Cochlear Implants: Past, Present and Future
Carolyn Smaka: It’s nice to have Anne Beiter from Cochlear here today. Anne, can you tell me about your professional background and how long you have been with Cochlear?
Anne Beiter: I am an audiologist and speech-language pathologist. I started working clinically with cochlear implants early in my career, and had the opportunity to be involved in some of the research at Stanford University led by Dr. Blair Simmons. I joined Cochlear as a clinical specialist in 1986, a few months after Cochlear gained its first FDA approval for post-linguistically deafened adults in late 1985. Once Cochlear gained FDA approval, there were many hospitals and clinics interested in beginning cochlear implant programs and my role was in educating professionals on the Nucleus 22 Cochlear Implant System.
Cochlear began a pediatric multi-center clinical trial in 1986 and received FDA approval in 1990 for children that were 2 years of age and older. More training specific to pediatrics was required after that approval, and I was very involved in clinical education and services.
Over the last several years, my role has evolved into a global clinical position, where I have the opportunity to interact in cross-functional ways, both in various regions around the world as well as with our global corporate office in Sydney, Australia.
Carolyn: Given your experience with cochlear implants, can you provide an overview of the changes these last 25 years, and where you think the future of the technology is going?
Anne: Certainly. There have been so many advances in the sound processing for hearing performance as well as in the sound processors which have gotten much smaller making them easier to wear for the children and adults. The first multi-channel implant was the Nucleus 22 system; it required recipients to wear a body worn sound processor that was similar to the old body style hearing aids. The early Nucleus 22 systems provided intra-cochlear bipolar stimulation, the implant did not have any extracochlear ground electrodes, which would allow the type of monopolar stimulation that we typically use today. The evolution in integrated circuit technology and electrodes has permitted either monopolar or bipolar electrical stimulation; these as well as additional technological enhancements have helped Cochlear make the processor much smaller to fit behind the ear. Also, these changes have led to advancements in sound coding strategies that have improved outcomes for recipients.
The first coding strategy in 1986 was a speech feature extractor, focusing on specific parts of the signal. It extracted the fundamental frequency for stimulation rate, and the first and second formants of the voice for place coding in the cochlea. Based on these features, specific electrodes across the array were chosen for stimulation. There was far less information provided about the acoustic signal and therefore less electrical stimulation of the cochlea than what we can deliver today.
The big breakthrough came in the 1994 when Cochlear received FDA approval for the spectral peak or SPEAK strategy. It divides the spectrum into 20 filter bandwidths. The strategy continually samples the outputs of those 20 filters and selects the six-eight filters that contain the largest amounts of energy (called maxima); selection of maxima varies over time and depends on the spectral composition of the signal. Then six-eight electrodes are stimulated sequentially in each analysis cycle.
The electrodes along the array are assigned tonotopically to filters, just like the cochlea. That is the electrodes at the apical end of the cochlea are assigned to low frequency filters and then electrodes are assigned to progressively higher-frequency filters moving to the basal end. This strategy provided greater information about the spectral composition of the speech signal than speech feature extraction, resulting in improved hearing outcomes for recipients.
Starting around 1995, work began on a new implant integrated circuit. After a clinical trial in the U.S., the FDA approved the Nucleus 24M cochlear implant in 1998. This was the first Nucleus implant that had 2 extracochlear ground electrodes in addition to the 22 intracochlear electrodes. That allowed the use of monopolar stimulation and along with the new integrated circuit, the development of two new coding strategies. One is called continuous interleaved sampling (CIS), developed in the late 1980s by Blake Wilson (Duke University), which stimulates on a fixed set of electrodes or channels and uses faster stimulation rates; it has also been used in other implant systems. The other strategy, called advanced combination encoder (ACE), uses components of both the SPEAK strategy (i.e., selection of different maxima based on spectral content) and the CIS higher rates, thus providing stimulation across all the electrodes within the cochlea at higher total stimulation rates. In September 2013, Professor Graeme Clark (Emeritus, University of Melbourne), Ingeborg Hochmair (MED-EL, Innsbruck) and Blake Wilson (Duke University) were honored with the prestigious Lasker-DeBakey Clinical Medical Research award for their development of the modern cochlear implant.
The ACE strategy moved recipients to a higher level of listening performance. Because speech understanding continues to improve, we have seen a broadening of indications for both adults and children. During this time period of coding strategy advancement, Cochlear also developed the first ear-level sound processor in 1998, which was part of the Nucleus 24 Cochlear Implant System. This was Cochlear’s second-generation implant system that brought together some new sound coding strategies, a new implant that allowed the coding strategies to be fully realized, and the first ever ear-level processor available to recipients as well. That first ear-level processor was made backwards-compatible to the original Nucleus 22 cochlear implant.
The introduction of ear level processors also allowed Cochlear to take advantage of dual microphone technology. Starting in 2005, our first generation of SmartSound processing was released. SmartSound algorithims, specifically SmartSound Beam and SmartSound zoom, were designed to improve hearing performance particularly in noise where we know hearing aid and cochlear implant users have the greatest difficulty. I am excited to tell you that in August Cochlear received FDA approval for the 9th generation Nucleus sound processor, called Nucleus 6. The Nucleus 6 provides continued advances in both design and technical capability. Specifically the Nucleus 6 includes new features that make it easier to use such as new wireless remote options, AutoPhone and AutoFM features and the first of its kind 2.4 GHz wireless connectivity that will be available with a simple software upgrade to the processor. The Nucleus 6 processor also contains a new microchip that offers the first data logging capability in a cochlear implant as well as the capacity for future upgrades in SmartSound processing.
Carolyn: You mentioned that the advances in technology have led to improved performance and outcomes. What does that mean on a functional level?
Anne: It is common now for implant recipients to have conversations on the telephone. This was something that was difficult in the past. The newest algorithms include input processing, which mitigates some of the problems of listening in background noise, and is also helped significantly by directional microphone technology. Additionally, we can employ focused directionality with a beam former that is either a fixed or adaptive beam former; it provides better understanding in difficult situations such as speech in noise or listening from a distance with a compromised signal-to-noise ratio. Listening in noise has always been difficult for anyone with hearing loss, but it is particularly difficult for those with cochlear implants. These new sound processing algorithms that are part of the implant programming have been beneficial to both adults and children. Listening in noise is one of the most important improvements.
Carolyn: You mentioned that the indications are broadening for both adults and children. Who is a candidate for a cochlear implant today?
Anne: Since 2000, children as young as 12 months of age with profound bilateral sensorineural hearing loss are candidates by Cochlear’s FDA approved indications. Children 12 to 24 months of age must have profound bilateral sensorineural loss with limited to no benefit from amplification. Children 2 years of age and older can have more residual hearing. The indication for these children is severe to profound hearing loss with limited benefit from amplification as demonstrated by a score of less than or equal to 30% on a speech perception test such as the Lexical Neighborhood Test (LNT) for children who can take speech perception tests. So the indication has decreased from 2 years to 12 months, and there has been a broadening of the audiological indication in terms of who could benefit from a cochlear implant.
In 2000, the adult indication was also broadened to include individuals with moderate to profound low-frequency hearing loss and profound mid- to high-frequency hearing loss. They may have functional aided low-frequency hearing, and that has been quantified as an aided speech recognition score on sentences of up to 50% in the ear to be implanted, and up to 60% in the best bilateral aided condition. The indication is for individuals 18 years of age and older, and it includes both pre- and post-linguistically deafened adults. There is no upper-limit age restriction for adults. There is good evidence in the literature of the benefits that older adults receive with a cochlear implant. As you know, there is heightened interest at present regarding how we can maintain adults’ cognitive functioning as they age. Certainly, providing useful hearing may be one of those factors. Perhaps adequate hearing may help slow down the process of cognitive decline that we observe in some older individuals. We can expect more research in this area.
Carolyn: That would certainly make sense. To go back to pediatrics for a moment, we know that normally-developing children with typical hearing have many important speech, language and auditory skills by 12 months of age. What is the reasoning behind the 12 month indication?
Anne: The 12-month indication is the result of the multi-center clinical trial that was designed to evaluate the safety and efficacy of the Nucleus 24 Cochlear Implant System for children as young as 12 months. We did not, in that study, include children younger than 12 months. Therefore, that is the approved FDA indication. The trial occurred in the late 1990s, about the time when universal newborn hearing screening was introduced but not fully implemented across the U.S. At that time, the diagnosis of profound hearing loss often did not occur as early as it does today. Today, many children have been diagnosed in the first few months of life and have received appropriate early intervention with amplification and habilitation based on the family’s desired method of communication. If children are not making adequate progress with hearing aids, then they are ready to proceed with a cochlear implant at their one-year birthday.
If we know the hearing status of an infant early in life, audiologists can make sure that the child is well-fit with amplification and can obtain all the behavioral information necessary for both ears. The goal is to provide early intervention and support that is most appropriate as soon as possible in order to avoid the speech and language delays you are talking about. With early intervention, we can monitor if the child is making the necessary and expected progress with amplification. Based on research in the literature, children who are implanted between 12 and 18 months of age without other factors that may contribute to developmental delay will often be ready to go to kindergarten with their typical-hearing peers. That is absolutely fantastic. These children usually show speech and language growth on par with their hearing peers. There is solid data in the literature indicating that many children who are implanted early can catch up to their typical-hearing peers for academic achievement as well as speech and language development. These are very promising studies.
Carolyn: Yes indeed they are. Are the criteria different in other countries?
Anne: Yes. The criteria may vary in other countries, depending on the regulatory bodies. Some but not all countries follow FDA guidance. It is a fact that children younger than 12 months are more routinely implanted in European and other countries.
Carolyn: What future trends do you see in cochlear implantation?
Anne: Because we have electrode arrays that are designed to be minimally traumatic to the inner ear, we expect to see broadened implant indications. Individuals with low-frequency residual hearing can be successful with a cochlear implant and a hearing aid. Surgical techniques continue to improve and we will see more hearing preservation in the implanted ear. We will have integrated processors where signal processing provides both electrical and acoustic-aided hearing in the same ear. These hybrid devices can be combined with a hearing aid in the contralateral ear. Audiologists will treat both ears, depending upon the specific needs of each person.
These trends are very exciting and important because unilateral deafness is a significant handicapping condition. If you have only one cochlear implant, you still have unilateral hearing loss. We want people to take full advantage of both ears using whatever technologies are most appropriate for them, be it a cochlear implant and a hearing aid, a cochlear implant with preserved hearing and a contralateral hearing aid, or bilateral cochlear implants. We certainly will see more bilateral implants with the new electrode arrays that are designed to preserve residual hearing.
At Cochlear, we have a portfolio of electrodes. The newest commercially available electrode is the CI422, which is a very slim, straight array that is designed for minimal insertion trauma and to preserve hearing structures of the cochlea. It is longer than the Hybrid L24 electrode array, which is currently available only as an investigational device in the U.S.
Certainly, Cochlear is always striving to make the cochlear implant easier to use, for audiologists as well as recipients and caregivers. We want individuals to have as much control over their hearing in as many situations as possible, so we are looking toward automation of the sound processor. That means recipients would not have to decide if they need to change programs or volume or sensitivity. Ideally, those sorts of changes could happen automatically and seamlessly for the individual so he/she does not have to make a decision about programs, coding strategies, or listening environments. Those sorts of improvements will be designed for children, adults and caregivers. We want parents to feel comfortable and confident that their child is getting the best hearing possible in whatever listening situation he/she is in. The Nucleus 6 data logging will let audiologists monitor how a child’s device is being used even when the parents cannot be there- such as at daycare or school. This insight can be very useful to the audiologist for programming and very comforting to parents as well!
There will be changes to the types of accessories available. There will be no need to have a direct input microphone or other audio accessory connected to your sound processor. It will all be done wirelessly. Eventually, there will be a totally implantable cochlear implant. There already is one used for research purposes in Australia. Researchers have implanted three individuals with a fully implantable device, and they have used it for a number of years. Those individuals have been invaluable in providing important information for the engineers regarding how they can improve a totally implantable implant that could eventually become commercial reality. The engineering world is busy with projects for simplification, miniaturization and making implants even better than they are today. Cochlear regularly surveys professionals, parents and recipients regarding what they would like in the implant system, and we take all that information very seriously as we develop new systems for individuals with hearing loss.
Carolyn: That is remarkable. I wanted to touch on the hybrid system. Can you talk about the benefit for the individual to use both acoustic and electrical stimulation in the same ear?
Anne: Just to be clear, in the U.S. the Hybrid L24 cochlear implant is an investigational device and currently is not approved by the FDA. However, there are implant recipients using commercially available systems that have preserved low-frequency hearing that is functionally useful when amplified. These individuals may choose to use a commercial in-the-ear hearing aid for example. Amplified low-frequency hearing provides cues that electrical hearing today does not do a good job of delivering, such as fine timing differences and preservation of fundamental frequency information, timbre of an instrument or pitch of a voice, for example. By providing acoustic and electric hearing in the same ear, you provide a more complete auditory spectrum. The cochlear implant is excellent at providing high-frequency information, which is the part of the spectrum that is important for speech intelligibility. Most of the intelligibility comes from the electrical hearing by virtue of the fact that these individuals do not have much if any aidable hearing beyond about 750 or 1000 Hz. But, that useful low-frequency hearing helps with sound segregation, identification of the speaker in a group of people, localization, listening in noisy places, music perception and appreciation.
Individuals report that with both electric and acoustic stimulation, the quality of sound is much fuller, clearer, and natural. Low frequency hearing provides a breadth of information about the quality of the voice and suprasegmental features that pertain to emotional feelings. You get some of this in bimodal stimulation as well (hearing aid in one ear and an implant in the contralateral ear), but if you can use the preserved hearing for both acoustic and electric stimulation in the same ear in addition to a hearing aid in the contralateral ear, some data show that is the best listening condition. Listeners obtain extra information from having low-frequency residual hearing in both ears.
Carolyn: I want to ask you about the Hearing Hub in Australia where some of the research on cochlear implants is being conducted.
Anne: The Hearing Hub opened in late April, 2013, and it is the most amazing place in the world for hearing research, in my opinion. It is an innovative partnership between several entities in Australia. It is centered at Macquarie University, and the partners include Cochlear, Australian Hearing, the Hearing Cooperative Research Center, which is a collaborative arrangement of many research entities, the National Acoustics Laboratory, The Sydney Cochlear Implant Center, which is the largest implant center in Australia, and also the Shepard’s Center, which is an institution that provides aural rehabilitation to infants and children who use hearing aids or cochlear implants, along with supporting their families.
The idea is that these groups work together collaboratively in research and education in audiology and speech-language pathology. There are also cognitive and language scientists, as well as psychologists working there. It brings together these dynamic forces to improve the technologies and services we can offer to individuals with hearing loss. There will be a lot of research and basic science taking place there, too. It is truly remarkable.
Carolyn: Anne, one of your colleagues referred to you as “a leader who has been a driving force behind the advancement of cochlear implant technology and its incorporation into audiology practice”. I am honored to have been able to tap into your insight about cochlear implants today. Thank you for your time!
Anne: It’s been my pleasure. Thank you for the invitation to speak with you today.