HYPERACUSIS

HYPERACUSIS

Introduction

Hyperacusis can involve loudness, annoyance, fear, and pain. We have noted that tinnitus is often accompanied by hyperacusis, and many current sound therapy protocols treat tinnitus and hyperacusis in parallel. One can readily imagine that sounds perceived as being very loud could easily become annoying. The anticipation of loud and/or annoying sounds could reasonably lead to the fear of these sounds. However, it is possible for sounds to be annoying or feared without being too loud. Patients also report that some sounds are physically painful, usually those perceived as loud. Occasionally, patients with tinnitus report that some sounds make their tinnitus worse. It is important to separate each of these symptoms, both for the patient and the clinician, to understand the problems carefully, and to offer treatment suggestions.

Neurophysiological Causes, Mechanisms, and Models of Hyperacusis

Anything that which causes a sensory/neural hearing loss can likely also cause hyperacusis. Hyperacusis can also occur without identifiable hearing loss. As a stimulus is increased, the activity of individual nerve fibers increases, and the number of nerve fibers activated increases (and usually its perceived loudness also increases). Moderately intense sounds might result in loudness hyperacusis if

1. greater than normal activity was produced on individual nerve fibers,

2. more nerve fibers were activated than normal, and/or

3. there was greater than normal synchrony across fibers

We suggest that hyperacusis might also be a function of such brain plasticity. Following a peripheral hearing loss, say at 4,000 Hz, nerve fibers in the brain that normally respond to 4,000 Hz begin to respond to other, nearby frequencies, for example, 3,000 Hz. This results in more nerve fibers in the brain responding to 3,000 Hz than would be present normally. If hyperacusis is related to the number of fibers activated, this could account for it as a phenomenon. Hazell (1987) suggested that hyperacusis might be the result of an “abnormal gain control.” It is as if the brain receives a lack of information after hearing loss and therefore turns up some hypothetical gain control.

EVALUATION OF HYPERACUSIS

Medical

The medical evaluation for hyperacusis parallels that for tinnitus. Some conditions have been associated with hyperacusis, including facial paralysis, head trauma, and metabolic disorders, infections (Lyme disease), and genetic (Williams’ syndrome) abnormalities.

Measuring Hyperacusis

LOUDNESS HYPERACUSIS

Loudness Discomfort Levels

Loudness discomfort levels (LDLs) can be performed with puretones at 500 and 4,000 Hz in each ear. We use the following instructions: “This is a test in which you will be hearing sounds in your right/left ear. We want you to decide when the sound first becomes uncomfortably loud.”

Magnitude Estimation of Loudness

It is possible to present tones and ask for a rating of loudness on a scale from 0 to 100, with 100 being the loudest sound a person can imagine. Hyperacusis scales have been developed to attempt

to differentiate loudness and annoyance and to ascertain a general idea of the impact of hyperacusis on a patient’s daily activities. The questionnaire asks individuals to consider several typical events they might encounter in their daily lives. They then separately rate the loudness and the annoyance for the same situations. For example, a patient may rate “telephone ringing in the same room” as 40 out of 100 on the loudness scale (with 100 being unbearably loud), whereas rating it as 85 out of 100 on the annoyance scale (with 100 being unbearably annoying).

ANNOYANCE HYPERACUSIS

In terms of hearing loss tinnitus, and hyperacusis the statement include items such as ‘you avoid shopping’ ‘you feel depressed’ and allow clinician to separate the impact on function that patient perceive from where hearing loss, tinnitus and hyperacusis. Another approach we have tried is to have patients rate recorded sounds. For example, we have patients rate recorded sounds of dishes hitting together, a lawn mower, and crowd noise. A multiple activity scale for annoyance hyperacusis, providing 15 situations (e.g., concert, shopping center, work, church, children). Subjects rated from 1 to 10 each of the “relevant” activities, which were averaged for a total score. They also had patients rate annoyance hyperacusis on a scale from1 to 10.

FEAR HYPERACUSIS

Patients can develop a fear of very specific sounds or categories of sounds (e.g., those containing high frequencies) or of any intense sound. The simplest approach may be to ask the patients to make a list of sounds they fear to determine if a specific pattern exists.

PAIN HYPERACUSIS

Some patients report that listening to some sounds create pain. Often, they are perceived as loud, and these patients typically have fear of these sounds.

TREATMENT FOR HYPERACUSIS

Counseling

In hyperacusis activities treatment, we include four sections.

1.         The first section is emotional well-being. Patients with hyperacusis are often anxious and distressed about being exposed to intense noise.

2.         The second section is hearing and communication. Some patients avoid communication situations where they expect there to be intense sounds. Sound therapy to reduce loudness hyperacusis should be able to provide some assistance with this. Others will avoid using hearing aids or use gain settings that are insufficient. Patients can set the maximum output of their hearing aids temporarily to a lower level (Search field, 2006) and gradually increase this over time.

3.         The third section is in the area of sleep. Occasionally, patients with fear hyperacusis will report that they do not sleep as well because of the anticipation of an intense sound. Partial masking sound therapy (e.g., playing music throughout the night) can be helpful for some.

4.         The fourth section is that some patients report that they have difficulty concentrating in anticipation of an intensesound. Again, partial masking sound therapy can be helpful.

Sound Therapies

One fundamental issue is whether to protect the ears from moderately intense sounds, for example, with earplugs. Some patients with severe hyperacusis do this on their own. Of course, everyone (including hyperacusis patients) should protect their ears from potentially damaging high-intensity sounds. However, protecting a hyperacusis patient’s ears from moderately intense sounds will not cure the patient’s hyperacusis. In fact, restricting one’s exposure to moderately intense sounds might have a further negative impact. One can imagine that if it is uncommon to hear a sound at 85 dB SPL, then whenever a sound of this level is perceived, it might result in an overreaction. There are currently five general sound therapy strategies that we are aware of for hyperacusis.

PARTIAL MASKING

Partial masking with a continuous background sound can be used to reduce the loudness and prominence of intermittent sounds that might otherwise be annoying. For example, low levels of music can partially mask background annoying traffic noise. Additionally, the low-level music can create a background whereby the patient is less likely to anticipate being disturbed while getting to sleep, sleeping, or concentrating.