Cochlear Implants Emerging Technology

ALDAcon 2003 included presentations from each of the three main companies that provide cochlear implants (CIs) in the US. We'll be presenting articles on each workshop over the next several weeks. This article covers the presentation by Cochlear Corporation, makers of the Nucleus CI.

The workshop entitled "Cochlear Implants Emerging Technology" was presented by Christine Writer of Cochlear America.

Christine began by determining the demographics of the audience, which consisted of several Nucleus 22 users, several Nucleus 24 users, and several people who are considering a cochlear implant.

Cochlear's mission is to improve the quality of life for people with hearing loss. They have made a commitment to life-long support for all of their implant recipients. Cochlear is the only publicly held company among the "Big 3" cochlear implant companies.

Cochlear embraces the following three important design philosophies:
1. Good science - We make every effort to ensure that our procedures and devices are safe. We don't bring a product to market until it's ready.
2. We make a lifetime commitment to our clients. We will continue to support the products that people are using.
3. Synergistic design - biology and physiology drive our design. We're cooperating with the body rather than fighting it.

Patient performance with cochlear implants has steadily improved. The open set sentence score has increased from 12% in 1981 to 90% in 2001. We expect the ADRO and Whisper technologies to improve performance beyond 90% in the near future.

Nucleus 22 Update

The ESPrit 3G behind the ear (BTE) speech processor is now available for Nucleus 22 users. This is a 3rd generation BTE processor. It includes a built-in telecoil, which may be used with or without the microphone. It also contains a whisper setting, which increases the amplification of the unit. That's very useful when listening to people who don't speak loudly. But it's not a panacea, because it amplifies other sounds, as well.

The ESPrit 3G includes access to Phonak MicroLink FM systems through a receiver that attaches to the bottom of the 3G. We have an exclusive agreement with Phonak. The 3G weighs just 12 grams, and comes in 12 colors. The average battery life using 3 zinc-air batteries is 64 hours, with a range from 32 to 103 hours.

Nucleus 3 System Update

The Nucleus 3 has a titanium casing cushioned in silastic elastomer, which provides industry-leading reliability.

It uses a self-curling perimodiolar array, which matches the shape of the cochlea. The array is held straight during insertion with a stylet. Once in place, the array hugs the interior wall, which is where the hearing nerve fibers are. In contrast, a straight array sits near the lateral (outside) wall, which is farther from the hearing nerve fibers.

The atraumatic design of the electrode array minimizes damage to residual hearing.

The Nucleus 3 System includes Neural Response Telemetry (NRT), which can determine how the nerve is responding to the implant. This is especially helpful for children or for someone who's been deaf for a long time.

With the magnet removed, the system is MRI compatible up to 1.5T tesla, which is the standard MRI strength.

The Nucleus 3 supports a wide range of custom speech coding strategies, including the Advanced Combination Encoders (ACE) strategy, which is the only dynamic adaptive sound delivery system.

Cochlear implant surgery has become so routine that it is now done on an outpatient basis. The average surgery is 1.5 to 2 hours, and the patient goes home the same day.

One of the things we're working on is the Nucleus 24 Contour Advance, which is a contour electrode with a soft tip. This array will produce minimal cochlear trauma, because minimum force is applied on the outside wall. But it also ensures consistent array placement next to the hearing nerve. This system is not yet in clinical trials.

Another product that's in the works is the Nucleus 24 Auditory Brainstem Implant (ABI), which is intended primarily for people with Neurofibromatosis Type 2 (NF2). Treatment for that disease includes severing the auditory nerve, which eliminates the use of a cochlear implant. So a device is implanted directly into the auditory brainstem. Performance with this device is not as good as with a cochlear implant, but it does help with speechreading. It can be implanted at the same time as the tumor removal that severs the auditory nerve.

Future Technologies

Cochlear currently has 222 research projects, including:
- More electrodes (which is tough with only 25 mm to work with in the cochlea)
- Safer, less invasive surgery
- Improved music appreciation
- A totally implantable cochlear implant
- A hybrid systems which uses a hearing aid for low frequencies and a cochlear implant for high frequencies
- Bilateral cochlear implants
- Higher reliability
- Improved power efficiency

The goal for the use of more electrodes is to produce an implant that uses hundreds of channels to mimic the performance of the normal ear. We are researching thin film technology to increase the number of electrodes in an implant and to automate the process of building an array. Current electrode arrays are made by hand; it takes a person about a day to make one.

The rationale for the hybrid system is that many people have quite good low frequency hearing and very poor high frequency hearing. Because the hair cells that respond to high frequencies are near the entrance to the cochlea, it's possible to insert a short array to stimulate the high frequencies, while leaving the low frequency hair cells (which are deeper in the cochlea) undamaged. We currently have 15 patients using this hybrid system, which includes an implant with only six channels.

Another research project is the use of bilateral cochlear implants. Current research indicates a number of benefits from bilateral implantation, including much improved ability to determine the source of sound. We are currently working on cost/benefit analyses to help persuade insurance companies to cover bilateral implantation.

Another experimental system that we use for research has all the electronics outside the body and a direct connection to the electrode array. The reason for this configuration is that we can easily do all sorts of experiments with different processing strategies, simply by changing external components.

We're also working on a totally implantable device (TIKI). There are some obvious advantages to having the entire device implanted. Some of the challenges include how to perform upgrades, how to charge the batteries, battery replacement, where to place the microphone (and how to ensure it doesn't pick up the heartbeat, breathing sounds, etc.)