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Figure: © Kiki Tikiriki/Stock Illustration Source
It took visits to five doctors over several months for Rob, a musician from Georgia who requested that his last name not be published, to be diagnosed with hyperacusis. At times, the process was scary and frustrating, he said.
As a musician, Rob was always careful to use hearing protection around loud music, including in clubs and at concerts, he said.
“In the work I do in a recording studio, I never set the volume loud.”
He acquired hyperacusis shortly after exposure to the noise of a pressure washer.
“I wasn't wearing hearing protection and didn't experience anything that was an immediate cause for concern,” Rob said.
However, when he put on a CD in his car 30 to 40 minutes later, the music sounded louder and exceptionally sharper than normal in both ears. A couple of days later, he started to experience constant pain deep in his left ear.
Rob then saw a neurologist, who suggested he undergo an MRI.
“The doctor didn't tell me anything about the importance of wearing hearing protection during the MRI, and what was moderate hyperacusis, at best, became severe hyperacusis,” he said.
A better understanding of hyperacusis is needed so that hearing healthcare professionals can more effectively diagnose and manage cases like Rob's, which have a great impact on a patient's quality of life. More research investigating the mechanisms of the disorder is crucial to improving treatment approaches and reimbursement policy.
Several therapies for hyperacusis do exist, and they have shown some success in relieving patients’ discomfort.
DEFINITION SOMETIMES UNCLEAR
The definition of hyperacusis varies and is sometimes unclear, said Jennifer R. Melcher, PhD, associate professor of otology and laryngology at Harvard Medical School. In her research, she describes the condition as intolerance to a level of sound. People with hyperacusis reach a point at which sounds are too loud, even at lower physical levels, she said.
Other terms used to describe decreased sound tolerance include phonophobia, the fear of a particular sound, and misophonia, a “negative reaction to a sound with a specific pattern and meaning,” according to Pawel J. Jastreboff, PhD, ScD, MBA, and Margaret M. Jastreboff, PhD, of Emory University School of Medicine. They describe hyperacusis as a negative reaction to a sound that depends only on the sound's physical characteristics, such as spectrum and intensity (Decreased Sound Tolerance (DST): Hyperacusis/Misophonia/Phonophobiahttp://www.hyperacusis.net/hyperacusis/misophoniaphonophobia/default.asp).
Figure: Jennifer R. Melcher, PhD
Richard S. Tyler, PhD, professor of communication sciences and disorders and of otolaryngology at the University of Iowa, describes four categories of hyperacusis: loudness, annoyance, fear, and pain. While he sees all of these subtypes intersecting in the clinic, epidemiological data on hyperacusis are lacking, “so it's hard to know how much overlap actually occurs,” he said.
In loudness hyperacusis, moderately intense sounds are perceived as too loud, while annoyance hyperacusis is “a negative emotional reaction to sounds,” Dr. Tyler said.
Fear hyperacusis is a negative response to sounds that may cause patients to avoid social situations or feel anxiety in anticipation of hearing these sounds. Pain is also associated with hyperacusis and may include a stabbing sensation at much lower sound levels than would typically prompt pain.
One type of hyperacusis may lead to another, Dr. Tyler said.
“If you experience loudness hyperacusis, emotional consequences may follow, leading to stress and annoyance, which eventually lead to fear of going to events and socializing,” he said. “Pain is a little more complicated because it consists of both a fundamental attribute and an emotional consequence.”
People with hyperacusis have increased activity in the tensor tympani muscle in response to some sounds, which can tighten the eardrum and lead to pain, said Dr. Melcher, citing research published in Noise & Health (2013;15[63]:117-128http://www.noiseandhealth.org/article.asp?issn=1463-1741;year=2013;volume=15;issue=63;spage=117;epage=128;aulast=Westcott).
“We often see pain in our patients,” said Fan-Gang Zeng, PhD, professor of otolaryngology in the School of Medicine and director of the Center for Hearing Research at the University of California, Irvine, and chair of The Hearing Journal’s Editorial Advisory Board.
“When the sound reaches a certain level, patients will say, ‘It's not just the loudness that's bothering me; it's the pinging sensation or tingling.’”
ONE IN 50,000
Hyperacusis is rare, affecting one in 50,000 people, according to the American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNShttp://www.entnet.org/content/hyperacusis-increased-sensitivity-everyday-sounds).
Prevalence rates were between eight and nine percent in a 2002 mail and Internet survey ( Int J Audiol 2002;41[8]:545-554http://informahealthcare.com/doi/abs/10.3109/14992020209056075), while other researchers have estimated a prevalence of two percent in the adult population. (Baguley DM, McFerran DJ. Hyperacusis and disorders of loudness perception. In: Møller A, Langguth B, De Ridder D, Kleinjung T, eds. Textbook of Tinnitus. New York, NY: Springer; 2011:13-24.)
Hyperacusis appears to result from reduced nerve input and response to sound, Dr. Zeng said. As a result, the brain has no choice but to increase gain, causing over-amplification in its attempt to compensate.
“The brain is dynamically changing in response to the environment and the pathological conditions in the ear,” he said.
With the loudness form of the condition, “there is likely greater activity on individual hearing nerve fibers and across more hearing nerve fibers than would occur in the normal ear without hyperacusis,” Dr. Tyler said.
If patients experience annoyance or fear, then the many corresponding emotional centers of the brain must also be activated. These networks are active for different types of stressors, not just hyperacusis, he noted.
Hyperacusis is frequently associated with noise exposure and tinnitus (see box), but many patients have apparently normal hearing thresholds, Dr. Tyler said.
Some patients with hyperacusis have high-frequency hearing loss, but the loss is not always reflected by the audiogram, Dr. Zeng said. Patients with hyperacusis are often bothered by sounds at all frequencies, provided they reach a certain decibel level, he added.
Figure: Fan-Gang Zeng, PhD
Conditions that are associated with hyperacusis include Bell's palsy, Lyme disease, depression, and autism, among others, according to the American Speech–Language–Hearing Association (ASHA)http://www.asha.org/uploadedFiles/AIS-Hyperacusis.pdf. In addition to noise exposure, causes may include physical trauma to the head or viral infection of the inner ear.
Audiologists can assess loudness hyperacusis by measuring loudness growth or loudness discomfort levels with pure tones, said Dr. Tyler, although some studies from the hearing healthcare literature use actual recordings of environmental sounds.
Dr. Zeng finds that exposing patients to a conversational sound level of 60 to 70 dB and asking them to indicate if this level is too loud helps determine if they have hyperacusis, he said.
Questionnaires are valuable for determining annoyance and fear components of the disorder, Dr. Tyler said. Generally, such assessments consist of subjective responses.
“If patients say they're afraid to go to work or the cafeteria because it's too noisy, then, clinically speaking, you know they have fear hyperacusis,” he said. Audiologists also need to ask patients if they are experiencing any associated ear pain, he added.
LOWERING THE VOLUME
Counseling and sound therapy are two common approaches to managing hyperacusis. They can help retrain the brain and reduce the physiological activity that leads to the condition, Dr. Melcher said.
Many counseling techniques are now available, Dr. Tyler said. For example, hyperacusis activities treatment includes components of cognitive behavior therapy, helping patients adjust their perceptions and providing techniques to improve concentration.
“And, of course, when people change their feelings and impressions about a condition, something in the brain changes as well,” Dr. Tyler said.
Sound therapy can be very effective for hyperacusis, he said. Data indicate that exposure to continuous low-level broadband noise can improve objective measures of loudness hyperacusis ( Semin Hear 2002;23[1]:21-34https://www.thieme-connect.com/products/ejournals/html/10.1055/s-2002-32944; Acta Otolaryngol 2005;125[5]:503-509http://www.ncbi.nlm.nih.gov/pubmed/16092541).
While continuous broadband noise has been used to treat tinnitus and is now advocated for hyperacusis therapy, “white noise is not very effective compared with modulated dynamic sounds,” Dr. Zeng said.
Another approach, successive approximation using high-level broadband noise, may be effective, said Dr. Tyler, adding that the therapy was recommended by the late Jack A. Vernon, PhD, cofounder of the American Tinnitus Association (ATA).
This form of sound therapy involves noise exposure that increases in loudness and duration over time. (Tyler RS, Noble W, Coelho C, Haskell G, Bardia A. Tinnitus and hyperacusis. In: Katz J, Medwetsky L, Burkard R, Hood L, eds. Handbook of Clinical Audiology. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:726-742.)
Figure: Richard S. Tyler, PhD
“We have also used successive approximation to the specific environmental sounds that bother a patient,” Dr. Tyler said, noting that this technique can be very helpful for children with hyperacusis.
If patients complain of hyperacusis at 50 dB, audiologists can expose them to a lower sound level and then gradually increase exposure over time in 5-dB steps until 50 dB is tolerable, according to an idea developed by Craig Formby, PhD, Dr. Zeng said ( J Acoust Soc Am 2003;114[1]:55-58http://scitation.aip.org/content/asa/journal/jasa/114/1/10.1121/1.1582860). Once 50 dB is acceptable, audiologists can continue increasing the sound level exposure in 5-dB steps.
Dr. Zeng and his colleagues have had some success with this adaptation process. However, the technique of “increasing tolerance has not been widely adopted,” he said.
“There are also questions about what is the most effective type of sound. Is it white noise, such as the ocean, or dynamic sounds, such as speech or music?”
Another approach to sound therapy includes partial masking with continuous background noise, which can help reduce the loudness of sounds that patients might find bothersome, Dr. Tyler said.
If the patient wears a hearing aid, the amplified sound levels may need to be lowered and then gradually increased to contend with hyperacusis.
UNCOVERING THE CAUSE
While therapies for hyperacusis are available, treatment codes are not, so reimbursement for audiologists is challenging, Dr. Tyler said.
Once more effective treatments are established, the healthcare system will likely provide better reimbursement, Dr. Zeng said. The effectiveness of hyperacusis therapy needs to be comparable to that of other reimbursable audiological treatments, such as cochlear implants, he said.
“First, you have to have the research, with good quality-of-life outcomes.”
Additional clinical trials are essential, Dr. Tyler said. Investigators need a better understanding of how to measure loudness hyperacusis while taking emotional influences into account. Studies also must evaluate the use of sound therapy and more specific counseling procedures for hyperacusis treatment.
In addition, further research needs to investigate the causes of hyperacusis, the physiological changes that occur in the inner ear and nerves, and the brain's response, in addition to how sound can affect pain receptors, Dr. Zeng said.
“We really need some kind of biomarker to objectively measure the condition,” he said. “It's almost impossible to create effective treatments until we know what causes the condition.”
In the case of Rob, the musician from Georgia, an audiologist at Emory University recommended Tinnitus Retraining Therapy (TRT) as a treatment for hyperacusis. However, Rob found the presentation of sound in TRT too difficult to tolerate, so he opted for customized pink noise.
His pink noise program used open-air headphones and started with a high-end frequency presentation of 3,000 Hz. He listened to this for eight hours a day at a low volume for three months, gradually increasing the volume during the second and third months. Rob also gradually increased the high-end frequency of the presentation, as well as the amplitude of selected frequency points.
He can now listen to 22,050 Hz. His loudness discomfort levels were originally in the 30- and 40-dB range, and now they're in the 90- and 100-dB range.
Overall, his therapy has taken about three years, and Rob said he believes his sound tolerance can further improve.
“It took me a long time to get there, but it's been very successful,” he said.
Hyperacusis and Tinnitus: Two Related, but Very Different, Conditions
When patients with tinnitus are tested for loudness discomfort levels, they often cannot tolerate louder sounds, as demonstrated in research by Jennifer R. Melcher, PhD, associate professor of otology and laryngology at Harvard Medical School, and colleagues ( J Neurophysiol 2010;104 [6]:3361-3370http://jn.physiology.org/content/104/6/3361.long).
“There's more hyperacusis in people with tinnitus,” Dr. Melcher said.
In MRI neuroimaging studies of patients, she found increased responses to sound in the inferior colliculus in people with hyperacusis, regardless of whether they had tinnitus. This finding demonstrates amplification in brain activity, which leads to a perception of loudness, she said.
When evaluating patients, practitioners should ask those who have tinnitus about loudness discomfort, Dr. Melcher said. Conversely, patients who present with hyperacusis should be evaluated for tinnitus, she said.
While a lot of patients with tinnitus have hyperacusis, some people with tinnitus say that loud noises make their tinnitus worse, and this symptom should not be classified as hyperacusis, Dr. Tyler said.
Even though hyperacusis treatment is rooted in tinnitus management, the two conditions are very different, Dr. Zeng said.
Tinnitus is the perception of sound when there is no external stimulus to the ear, he noted. Hyperacusis is over-reaction to external sound.
“You have to have an external stimulus that is perceived as loud,” he said.
