Decreased sound tolerance (DST): hyperacusis and misophonia
Pawel J. Jastreboff, Ph.D., Sc.D., M.B.A. and Margaret M. Jastreboff, Ph.D.
Emory University School of Medicine & Jastreboff Hearing Disorders Foundation, Inc.
(This text contains some information which was presented at the lecture during AAA Annual meeting, Boston 2012)
Sounds of different pitch, loudness, spectral complexity, and duration may be to some people pleasant, but to others neutral, the same sounds can be unpleasant, uncomfortable, annoying or even hurtful to others. There are many studies related to the effects of sound on humans focused on psychological consequences, general health issues, engineering challenges, development of new technologies, environmental problems. Studies with the use of non-verbal digitized sounds showed that when presented on a comfortable level, on the average they induce similar emotional responses in people from different countries and backgrounds. Nevertheless, there is a significant group of people whose lives are significantly affected in the negative manner by the sounds not significant to other people and who suffer due to decreased tolerance to sound. Interestingly, it is not simply the loudness, pitch, and duration of sound which cause a problem, but these factors are most commonly considered when offering advice to patients. In the case of sensitivity to louder sounds the most common advice is to use ear protection and avoiding these sounds, which unfortunately frequently leads to worsening of the problem. Moreover, patients' complaints are frequently classified as exclusively psychological or behavioral problems and treated accordingly to this diagnosis. It is not unusual that patients' problems are simply ignored and there is no help offered.
Decreased sound tolerance may have profound impact on patients' lives as it may restrain exposure to louder environment, prevent them from work, reduce social interactions, negatively affect family life and, in extreme cases, it may control the patients' life. Even milder severity DST could affect quality of life by interfering everyday activities, e.g., driving car, shopping, going to restaurants, going to movies, attending sport events, use of noisy tools, hair dryer, vacuum cleaner, lawn mower, listening to music or TV.
Certain triggering factors for DSTare commonly reported by patients such as: chronic exposure to sound, e.g., at work, school, explosion and impulse noise, e.g., guns, fireworks; head injury, surgery of the head (particularly involving ear); stress associated with an event / activity involving sound, e.g., dental procedure, wedding, concert, participating for first time in summer camp, eating in new, stressful surrounding, cafeteria in new school or in college, sound of eating of a new unfriendly person, sounds after moving to a new house or to college. Some medical problems are linked to DST with tinnitus being most common. Lyme disease, withdrawal from benzodiazepines and tensor tympani syndrome, some surgical procedure, genetic disorder (William syndrome) and autism have been linked to DST as well.
There is still lack of agreement regarding definition of decreased sound tolerance. Decreased sound tolerance canbe defined as being present when a subject exhibits negative reactions as a result of exposure to sound that would not evoke the same reaction in an average listener. Reported reactions include discomfort, distress, annoyance, anxiety, variety of emotional reactions, pain, fear and other negative responses. In the past two phenomena, hyperacusis and phonophobia have been linked to DST: 1) Hyperacusis - when subject reacts negatively to all "louder sounds" and 2) Phonophobia - when subjectis "afraid of specific sound or one's own voice."
In 1990's when TRT was developed and used to help tinnitus patients, it became obvious to us that many tinnitus patients and actually some people without bothersome tinnitus as well, complain about discomfort caused by sound. In our work we always pay big attention to patients' description of their problems and through this we have been gradually accumulating clinical knowledge on how to help patients in the most effective manner. In 2000 it become evident that while about 60% of our tinnitus patients exhibited DST, only a minority of them reacted to loud sound disregarding their meaning and situation when they were exposed to sound. The majority of patients reacted negatively only to specific patterns of sound frequently (but not always) associated with specific situations /places, e.g., neighbor playing music; sound of eating, chewing, swallowing at home or at school; voices of specific people, clicking sound, e.g., copy machine; running water; crackling sound, e.g., paper, fireplace; high flying airplanes. At the same time these patients could tolerate even high level of other sounds, e.g., loud music or noise of busy street. This category of patients did not fit into a hyperacusis category. A relatively small group of patients expressed fearful reactions to sound while others talk specifically about different emotions, e.g., discomfort, dislike and they were strongly opposed to their condition being described as phonophobia.
With some hesitation regarding introducing a new term it appeared to develop a word describing these complaints. We askedfor help from Guy Lee, Don at St. John's College of Cambridge University, U.K., an expert in Greek and Latin literature, to provide a list of pre- and postfixes which would convey a negative reaction/attitude to something. He sent us about 20 different words, but none were perfect. Finally we decided on the prefix"miso" meaning "hate" in Greek and we proposed the new term, misophonia, to describe this subtype of DST. To avoid word "hate," which is very powerful and has very strong negative meaning, we used in writing or lectures a "diluted/milder" wording "strong dislike" or even simply "dislike." Unfortunately, some professionals and patients took the word literally and started to associate misophonia with dislike of sound in general.
The term was introduced into public domain in 2001 (Jastreboff, M.M., Jastreboff, P.J. Hyperacusis. Audiology On-line, 6-18-2001) and in peer-reviewed journal in 2002 (Jastreboff, M.M. and Jastreboff, P.J. Decreased sound tolerance and Tinnitus Retraining Therapy (TRT). Australian andNew Zealand Journal of Audiology. 24(2):74-81, 2002). DST results from the summation of the effects of hyperacusis and misophonia. The analysis of conditions when hyperacusis and misophonia manifested themselves indicated different physiological mechanisms of hyperacusis and misophonia. Therefore we have proposed two types of definition for component of DST: behavioral and based on presumed mechanisms involved in hyperacusis and misophonia.
From the behavioral point of view hyperacusis (occurring in about 25-30% of tinnitus patients) is characterized by negative reaction to a sound which depends only on its physical characteristics (i.e., spectrum, intensity). Time course (coded in the phase of spectrum) and meaning of the sound are irrelevant as well as the content in which a sound occurs.
Misophonia (occurring in about 60% of tinnitus patients) is characterized by negative reaction to a sound with a specific pattern and meaning. The physical characteristics of a sound (its spectrum, intensity) are secondary. The reactions to sound depend on a patients' past history and depends on non-auditory factors, e.g.,patient's previous evaluation of the sound, the patient's psychological profile, and the context in which the sound is presented. Under this definition phonophobia is a special case of misophonia when fear is a dominant emotion. Misophonia increases awareness of external sounds and somato sounds (e.g., eating) which are normally habituated and misophonia frequently induces tensor tympani syndrome. Note that both hyperacusis and misophonia are evoking the same emotional and autonomic (body) reactions and it is impossible to discriminate between them on the basis of observed reactions.
In mechanism-based definitions hyperacusis reflects abnormally strong reactivity of the auditory pathways to sound (overamplification of sound-evoked activity), which only in turn yields activation of the limbic and autonomic nervous systems (which are responsible for emotional and body reactions). The functional connections between the auditory, the limbic and autonomic nervous systems are normal.
On the other hand misophonia reflects abnormally strong reactions of the autonomic and limbic systems resulting from enhanced functional connections between the auditory, limbic and autonomic systems for specific patterns of sound. In pure misophonia the auditory system will function within the norm. Note that there is a clear analogy between the mechanisms of tinnitus and misophonia - the difference is in the initial signal, but the mechanisms which generate these reactions are the same and involve conditioned reflexes.
Diagnosis of hyperacusis and misophonia is complex. Typically patients combine and confuse hyperacusis and misophonia. Typically audiological evaluation of DST involves measurement of Loudness Discomfort Levels (LDL), i.e., measuring for pure tones of different frequencies and the sound level when the patient reports strong discomfort. For people who do not report problems with DST the average value for all tested frequencies is about 100 dBHL. LDL, however, are not sufficient for the diagnosis of hyperacusis or misophonia. When a patient has hyperacusis the LDL show lower values (average typically in 60-85 dB HL range), but low values alone are not proving the presence of hyperacusis as they may be due to misophonia! In misophonia both normal and low values are possible (range of 20 to 120 dB HL). Therefore, a specific, detailed interview is crucial for diagnosis. Comparison of an audiogram and LDL may, however, provide an assessment of the extent of misophonia for some patients and the method has been described in our 2002 paper.
In practice hyperacusis and misophonia frequently occur together in varying proportion, and in patientswith significant hyperacusis misophonia is automatically created, as normal sounds will evoke discomfort, and therefore create the conditioned reflexes. Once misophonia is established, the reactions are governed by principles of conditioned reflexes,e.g., reaction to the sound will be very fast and will occur without need forthinking about the meaning of the sound, or belief that the sound is bad for them.
Common recommendations for treatment of decreased sound tolerance are not necessary helpful and actually may create the increase of the problem, e.g., "avoid sound" or "use ear protection" because it will increase hyperacusis. Medications have no impact on DST, but may have potential negative side effects. Use of sound therapies based on desensitization may be helpful for hyperacusis, but have no or limited effect on misophonia.
Evaluation and treatments of DST is included as an imperative and obligatory element of Tinnitus Retraining Therapy(TRT). Certain points are particularly important.
First, there is a need to properly diagnose and differentiate hyperacusis and misophonia as while patients' reactions to sounds may be the same, but treatments of hyperacusis and misophonia are distinctively different.
Second, effective treatment for hyperacusis is not helpful for misophonia!
Third, effective treatment for misophonia is not particularly helpful for hyperacusis.
Fourth, when both hyperacusis and misophonia are initially present and hyperacusis is successfully treated, typically misophonia increase and there is no improvement observed at the behavioral level.
Hyperacusis is treated in TRT by desensitization with variety of sounds combined with specific counseling aimed at DST. In the case of normal hearing ear level sound generators are recommended as a part of the sound therapy. When hearing loss is present then combination instruments are optimal and sound generators are not recommended. It is especiallyimportant for hyperacusis patients to have an enriched sound environment day and night, 24/7. This method is very effective and in majority of cases it is possible to achieve the cure.
Treatment of misophonia with TRT is much more complex and takes longer time. Misophonia should be treated simultaneously with hyperacusis /tinnitus. In addition to specific counseling, patients are advised to follow one of 4 categories of protocols which attempt to create an association between variety of sounds with something positive. Protocol (1) has been published in our 2002 paper. These protocols are further modified to fit the needs of individual patients and typically more than one protocol is used. Note, that while misophonic patients frequently benefit from the use of ear level sound generators, they are not necessary for successful outcome of the treatment. Sound generators alone without specific protocols for misophonia have very limited usefulness. Duration of treatment is generally similar to duration of tinnitus treatment, but success rate is very high and in majority of cases it is possible to achieve a cure. Interestingly, successful treatment of misophonia restores habituation of external sounds and somato sounds and typically removes tensor tympani syndrome.
The concept of misophonia is gradually gaining recognition. In recently published prestigious Texbook of Tinnitus misophonia is mentioned numerous times through the book and is discussed in detail in three chapters (Baguley, D.M., McFerran, D.J. Hyperacusis and Disorders of Loudness Perception. Ch 3: 13-23; Moller, A.A., Misophonia, Phonophobia, and"Exploding Head" Syndrome. Ch4: 25-27, 2010; Jastreboff, P.J.Tinnitus Retraining Therapy. Ch 73:575-562. In: Texbook of Tinnitus. A.Moller, T Kleinjung, B. Langguth, D. DeRidder editors, Springer, 2010).
The main points toremember:
· Decreased sound tolerance accompany tinnitus insignificant proportion of cases (~60%)
· Detailed evaluation is necessary to diagnose the presence and extent of hyperacusis and misophonia as while patients' reactions to sounds may be the same, but treatments are distinctively different
· Special protocols for misophonia are necessary
· The use of ear level sound devices is crucial in hyperacusis patients
· Misophonic patients commonly benefits from sound generators as well, but it is possible to treat misophonia without any devices
· Significant improvement is observed in nearly all cases with decreased sound tolerance, but both hyperacusis and misophonia need to be treated concurrently
· In majority of cases it is possible to achieve the cure for both hyperacusis and misophonia
· Treatment of hyperacusis and misophonia increases effectiveness of tinnitus treatment and in some cases is crucial for achieving tinnitus control.