THE EAR FOUNDATION-TWILIGHT LECTURE
SUSAN WALTZMAN: "BILATERAL COCHLEAR IMPLANTS: CANDIDACY, OUTCOMES,
RESEARCH" 26 JUNE 2008
SLIDE 1: SUSAN: Well, thank you very much. It's a pleasure to be
here tonight. And bilateral cochlear implants is a favourite topic of all
of us today in cochlear implantation and those of us doing some research
in that area.
So let's see what we mean when we talk about using two ears, binaural
hearing, and then we'll work our way into bilateral implants.
SLIDE 2: Well, what are some of the characteristics of binaural
hearing? Well, one very important one is the head shadow effect. When
speech and noise are separated and you listen with the ear, we all do it,
with the better signal-to-noise ratio.
Then the other big issue is binaural summation, which is redundancy,
the same information going into both ears.
And the third is the squelch effect, speech and noise the same as this
are also separated, but there is central auditory processing which
integrates the stimulus for each ear and basically makes more sense of it.
SLIDE 3: So, if one has normal hearing, you have two functioning ears.
And what does that allow those of us with two normal ears to do?
Well, it allows us to hear more efficiently in noise and in the
environment and allows us to locate where a sound is coming from. It also
detects differences in timing and loudness levels between the two ears,
which does help us define a signal and identify it.
Listeners with normal hearing in only one ear, however, could suffer
significantly in their ability to localize and to perform these other areas.
SLIDE 4: What about if you have binaural hearing with hearing aids?
Is that the same as two normal ears? Well, improved dynamic localization
ability, if you have hearing aids, particularly distance and movement. And
what that is is, what I mean by "dynamic localization" is it would be my
natural tendency if I weren't pod casting right now to be walking back and
forth. And so if you have two ears that are hearing, whether it's via
hearing aids or normal hearing ears, you would be better able to understand
me while I was walking back and forth.
Also there's better management with hearing of demanding
conversational situations. You can follow two speech streams sometimes.
You can ignore one while you focus on the other.
SLIDE 5: So what about people with cochlear implants? Well, people
with one implant who don't use a hearing aid in the opposite ear do not
benefit from most of the advantages of hearing with two ears.
SLIDE 6: People with a cochlear implant in one ear and a hearing aid
in the other ear have the potential to use binaural hearing. However, there
are some issues. There are differences between the signals. One is an
acoustic signal, one is an electrical signal, and that indeed may reduce
Very often, especially with profound hearing loss in both ears, it's
the implant that provides the more functional ear. And therefore, what
we've experienced with a lot of our patients is that the hearing aid only
complements the information received. But there are some people who wear
it because they say it gives them a "more balanced feeling".
SLIDE 7: Binaural hearing with cochlear implants. Well, it's
redundancy using binaural summation that we spoke about before. You have
advantages in understanding speech in noisy situations as well as
localization. You have central neural integration. Those cues of timing
and loudness will help in speech understanding.
SLIDE 8: From a very practical standpoint, the "better" ear is always
implanted. If you have two cochlear implants and we're always deciding
and I'm sure Gerry is smiling, which is the better ear to implant, which
ear should we implant? Especially when both have a profound hearing loss,
everything remains equal. Well, if you give somebody two implants, you
don't have to worry about that.
The patient is also never without sound. I wish we lived in a world
where technology (inaudible). But technology isn't. Devices fail. And
when they fail, I can tell you that we get either pretty hysterical adults
or hysterical parents coming in. I must say with the parents, they're
infinitely more hysterical than the children. When a device fails, parents
come in with the child and the child will say: Hurry up, fix it. And the
parents say: When can you fix it?
If you have two implants, it's less of an issue because there's one
that's working. Hopefully they don't both fail at the same time.
And subjective reports, which we'll talk about later on, are
extraordinarily positive. They're a little bit amorphous and a little bit
subjective, which is something that we're going to talk about because
insurance companies in the United States do not like to pay for things that
are amorphous and subjective because they need concrete data.
SLIDE 9: But the issue with bilateral implants, especially if you
already have one, it's not as dramatic as going from no implant to one --
from no implant to one implant. It isn't as dramatic if you're getting
a second implant later on. There are risks in the surgery, a second
The cost, the cost is expensive. And the question that we are faced
with constantly in the U.S. and I'm sure that you are faced with it here
as well, show me that it's worth it. Show me that the cost, that the benefit
is worth the cost.
Saving the ear. We hear that argument a lot. Well, what if there's
hair cell regeneration? And what if you can do something that will allow
us to use what's left in that ear? Well, again, we'll talk about this a
little bit more towards the end of this talk; but truthfully, that's not
going to happen in our lifetime. It works very well on birds. But even
if you regenerate a hair cell, that's anatomic. There's nothing to say
that from a physiological standpoint it's going to work the way it needs
to work. So this saving the ear might not really be the best argument.
The other issue about saving an ear, if that's the reason, for new
technology. What about waiting for something new to come out? Well, it
depends on what you're losing in the interim especially. So I think it's
worth discussing, but I am not sure about that argument. Not everyone
benefits for the same degree and I think this is really a critical question.
If somebody has one implant and gets a second one, not everybody is
going to do phenomenally well with that second one. It's not necessarily
going to make the huge difference that that first implant made. So I think
these are all issues that need to be discussed with the patients, with the
parents, before deciding on whether or not a second implant is appropriate.
SLIDE 10: What are the choices when we talk about binaural hearing?
Well, there's two hearing aids. There's a hearing aid plus an implant and
there are two implants.
SLIDE 11: All of them show improved localization and speech
understanding in noise. Binaural benefit from poorly performing ear, but
I can tell you what we have found. If you had a similar experience. When
you give them a cochlear implant and you give them a hearing aid, the
cochlear implant is usually the one that gives them the most benefit. They
take that hearing aid and they say forget it. We're just not getting enough
benefit from it. So they're losing the possibility of having some
advantage from that hearing aid on the other side.
SLIDE 12: When you get a sequential implant, and I'm going to show
you some of our data which Gerry unfortunately had to suffer through with
me. That work is published in Otology Nerotology.
It takes time to improve. It does take time to improve. Most people
think they have one implant and get a second one quick. It's not quick
at all and there is an adjustment time.
The benefit depends on the hearing loss and the similarities between
the ears. You can't look at implants or hearing aids or make any of these
kinds of decisions without paying very close attention to what the
differences are between the two ears.
The benefit depends on the fitting. Make no mistake that if devices
are not programmed appropriately, unilaterally, yes, we know, but
bilaterally as well, there will be much less benefit.
And again, benefit depends on the processing. Most importantly,
benefit also will depend on the follow-up care.
SLIDE 13: So preliminary considerations. Good hearing in both ears,
two hearing aids. That's a pretty simple one.
Poor hearing in both ears, cochlear implant. Usable hearing in one
ear. Take away that usable hearing, cochlear implant plus a hearing aid.
SLIDE 14: Never underestimate the value of what we do to make that
decision. You need aided speech perception left, right and binaural.
We've had people come to us and say, should I get two implants. And
all they are bringing in is an audiogram. Not good enough. You need all
of the speech perception tests. You need a whole battery of tests to know
what the situation is.
SLIDE 15: Well, simultaneous bilateral. What about getting two
implants at the same time? Most recently, and I am going to give you some
references of some recent literature, average group results do show better
performance in quiet and in noise. Notice this phrase here: "average
Better localization. Improvement in quality of life and favourable
cost-utility in those with profound hearing. Again, it depends on the
hearing in each ear.
SLIDE 16: So, let's look at these individually. Speech
understanding in quiet. On average, bilateral cochlear implants does
significantly better than unilateral in both children and adults. And I'm
giving you some information here. These are some very, very recent
articles. This is out of Iowa and this is out of our group at NYU.
SLIDE 17: Speech understanding in noise. The largest benefit for
speech understanding in noise are from those people who can take advantage
of the head shadow effect, but there is also some association recently in
the literature with summation and squelch. And these are the articles that
you can take a look at that will also reference older literature: Buss
2008, and Ruth Litovsky and her group from Wisconsin in 2006. She's done
a lot of work in areas certainly in localization.
SLIDE 18: So here we go. So for localization, two cochlear implants
are typically better than a cochlear implant plus a hearing aid or one
cochlear implant. And interestingly, this localization ability appears
to develop more rapidly in adults than it does in children.
And there is a lot of literature in this area that you can refer to,
some new ones and some older ones, but they all look at this issue of
localization and how it develops. Why it develops more quickly in adults
than in kids so far that the literature has shown.
SLIDE 19: Now let's look if you have one implant. Why should I get
another one? Why has that come up even as a question?
SLIDE 20: The benefits of binaural hearing, which we just spoke about
have been really well documented.
The positive results of some bilateral implant users now have led many
adults and parents of children for their children to explore the viability
of getting a second implant.
SLIDE 21: There are some issues, however. Some electrophysiologic
data have suggested the longer time between implantation, the longer you
wait between getting the first and second implant, the greater the
possibility of poor performance.
But there isn't very much information on whether or not this
(inaudible) clinical use. In other words, we know if you look at some of
the measures electrophysiologic data, there's no question that the longer
the time between implants, the poorer those tracings are from an
electrophysiologic. But as we all know, electrophysiology doesn't
immediately and always translate into clinical outcomes.
SLIDE 22: So, what we wanted to do was look at speech perception
outcomes in both children and adults who have one implant and then wanted
another one. And we wanted to look at the effect of these different
variables, the length of deafness in that non-implanted ear, the age and
time of the second implantation, and the time between the implant on
SLIDE 23: So here are the two groups: We had 22 adults, 18 years or
older. The mean age of implantation in the second ear was 47. The mean
duration of deafness in the second ear was pretty long at 38 years. That's
a very long length of deafness. And the meantime between the first and
second implant was 6 years, also pretty long if you look at the
electrophysiologic data with a very large range from one ear to 15.
SLIDE 24: We had 43 children. The mean age of the second --
implantation of the second ear was 8 years, and it was the same duration
of deafness, they were congenitally deaf. The mean time between the first
and second implant, well that's pretty interesting, was five years. It's
a long time in the life of the child especially when the mean age of
implantation was 8 years and the range was 8 months to 15 years.
SLIDE 25: What did we do? We had evaluations that were performed
prior to the second implantation. And we're calling the second
implantation Ci2. And we looked at results 3 months post second
stimulation. And we used standard pure tone audiometry and speech
perception, the usual test battery.
SLIDE 26: Preoperative, looked at the first ear alone, the second ear
with the hearing aid alone, and the Ci1 and the second ear with the hearing
aid together. So we looked at every possible scenario. We looked at the
binaural conditions with the implant in the first ear and the hearing aid
in each ear separately.
And three months post-op, we still looked at the first ear alone, we
looked at the second ear alone and we looked at the two ears together both
SLIDE 27: So we were a little bit surprised. A little bit, but not
terribly. We were pleased to see that the first ear didn't change. That
by operating on the second ear, nothing terrible happened to the first one.
(Inaudible) CNC words, which were pretty low with the hearing aids
and after only three months with -- three months -- this is the average
that it was. And I mean, yes, from a research standpoint incredibly
statistically significant, but more importantly (inaudible). We were very
pleased to see the benefit.
We were also pleased to see that even the bilateral benefit showed up.
Very often when you look at -- try to look at bilateral benefit, when
somebody has one implant, they're doing so well with that implant that you
add a second implant. (Inaudible) our perception tests are just not
sensitive to do that. But we did show and this is again only after 3 months.
SLIDE 28: Here are some adult sentences in noise. Again, no harm to
that first ear and an amazing result on that second ear. Their sentences
in quiet went from about 12 percent to more than 70 percent score in three
And again, we're showing obviously this pre-op score is a reflection
of that Ci1, but we're still showing a benefit that goes from about 72
percent to about 85 percent.
SLIDE 29: We separated it just for curiosity because all this talk
about, well, if you have one implant for five years and it's five years
or more and you want that second implant, you absolutely (inaudible).
Because here the adult with only greater than five years between Ci1
and Ci2 and you see where you can see the purple pre-op the score was --.
And look at their performance with that implant.
Now does everybody do well? No, and I think that's another reason,
a reason to look at individual data.
Here this individual showed a very modest gain. This individual a
modest gain. And some of them, I would say that's...
SLIDE 30: Well, what about children? And children, of course, are
the toughest group because you're dealing with parents who really want the
best for their children. And we'll talk about this a little more, but when
you're -- like is it really very complicated. It may seem complicated to
them, but it's not for everyone.
But when you get to be 8 or 9, preschool and you are -- I think a lot
-- But when you're 2 and 3 and you're doing very well with that one implant,
you don't always think you need a second implant. The parents say, look
how great he's doing. He's learning language. He's getting all of this
intervention, all of this appropriate therapy, the device is working great.
I don't really want him to have another surgery and that's a perfectly
good argument. And they come back when they are 8 or 9 and they're saying,
well, he's coming home exhausted from school. I think that's something
that we hear more than anything else. He's working so hard or she is working
so hard to listen and it's exhausting and they're having trouble.
So we wanted to address the issue and be able to show well, is it viable
to really... So here we go. I am not showing you CI alone results again
because happily they are the same as they were with the adult. The first
implant did not change. The performance didn't change.
So we're going to concentrate on the second implant alone and on the
bilateral scores. And these are the different tests we used. I don't know
if you use these here. These are the multi-syllabic word tests, a
monosyllabic word test for children. Another monosyllabic word test for
children. The HINT sentences in quiet and the HINT sentences in noise.
So we tested them in virtually every condition. And well, as you can
see here, if you look at these multi-syllabic word tests, there was an
improvement in that second ear. Again, this is just after 3 months. And
even if improvement in the bilateral condition, really for every test. And
for every test as well an improvement in that second ear with that implant.
This is for monosyllabic words going from about 2 percent to really over
60 percent in 3 months is pretty impressive, I think.
By the way, these users were both Nucleus Cochlear Corporation users
and Advanced Bionics and we did not detect any difference.
So here we go. They improved on absolutely every perception test that
we could conjure up.
SLIDE 31: So, what did you see here? Well, we saw significant
improvement in the second implanted ear and in the bilateral condition for
children and adults despite the time between implantation or the length
But interestingly enough, what we found was significant and this was
very interesting to me, to all of us, the age of first implantation was
a significant variable in the children. The younger the child was when
he or she received that first implant, the better the performance of the
So implanting younger is better right when you're getting one implant
for sure. And it may assist you in doing better if the parent decides to
wait to get the second implant and not get them simultaneously. And I have
to tell you there are reasons and we'll get into that.
But this was a very interesting finding. A very, very interesting
finding for us. And you know it does make sense because when you stimulate
electrically, you're stimulating areas that may indeed help you preserve
what's in the other ear.
SLIDE 32: Bilateral difference. What do we hear? What do we hear
from people who get a second implant?
Now we know if you get two at a time, that's great. We know what happens
there. When you have one and get a second one, they report ease of
listening. It's just easier.
Again, always have an implant in case of breakdown failure, battery
life. These devices have issues with battery life. And so it helps if
you can always have one on. But again, I go back to the fact of the second
implant that it depends on the hearing in that non-implanted ear. It's
not straightforward at all.
SLIDE 33: Now how can it make a difference? Hear with greater ease
in more places. You understand better in noisy situations. Binaural
redundancy proves to be true. You know where sound is coming from without
looking. And the social aspect have shown themselves, although it's very
These have shown themselves to be extremely important, extremely
important, particularly to children. We get reports that: Oh, my son goes
now into the lunchroom during lunch where he wouldn't before. He has a
much easier time at recess than he ever did before. And so the social
aspects of what children are willing to do seem to be greatly affected by
the second implant.
SLIDE 34: So bilateral implantation is appropriate in appropriately
selected candidates. And again, you have to look at the hearing. That's
very important. Somebody has usable hearing in one ear, you need to define
how usable that hearing really is. You need to know what's really happening
with that hearing and how much benefit they're getting from it.
If it's bilateral simultaneous that's being considered, you want to
know if the ears are balanced. Is that the right way to go. It's a
bilateral profound hearing loss in both ears, that sort of makes the
decision easier. Definitely easier because you're not dealing with any
usable residual hearing.
Benefits derived certainly can be significant. Surgical procedures
are very well tolerated. We haven't had any issues. And the benefits for
most people outweigh the risks.
SLIDE 35: The issues. There are still remaining issues. Cost,
including programming time. There is a significant cost to having two
implants versus one. And I include in that the programming time of the
device. If you are programming two implants and it's an art and it's a
science. You just can't program each one separately, quickly and hope that
they're going to work together, they don't always. And so the programming
of these devices can be infinitely more challenging for two than for one.
And you need experience for that. There is research ongoing now on
how to really program bilateral cochlear implants, be they simultaneous
or sequential. There are some people at NYU, some of my colleagues Mario
(inaudible) is doing some work on that. And hopefully we'll get some
answers on how to best program these children.
Cost utility. Cost utility is very, very big with insurers. And so
they say, show me. Show me that two implants are going to work better for
this child, for this adult than one.
And I have to say the published literature, which is all that people
really look at, has been to date a little bit sparse. We're seeing more
and more of it, but it's been somewhat sparse in terms of actually proving
that two implants are positively absolutely better than one.
We didn't have this issue. We didn't have this issue with one implant.
It was easy to prove that one implant was better than a hearing aid in
somebody with a profound hearing loss. It's proving more difficult to show
that two are for a variety of reasons. One because they're doing so well
with one that our tests are not perhaps sensitive enough, all of them, to
be able to show the difference as easily. It can show -- as you can see,
we did show it a little bit.
The cost utility, Miyamoto just had an article, he's from Indiana
University. And very recently, just last month came out with an article
on cost utility showing that indeed bilateral cochlear implants are better
than one. So if you look at that, I'm not -- I am hardly an expert or even
close to it on knowing all these cost utility measures. I don't even know
what it means most of the time, but I do know, you know, the cost benefit
ratio is something I understand a little bit more, but it's something that
I know that this is very expensive to do and it's our obligation to show
And unfortunately, just saying that my son can hear better in the
lunchroom or does better socially, although extremely important, is not
a convincing argument for insurance companies or anybody who needs more
So, is there enough evidence? I think evidence is really mounting.
And hopefully it will continue to mount in the published literature that
we can definitively say that "yes".
SLIDE 36: Well, what about simultaneous implants? Can a parent come
in whose child is a candidate for simultaneous implantation? Again it
depends on the hearing in both ears. It's very often a very difficult
decision. And so everybody -- the question is, is there harm in waiting?
And I have to say we at NYU, I smile when I say it and Gerry well knows
this and Sue knows it, we've been pretty aggressive in the patients that
we will implant within limits, but we have been conservative when it comes
to recommending to parents that they absolutely must get two implants at
the same time because it's more than just the hearing. You know, adults
say we had when we were only doing unilateral implants, everybody, all of
the adults would come in and say, well why don't you give me two. And we
would say, we don't know how one works yet, so give us time and maybe we
When we started doing clinical trials on these sequential implants in
adults, we sent out letters to these hundreds of patients, adults, who had
requested a second implant. You know how many of them got them? Five.
Why? Because they said, no, I'm doing great with one. I don't need that
second one now. Can't argue with that. Just can't argue with that for
What about for a child? What about these other arguments? Well, so
you need a comfort zone. What are they comfortable with? If they're more
comfortable, sometimes if we're doing these children younger and younger,
tomorrow I am going to talk about the under 12 months.
Now you have a parent come in, two normal hearing parents come in, and
that's 99.5 of our pediatric population, the children are from normal
hearing parents, you have them come in, they just have been told that they
have a deaf child, the child is 7 months old, 8 months old, however old
he is, and not only are you talking to them about fitting this child with
a cochlear implant, you're saying give him two. Now that could be a little
harsh for some people to take. Now some are fine. Some parents have come
in and said: Well, he's got two ears, doesn't he? And they're both
profoundly deaf, let's give him two. And that's fine.
But those who are a little bit more reserved about it or frightened
about it, there's no reason not to give them the option of waiting, whether
it's waiting 6 months, a year, or two years. Yes, do you want to wait a
longer time, despite what our research shows that you can wait and still
benefit, not everybody, you know, will benefit equally when you wait.
So is it better not to wait too long? Possibly, probably. Most
definitely, actually. But the truth is it's not going to do anybody...
SLIDE 37: So what does really the future hold for all of this? Well,
basic research in hair cell regeneration is ongoing. Stem cell research
is ongoing. It's all very exciting. But a clinical application is decades
away, decades away for humans.
So I think that we need to be realistic because this is something that
we get asked all the time, what about stem cell? What about hair cell
But if you listen to the people who are doing all of this research,
they're going to tell you as well, it's decades away. And even when we
can regenerate, we don't know what it's going to give. So I think they're
not an option.
If that's the argument for waiting, it perhaps is not the best argument
That's it. I thank you very much.