Tinnitus

Tinnitus is commonly described as a ringing in the ears, but it also can sound like roaring, clicking, hissing, or buzzing. It may be soft or loud, high pitched or low pitched. You might hear it in either one or both ears. Roughly 10 percent of the adult population of the United States has experienced tinnitus lasting at least five minutes in the past year. This amounts to nearly 25 million Americans.

Tinnitus (pronounced tin-NY-tus or TIN-u-tus) is not a disease. It is a symptom that something is wrong in the auditory system, which includes the ear, the auditory nerve that connects the inner ear to the brain, and the parts of the brain that process sound. Something as simple as a piece of earwax blocking the ear canal can cause tinnitus. But it can also be the result of a number of health conditions, such as:

• Noise-induced hearing loss
• Ear and sinus infections
• Diseases of the heart or blood vessels
• Ménière’s disease
• Brain tumors
• Hormonal changes in women
• Thyroid abnormalities

Tinnitus is sometimes the first sign of hearing loss. It also can be a side effect of medications. More than 200 drugs are known to cause tinnitus when you start or stop taking them.

People who work in noisy environments—such as factory or construction workers, road crews, or even musicians—can develop tinnitus over time when ongoing exposure to noise damages tiny sensory hair cells in the inner ear that help transmit sound to the brain. This is called noise-induced hearing loss.

Service members exposed to bomb blasts can develop tinnitus if the shock wave of the explosion squeezes the skull and damages brain tissue in areas that help process sound. In fact, tinnitus is one of the most common service-related disabilities among veterans returning from Iraq and Afghanistan.
Pulsatile tinnitus is a rare type of tinnitus that sounds like a rhythmic pulsing in the ear, usually in time with your heartbeat. A doctor may be able to hear it by pressing a stethoscope against your neck or by placing a tiny microphone inside the ear canal. This kind of tinnitus is most often caused by problems with blood flow in the head or neck. Pulsatile tinnitus also may be caused by brain tumors or abnormalities in brain structure.

Although we hear tinnitus in our ears, its source is really in the networks of brain cells (what scientists call neural circuits) that make sense of the sounds our ears hear. A way to think about tinnitus is that it often begins in the ear, but it continues in the brain.

Scientists still haven’t agreed upon what happens in the brain to create the illusion of sound when there is none. Some think that tinnitus is similar to chronic pain syndrome, in which the pain persists even after a wound or broken bone has healed.

Tinnitus could be the result of the brain’s neural circuits trying to adapt to the loss of sensory hair cells by turning up the sensitivity to sound. This would explain why some people with tinnitus are oversensitive to loud noise.

Tinnitus also could be the result of neural circuits thrown out of balance when damage in the inner ear changes signaling activity in the auditory cortex, the part of the brain that processes sound. Or it could be the result of abnormal interactions between neural circuits. The neural circuits involved in hearing aren’t solely dedicated to processing sound. They also communicate with other parts of the brain, such as the limbic region, which regulates mood and emotion.

Noise-induced hearing loss, the result of damage to the sensory hair cells of the inner ear, is one of the most common causes of tinnitus. Anything you can do to limit your exposure to loud noise—by moving away from the sound, turning down the volume, or wearing earplugs or earmuffs—will help to lessen the likelihood that you will experience tinnitus.