february 5 th 2002

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February 5th 2002

Cochlear Implants for Reviewers

A presentation made to the ENT section of the FDA

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1: The Design of History

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Early Efforts: The Tonotopic Theory

Based on the work of von Békésy, most early cochlear implant researchers as-sumed that the only viable way to stim-ulate the cochlea was to place electrodes along the basilar membrane and stimulate the dendrites which were presumed to be present: “place = frequency”Dr. Fred Linthicum of House Ear Institute subsequently demonstrated histologically that lack of hair cells generally meant lack of dendrites, and it is now universally assumed that the spiral ganglion cells within the modiolus are the site of stimulation

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Early Efforts : The Tonotopic Theory

Dr. House accepted the tonotopic theory, and, with the help of some volunteer patients, implanted hard-wired, 5 electrode systems to develop a usable deviceHe found that his patients did not report great differences between “place” (tonotopic) stimulation and general stimulation (unpublished data)

This would not, could not be the case if it were required to stimulate tonotopicallyOther researchers reported similar resultsThis was very strange— inexplicable, in fact— but the clinical result was undeniable

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Single Electrode Implants: Overview

As a result of these clinical results, the first single electrode cochlear implants— indeed, the first practical cochlear implants of any sort— were developed

Incoming sounds were amplitude modulated on a full-time, 16-24 kHz signal and injected into the cochleaThe field developed is apparently present globally, stimulating all spiral ganglion cells and nerves simultaneouslyThese are “analog presentation” cochlear implants

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Single Electrode Implants: Overview

From the beginning, it was assumed— without clear evidence and for reasons that we will explore— that multiple electrode (“multiple channel”) cochlear implants would work better

“Until… multichannel prostheses become a reality, one must consider the question of whether or not it is reasonable to continue implanting single-channel prostheses.”“Above all, a single channel auditory input will not provide a speech input that either sounds speech-like, or is understandable.”

– Bilger RC, et al. Implanted auditory prosthesis an evaluation of subjects presently fitted with cochlear implants. Trans Am Acad Ophthalmol Otolaryngol 1977 Jul-Aug;84 (4 Pt 1)ORL-677-82.

The Bilger report on a handful of early single electrode patients inferred these criticisms in 1977, before any multiple electrode devices were even available for comparison, and no data provided support such conclusions; they appear to be based entirely in theory

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Early Efforts : Multiple electrode devices

In such a climate (as indicated by the Bilger quotes) it is not surprising that other researchers started by building multiple electrode devices; they never tried any alternatives

With early designs, it was impossible to stimulate the cochlea at multiple sites simultaneously because of unwanted signal interactionsBecause of the capacitive nature of the cochlea, stimulation had to be followed by “radio silence” to allow charges to drain awayThese devices used pulsatile stimulation, shifting rapidly between frequencies (sites of stimulation)

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Early Efforts : Multiple electrode devices

Multiple electrode implants:Incoming sounds are separated into different frequency bandsEach frequency band is assigned to a different electrode pairWhen stimulating for the higher frequencies, the frequency of the stimulating signal has not been thought to be important (i.e. 1200-1500 pps is common)Stimulation is pulsatile and discontinuous (staccato)These are “pulsatile presentation” cochlear implants

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Two Basic KindsAs a result of this history, there are two basic kinds of cochlear implants

multiple, long electrode single, short electrode (pulsatile presentation) (analog presentation)

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2: Design, Function, Surgical Placement

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Single Electrode Implants: Design

Many different kinds of “analog presentation” implants can be imagined, but the specific design of the current AllHear devices is rather simpleThe internal receiver consists of few parts:

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The external processor, as yet, is likewise very simple:

B atte ry

C o ilM agne ticinsert

M icrophone

Volum econtro l

E lectron icspackage

C oil

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The external processor amplifies sounds and combines them with a 16-24 kHz carrier (amplitude modulation)The AC output is sent through the external coil, which develops an alternating magnetic fieldThis field interacts with the internal coil, inducing a corresponding AC current which is sent through the electrodesThe present design processor uses “clipping” to control overloud signals

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Single Electrode Placement

Insertion of no more than 6mm preserves cochlear structures and residual hearing…

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Multiple Electrode Placement

“Deep insertion” of 20mm or more is known to destroy cochlear structures and tends also to damage residual hearing…

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Multiple (long) vs. Single (short)

The contrast between the two provides for greater safety during the surgical procedure

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3: The Perception of Percept

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Single Electrode: the perception of percept

All presently manufactured cochlear implants approved for general use in the US, Europe and Japan use multiple electrodesIf, as Dr. House found, there is little difference between patient percept whether using one or several electrodes internally, where external processor electronics are held constant..

Why is this the case? Why does “everyone know” that multiple electrodes are better?

The answer is the result of a cascade…

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Early 3M/House processors were not designed to provide good speech reception, they were designed only to provide access to environmental soundsThis, because at the time no one thought that these new devices– cochlear implants– would actually provide patients with good enough sound so they would understand speechThus incoming sounds were deliberately restricted in frequency bandwidth, reflecting safety concerns, and these low expectations This became a self-fulfilling prophecy, as a circuit diagram of the original device shows…

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Fretz RJ, Fravel RP. Design and function: a physical and electrical description of the 3M House cochlear implant system. Ear Hear 1985 May-Jun;6(3):14S-19S

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Restricting frequencies to below 2700 Hz— eliminating some 35% of the frequencies important to understanding English— means that consonant sounds would be more difficult to hearIndeed, these processors had several other inherent, performance-limiting problems:

They did not use modern compression, but rather “clipping”, which tends to introduce increasing distortion at full volumeThey had noisy circuitry, degrading the S/N even in quiet conditions…And they had other, “non-electrode” problems

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If we were to compare two hearing aids, one of which offers the full range of frequencies important to understanding speech, and the other of which deliberately restricted frequencies (excluding some 35% of the information in speech)… …one of which offers compression and the other of which does not……one of which offers a relatively clean signal and the other of which has considerable added noise…With which one would we expect patients to do better?

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The 3M/House and 3M/Vienna devices were termed “single channel”, and this was assumed to be their pivotal “defining” characteristic, even though (for example) the Vienna device was extra-cochlear!The limits of the processor were not considered, and no data exist which offer information about how changes to single electrode, analog presentation processors affect patient perceptDoes it make sense to assert, without one scintilla of supporting evidence, that the perceptual limits experienced by patients were (solely, or even primarily) due to the use of one electrode?

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To gain a proper perspective on this subject, it is crucial to realize that every theoretical objection to these devices, on analysis, centers around the assumption that good frequency information cannot be provided when using a single electrode

Sound is pitch, timing, loudness; frequency is the pivot

Thus if it can be shown that such devices can provide good frequency information…

then previous assumptions are shown to be wrong… …and any prejudice against these devices centering around the electrode must be re-examined and perhaps discarded

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The issue of quality of percept is obviously central, but putting it aside for the moment, let’s examine some other facets of the comparison…

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4: Tono topics

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Considering the T-TheoryFor the sake of this discussion, let’s assume that the tonotopic theory can be stated as:

We must stimulate the cochlea according to the expected “place” of the frequency-of-interest, in order to provide a percept of that frequency

Please note the use of the word “must”, which clearly informed Dr. Bilger’s idea about this theory:

“…single channel auditory input will not provide… speech… that is understandable…”

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“Channels”: a slight digression

“Above all, a single channel auditory input will not provide a speech input that either sounds speech-like, or is understandable.”

Simply because we have created a name for something, does that thing exist? (“multiple channel”, “single channel”) What is a channel? It would seem that either “a channel” is a single frequency (or narrow band noise), or it has no meaning whatsoeverFor multiple electrode CIs it may make sense to refer to “channels”, but it makes no sense when referring to analog presentation CIsWe believe we can demonstrate that “single channel” as a term applied to single electrode devices has no scientific content

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Considering the T-Theory

The tonotopic theory appears to work, based on the success of present devices, and studies showing that the place of stimulation within the cochlea is associated with different pitch perceptsBut is there evidence for the possibility of successful non-tonotopic stimulation?And if so, how would one fit these two (different?) modes of stimulation into a “unified theory” of cochlear stimulation?

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Considering the T-TheoryIn fact there is good evidence for the success of non-tonotopic stimulation

For example, in Appendix G of The Audiologist's Handbook for the Mini System 22 (Cochlear Corporation, April 1993) the following quote is found:

“The [Cochlear Corporation's Mini 22] cochlear implant can produce two types of stimulation, bipolar and common ground (CG)... Typically, the lowest thresholds are obtained in CG stimulation because of the wider current spread.”

“Common ground” means currents spread globally— non-tonotopically— within the cochlea

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Considering the T-Theory“Wider current spread” engulfs more nerves— but studies done comparing CG to bipolar for this device do not appear to show significant differences in percept

“…results indicate that… restriction of the size of the neural population activated by individual channels of the prosthetic is not necessarily advantageous.”

– Pfingst BE, Zwolan TA, Holloway LA. Effects of stimulus configuration on psychophysical operating levels and on speech recognition with cochlear implants. Hear Res 1997 Oct;112(1-2):247-60

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Considering the T-Theory“Bipolar” stimulation is stimulation of closely paired electrodes; “monopolar” stimulation is stimulation of an active electrode coupled to an extra-cochlear groundClearly, monopolar stimulation would lead to wider current spread, and should reduce frequency discrimination because it “breaks” tonotopicity…

“An assumption that bipolar stimulation should provide better speech understanding… has not been confirmed in this study. We found… no significant difference… on any tests when subjects were compared using monopolar or bipolar stimulation modes and the same coding strategy…”

– Battmer RD, Martens U, Gnadeberg D, Hautle K, Lenarz T. Comparison study of patients using either the Nucleus Minisystem-22 in bipolar mode or the Nucleus 20 + 2 in monopolar mode. Ann Otol Rhinol Laryngol Suppl 1995 Sep;166:349-51

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As well, no long electrode, pulsatile presentation implant currently in production reaches more than 25 mm into the cochlea, whereas the basilar membrane is generally quoted as being 35 mm longThat is, no pulsatile presentation cochlear implant stimulates the apex of the cochlea, where low frequencies (1500 Hz & lower) are apparently resolvedYet patients using these devices apparently hear and resolve these low frequencies…

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Some proponents of the tonotopic theory will tell you that such patients “hear” unstimulated low frequencies because such frequencies are at or below the firing rate of the nerves (~500 cps), or that some other mechanism (volley theory) allows for that perceptBut does it make sense to assert that the cochlea has one mechanism to hear low frequencies, and another to hear high frequencies?

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Occam’s razor: Rather than assuming, simply to safeguard a tenuously-based theory, that there are two mechanisms, it would make more sense to assume that there is only one mechanism being exploited in several ways… But if there is only one mechanism, what might it be?Consider the work of Kiang…

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The Studies of KiangKiang recorded from an electrode in a single auditory nerve axon in intact cat cochleaeOver a period of years recordings were made from hundreds of VIII nerve axons

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The Studies of Kiang

Kiang then presented the cat’s ear with a stimulus at a certain decibel level (loudness), where the tone (frequency) was increased continuouslyWhile this steadily rising tone at a given decibel level was being presented to the cat’s ear, Kiang recorded the frequency at which the single nerve fiber in which he had his probe began to fire, and the frequency at which it stopped firing

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The Studies of KiangThen he repeated the “rising tone” stimulus at a lower decibel level, with his probe in the same nerve fiberEventually, at a low enough decibel level, he found that each nerve would fire at only one very specific frequency, which he called “the characteristic frequency”At a given decibel level then, Kiang found out the range of frequencies to which a specific nerve fiber would react, and he produced charts of those reactions…

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The studies of Kiang

Recording with stimulus at 60 dBA specific nerve fiber reacts from 180 to 900 Hz at 60 dB

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Recording with stimulus at 40 dBThe same nerve fiber reacts from 330 to 500 Hz at 40 dB

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Recording with stimulus at 20 dBThe same nerve fiber reacts only to 490 Hz at 20 dB

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Kiang’s conclusionsIf the volume of the stimulating sound is high enough, a nerve fiber will fire across a broad range of frequenciesWhen the volume of stimulation is reduced, the nerve fires across a narrower range of frequenciesAt the lowest volumes where the nerve will stimulate, only one frequency causes that nerve— and few if any others— to fireAgain, Kiang called this its “characteristic frequency”

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Speculation…Obviously Kiang was working with sound stimulus, not electrical stimulusEven still, surely his work provides a useful means of thinking about electrical stimulation, because it seems sensible to assume that some or much of the preference for frequency resides within the nerve itself, and the nerve is an electrical organ…And if the nerve has “preference”, might it not be that intense pulsatile electric fields can overwhelm the nerve’s characteristic frequency, whereas less intense, analog fields tend to allow that preference?If so, then place stimulus must be intense stimulus, but more benign global stimulus may be analog in nature

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Speculation…

That is, tonotopic, pulsatile stimulation works by overwhelming the nerve’s tendency to respond only at its characteristic frequency…

It can be stimulated, if we hit it hard enough

…and analog stimulation works precisely by exploiting characteristic frequency …

It will respond to its characteristic frequency, if present

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5: “Doctor, is there a pulse?”

“Digital electronics deals with 1's and 0's, the language of logic,” explains Tilde, “whereas analog electronics deals with waves, the language of sound.”

Smithsonian Magazine, February 2000, “Redefining Robots” p 96

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Using pulses: a slight digression

The pulsatile stimulation used by CIs is locally very intenseThe purpose is to cause all nerves local to the stimulus to “fire” simultaneously; to “entrain” them; to stimulate a “volley”Consider: What this means is that the stimulation involved must necessarily result in either a single tone, or narrow band noiseRemember: it is apparently not the frequency of stimulating signal that provides the result… It is the local intensityThe number of electrodes therefore equals the number of frequencies or “channels” (CII possible exception)

Multiple electrode devices therefore offer a “set” of discrete frequencies, not a continuous range of frequencies

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So, are nerves “digital”? Are pulses the best way to interact with them?In fact, recent research is beginning to uncover the much more subtle, entirely more ubiquitous and rather complex analog nature of nervesWhy should we believe that the inner ear, which has never naturally produced nor experienced anything like a sharp rise-time, square wave pulse, would offer a better response to a pulsatile vs. an analog stimulus?

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Beyond the fact that pulses were required to get multiple sites stimulated in rapid and sequential fashion, there were historical reasons for using pulsesEarly (and continuing) research done on nerve stimulation required large artifacts in order to “discover” nerve responses in the electrically noisy biological environmentRecordings were made of the response to hundreds or thousands of stimuli, the results were time normalized and averaged, and a waveform resultedSharp rise times— which characterize pulses— were therefore the stimulus of choice, because they invoke large artifacts which are easy to see, “on average”…

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But this is the scientific equivalent of looking for one’s keys under the streetlightCertainly the approach yielded results, but it also encouraged researchers to believe that the only nerve responses worthy of research were large affect responses— the ones which were easiest to seeYet such responses are arguably completely artificial, and might only be produced by using pulses to invoke them, meaning that at best they offer us a picture of a nerve under considerable stress…The generally unchallenged idea grew up that nerves are digital, they “fire”, they are either on or off

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“Jerome Lettvin… MIT professor of both physiology and engineering… says, ‘We are not digital machines, we are analog devices. All our neurons are analog devices, and anyone who tells you otherwise is talking nonsense.’ ”

– Smithsonian Magazine, February 2000, “Redefining Robots” p 96

Digital technology throws away direct information to increase derived accuracy; analog technology relies on direct information, often at the expense of derived accuracy Digital systems measure; analog systems compareSensory systems appear generally to prefer more information (and comparison) over greater accuracy (and measurement)

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6: Single vs. Multi

Less is more, more or less?

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Multi vs. Single: Established Facts

A single electrode CI design has a number of advantages over multiple electrode designs, in several important areas

•Preservation of hearing•Reduced expense•Ease of setting

•Higher bandwidth•Cleaner signal

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6a: Single vs. Multi

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Multi Disadvantages: Setting Devices

Properly setting multiple electrode implants is very difficult and expensive16-22 active electrodes, 4 key parameters each, some or all electrodes can be fired, ganged or single electrodes, several different “strategies”; all interactive and inter-related, one to another, and therefore highly complexInitial “mapping” generally takes several sessions, consuming between 5 and 20 hours; and it may take longer…

“Refining the programming of a cochlear implant can be a tedious process that can take a year or more of hard work before patients can hear clearly.”

– Chris Bertrand, CEO of MED-EL North America

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Multi Disadvantages: End-User Expense

Multiple electrode implants are expensiveThe standard quoted price for multiple electrode implants is $50,000 to $75,000 (implant cost: >$20,000)The average per capita yearly income in the US is $36,000The average per capita yearly income in China is $1,500

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Multi Disadvantages: Single channel?

Because of “unpredictable fluctuations in loudness” if multiple signals are injected simultaneously into the cochlea, then for the market leader CI, only one electrode pair (or a set of ganged electrodes) is fired at any one momentThus from the point of view of time, the device is “single channel”

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Multi Disadvantages: “Bandwidth”

The concept of bandwidth has to do with the amount of information one can provide across a certain link or pipe in a given unit of timeFor CIs, bandwidth would have to do with…

the abstract ability of the damaged hearing system to resolve pitch, timing and loudness from the best possible information, and…the abstract ability of the CI to provide pitch, timing and loudness cues

To the degree possible, one must try to separate the limits of the hearing system from the limits of the mechanismBecause we are always measuring the latter via the means provided by the former, we as yet have poor information about the true potential of the damaged hearing system…

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Multi Disadvantages: Limited Bandwidth

We can, however, infer some things about the bandwidth of multiple electrode CIs

Only a portion of the frequency spectrum is provided at any one momentTime is also underutilized, as stimulation is followed by silence (staccato)Depending on how the device is programmed, it may only be able to provide 5% to 60% of the information available in the full ambient signal

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As mentioned, when we try to discover the bandwidth limits of the damaged hearing system, we should recognize that we may be measuring the mechanism, not the systemAn example is provided by studies which show that between four and ten electrodes are all that is required for speech receptionSuch studies depend entirely on the specific forms of pulsatile processing which were used, so it seems unwarranted to assume that we have learned very much about the underlying systemThe means used are also language-specific, and this again indicates they are not fundamental enough…

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“Speech processing” (SP) overcomes bandwidth limits to some degree, generally by sacrificing full access to a variety of soundsSP has inherent bias with regard to languageThis is not to say that SP is a poor choice; it may be necessary, particularly for those with the most damaged hearing systems, even if the means of stimulus provides better bandwidthSP is highly likely to be more effective with greater device bandwidthBut the “philosophy” of multiple electrode CI design is fundamentally different from the philosophy of hearing aids, where clarity at volume is the primary goal

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Multi Disadvantages: Noise Is Inherent

Because multiple electrode designs stimulate the cochlea using pulses, they cannot faithfully recapitulate analog waveforms within the cochlea“Aliasing” must result, essentially introducing distortion or noise into the signal providedIt appears that the only way to overcome such limits is to move toward fully analog signalsHigher rate pulsatile systems are a step in this direction, and we would expect them to show better results because of increased bandwidth and clarity

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Multi Disadvantages: Noise Is Inherent

“Because multiple electrode designs stimulate the cochlea using pulses, they cannot faithfully recapitulate analog waveforms”

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Multi Disadvantages: Cochlear Destruction

Numerous studies have shown that the insertion of a multiple electrode– long electrode– CI destroys irreplaceable cochlear structures, including the basilar membrane, hair cells, and spiral ganglion cells

“There is general agreement that [such] damage… may lead to severe neural degeneration.”

Kennedy DW: Multichannel intracochlear electrodes: mechanism of insertion trauma. Laryngoscope. 1987 Jan;97(1):42-9.

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Other studies have shown that the intense stimulation used in multiple electrode devices, in itself, might be destructive

“Earlier studies established damage thresholds for both acute (…70 µC/cm2) and chronic (…15-20 µC/cm2) stimulation…”

Duckert LG, Miller JM: Mechanisms of electrically induced damage after cochlear implantation. Ann Otol Rhinol Laryngol. 1986 Mar-Apr;95(2 Pt 1):185-9.

“…the charge density for the analog sinusoidal output at 1000 Hz is 379 µC/cm2… As the stimulus frequency drops, the charge density increases until it reaches 667 µC/cm2…”

Advanced Bionics IDE submission

667 µC/cm2 is nearly 10 times the acute damage threshold reported by Duckert, and approximately twice the level at which electrode gassing has been reported to occur (by Brummer)

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This is another consequence of using these very intense pulses, and further evidence of the fact that they are biologically unknown…However, since we do not have significant numbers of reports of long-term degradation of percept (which we might expect in the case of destructive stimulus), we have to conclude that the cochlea is more tolerant than we had thought, or that the damage being caused does not degrade percept, as might be the case depending on the mechanism of stimulation and the site of the damageClearly the final word is not yet in…

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6b: Single vs. Multi

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Single Advantages: Setting Devices

Properly setting single electrode analog implants is very easy, and inexpensive“Setting” is essentially the same as adjusting a hearing aidThus the expertise required is available in every city and town, wherever there is a HA professionalEverything needed can be put into a standard desktop computer (NOAH), or a handheld (Palm Pilot), and can be made prescriptive (NAL-NL1, etc.)This has profound implications for the distribution of cochlear implants, and the shape of the market…

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Single Advantages: End-User Expense

The standard quoted price for single electrode implants is $15,000 (implant cost: $6,000-8,000)We believe it would be possible to develop a low-cost ($1,500) deviceNo other cochlear implant design type could possibly penetrate the world market…

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Single Advantages: Full Bandwidth

While the limits of the damaged hearing system remain unknown, there is evidence that the analog presentation approach holds promiseSingle electrode analog implants apparently provide access to many or all frequencies (more information momentarily)

Single electrode analog presentation cochlear implants can provide

The full frequency spectrumFull-time, withPure analog presentation

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Single Advantages: Noise is Avoidable

Single electrode analog implants can apparently provide clean signalsIn advanced hearing aid technology, digital representations are converted to analog sound for presentation via a speaker (“Digital” is good, when restricted to the inside of an amplifier)

Advanced single electrode analog implants will work in exactly the same way, except they will provide output to a coil

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Single Advantages: Cochlear Preservation

Insertion of short electrodes generally preserves cochlear structures

“Thus, there is no evidence that the short 6-mm electrode used in the 3M/House implant will necessarily destroy residual hearing that might be present in a child receiving this implant.”

Dye et al: Measurable Residual Hearing Following Cochlear Implantation. In Meyers et al: Advances in Otololaryngology Vol 4; St. Louis Mosby Year Book: 1990 61-79

Statistics are as yet unavailable, but it may be that the rate of iatrogenic hearing loss from short electrodes is roughly equivalent to stapes surgery, which is generally <1%

Stimulation levels are <1 µC/cm2 primarily because stimulation never falls below 16 kHz

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The Matter of Proof

Clearly, single electrode, short electrode, analog presentation cochlear implants have a number of significant medical and strategic commercial advantagesThe facts presented prove greater safety, and they demonstrate the considerable potential of this technology to be improvedBut is there strong evidence of efficacy?Can patients using these devices gain a good percept?

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7: Proof of Life

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The Matter of Proof

Again, please remember: it is crucial to realize that every theoretical objection to these devices, on analysis, centers around the assumption that good frequency information cannot be provided when using a single electrode

“Above all, a single channel auditory input will not provide a speech input that either sounds speech-like, or is understandable.”

Please also note that we are discussing evidences of the potential of a technology, not proof of the efficacy of a device which is only one of several possible implementations of that technology…

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The Matter of Proof: “MF”Age 19, implanted age 15 mo. with 3M/House, upgraded to AllHear processor in 1993Favorite HS class German, plays the saxophoneDaily telephone useEvaluated at University of Iowa by Dr. Bruce Gantz: Test results

34.7% HINT sentences38.0% CNC words58.7% CNC phonemes

These scores are impossible to a patient who is getting only one or a limited number of frequencies

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The Matter of Proof: “MF”

Dr. Gantz’s team reported that:“[MF] is an extraordinary young man who has developed excellent speech, language and reading skills such that he does better on standardized testing than almost all of his peers who have had hearing all their lives…”

MF achieved these results using a processor without modern compression, using clippingWhat might he do with a better processor?

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The Matter of Proof: “JF”

Age 20, implanted age 3 with 3M/House, upgraded to AllHear processor in 1993Daily telephone usePlays guitarEvaluated by Dr. Gantz’s team: Test results

40.8% HINT sentences

22.0% CNC words

34.0% CNC phonemes


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The Matter of Proof: “JF”

Dr. Gantz’s team reported that:“…[JF] has developed excellent speech, language and reading skills such that he does very well on standardized testing, when compared with his peers who have had hearing all their lives…”

JF achieved these results using the present-design OTHWhat might he do with a better processor?

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The Matter of Proof: “JR”

Age 22, implanted age 5 with 3M/House, subsequently upgraded to AllHear processorSchooled without an interpreterDaily telephone useEvaluated by Dr. Gantz’s team: Test results

59.3% HINT sentences

18.0% CNC words

43.3% CNC phonemes


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The Matter of Proof: “JR”

Dr. Gantz’s team reported that:“…[JR] has developed excellent speech, language and reading skills such that he does very well on standardized testing, when compared with his peers who have had hearing all their lives…”

JR achieved these results using the OTHWhat might he do with a better processor?

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The Matter of Proof: “TL”Age 22, implanted age 3 with 3M/House, upgraded to AllHear processor in 1993Honors student at her university (now graduated)Attended classes with no interpreterDaily telephone use

“ …(TL) is a superior user… Her performance on a modified version of the Glendonald Auditory Screening procedure [was equaled by only] 1.5% of the total 126 subjects…”Chute PM, Hellman SA, Parisier, SC, Selesnick SH: A matched-pairs comparison of single and multichannel cochlear implants in children;Laryngoscope 100 January 1990, p 25-28

This was in 1990. She attained this result using a 3M processor.

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The Matter of Proof: “TL”

[TL] is an extraordinary user, without question. So were the two other children who equaled her performance in the Chute study. We have three extraordinary users using two different kinds of implants

However, to assume that [TL] was so extraordinary that, using a cochlear implant which provided only one frequency, she was able to equal the performance of the very best users from among this relatively large group, is completely beyond belief

Her score would surely have been impossible to someone getting very limited information from their CI

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The Matter of Proof: Many patients

“We evaluated the ability of profoundly deaf children using the 3M/House single-channel cochlear implant to understand speech without the aid of speechreading… Fifty-two percent demonstrated some open-set performance on word identification…”

Berliner KI, House WF, Tonokawa LL: Open-set speech recognition by children with a single channel cochlear implant; Transactions of the American Oto Society, 1989

Again, these children were using processors with known and significant deficiencies…

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The Matter of ProofThus it is clear that a single electrode can provide access to many frequenciesIndeed, to generalize, one may say that we have an adequate demonstration that a ubiquitous AC current in the cochlea can apparently provide a percept of soundThis demonstration completely negates the objection lodged against single electrode devices so many years ago, and unquestioningly continued through the presentThat is, we have shown that “single electrode” is far different from “single channel” (i.e. 1 electrode = 1 frequency)

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The Matter of Proof

In sum, patients using single electrode devices, indeed when using external processors with significant internal noise & distortion, and without benefit of modern compression, have demonstrated strong abilities; some are in the first rank of cochlear implant usersWhat might they do with superior technology?

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8: Summa

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Multiple Electrode Implants…

…are very sophisticated devices, known to work relatively well for patients They are also:

Complex (internal electronics)

Expensive ($20,000-$30,000)

Destructive (long electrodes destroy the inside of the cochlea)

Difficult and expensive to set (requires computer)

Power hungry (new or recharged batteries every day)

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Single Electrode Implants…

…are relatively simple devices, and have been shown to work relatively well for some patients, although statistical proofs are still lacking As well, they are:

Simple (no internal electronics)

Less expensive ($6,000-$8,000)

Safe (short electrodes preserve the cochlea)

Easy to set (requires screwdriver or Palm Pilot)

Power conservative (batteries last 10-14 days)

february 5 th 2002

Documents

multiple electrode devicesin

practical cochlear implants

electrode systems

fdacochlear implants

place tonotopic stimulation

cochlear implant researchers

multiple sites

singlechannel prostheses