Tinnitus can be perceived in one or both ears or in the head. It is usually described as a ringing noise, but in some patients it takes the form of a high pitched whining, buzzing, hissing, humming, or whistling sound, or as ticking, clicking, roaring, "crickets" or "tree frogs" or "locusts", tunes, songs, or beeping. It has also been described as a "whooshing" sound, as of wind or waves.. Tinnitus can be intermittent or it can be continuous. In the latter case, this "phantom" sound can create great distress in the sufferer.
Tinnitus is not itself a disease but a symptom resulting from a range of underlying causes. Causes include ear infections, foreign objects or wax in the ear, nose allergies that prevent (or induce) fluid drain and cause wax build-up, and injury from loud noises. Tinnitus is also a side-effect of some oral medications, such as aspirin, and may also result from an abnormally low level of serotonin activity. It is also a classical side effect of Quinidine, a Class IA anti-arrhythmic. In many cases, however, no underlying physical cause can be identified.
The sound perceived may range from a quiet background noise to one that can be heard even over loud external sounds. The term "tinnitus" usually refers to more severe cases. Heller and Bergman (1953) conducted a study of 80 tinnitus-free university students placed in an anechoic chamber and found that 93% reported hearing a buzzing, pulsing or whistling sound. Cohort studies have demonstrated that damage to hearing (among other health effects) from unnatural levels of noise exposure is very widespread in industrialized countries. Because tinnitus is often defined as a subjective phenomenon, it is difficult to measure using objective tests, such as by comparison to noise of known frequency and intensity, as in an audiometric test. The condition is often rated clinically on a simple scale from "slight" to "catastrophic" according to the practical difficulties it imposes, such as interference with sleep, quiet activities, or normal daily activities. For research purposes, the more elaborate Tinnitus Handicap Inventory is often used.
Objective tinnitus, however, is quite uncommon. Often patients with pulsatile tumors will report other coexistent sounds, distinct from the pulsatile noise, that will persist even after their tumor has been removed. This is generally subjective tinnitus, which, unlike the objective form, cannot be tested by comparative methods.
If a subject is focused on a sample noise, they can often detect it to levels below 5 decibels, which would indicate that their tinnitus would be almost impossible to hear. Conversely, if the same test subject is told to focus only on their tinnitus, they will report hearing the sound even when test noises exceed 70 decibels, making the tinnitus louder than a ringing phone. This quantification method suggests that subjective tinnitus relates only to what the patient is attempting to hear. Patients actively complaining about tinnitus could thus be assumed to be people who have become obsessed with the noise. This is only partially true. The problem is involuntary; generally complaining patients simply cannot override or ignore their tinnitus. The noise is often present in both quiet and noisy environments, and can become quite intrusive to their daily lives.
Subjective tinnitus may not always be correlated with ear malfunction or hearing loss. Even people with near-perfect hearing may still complain of it. Tinnitus may also have a connection to memory problems, anxiety, fatigue or a general state of poor health.
Other possible mechanisms of how things can change in the ear is damage to the receptor cells. Although receptor cells can be regenerated from the adjacent supporting Deiters cells after injury in birds, reptiles, and amphibians, in mammals it is believed that they can be produced only during embryogenesis. Although mammalian Deiters cells reproduce and position themselves appropriately for regeneration, they have not been observed to transdifferentiate into receptor cells except in tissue culture experiments. Therefore, if these hairs become damaged, through prolonged exposure to excessive decibel levels, for instance, then deafness to certain frequencies occurs. In tinnitus, they may falsely relay information at a certain frequency that an externally audible sound is present, when it is not.
The mechanisms of subjective tinnitus are often obscure. While it is not surprising that direct trauma to the inner ear can cause tinnitus, other apparent causes (e.g., temporomandibular joint disorder (TMJ) and dental disorders) are difficult to explain. Recent research has proposed that there are two distinct categories of subjective tinnitus: otic tinnitus, caused by disorders of the inner ear or the acoustic nerve, and somatic tinnitus, caused by disorders outside the ear and nerve but still within the head or neck. It is further hypothesized that somatic tinnitus may be due to "central crosstalk" within the brain, as certain head and neck nerves enter the brain near regions known to be involved in hearing.
While most discussions of tinnitus tend to stress physical mechanisms, there is strong evidence that the level of an individual's awareness of their tinnitus can be stress-related, and so should be addressed by improving the state of the nervous system generally, using gradual, unobtrusive, long-term treatments.
It is also important to check medications for potential ototoxicity. Ototoxicity can be cumulative between medications, or can greatly increase the damage done by noise. If ototoxic medications must be administered, close attention by the physician to prescription details, such as dose and dosage interval, can reduce the damage done.
Causes of tinnitus include:
Although there are no specific cures for tinnitus, anything that brings the person out of the "fight or flight" stress response helps symptoms recede over a period of time. Calming body-based therapies, counseling and psychotherapy help restore well-being, which in turn allows tinnitus to settle. Chronic tinnitus can be quite stressful psychologically, as it distracts the affected individual from mental tasks and interferes with sleep, particularly when there is no external sound. Additional steps in reducing the impact of tinnitus on adverse health consequences include: a review of medications that may have tinnitus as a side effect; a physical exam to reveal possible underlying health conditions that may aggravate tinnitus; receiving adequate rest each day; and seeking a physician's advice concerning a sleep aid to allow for a better sleep pattern.
Notable sufferers of tinnitus include: