By Dr. Max S. Chartrand Ph.D.

This presentation steps the reader through the fundamentals of one of the most effective tinnitus treatment programs in the world today, and compares the underlying physiological model to Dr. Chartrand's current methodology.

TRT: Pioneering Research into the Mind of the Tinnitus Sufferer

A report on the relevance of TRT in current amplification strategies in patients for whom tinnitus is also a complaint.

In 1993, the author published an article in this journal titled "Tinnitus Management in the Dispensing Practice"1. Its purpose was to help define the role of dispensing professionals in the management of their patient's tinnitus as an adjunct to fitting hearing aids under best practice standards.

Also, in that article, was cited the groundbreaking work of several tinnitus research pioneers as foundational to some of the benefits that were reported as a result of appropriate amplification strategies: 1)Residual Inhibition (RI), Environmental Masking (EM), Auditory Reattention (AR), and Stress Relief (SR).

In retrospect, it turns out that eclipsing the author's study of the above benefits was an even more profound work under development by Pawel Jastreboff, Ph.D., D.Sc. and associates at the University of Maryland, and by Jonathan Hazell, FRCS, and associates at the Tinnitus and Hyperacusis Centre in London, England. This work has been titled Tinnitus Retraining Therapy (TRT).

Dr. Jastreboff has since transferred the TRT project to Emory University in Atlanta, where he and his colleagues continue its development and worldwide implementation. A recent visit between the author and Dr. Jastreboff helped bring us up to date on TRT principles as they correlate to the tinnitus management principles promoted in the 1993 article.

Because tinnitus is often a multidisciplinary, multifaceted effort2,3 Hearing Instrument Specialists® represent an important team player in the community healthcare team. For appropriate fitting of hearing aids may constitute the single most important component of remediation for patients who suffer from tinnitus and hearing loss simultaneously.4 However, understanding the foundational principles behind TRT and when to refer patients for such therapy can add an important dimension to tinnitus management within a multidisciplinary framework.

Patient Classifications

The Jastreboff neurophysiological model5 helps us understand first, how the perception of subjective tinnitus develops in most patients, and secondly, why hearing aids are so vital in hearing impaired cases for the management of tinnitus. He also describes accompanying hyperacusis, which, in the hearing aid patient, is manifested as recruitment, or the recruiting of a larger than the usual number of cochlear hair cells and more neural involvement at the cortical level. Hyperacusis is suspected to afflict, to widely varying degrees, the vast majority of sensorineural cases6, so addressing recruitment complaints in the course of hearing instrument dispensing becomes a related issue to the remediation of tinnitus complaints, as well.

Jastreboff classifies tinnitus patients at his clinic into five specific treatment categories7, according to manifestations of hearing loss, hyperacusis, and tinnitus:

• 0. Minimal symptoms, not requiring prolonged intervention
• 1. Significant tinnitus without significant hearing loss
• 2. Significant hearing loss with tinnitus
• 3. Hyperacusis
• 4. Hyperacusis with prolonged symptom enhancement by environmental sound exposure

For our purpose here, we will focus on classification #2 patients: Tinnitus patients who also suffer from significant hearing loss, and for which amplification can be a requisite part of their treatment regimen. This would, of course, include many patients that Specialists® see routinely in their practice. It would also include tinnitus sufferers seen by other health professionals, and who've not yet been referred for auditory testing.

Figure 1 Here

Figure 1 The Jastreboff neurophysiological model used in his Tinnitus Retraining Therapy (TRT)

Tinnitus Retraining Therapy (TRT) Explained

According to the Jastreboff model, the goal is not necessarily to eliminate the tinnitus, but through practiced exposure to "environmental sound enrichment"8 and rehabilitative counseling, the patient is able to develop habituation or acceptance of the tinnitus sound until it no longer disrupts their quality of life. Of course, for hearing impaired patients who meet criteria for amplification, part of the sound enrichment process involves wearing hearing aids.

Figure 1 shows the neurophysiological basis for the Jastreboff model, while figure 2 demonstrates the relationship between auditory and sensory pathways, and the aversive conditioned reflex. Both of these demonstrate plasticity of the human brain, both as an aberrant perception of unwanted noise (tinnitus) and the development of habituation.

Figure 2 Here

Figure 2 Model for describing relationship between auditory and extra-auditory pathways, and the adversive conditioned reflex.

While the neurophysiological model and TRT protocols do not necessarily explain all causal factors and sites of lesion---which manifestations can be nearly as varied as the individuals suffering from them---they do illustrate that:5

• The "limbic (emotional) and autonomic nervous systems are involved in contributing to tinnitus annoyance."
• When tinnitus is disturbing to the sufferer it interrupts natural homeostasis (or one's emotional balance)
• After undergoing "sound enrichment" (including wearing amplification) the regenerative nueroplasticity of the brain allows one to habituate or neutralize negative associations of tinnitus
• Due to recruitment in the central auditory system hyperacusis frequently accompanies or co-acts with tinnitus

Remediation pathways for TRT involve: 1) intensive patient counseling and education, and 2) sound therapy. Dr. Jastreboff goes on to explain:

"Counseling sessions are aimed at the (patient's) reclassification of tinnitus into a category of neutral signals. During the sessions, tinnitus is demystified and patients are taught about physiological mechanisms of tinnitus and its distress, as well as the mechanisms through which tinnitus habituation can be achieved.

"The second element of TRT is sound therapy. Constant low level broadband sound decreases the differences between tinnitus-related and background neuronal activity. Consequently, the strength of activation of the limbic and autonomic nervous systems, which at the behavioral level is reflected by a decrease in tinnitus-evoked annoyance, is reduced." 9

At the heart of TRT is utilization of sound therapy, which is the opposite of the quiet environment in which tinnitus has been provoked10. For the hearing impaired patient, appropriate amplification can also provide the needed broadband noise backdrop by introducing "environmental masking"1. But, also important are the hours in which amplification is not worn, during sleep for instance. Since the most desirable environmental sounds are those that occur naturally, TRT therapists counsel for various strategies and equipment to be used during the hours of sleep, such as wind blowing, ocean waves, sounds of nature, etc.). These are tailored to each patient's needs and circumstances.

The hope is that, over time, a round-the-clock enrichment process satisfies the subconscious (central auditory and limbic) need to put balance back into the normal "primitive" backdrop of life, so that the patient ultimately achieves habituation (or subconscious acceptance) of the tinnitus sound itself.

Emotional Associations

Hazell refers to the underlying neuromechanics of tinnitus as "the mechanism of aversive reactions"5. Not unlike Ramsdell's auditory model (see figure 3) of three listening levels in human hearing12--- 1) Primitive, 2) Signal, and 3) Linguistic Communication---Hazell describes the subconscious components of hearing that are controlled primarily by limbic and autonomic nervous responses to sound in the environment.

Figure 3 Here

Figure 3 Chartrand's model illustrating a new way to view Ramsdell's 3-tier auditory receptive model. In this way, the symbolic (communication) level is defined at one extreme by non-verbal background (primitive) and at the other extreme by alerting (signal) level, which transcend abstract interpretation and connect with autonomic (involuntary) responses.

Some aversive reactions affect varying parts of the brain, the amygdala, for instance, which is involved with fear, fight or flight, startle, anger, annoyance and preparation for danger11. Consequently, physical responses such as muscle tension, sweating, increases in heart rate, and adrenalin secretion may be incited in the hearing impaired individual that would not affect a normal hearing individual in the same way.

While the normal ear is able to detect extremely quiet sounds (approaching 0 SPL @3-4KHz) and yet tolerate loud sounds up to an incredible 130dBSPL, an impaired cochlea loses the ability to hear soft sounds and, conversely, the ability to tolerate loud sounds (recruitment). This narrowing of the dynamic range is created primarily by "abnormal loudness growth", in some cases increasing in perceived loudness growth as much as 3, 5 or 10dB per actual decibel!

As Hazell describes8 the phenomenon, "More nerve fibres are switched on or ‘recruited'." At the central auditory level, sound is analyzed to extract meaningful messages or signals from an otherwise meaningless background of noise. "Often the signal is relatively weak in strength, but strong in meaning." Hence, when ordinary background (primitive) sounds move into the signal level of hearing because of hearing loss, even softer (yet audible) sounds add to the limbic imbalance, with increased levels of distress.12

In a recent interview13, Jastreboff asserted, "The natural system works in AGC, not linear mode, with the central auditory process determining to what degree one's subjective sensitivity changes." Silence, whether real or caused by loss of hearing, is perceived at the central auditory level can be interpreted as a signal for danger, according to Jastreboff and colleagues.

Parallels with Current Dispensing Practice

In light of the above, there appears to be some parallels between TRT and other tinnitus amplification management strategies taught dispensing professionals by this author:

• Auditory Reattention (AR)14,15,1, or the redirection of one's attention away from the tinnitus complaint and toward actual (amplified) signals from the environment. This aspect corresponds to the TRT ideal utilization of "natural" sounds rather than "contrived" sounds, such as white noise masking or radio static.
• Environmental Masking (EM)16,17 comparable to the "low level masking" of TRT, is generated in the hearing aid circuit by simply amplifying sounds naturally occurring in the environment. For patients whose complaint is that tinnitus is heard only in quiet, it is possible to eliminate most of that complaint by bringing abnormal thresholds closer to the normal hearing levels.
• Residual Inhibition (RI)18,1,2-although dependent upon appropriately fitted amplification, may actually be a temporary manifestation of the habituation found in TRT. In such a comparison, the efferent response (which incites tinnitus or its "phantom hearing effect") that results from auditory deprivation of damaged hair cells in the cochlea would relax. This can bring about at least a temporary lessening of the tinnitus loudness in many cases. In this way, TRT habituation might at least partially be explained along the lines of the Ramsdell psychoacoustic model of three levels of hearing.7
• Stress relief (SR)19,20,21- A combination of any of the above, coupled with patient counseling and education, can bring about lessened stress over the tinnitus complaint. This is a central component of TRT, as limbic involvement is considered primary to the aversive stress response, while the tinnitus manifestation itself is considered secondary.

In Summary

Over the past 3 decades, there have been virtually hundreds of strategies devised for managing, reducing or eliminating tinnitus. However, because each school of thought presents a different physiological model, most have failed to achieve universal application. Hence, lack of reproducible treatment outcomes has led many medical and health professionals to conclude that there is "nothing that can be done" for tinnitus complaints, often advising patients to "learn to live with it"22. Certainly, there appears to be inordinate skepticism that there even exists a viable approach to the problem of tinnitus23.

But TRT presents a model that can be used almost universally, in conjunction with other strategies appropriate to each individual patient including biofeedback, (environmental) masking, residual inhibition, allergy remediation, nutritional/medication therapy, or stress management counseling24. Hence, remedial protocols that are tailored and work in combination within a multidisciplinary framework assure a greater degree of success for larger numbers of tinnitus sufferers.

References

1. Chartrand, M.S., "Tinnitus Management in the Dispensing Practice", Audecibel, Livonia, MI, fall issue, pp 7-10 (1993)

2. Chartrand, M.S. "Tinnitus & Amplification", Audecibel, Fall, Livonia, MI: International Hearing Society, pp. 18-21 (1989).

3. Chartrand, M.S., "Inferential correlates derived from a survey among hearing health professionals", Rye, CO: Aural Rehab Concepts, (1994).

4. Nodar, R., "Techniques for Tinnitus Mangement", Hearing Professional, International Hearing Society, March-April, pp. 5-8 (2002).

5. Hazell, J.W.P., "The TRT method in practice", VI International Tinnitus Seminar, London: Ed Hazell Publications THC, pp. 92-98 (1999).

6. Hazell, J.W.P. et al, "Hypersensitivity of Hearing", www.tinnitus.org, October (2002).

7. Jastreboff, P.J., "Tinnitus as phantom perception: Theories and clinical implications", in Mechanisms of Tinnitus, eds. Vernon, J. and Moller, A., Massachusetts: Allyn & Bacon, pp. 73-87 (1995).

8. Hazell, J.W.P., "Environmental sound enrichment", www.tinnitus,org, June (2001).

9. Jastreboff, P.J., and Jastreboff, M.M., "Tinnitus Retraining Therapy: An Update", www.audiologyonline.com, Archives, (2002)

10. Shedrake, J.B., Hazell, JWP and Graham, RL, "Results of tinnitus retraining therapy", VI International Tinnitus Seminar, London: Ed Hazell Publications THC, pp. 292-296 (1999).

11. Chartrand, M.S., Audition, Cognition & the Human Brain, a 12-hour continuation education course, Livonia, MI: International Institute for Hearing Instruments Studies (1999).

12. Chartrand, M.S., Hearing Instrument Counseling: Practical Applications for Counseling the Hearing Impaired, Livonia, MI: International Institute for Hearing Instruments Studies, pp. 19-26 (1999).

13. Chartrand, M.S., Notes from telephone/TDD interview with Dr. Jastreboff for this article, Rye, CO: DigiCare Hearing Research & Rehabilitation, October 10, 2002.

14. Wilson, J.P., "Evidence for a Cochlear Origin for Acoustic Re-admissions et al", Hearing Res 2:233-252 (1980).

15. Kemp, D.T., "Simulated Acoustic Emissions from Within the Human Auditory System," Acoust Soc Am 64:1386-91 (1978).

16. Vernon, J., "Advancements in Tinnitus Management Strategies", California Hearing Health Practitioners of California, Annual Seminar, Long Beach, CA (1996)

17. Vernon, J., "Current use of Masking for the Relief of Tinnitus", Tinnitus, Pathology and Management, Kitahara, ed., pp. 96-106 (1988).

18. Vernon, J., "Attempts to Relive Tinnitus", J Amer Audiol Soc 2:124-131 (1977).

19. Sweetow, R., "The Tinnitus-Masking Efficiency of High-Frequency Hearing Aids", Hearing Journal 44:4, pp. 24-34 (1991).

20. Surr, R.K., Montgomery, A.A., and Mueller, H.G., "Effect of amplification on tinnitus among hearing aid users", Ear and Hearing, 6:71-75 (1985).

21. Sheldrake, J.B., Jastreboff, P.J., Hazell, J.W.P., "Perspectives for total elimination of tinnitus perception", Proceedings of the 5th International Tinnitus Seminar, Portland, Oregon, 1995, eds. Reich, G. and Vernon, J., Portland, OR: American Tinnitus Association, pp. 531-537 (1996)

22. Chartrand, M.S., and Chartrand, G.A., "Participant Prospectus TA2002 Study", from Tinnitus and Amplification 2002 Study, DigiCare Hearing Research & Rehabilitation, Rye, CO (2002)

23. Nagler, S. M., "The First Nail in the Coffin", Otology & Neurotology: An International Forum, 22:4, pg. 429 (2001).

24. Gold, S.L., Gray, W.C., Jastreboff, P.J., "Audiological evaluation and follow-up", Proceedings of the 5th International Tinnitus Seminar, Portland Oregon, 1995, eds. Reich, G., and Vernon, J., Portland, OR: American Tinnitus Association, pp. 485-487 (1996).