Tinnitus in Wikipedia
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(Source - Retrieved 2006-09-07 14:20:35 from http://en.wikipedia.org/wiki/Tinnitus)
Tinnitus (ti-NIGHT-us or TIN-i-tus) is the perception of sound in the absence of a corresponding external sound. It can be perceived in one or both ears or in the head. Tinnitus is the Latin word for "ringing", and usually it described as a ringing noise, but some describe buzzing, humming, whistling, tunes, or songs.. Tinnitus is not itself a disease, but an unwelcome symptom resulting from a range of underlying causes.
The sound perceived may range from a quiet background noise to a signal loud enough to drown out all outside sounds. The term 'tinnitus' usually refers to more severe cases. A 1953 study (Heller and Bergman) of 80 tinnitus-free university students placed in a soundproofed room found that 93% reported hearing a buzzing, pulsing or whistling sound. However, it must not be assumed that this condition is normal -- cohort studies have demonstrated that damage to hearing from unnatural levels of noise exposure is very widespread in industrialized countries. (see noise health effects)
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. 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.
In a minority of cases, a clinician can perceive actual sound (e.g., a bruit) emanating from the patient's ears. This is called objective tinnitus. Objective tinnitus can arise from muscle spasms that cause clicks or crackling around the middle ear. Some people experience a sound that beats in time with the pulse (pulsatile tinnitus). Pulsatile tinnitus is usually objective in nature, resulting from altered blood flow or increased blood turbulence near the ear (such as from atherosclerosis or venous hum), but it can also arise as a subjective phenomenon from an increased awareness of blood flow in the ear. Rarely, pulsatile tinnitus may be a symptom of potentially life-threatening conditions such as carotid artery aneurysm or dissection .
Causes of subjective tinnitus
Tinnitus can have many different causes, but most commonly results from otologic disorders - the same conditions that cause hearing loss. The most common cause is noise induced hearing loss, resulting from exposure to excessive or loud noises. Ototoxic drugs can cause tinnitus either secondary to hearing loss or without hearing loss, and may increase the damage done by exposure to loud noise even at doses that are not in themselves ototoxic.
Causes of tinnitus include:
Mechanisms of subjective tinnitus
The inner ear contains many thousand minute hairs which vibrate in response to sound waves. Receptor cells (hair cells) in turn send signals to the brain which are interpreted as sound. 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 volume, 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's not surprising that direct trauma to the inner ear can cause tinnitus, other apparent causes (e.g., 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.
Because tinnitus and hearing loss can be permanent conditions, precautionary measures are advisable. If a ringing in the ears is audible after exposure to a loud environment such as a concert or work place, it means that damage is being done. Prolonged exposure to noise levels as low as 70 dB can result in damage to hearing (see noise health effects). If it is not possible to limit exposure, wearing earplugs or ear defenders can be advantageous. For musicians and DJs, special musicians' earplugs can lower the volume of the music without distorting the sound and can prevent tinnitus developing in later years.
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.
There are many treatments that are effective for tinnitus resulting from a particular cause, but none that is effective in every case. Conversely, tinnitus may resolve without any treatment. Effective treatments include:
- Gamma knife radiosurgery (glomus jugulare)
- Shielding of cochlea by teflon implant
- Botulinum toxin (palatal tremor)
- Propranolol and clonazepam (arterial anatomic variation)
- Drugs and nutrients
- Avoidance of caffeine, nicotine, salt 
- Avoidance of or consumption of alcohol; 
- Zinc supplementation (where serum zinc deficiency is present)
- Acamprosate 
- Etidronate or sodium fluoride (otosclerosis)
- Lignocaine or anticonvulsants (usually in patients responsive to white noise masking)
- Melatonin (especially for those with sleep disturbance)
- Sertraline 
- Electrical stimulation
- Transcranial magnetic stimulation or transcranial direct current stimulation 
- Transcutaneous electrical nerve stimulation
- Direct stimulation of auditory cortex by implanted electrodes
- Repair of perilymph fistula 
- External sound
- Tinnitus masking (white noise)
- Tinnitus retraining therapy
- Auditive stimulation therapy (music therapy)
- Compensation for lost frequencies by use of a hearing aid. $$
- Ultrasonic bone-conduction external acoustic stimulation
- Avoidance of outside noise (exogenous tinnitus)
- Cognitive behavior therapy
A Tinnitus FAQ lists many other potential therapies.
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, counselling 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 tinnitis on adverse health consequences include, a review of medications that may have tinnitus as a side affect, a physicial exam to reveal possible underlying health conditions that may aggrevate tinnitus, receiving adequate rest each day, and seeking a physician's advice concerning a sleep aid to allow for a better sleep pattern.
- OHSU Tinnitus Clinic
Categories: Articles lacking sources | Otolaryngology
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