Tinnitus and Hyperacusis
Tinnitus is the perception of sound in the absence of a corresponding external sound. Many individuals experience a ringing sensation but tinnitus can also be perceived as a hissing, crackling, crickets, or roaring sound. Tinnitus is very common with an estimated 40-50 million Americans experiencing it on a regular basis. Of these, about 1 in 4 find the tinnitus has a significant or disabling impact on their daily life.
Hyperacusis often occurs along with Tinnitus (although it can exist independently). Hyperacusis is an increased sensitivity to the loudness of everyday sounds. Individuals with hyperacusis often avoid certain environments because of the loudness of sounds and noises encountered. Some individuals wear earplugs throughout the day. The same physiologic mechanisms that can lead to tinnitus can also lead to hyperacusis, one reason these conditions often co-occur.
What Causes Tinnitus?
This is the most common question posed by tinnitus sufferers. In some cases, the tinnitus is associated with a medical issue such as a lesion on the hearing nerve, Meneire's Disease, TMJ, circulatory issue, etc. Tinnitus commonly occurs along with hearing loss. Therefore, a medical evaluation by a physician and a comprehensive audiologic evaluation are recommended when someone is suffering from tinnitus.
In most cases, however, there is no specific anatomical problem or illness causing the tinnitus that is then treated with medication or surgery. Fortunately, our understanding of tinnitus and hyperacusis has increased significantly over the past decade and there is an emerging consensus on the physiologic nature of these conditions.
Your ears are connected to your brain. This may seem like a simple concept, but we often associate any hearing difficulty, including tinnitus, with a problem in the peripheral auditory system (i.e., your ear canal, middle ear, or inner ear). The peripheral auditory system takes an acoustical signal and changes it to an neural signal that can be passed along by the central auditory nervous system to your brain. An important part of the brain associated with hearing is the auditory cortex. Other parts of the brain are involved as well. Suffice to say, the entire auditory system is very complex and things can go awry at different levels of this system.
Most individuals have experienced occasional tinnitus at some point in their lives. Occasional tinnitus is analogous to a nervous "twitch". Something that happens occasionally and is caused by spontaneous activity in the nervous system. In one classic study, individuals with normal hearing were placed in a soundproof booth for an extended period. No sounds were presented while they were in the room. Yet when asked if they had heard anything, most of the participants reported "hearing" a variety of sounds.
There are several theories on why persistent tinnitus develops in certain cases and why the impact varies from person to person. One aspect that most researchers agree on is that tinnitus involves both a neural and a perceptual component. There is often a trigger event that precedes the perception of chronic tinnitus.
This can happen after exposure to a very loud noise or blast when there has been some damage to the auditory system. Onset is not always associated with an acoustic trauma, however. Perhaps you had very soft tinnitus that was not typically noticeable. You then get an ear infection or bad cold and become "stuffed up". This makes the tinnitus louder in the same way that plugging up your ears makes your own voice sound louder. Once you start tuning in to the tinnitus, it may not go away once the infection or cold clears up.
For other individuals, tinnitus comes on gradually and progresses over time. This often occurs in conjunction with progressive hearing loss. Your auditory system is organized in such a way that different pitches are processed in different areas. Let's say you have a significant hearing loss for higher pitched sounds. The part of your brain that processes higher pitched sounds receives less information as the hearing loss progresses, especially if the individual is not wearing hearing aids. The brain starts to look for the "missing sound". This can lead to hyperactivity in the hearing part of the brain and can be a factor in the perception of tinnitus.
How an given individual reacts to the tinnitus is just as important, if not more important, than what caused the tinnitus to begin in the first place. The reaction has implications for what the impact will be on daily life. As you tune in and notice the tinnitus more, a feedback loop can be created. You notice the tinnitus and know it should not be there. Stress level can rise and adrenaline associated with the "fight or flight" response can kick in. All this contributes to the negative emotional response. Individuals who do not experience tinnitus may have difficulty understanding why you can't just ignore it. That like asking someone not to picture the color red. It will probably be the first color their mind conjures up.
In this video, Dr. Robert Sweetow explains the relationship between tinnitus perception and emotional response:
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