Dr. Ross on Hearing Loss
Developments in Tinnitus
by Mark Ross, Ph.D.
The topic of tinnitus often arose during my days as a teacher and clinical audiologist. For the most part, my responses simply regurgitated the conventional wisdom of the time, i.e., that tinnitus was a common problem, of unknown and varied origin, and that there were no sure-fire cures for the condition. Basically, I sloughed the topic off, primarily because there really wasn't that much solid information that could be conveyed. This is not to deny that for many people, tinnitus was a major problem. It certainly was. Some suffered acute emotional distress because of the persistence of sounds in their head every waking hour of the day and night, sounds that they could not ignore and that affected every aspect of their lives. And the more they focused on the condition, the worst it seemed to get. Basically, what we advised such people was that they simply had to learn to live with the condition, not a very helpful or hopeful response for people who were in acute discomfort.
Recently, I came across an article on tinnitus in the Journal of the American Academy of Audiology that stimulated my interest again in the topic. Evidently, researchers and clinicians have not been idle, with much good work continuing on this topic over the years. While recent work has affirmed the view that tinnitus has multiple origins and that no single miracle "cure" has been identified, still much more is known now about the phenomenon than we were aware of previously. I'll be reviewing some of this later, but first a review of the fundamentals.
Description, Demographics and Causation
Tinnitus is a term that is applied to the perception of sounds in one or both ears, or in the head in the absence of an external auditory stimulus. People's descriptions of these sounds include such expressions as clicking, hissing, whistling, and roaring. It may appear to be steady or intermittent, with a fairly wide range of perceived loudness. When, by using psychoacoustical procedures, its loudness is compared to objectively applied stimuli, the perceived sensation level rarely exceeds 7 or 8 dB. Considering this relatively low figure, clearly the subjective appraisal of the tinnitus is a dominant feature of the phenomenon, an observation that underlies one of the current therapeutic procedures that will be discussed (the Jastreboff technique). In other words, the annoyance that people feel from the tinnitus has no relationship to the psychoacoustical manifestations of the tinnitus: two people with exactly the same description of tinnitus can differ dramatically in the level of annoyance that they experience.
According to the American Tinnitus Association, over 50 million Americans experience tinnitus. Of these, some 10 to 12 million are sufficiently disturbed by the phenomenon that they feel compelled to consult a physician. Of these, about 2 million may be so emotionally affected that they have difficulty in leading a normal life. Often, they report that the tinnitus makes it difficult for them to fall asleep or to go back to sleep once awakened. They often feel depressed, frustrated and irritable and find it difficult to concentrate on necessary tasks. Indeed, some people have been so disturbed by the continuing experience of tinnitus that they chose to have an auditory nerve severed, sadly to little avail.
We know that tinnitus is a phenomenon that may be initially triggered by a host of factors. Evidently, the most common is some kind of damage or disturbance in the cochlea itself. This can be secondary to a noise induced hearing loss, various kinds of medications or chemical compounds. There is a high correlation between hearing loss and tinnitus, though it should be noted that many people with hearing loss are not disturbed by tinnitus while some people with perfectly normal hearing may be distressed by its presence. Other causes of tinnitus include head injury, genetic predisposition, vascular abnormalities or even wax in the ear canal. Tinnitus, therefore, is a description of a symptom that can, and is, produced by one (or more) of a large number of underlying conditions.
The perception of tinnitus may build up slowly or be the consequence of a clearly definable event. I know someone who developed severe tinnitus after slamming a toilet seat down in a closed cubicle. In this instance, the condition remained troublesome for many months before it receded from the person's awareness. Some writers on the subject consider the phenomenon a perfectly normal event in the nervous system, one that is always there but at a subconscious level. Apparently, the auditory neural system of a live human being routinely generates random or semi-random electrical discharges. It is only when these sensations are associated with some significant positive or negative event, or when the person consciously and continuously focuses on them, that they enter awareness and may become a problem.
A large number of treatment options to alleviate the symptoms of tinnitus have been described, with varying anecdotal and experimental reports of effectiveness. But before anybody who is really disturbed by tinnitus undergoes any treatment option, it is a good idea for that person to be examined by a professional or center that is thoroughly familiar with the recent developments on the topic. Insofar as tinnitus is concerned, the first lesson of all, as with hearing loss, is not to underestimate its impact upon the affected person. Treatment options should not be casually dispensed or unthinkingly accepted. The American Tinnitus Association is an excellent resource for further information (http://www.ata.org).
A number of tinnitus sufferers have tried various kinds of herbal or homeopathic preparations, while others have used acupuncture, magnets, or hypnosis in an attempt to alleviate their situation. Research has not conclusively supported any of these approaches. A biofeedback approach, designed to reduce the body's reactions to stress, reports some temporary success in alleviating tinnitus. The belief here is that the tinnitus sensation may be reduced when people are able to curtail or modify the stress in their lives. A similar reduction in the tinnitus has been noted, at least temporarily and for some people, when someone takes anti-anxiety, antidepressant, anticonvulsant or even anesthetic drugs. Evidently, stressed people judge tinnitus to be a more disturbing experience than they would if they felt more relaxed. Conversely, the tinnitus experience itself can contribute to the feelings of stress. It should be noted that none of these medicines act directly upon the tinnitus, and none should be tried unless prescribed by a physician. In these instances, the major treatment focuses on the stress, with any reduction of the tinnitus a secondary (but very welcome) effect.
Evidently, cochlear implants have helped reduce the experience and annoyance of tinnitus in about half the people who received implants. A number of mechanisms have been invoked to explain this occurrence. First, any remaining hair cells in the cochlear have either been destroyed or rendered ineffective by the electrode inserted into the cochlear. Thus this eliminates the random electrical discharges in the hair cells that may be a precursor to the tinnitus experience. The tinnitus may also be rendered inaudible because of the electrical stimulation of the auditory nerve delivered by the implant.
In a study published in the Laryngoscope a few years ago, one investigator evaluated all the controlled clinical research studies concerning tinnitus remediation that took place between l964 and l998. Sixty-nine such studies were identified. The studies evaluated a large number of different drugs and procedures. These included such approaches as psychotherapy, electrical/magnetic stimulation, acupuncture, masking, biofeedback, and hypnosis. The author concluded by stating that there was no single treatment that could be considered effective in providing a long-term, permanent reduction to the presence or annoyance of tinnitus, although he believes that the evidence suggests that counseling and antidepressant drugs can be helpful in some instances.
These results are not surprising, since as has been noted, there are many reasons for the initial onset of tinnitus and it is therefore unlikely that any specific treatment can be generally effective. An example of how treatment can be effective when a specific cause is identified occurs with a temporomandibular joint (TMJ) dysfunction. In this disorder, a misalignment of the jaw joints and jaw muscles may, besides causing pain during eating, also induce tinnitus because the muscles and nerves in the jaw are closely connected to the ear. When the underlying TMJ condition is resolved (by a dentist or oral surgeon), then the tinnitus disappears. Ordinarily, however, since identifying a specific cause is difficult, the most effective current treatment focuses not on the etiology, but on the similarity of the symptoms, which is what masking techniques do.
Masking techniques (or sound-based relief) is a therapeutic procedure whereby an external stimulus, deemed to be a more acceptable sound experience than the tinnitus, is used to mask the internal sound sensations. A sound generator that looks like a behind-the-ear hearing aid delivers either a broad band noise signal, or one that is filtered to reflect the tonal sensation of the tinnitus. In the classic procedure, the loudness of the external sound is increased until the tinnitus is no longer audible. This was first used in l976 and it remains one of the most frequently applied therapeutic procedures for tinnitus. Even the proponents of the procedure, however, would agree that this only provides help during the period the sound generator is actually being used. There may be some cessation of the tinnitus immediately after the generated sound is terminated (termed "residual inhibition"), but shortly thereafter the tinnitus reoccurs and is as annoying as ever.
For those people with hearing loss and tinnitus, a hearing aid will provide some relief. Even when no one is talking, provided there is ambient noise present, the hearing aid amplification can completely or partially mask the tinnitus sensation. Perhaps for this reason, tinnitus authorities stress that complete quiet is not a helpful listening condition. Combination devices are available that incorporate both a noise generator and a hearing aid. The sound generator is activated during periods of quiet when little sound amplification is occurring with the hearing aid. To assist in sleeping, various kinds of augmentative devices can be used at the bedside. These would include detuning an FM radio or listening to various CDs that have been specifically developed to provide tinnitus relief. All of these external noise stimuli are deemed to be more acceptable than the internal tinnitus sensation.
Because various kinds of noises have been used to provide tinnitus relief, the question arises about their relative effectiveness. This was the question asked in a recent study published in the Journal of the American Academy of Audiology. As a matter of fact, it was this study that motivated me to select this topic for the current article. The purpose of the study was to investigate the relative effectiveness of a number of different sounds that have been used for the purpose of providing tinnitus relief.
The study defined "tinnitus relief" as any reduction in the sense of annoyance (anxiety, irritation, frustration, anger or displeasure) associated with the conscious perception of the tinnitus sound. Two types of general masking noise were used. The first was one that is conventionally used at the present time for tinnitus masking, i.e., various filter patterns of noise. The other was computer-generated noise designed to simulate naturally occurring sounds, such as running water and the sounds of nature.
The results showed that all the sounds - on average - provided some tinnitus relief. The most effective stimuli, however, were the sounds that simulated the sounds of nature, inherently more pleasant stimuli than filtered noise. As the authors' note, while the spectrum of these more effective stimuli was similar to the more conventional filtered noise types, the nature sounds were dynamic in that they include short-term variations in the sound stimuli. It was this characteristic that was thought to be the primary reason they were more effective in reducing the annoyance of the tinnitus sensation. The conclusion was that various sounds differ in their ability to provide sound-based relief; clearly, this is a factor that must be incorporated in therapeutic measures that require some sort of external stimuli.
The Jastreboff Technique or Tinnitus Retraining Therapy (TRT)
Developed in l990 by Dr. Pawel Jastreboff, TRT seems to be emerging as the single most practiced procedure used with tinnitus. It has its basis on a neurophysiological model that incorporates a number of documented phenomena including habituation, classical conditioning, central auditory processing, cortical plasticity and the neural mediation of emotions. Each phenomenon is a component of the overall model, which identifies the interconnected neural structures involved with tinnitus and, most importantly, its associated emotions.
While the TRT method does not ignore the etiology of tinnitus, it does not focus on it either. Its emphasis is on the tinnitus sensation itself and the reactions of the person who experiences it. External sounds that are not threatening or that have no negative associations of any kind are soon ignored (or habituated). Thus the constant drone of a refrigerator or noisy traffic can be relegated to an unconscious level and virtually ignored. And there they remain unless some dramatic change occurs (i.e., a broken compressor or the sounds of a fire engine). On the other hands, external sounds that have important signal and warning associations (i.e., a baby's quiet whimper in the next room) will produce an immediate reaction by a young mother (who could well ignore a siren outside her house in an attempt to catch up on some sleep!). In other words, habituation to meaningless sounds ordinarily occurs fairly rapidly, but does not happen when the sound has important associations (either positive or negative). The same logic is applicable with tinnitus, in which the sounds are internally generated and perceived.
The goal of TRT therapy is to keep the tinnitus from evoking negative associations that involve the emotional centers in the brain or "the fight or the flight reactions" of the autonomic nervous system. The idea is to demonstrate to the person that tinnitus does not portend a significant health problem, that its objective correlate is really quite minimal (perhaps 7 or 8 dB) and that it will become less disturbing the less they focus on it. The purpose is not to eliminate the tinnitus sensation (desirable as this may be) but to help the person so habituate to its presence that it is no longer threatening or annoying. While the neural discharges transmitting the tinnitus sensation may still be present, its negative and emotional associations are peeled away, leaving just a non-threatening neural activity that can be relegated to the subconscious auditory system and consciously ignored.
This is ordinarily accomplished via a twofold approach. In the first, a tinnitus masker is used to diminish, but not eliminate, the tinnitus sensation. By mixing a more pleasant, external sound stimuli with the tinnitus, the intention is to reduce the annoyance level that people experience to the tinnitus alone. This makes it easier to eliminate the negative associations and thus habituate to its presence. But the masker cannot be set so high as to obliterate the tinnitus, since one cannot learn to habituate to a stimulus that is not perceived.
The other approach is basically educational, combined with directive counseling. The TRT model is presented to the tinnitus sufferer in all its neurophysiological detail. The various levels of the auditory system are reviewed, as is the way the brain operates on meaningful and meaningless sounds. The entire process of hearing is demystified with the tinnitus sensation placed in an overall neurophysiological context. This approach is unashamedly cognitively based; the tinnitus sufferer is not merely a "patient", but a student as well. Conveying this information and making sure that it is fully comprehended will take some time. The therapy program may last up to 18 or 24 months, perhaps meeting monthly in the beginning and less so after six months or so.
I do have to admit that when I first read of TRT, it sounded rather strange to me. It seemed as though it was based on convincing people that their tinnitus really wasn't bothering them after all, that their reactions to it were under their control, and that their continued annoyance to its presence was their entire fault. It seemed too much like blaming the victim. But the people who developed TRT, the published research that has been done on its effectiveness, and the many centers that now practice it testify otherwise. Some of these centers - several of whom I know personally - report a success rate of 80%, far in excess of other forms of tinnitus therapy, "success" being defined as a reduction in annoyance. Clearly, TRT has entered the mainstream.
Often, tinnitus does not appear alone, but in combination with hyperacousis, which is defined as an extreme sensitivity to environmental sounds. Some authorities believe that it may be the phobic reaction to the tinnitus that is primarily responsible for the acute sensitivity to sound, which then develops into hyperacousis. People with this problem may be reluctant to leave their homes because of their fear of being suddenly exposed to intolerably (for them) loud sounds. They may use earplugs or earmuffs to "protect" their hearing. Indeed, ten years ago I described in this journal a "reverse" hearing aid designed to reduce environmental sounds for people with hyperacousis. According to the rationale underlying TRT, these "remedial" steps were exactly the wrong procedure to use with such people. Instead of protecting them, all it does is increase their fear and anxiety about sound exposures.
TRT uses the same rationale to treat people with hyperacousis as it does with people who suffer from tinnitus. Often treatment for tinnitus and hyperacousis go hand in hand. In both cases, the experienced stimuli (internal or external) are much less significant than the associations that develop in conjunction with the sensation. In both cases, it is necessary to desensitize the overt responses, to learn that the auditory experience itself portends no serious problem, but rather that it is the web of negative associations that are responsible for the fear and anxiety the sensation induces.
Even the most optimistic boosters of TRT do not claim that they can alleviate the symptoms of tinnitus for everyone that suffers from this condition. And there is still much work to be done regarding its classification and origins. But, spearheaded by the American Tinnitus Association and such centers as the National Center for Rehabilitative Auditory Research in Oregon, progress is being made. At the least, we can say that tinnitus is not the completely untreatable condition I thought it was many years ago.