I first heard the term “Hybrid cochlear implant” when I met David Dorsey (his interview also appears in cochlearimplantbasics.com ) in 2017. He had enough residual hearing that he was investigating these devices.

A hybrid, as the name implies, combines a cochlear implant to assist those missing frequencies along with a hearing aid to help the natural acoustical ones.
It was David who mentioned Dr. Bruce Gantz as the expert in hybrid cochlear implants and he was willing to travel from Florida to Iowa for the surgery.
I interviewed him not long after his activation in 2019. In 2021 he returned to Dr. Gantz to receive his second hybrid for his other ear.

Dr. Gantz has been in the field of cochlear implants for four decades. All the way from the pre-FDA approval days to the most recent advancement, robotic cochlear implant surgery. He explains why robotic surgery is the key to better retention of residual hearing.

Dr. Gantz took time from his busy schedule to sit down with me to talk about the history of his involvement with cochlear implants, his specialty and the exciting development of robotic surgery and his vision of the future.

Transcript

Richard:
Cochlear Implant Basics is a site for candidates and their families and friends. If you have been told you qualify for a cochlear implant, these podcast interviews tell how receiving a cochlear implant can be a life changing experience. You will meet recipients who face a hearing loss and the hearing aids could no longer provide comprehension of speech or music. They faced growing isolation, inability to socialize, or compete in the world of business. The joy of music disappeared. They explained how receiving a cochlear implant changed their lives. Welcome to Cochlear Implant Basics. A reminder, Cochlear Implant Basics is not sponsored by anyone nor is it offering medical advice. Please consult your own healthcare provider.

Richard:
Good morning. We are talking this morning to Dr. Bruce Gantz, and I’d like to start if you give me your name, the date and the city that you’re in.

Dr. Bruce Gantz:
My name is Bruce Gantz. This is November 16th 2021.

Richard:
And what city are you speaking from?

Dr. Bruce Gantz:
I’m in Iowa City, Iowa at the University of Iowa.

Richard:
Terrific. I’m so glad you sat down to talk with me this morning because I have a lot of questions about hybrids. Give me a little bit of background how you got into the field and where you are today?

Dr. Bruce Gantz:
So I’ve been practicing for over 40 years. Originally when I went to medical school, I was interested in cranial facial surgery and cleft palates, and I thought that’s something that was very interesting and it led me to otolaryngology. And lo and behold, I found out that the ear and neuro-otology was really much more exciting than dealing with patients with plastic surgery issues. And so I’ve been fortunate throughout my career to train at outstanding institutions. The University of Iowa and Dr. Brian McCabe was an outstanding otologist, neuro-otologist. And then I was able to train in Switzerland with Professor Ugo Fisch at the University of Zurich, who was an extremely innovative skull-based surgeon. And that’s where I really started to explore cochlear implants more.

Dr. Bruce Gantz:
During my residency, I was sent to Bill House by Dr. McCabe to learn how to put in a single channel cochlear implant. And I spent two weeks in Los Angeles meeting with Bill and Derald Brackmann, and a number of the other people, and Laurie Eisenberg and people that were involved in the cochlear implant team at that time. This was in 1979. And so we put in our first cochlear implant at the University of Iowa in 1980, in the spring of 1980.

Richard:
Was it FDA approved at that time? Or you were on the outside of it?

Dr. Bruce Gantz:
That was on the outside of the FDA. The FDA did not have a lot of control of implants at the time. And I can tell you about an experience bringing back implants in my suitcase from Europe, in which the FDA, they really weren’t that interested in implants at that time. It was really a group of individuals in different centers that were really developing cochlear implants. And I learned in Europe about the Vienna implant, which became MED-EL. I met Ingeborg and Erwin Hochmair in 1982. And I met Kurt Burian who is the surgeon that actually put the devices in, and I watched him do that. I went to Paris and I met Chouard and watched him place different electrodes in cochleas drilling individual holes, and then saw these patients. I met Bonfi who was another surgeon in Europe, Douek in London.

Dr. Bruce Gantz:
So, I had quite an exposure to different individuals. And I learned that we were not going to build a new implant at Iowa. But one of the opportunities at the time were to do some uniform measurements of outcomes in these patients. And that’s how we evolved as a center where we developed some testing strategies with Dr. Richard Tyler, who is the audiologist at the time with us, and we developed the Iowa protocol. And we then started to apply for research money through the NIH. The first time that we applied, we were summarily dismissed. We learned a lot about grantsmanship, and they brought me onto a committee in the Neurology Institute to look at clinical trials. And we then developed a system that we have been able to continue to parlay through seven five-year cycles over the past 36 years. That is how I have gotten involved with cochlear implants.

Richard:
Your cycles of grants obviously led to advancements in every step of the way. And I think what the listeners are interested in right now is how you got involved in the hybrid cochlear implant. If you could explain that to us and how you got involved in that.

Dr. Bruce Gantz:
Well early on, we were only implanting individuals that were so profoundly deaf that they couldn’t even hear themselves talk. Many of them had been deaf for 40 to 50 years.

Richard:
That would be me. That would be me.

Dr. Bruce Gantz:
Yes. And we started exploring different criteria. A group of us actually felt that individuals that had more residual hearing and less duration of deafness, which was one of the issues that we were exploring at the time, actually did better. And so we started thinking about ways in which we could potentially expand the criteria to people with a little more residual hearing. At the same time, I had become involved with Graeme Clark’s group in Australia and Cochlear Corporation. We were the first people to actually put in a multi-channel cochlear implant in the United States outside of Melbourne, Australia in 1983. That was almost 40 years ago. And so we’ve had a good collaboration with them over the years. And I brought this concept to them to explore. And we actually designed an electrode in 1998 in which it was going to be shorter because my objective was to try and do as least damage as we could in the inner ear. And I knew that Bill House and his team had used single channel implants in a few patients to suppress tinnitus.

Dr. Bruce Gantz:
They were able to do that in some patient and they preserved some residual hearing. These were not deaf patients at the time. And so, I thought originally that we would use a six-millimeter implant just like Bill House, multi-channel. We designed it with six channels, and we got FDA approval in 1999 to actually implant the patients. We implanted three patients with a six-millimeter device, and we learned some very interesting things. First of all, we were able to preserve residual hearing in all three. We were able to preserve not only their level of identification of pure tones, but we were able to preserve their residual acoustic discrimination. And so that was really an eye-opening experience for us. It’s better to be lucky than good, right? And we turned these patients on. And what we found was that it was very high frequency because it was very much in the first few millimeters of the cochleas, and these patients got some benefit out of it.

Dr. Bruce Gantz:
But they were disturbed about the high frequency pitch that they were perceiving in this area, because we were probably at 20K to maybe 8K in the area that we were stimulating. So, we went ahead and stopped that. And we got permission to go with a longer device and we went 10 millimeters, and we put the electrodes a little bit more apical so that we got past this first four to six millimeters of very high frequency area. And fortunately, we did pretty well with that device. The S8 was a device that was the first hybrid that we actually used in a clinical trial of about 80 patients over a long period of time. And I can tell you that I still have some of those patients that were implanted in 2000. It was in 2000 that we implanted the 10-millimeter device that still have residual acoustic hearing today 20 year later. So the idea evolved out of that experience. We were not the first to publish this data.

Dr. Bruce Gantz:
We did not publish our first three cases because we wanted to wait and see what happened. Unfortunately, there was someone else in Europe that published one single patient that beat us to it. But that’s life. Anyway, we have continued to explore acoustic plus electrical processing. What we identified with these patients early on was the fact that when you preserve that low frequency hearing, the real advantage was that you improved your hearing in noise, because what that low frequency did was allowed the listener to discriminate the vocal cord vibration or the fundamental frequency from the surrounding noise. And with electrical processing, we can’t do that very well.

Richard:
I have a question for you right now. You were looking at candidates, how much residual hearing did they have? Is there a percentage wise basis that you decided to do the hybrid?

Dr. Bruce Gantz:
So, at the time, we were looking at people that had low frequency hearing around 60 decibels in the lows, 125, 250 and 500. And above that, they could be profound, 80+ dB. We found out that we could preserve acoustic discrimination by not going very far into the cochlear. There were two other advantages. So that first is hearing better in noise. And our patient populations are much better in acoustic plus electric than they are electric only in hearing in noise. And they also get the perception of melody and music because of the low frequency information that is still there. And so that was a real advantage to our patients, so they could hear music and appreciate melody. The third advantage was that if you preserved residual hearing in both ears in the low frequency, your spatial hearing where your localization was preserved, we found out early on in our experimental work with binaural implants that people that have two implants can actually tell where a sound is coming from.

Dr. Bruce Gantz:
Whereas if you have one implant and some residual hearing acoustically on the other ear, you have no spatial orientation. And that was an eye opener to us that if you preserve low frequency in both ears, then they had spatial orientation again, that they could localize sound. So those were the three real advantages of preserving low frequency hearing. Unfortunately, our electrical processing algorithms in all of our cochlear implants do not provide that low frequency fine structure that is important to hearing the differences in noise and melody. And we’ve never been able to develop algorithms that are really able to do that. Now, we have a few people that are real stars that use cochlear implants with electrical processing and can experience music and understand music. I have a woman who actually was a piano teacher, and she judges piano competitions with a cochlear implant in place, which blows me away.

Dr. Bruce Gantz:
But it’s possible in some patients. So that’s how we got involved with the hybrids, and we are continuing to explore that. We know that it takes time for people with acoustic plus electric hearing to actually get that centrally and fuse that information that initially when they’re programmed, they do not like it. And because of that reason, we have many audiologists and people in the implant world that don’t believe that this is very worthwhile. But I can tell you-

Richard:
That misconception is something I fight all the time. That’s a number one issue of a misconception that keeps people on the fence. So, it annoys the hell out of me.

Dr. Bruce Gantz:
So unfortunately, once you put an implant in that destroys the residual hearing, you’re not going to ever get that back. And so, we have to develop strategies that were better at preserving low frequency. I can tell you that our 10-millimeter devices are the best. We have about 75 to 80% preservation of acoustic discrimination with those shorter devices. The longer devices are not quite as good.

Richard:
I have a question at this point, the first three you implanted with the very short device that were annoyed by the high frequency, did you re-implant those people? Or do they just live with it?

Dr. Bruce Gantz:
No, we actually did explant two of them with actually standard devices, because we didn’t know if we could keep the residual acoustic hearing.

Richard:
Part two of my question is this, you’re talking of the length of the electro array. Now, some of the companies claim they have the longest array possible, and people are confused sometimes if the longer array helps them better with discrimination or just the overall experience. Is there something in the longest array that helps? I understand, yes, probably not going to preserve residual hearing if you go that long. What’s your experience in that area?

Dr. Bruce Gantz:
So, I will tell you that the brain has the capability of transferring frequency information so that we can accommodate to the place pitch, okay? And the cochlear is tuned like a piano. The highs are in one area, the lows are in the other. And we know that if you want to get better pitch matching initially, if you put a longer electrode in, the patient will be more satisfied. And I will tell you that when we are doing patients with single-sided deafness and they have pretty normal hearing in one ear and you put the implant in the other ear, we found that a longer electrode allows them to adapt more quickly, okay? Now, we also know that in the patients with shorter arrays that are preserving residual hearing that you can adapt to the place pitch offset of up to four octaves. You can transfer that over time. But it’s not immediate. It may take six months to a year to get that transposition.

Dr. Bruce Gantz:
But the brain can learn that there’s new regions being stimulated with higher frequency that can be perceived as low frequency. You can put the low frequency information in a high frequency area and the brain will then accommodate to it. But it doesn’t happen overnight. And that’s part of the issue with the hybrid implants in patients that they have to know that they have to accommodate to this place pitch shift. And it takes a little bit of time. But once you get it, it’s very beneficial.

Richard:
Is there a special rehab patients have to do?

Dr. Bruce Gantz:
We send them home with some recordings to listen to. We have them listen through their implant only for periods of time during the day to help reorganize this information. But it takes time and individuals differ on how much time it takes. And it probably has something to do with their cognitive function. We all don’t learn at the same rates and that’s part of the variability and performance of all of these devices. We have some stars in every device and we have some failures. Or not failures, but not as good in every device.

Richard:
Okay, let’s not talk about failures here.

Dr. Bruce Gantz:
No.

Richard:
[inaudible 00:18:51] I have reminded people that there are no guarantees in life, but the vast, vast, vast majority of cochlear implant recipients get optimal results, but life does not have any guarantees.

Dr. Bruce Gantz:
You’re exactly right.

Richard:
I’d like to ask you, a candidate comes to you, you’re doing the qualification to see if they’re a candidate. And I believe from my experience of talking to hundreds of candidates, when the word hybrid comes up, I say, “I don’t know how they qualify you for that.” Do you ever discourage somebody from going along with the hybrid? Can you talk about the qualification process?

Dr. Bruce Gantz:
Sure, okay. So, we know that when we put in an implant in the inner ear, we lose about 15 decibels in pure tone thresholds. And it probably has to do with the mechanics of the traveling wave in the inner ear. Some people don’t have that as much, some people have more. So, we figured that we want to start with someone that has pretty good low frequency and not somebody that has marginal low frequency. And you have to realize that there’s another concept we haven’t talked about, and that is functional and non-functional acoustic hearing. So, this concept evolves out of the fact that when you amplify acoustically, there are certain limits that the ear has. And somebody that has about 85 decibels of low frequency hearing in the 125, 250 and 500, if you amplify them as much as you can amplify them with a hearing aid, they’re not going to get any information. So that functional ability, it’s better if you have somebody at above 80 decibels with their residual hearing.

Dr. Bruce Gantz:
So, we want to start with people better than 55 decibels in the low frequencies. If we lose 10 to 15 dB, you’re down to maybe 70, and we can amplify 70 with an acoustic hearing aid. If you don’t have that, then we discourage using the hybrid because we’ve tried it in people between 55 and 80 and we find that we can’t amplify acoustically if we don’t have the drivers to use that residual acoustic hearing. So that’s how we would help make that decision.

Richard:
Some surgeons leave it to the candidate to choose which company based on the implant array. How do you choose the array you’re using with the patients because people ask about that all the time?

Dr. Bruce Gantz:
Well, I will tell you that three companies that are out there right now provide a pretty good product. I mean there have been missteps by all three companies. They had issues and recently the latest issue has come with Oticon, which just trying to get started in the United States. And they had a recall. But every one of the companies, Advanced Bionics, Cochlear Corporation, or the Nucleus device, and MED-EL have all had issues over time. So, in actual fact, if you have a standard cochlear implant patient, you’re not trying to do anything special and you’re not concerned about preserving residual hearing or something like that. All three devices provide an average improvement in word understanding to around 50% word understanding, 50 to 60% word understanding, with an electrical only a processing.

Dr. Bruce Gantz:
When we are talking about hybrid or preserving residual hearing, sometimes we are asking patients to participate in certain research projects that we do. And one company may have a device or a design that we are more interested in exploring questions, and we will ask them if they would participate in this research. And so I will tell you that right now, you toss a coin in the air as to the reliability of these devices now in the longstanding lasting of the three companies that are out there. So, I can’t tell you that one company is better than the other. Sometimes, the audiologists like the interface and the setting of the device with one company versus the other, and the next company leapfrogs them. And we now are interested in questions about measuring impedance or the amount of current that is being able to be measured through the device and in the cochlea so that we can look at the long-term residual hearing.

Dr. Bruce Gantz:
We think that measuring impedance remotely with a patient at home and through their telephone, we might be able to tell them if things are changing in the inner ear that maybe they need to come back to the center and we will try to do some things that might change that. So, there are all questions that we are addressing that may be different than a cochlear implant group that is just putting in cochlear implants that are not asking the research questions that we’re asking.

Richard:
My question was really more not toward the reliability, but about the differences in the ability to hear. What you’ve answered, the new advancement and remote monitoring is very exciting.

Dr. Bruce Gantz:
Yes.

Richard:
But I’m most excited about the article I read about you recently of the robotic surgery for cochlear implant. And I’m sure my listeners are going to be hanging onto every word you’re about to tell us.

Dr. Bruce Gantz:
So Marlan Hansen is a faculty member that is now the head of the department. I stepped down as the head of the department in July and Dr. Hansen now became the department head at the University of Iowa Carver College of Medicine. So Marlan and I worked together for the last 20 plus years. He was actually a resident in our department and then went out to the House group and trained in neurology and came back. And he had another one of our residents who was an engineer and was one of our research residents spending seven years instead of five years in the residence, Chris Kaufmann developed a strategy to implant a cochlear implant at a very slow rate with a motor or a robot. And so, this device is called IOTA-Soft, the company is iotaMotion. So Marlan Hansen and Chris Kaufmann developed this company as a spinoff because they got a small business administration grant from the NIH to develop the company. And so, they had to develop the company.

Dr. Bruce Gantz:
And just in the last month, we got FDA approval for the robot IOTA-Soft. So, we did a clinical trial here with the motor and we implanted, I think it was 15 patients, and we had really good results. We did not try to preserve hearing with these. It was just the concept of safety and efficacy of implanting. This is a disposable robot that is a one-time use. And so, it didn’t have to go through the rigors of implantation that the FDA requires of years and years of trials, because we were not implanting anything. And so, the advantages of this robot are that we can place the implant into the cochlear at 1/10th of a millimeter per second. You can hardly see it move. And Marlan and Chris Kaufmann did some animal experiments demonstrating that when you are putting the electrode in by hand, it’s jerky, even the best surgeons. I’ve been doing this for a long, long time, and my ability to put the device in very slowly is not as good as the robot.

Dr. Bruce Gantz:
And so, what they determined was that when you implant this device slowly, there’s less damage to the lining of the inner ear on the inside called the endosteum. And so, the inner ear is protective of the brain and this endosteum layer on the inside of the inner ear, if there’s an infection, sometimes it ossifies to protect the brain from an infection getting into the brain because there is a connection between the inner ear in the brain. So, trying to do the least amount of damage to the endosteum is really important when you’re putting in these devices. We try to put them in slowly, maybe over a 10-minute period. But when you’re doing it with a robot and it’s just constantly going in there so slowly that you can hardly see it move, it’s doing the least amount of damage. And so that’s the objective in using the robot. We are about to start now with some patients now that we have FDA approval with some patients that have residual hearing.

Dr. Bruce Gantz:
And we’re hoping that using the robot plus we also have strategies called electrocochleography, which we can measure the activity of the hair cells we’re putting in the implant. And we know that if we maintain a certain response that we are probably not touching the basilar membrane and where the hair cells are, and we’re probably doing less damage. So, the combination of using the robot with electrocochleography I think is going to help us improve our rates of preservation of low frequency hearing, and I’d like to get to 95% preservation of hearing a year down the line. And I think if we did that, then people would be much more apt to move forward with preservation of hearing.

Richard:
I agree with you, and I’ve just marked it in my calendar interview you a year from now. So, we can do a follow up at that point. Like I said, this is very exciting news. My mission from the beginning is to get people off the fence because less than 5% of the people who could be helped with the cochlear implant move forward. And the preservation of residual hearing is a very important topic. It comes up all the time. So, I’m very excited about that.

Dr. Bruce Gantz:
I tell patients and I tell my colleagues and my surgeon colleagues that you only have one chance to preserve this hearing. And if you lose it, then it’s a disadvantage for the patient. For the most part, you’re going to get an improvement in hearing in quiet, but we need more than that. We don’t live in a quiet world. It’s hard to watch TV with a hearing aid and it’s hard to watch TV with an implant if you don’t use closed captioning. Correct?

Richard:
I don’t watch TV, so I’m-

Dr. Bruce Gantz:
Okay.

Richard:
I’m not the guy to ask. I still prefer to read. Let me ask you again. Now, the future of robotic surgery is everywhere, whether it’s joint replacement, heart valves, whatever it is. Where do you see the future of cochlear implant robotics five years down the road?

Dr. Bruce Gantz:
Well, I will tell you that we’re working on some other potential issues here, and one of the reasons to use the robotic system in the first place was that if we put the implant in 10 or 12 millimeters and a patient lost residual hearing, could we move the electrode more into the cochlear to maybe take advantage of that low frequency region that you were just talking about? And we know that there’s a trade off with implanting longer versus shorter. Longer you implant it, the less likely you are likely to save hearing. But could we develop a strategy which we implant the patient maybe 10 or 12 or 14 millimeters. And then if they lose residual hearing, can we advance it? And so that’s the concept that we’re working on now. And we think we have a strategy that could allow that to be happening.

Dr. Bruce Gantz:
We know that if you have to open up the ear and the mastoid and try and advance the electrode, there’s so much scar tissue in the mastoid that it sometimes is difficult to separate the implant from the scar tissue. And so, the company iotaMotion is developing a strategy that you could do this without having to open up the ear again.

Richard:
This is absolutely incredible.

Dr. Bruce Gantz:
I think that in the future, we’re going to not wait so long to start implanting people. When they have difficulty hearing in noise and they are withdrawing from society, and we know that that can impact cognitive function, why wait for 10 years until they become an implant candidate before you implant them? When we think we might be able to help them earlier, maybe prevent, or I’m not certain that we would ever cure the cognitive decline, but maybe we will postpone it by providing the stimulus of the acoustic information that seems to be so critical for individuals to interact socially. And so I think that’s where we’re going to be going. I think we’ll continue to expand the criteria for selection. We will hopefully take people that have less than 50% word understanding and be able to provide them with 80 or 90% word understanding and may be able to hear 70 or 80% of the words in noise. Wouldn’t that be nice?

Richard:
That would be fantastic. I have to tell you, this is one of the most interesting interviews I’ve done in two years, and I really appreciate your time. Do you have anything you’d like to leave listeners with before we sign off?

Dr. Bruce Gantz:
I just think, Richard, that I appreciate what you’re doing. We need individuals like you that are supportive of implants and supportive of the technology and supportive of the growth of the technology. And we’ll continue to work here at the University of Iowa looking at the interaction between cognitive function and the implant. I will tell you that we are doing some very interesting studies about how words are formed centrally, looking at eye tracking and looking at PET scanning images of tracks of the auditory system. And we know that when you preserve residual hearing, the ability of the brain to recognize the word more quickly occurs much better if you have some acoustic information there than if you just have electrical processing. We know that for a person like you that just has an implant or two implants, you are delayed about 75 milliseconds for each word that you are hearing, because you wait until the word is said instead of trying to recognize the word when each phoneme is said or each syllable.

Dr. Bruce Gantz:
Most people with normal hearing can start to recognize the word on the first or second syllable in the word and people with implants wait 75 milliseconds after the start of the word. And what happens then is that the frontal area of the brain, the inferior frontal cortex, becomes more involved in some confusion. And we’re not using the areas of the brain in the left temporal area, in the super marginal gyrus that is used to recognize words more quickly. And so this is the work that we’re doing to try and enhance and improve cochlear implants for patients.

Richard:
This is absolutely fantastic. I really appreciate your time and I’m sure hundreds of our listeners are going to be hanging on to every word like I said at the beginning. So, thank you so much, Dr. Gantz.

Dr. Bruce Gantz:
Well, thank you, Richard, for asking me to participate. Glad to help.