Tinnitus is usually caused by an underlying condition, such as age-related hearing loss, an ear injury, or a circulatory system problem. For many people, tinnitus improves with treatment for the underlying cause or with other treatments that reduce or mask noise, making tinnitus less noticeable. Tinnitus can occur anywhere in the auditory pathway, from the outer ear, through the middle ear and inner ear to the auditory cortex of the brain, where it is thought to be encoded (in a sense, printed). One of the most common causes of tinnitus is damage to the hair cells in the cochlea (see Ear Pathways and Tinnitus).
These cells help transform sound waves into nerve signals. If the brain's auditory pathways or circuits don't receive the signals they expect from the cochlea, the brain, in effect, increases the gain in those pathways in an effort to detect the signal in the same way that the volume on a car radio increases when it comes to finding the signal from a radio station. The resulting electrical noise takes the form of tinnitus, a sound that is sharp if the hearing loss is in the high-frequency range and low-pitched if it is in the low-frequency range. This type of tinnitus looks like phantom limb pain.
In an amputee, the brain produces abnormal nerve signals to compensate for the lack of information. The exact cause is unknown, but most experts believe that nerve damage caused by noise exposure is the main reason. The current theory is that damage or dysfunction occurs along the nerve pathways that detect sound waves and send sound to the brain. This causes interruptions in hearing and sound processing, including tinnitus.
Tinnitus is a common problem that may be a sign of an underlying medical condition, including hearing loss. The most common medications known to cause tinnitus are nonsteroidal anti-inflammatory drugs (such as aspirin and other over-the-counter pain relievers), diuretics, certain antibiotics and cancer medications, and quinine, an anti-malaria medication. Continuous, constant, acute tinnitus (the most common type) usually indicates a problem with the hearing system and requires hearing testing by an audiologist. Between 50 and 60 million people in the United States suffer from this condition; it's especially common in people over 55 and is strongly associated with hearing loss.
Anemia, allergies, affected earwax, diabetes, and underactive thyroid gland (hypothyroidism) are common medical conditions that may be associated with tinnitus and sometimes with hearing loss. Regular exposure to loud noises produced by heavy equipment, chainsaws, or firearms are common causes of hearing loss and tinnitus. Some of the common underlying heart causes of tinnitus are high blood pressure, turbulent blood flow, heart disease, and malformations of the small arteries. If common causes of tinnitus are ruled out, your doctor will refer you to another specialist for further evaluation and treatment.
