Dr. Ross on Hearing Loss
Reflections on My Cochlear Implant: Part 1
by Mark Ross, Ph.D.
As this article is being written, I am scheduled to receive a cochlear implant (in late December). What I would like to do in this paper is review my personal experiences leading to my decision to acquire an implant, and include some of the professional issues that were raised for me. In a subsequent article, once I’ve acquired and used the implant for a while, I will make some observations on the adjustment and rehabilitation process, again from both a professional and personal perspective.
I’m sure that my experiences leading to the decision to get an implant were no different than those confronted by thousands of other current implant users. Like them, I experienced declining auditory abilities, to the point where many verbal interactions became very difficult and often impossible. Superficially, I appeared to be doing acceptably well, particularly on a one-to-one basis or when I was controlling the conversation. This can be attributed, I believe, to my ability to compensate by using visual and non-verbal clues, to predictable situations, the innate redundancy of the English language, and some creative guessing on my part. But it was (and is) tough going. Only I (and my wife) really know how much effort I put into these discussions and what I was actually missing.
Having an easy conversational exchange, where I could comprehend both the speech directed to me and towards others in the group, just doesn’t happen anymore. In many small group situations, even when “clear speech” is practiced when someone talks to me (often at my insistence), this speech modification is rarely followed for conversations between the normal hearing participants. In some ways, the most frustrating experience of being severely hard of hearing occurs when I am sitting at a table with three or four people and unable to participate fully in the exchanges, simply because I can’t comprehend what they say to each other. And it happens even among members of my own family whose love and respect for me cannot be doubted. For me, an improved (not perfect!) ability to participate in such group conversations will serve as my major criterion for a successful implantation.
During this period of declining auditory abilities, I often upgraded my hearing aids to compensate for the progression in the hearing loss. I was determined to squeeze out every dB of audible speech possible in every situation. Since I kept up with new developments in hearing aids, I knew what was available; and, fortunately, I am usually able to try promising new hearing aids, which has often helped. However, I finally reached a point, about a year ago, where I was ready to get an implant. I could no longer understand on the telephone using just my right ear (I now routinely use both my ears on a telephone with a neckloop). At that time, however, some power digital aids were introduced that included effective feedback management systems. This meant that I could obtain about 10 dB more effective amplification without feedback, and this made all the difference for about a year. But my hearing loss, particularly in my right ear, continued to worsen, and soon the additional amplification possible with these new aids had less and less practical significance (though some aided audibility was still possible). My hearing thresholds now average about 110 dB in the right ear (95 dB or so in the left). The fact that I could do as well as I did for as long as I did is testimony to the marvelous advances in hearing aids. But given that I believe I had reached the maximum hearing aid benefit possible, and coupling that with the impressive progress made by cochlear implants in the last few years, it seemed past time to make the implant decision for myself.
It is important to note that the potential benefits of any hearing aid are ultimately fixed by the limits imposed by a damaged auditory system. No hearing aid can exceed these limitations. If the hair cells in some portion of the cochlea are dead, then they cannot trigger neural impulses no matter how much amplified sound is delivered. Additionally, even when they are not completely dead or are absent, scattered dead and damaged hair cells will produce fundamental psychoacoustic abnormalities that will likewise limit the basic speech perception capacities of that particular ear. Audiologists try to fit hearing aids with the kinds of “prescriptions” and features that will enable them to get as close to these physiological limits as possible. Also, much can be accomplished with current technology that is not being fully exploited (e.g., personal FM systems). Eventually, however, the speech analytic capacities of the ear will have been reached, no matter how much “better” (or more expensive) the hearing aids are. When these limits fall significantly below the average results now obtainable with a cochlear implant, then the time has come to consider an implant.
But it wasn’t easy for me to make this decision for myself. In the last fifteen or twenty years, I have suggested the possibility of a cochlear implant to many people (referring them to cochlear implant centers). Although it was a move I encouraged, it was never a recommendation that I made lightly. But it was one I was glad to make; I well remember the difficult situations that existed in the years before implants were developed, the options that did not exist for late-deafened adults and deaf children. But now that I myself was the patient, the decision seemed to take on a whole different order of difficulty and conflict; it was a lot easier to suggest that someone else consider an implant than to get one myself. I still wonder if I’m doing the right thing (even now, as I’m writing this section three days before my surgery).
What finally tipped the scale for me personally was my daughter’s reaction when, upon arriving for a visit to our home, she opened the car door and the first thing she remarked was how wonderful the birds sounded, that they didn’t seem quite so musical in New York City where she lives. I didn’t hear a thing. My inability to hear them happened so gradually that I really wasn’t aware that I was not hearing them. Perhaps they weren’t around? It turns out that they were all around; I was just not “tuned in.” It was not only bird songs that I was missing, but most of the high frequency components of speech, those elements particularly important for the perception of phonetic elements. It is the absence of these elements from my perception that explain much of my difficulty in comprehending speech. One can go only so far in using linguistic predictability to comprehend unheard elements; at some point, having sufficient acoustic information is critical. I had reached that point.
My next step was to refer myself to a cochlear implant center and go through its routine procedures. As a veteran with a service-connected hearing loss, I elected to obtain my implants through the V.A. As it happens, in New York the well-reputed NYU Cochlear Implant Center manages this responsibility for the VA., with many of the professional personnel holding joint appointments. All my pre-op testing was conducted at the NYU Center, as will most of the programming procedures to be conducted after the implant is activated.
The results I obtained on the speech tests presented me with a quandary. If one judges implant candidacy primarily upon sentence recognition scores, then I was not a candidate since I obtained scores in excess of the usual criteria (50% or less in the ear to be implanted and no more than 60% bilaterally). But I achieved my relatively high scores with a great deal of effort, using my knowledge of the language to make linguistic predictions, and rarely being completely sure that my choices (or guesses) were correct. As long as I could hear part of the sentence, I could often figure out the rest. Many people with long-standing hearing losses possess similar capabilities. Generally, current audiological tests administered to any person with a hearing loss - implant candidate or not - do not measure the effort required to comprehend speech, the time it takes to make a decision, or the confidence with which a decision is made. But these factors define the reality situation confronting a hearing-impaired person who is attempting to understand speech. It often takes me longer to figure out what someone has said and I expend much more energy doing this than someone with normal hearing. And I am never quite sure that I’m completely correct.
My basic acoustic potential was much more accurately reflected in my scores in a test in which linguistic competency was basically irrelevant (a monosyllabic word recognition test). In this test, I obtained an 18% score in my right ear. It was this score that validated my decision to get a cochlear implant. And any objective evidence regarding the efficacy of the implant will have to be demonstrated primarily by significant improvements in this score.
As an audiologist, I’ve counseled many people regarding what realistically can and cannot be expected from a hearing aid. We know that hearing aids usually do “aid” hearing, but also that they cannot completely replace natural hearing. This is a message that ethical hearing aid dispensers consistently convey to their clients. The need to do this is even truer for potential cochlear implant candidates. Audiologists will emphasize, over and over again, that the cochlear implant, while a truly marvelous technical creation, is not going to replace a normal cochlea. People cannot enter the implant process expecting to exit with normal hearing. So “realistic expectations” is always an important component of the pre-implant counseling process. I know all this, and I am aware that I must be realistic in my expectations, and I believe I am. But at the same time, unbidden and lurking not far beneath the surface, are my unrealistically high hopes. Not that I will wind up with normal or close-to-normal hearing – I can’t imagine that result even in my wildest daydreaming – but that I will, for example, be able to function fairly normally in challenging group conversational situations. Rationally, I know this is unrealistic, but irrational hope cannot easily be contained.
The point is that it is currently impossible to predict precisely just how a specific person will function when using a cochlear implant. The group results to date have been impressive. There is no doubt but that the overwhelming majority of new implant users hear better with the implant than they did before, with hearing aids. Still, one does put one’s residual hearing in the implanted ear at risk when the internal electrode is inserted into the cochlea. So if a person has something to lose then the decision to be implanted means balancing the probability of losing one’s natural hearing with the strong possibility that the overall results will be favorable. Of course, the worse one’s natural hearing is, the better the chances are for net gains in speech perception. In my case, the odds seem to be in my favor and so I am going ahead with it. Nonetheless, it would not be honest for me to suggest that I do not feel any apprehension that I will lose this particular bet. Of course I do. So, I suppose like most people embarked on this course, I am balancing “realistic” expectations, my highest hopes, and my underlying apprehensions.
Then the time came for me to make a decision regarding which one of the three current cochlear implants to request. From everything I have been able to determine, from the research and from anecdotal reports, people do well with all of them; no one of them stands out as clearly superior to the other two. In actuality, because of my personal comfort zone, I limited my decision to a choice between the two which have been marketed the longest in the U.S. and with which I’m most familiar. These were the implants manufactured by Advanced Bionics and by the Cochlear Corporation.
I spent quite a bit of time reviewing these companies’ websites, communicating with their representatives, and discussing the pros and cons of each with various colleagues. Each time I looked at the technical specifications and marketing claims of either implant, or each time I listened to an advocate, I was convinced that that was the one for me. I wavered back and forth between the two. Both made convincing cases and both appeared to be designed to maximize the amount of speech information available to a listener. While each has unique features, these differences (such as they are) do not seem to result in speech recognition scores clearly superior to the other. What it seems to come down to, at least to my way of thinking, is the immense contributions made by the human brain in the speech recognition process. Evidently, the acoustic raw material (transformed into electrical impulses) that either implant provides to the central auditory system permits fairly equal auditory learning to take place. Finally, I decided on the implant manufactured by the Cochlear Corporation, but I do want to make clear that I could as well have decided on the one made by Advanced Bionics. Both companies have recently introduced new models that seem to be “state of the art” systems (at the present time only!!!). I would have been as comfortable with my decision with either – and as apprehensive.
As I considered the pros and cons of either implant, it was also apparent that one crucial consideration, applicable to all implants, is how the device is programmed (the “map”). Unlike hearing aids, this is not a pre-programmed response pattern that depends primarily upon variations in audiometric results. With hearing aids, all that is necessary is to plug the audiometric results into the fitting computer and a “prescribed hearing aid response” (or several) emerges - to be “fine-tuned” later as required. The people receiving implants, on the other hand, begin at ground zero; all are considered to have a non-functioning cochlea. Therefore, an audiogram is irrelevant for the mapping process. Because of the likelihood of individual differences in the survival of various auditory fibers in the auditory nerve, and because of variables associated with the insertion of the internal electrode, it is impossible to create a standard program for each individual. There are default measures, to be sure, gained from research and from generalizing the results taken from thousands of people who have already been fit, but some actual programming measures still have to be taken. Only a few at first, for the youngest children, since they are unable to make the necessary voluntary responses; these are supplemented by interpolations and general estimates in setting some of the dimensions. These settings are refined later as the child gets older and can participate in the test. Adults, on the other hand, have to go through the entire mapping sequence, a process that will take a number of hours. Even now, before I am actually implanted, the NYU Cochlear Center has scheduled me for four follow-up appointments subsequent to the device’s activation.
The process of mapping actually begins in the operating room. My audiologist will be there during surgery to measure the viability of each electrode electronically (impedance and neural response telemetry). Then an X-ray will be taken and if the scan looks good, the surgeon will close the incision. Once the incision has healed and the implant’s external component placed in position, the implant will be activated. At this time, the audiologist will commence her/his critical role in programming. The more I have gotten into this, the greater is my appreciation of this whole new world of professional challenges facing audiologists. Mapping (or programming) the implant is a complex process, depending, it seems, equally on the client’s responses and the competency of the audiologist. Clearly, it is not a “cookbook” procedure. From everything I’ve been able to gather, the “art” of working with human beings, plus the ability to interpret a client’s overt or involuntary responses, is a key ingredient to a successful map. An overriding goal is to “map” as much of the acoustic input as possible into the electronic dynamic range determined during the mapping process.
The audiologist determines the amount of electrical current necessary to produce an audible sound in each electrode (the “T” level), and then the current level which produces a loud, but comfortable audible sensation (the “C” point). The difference between these two points is the electrical dynamic range. The audiologist also has to make a number of other programming decisions, such as the rate of stimulation, the bandwidth of each electrical pulse and the acoustic frequencies to assign to each electrode. Other controls (such as microphone sensitivity) are under the control of the user, but it is important to realize that variations in one setting may impact upon others. This is evidently where the “art” of mapping comes in, where the audiologist will make changes depending upon the experiences of the user. Also, maps may change over time, though I’m not yet sure why. Possibly a certain amount of neural adaptations occur at certain frequency and contact positions, to the extent that it is necessary to reset some of the initially mapped parameters. This is an area that I expect to learn much more about as I proceed with my own mapping. I’m afraid the audiologist who will be working with me (who has been gracious and forthcoming) is going to be faced with a patient with lots of inquisitive questions. In my next article, I’ll comment on what I will have learned about mapping as I went through the process myself as a patient.
The organized and careful follow-up testing that is done for people receiving cochlear implants does raise a question about the relative absence of such care for people wearing hearing aids. People listening through hearing aids want to, and need to, hear as much as they are able to with their device. After all, what is heard through a hearing aid is no less significant than what is heard via an implant. Yes, I know that implants were designed for people with more severe hearing losses than hearing aid users usually have. And I know that implants require a time-consuming activation process that necessitates special training and skill on the part of the audiologist. But that does not mean that the selection and fitting of hearing aids is a trivial and superficial process in comparison. On the contrary, to do it right and to be assured that a person is obtaining the most hearing benefit that can reasonably be expected takes skill, special knowledge, and time. I have no quarrel with the care with which implants are fit and followed up; my concern is that this same degree of commitment is also required when it comes to hearing aids, something that is more often lacking than present.
For example, the American Academy of Audiology-recommended guidelines in fitting hearing aids includes the necessity of measuring the output of a hearing aid in the real-ear. What this measure requires is the insertion of a very fine tube into the ear canal, alongside a hearing aid and extending slightly beyond it. This tube leads to a microphone that measures the amplified sound in the ear canal between the tip of the ear mold and the eardrum. It is the best direct measure of hearing aid performance currently available. By plotting the amplified sound on the same chart as a person’s hearing thresholds and loudness tolerance levels, a single graphic displays the degree of aided audibility across frequency. No other audiological measure can do that, not traditional coupler measures nor the programming computer used in fitting hearing aids. Real-ear measures permit a visual display of what a particular person actually hears with the hearing aid in his or her ear. But only a relatively few audiologists (about 20%) routinely do real-ear measures in their hearing aid fittings. And there are other tests and measures which can be used to evaluate and to modify the performance of hearing aids, such as speech-in-noise measures, which only a minority of hearing aid dispensers routinely administer. When it comes to implants, audiologists generally do not short-change the evaluation or follow-up process; it’s all considered necessary. My hope is that the same degree of care and concern shown with implants also be provided to people wearing hearing aids. In my case, I can almost hear my left (hearing aid aided) ear complaining about the extensive services, its sibling (my right, soon-to-be implanted ear) has and will be receiving compared to what it receives.
The surgery date has come and gone and I’m now one week into the recovery process. I was advised that the surgery itself is a “minor” procedure, and I always thought it was. However, when one is the recipient, no such procedure can be considered “minor.” In anticipation, I still worried about the general anesthetic, about pain, and about the success of the operation. Fortunately, my worries were groundless. I had a first-class group of professionals taking care of me, which was comforting. During surgery, the audiologist determined that all the electrodes were fully functional, i.e., that I will be starting this particular game with a “full deck.” Now all I have to do is wait until the next challenge: the first activation date. Initially, realistically, I expect to hear sound- gibberish through the implant, sounds that - with time and training - will organize itself into intelligible speech. But still, unrealistic as it may be, I hope for more immediately. When next I write, we’ll see what the reality is.