Intensity or Amplitude can be compared to the camera's dynamic range.

Harmony BTE (new processor)

Our new processor is the Harmony BTE. We have maintained accessory compatibility with the Auria, so all of your Auria accessories will work with the Harmony. It features:
- Smallest, least conspicuous headpiece
- Durable processor engineered to withstand rain, sweat, and moisture
- Only processor that supports 120 channel
- Built in Telecoil
- Improved battery life - 50% better - up to 18 hours on a battery
- Built in multi-function LED status indicator, which provides a lot of information, including an indication of how much battery life remains