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Tinnitus is the hearing of sound when no external sound is present. While often described as a ringing, it may also sound like a clicking, hiss or roaring.〔 Rarely, unclear voices or music are heard.〔 The sound may be soft or loud, low pitched or high pitched and appear to be coming from one ear or both.〔(【引用サイトリンク】url=http://www.nidcd.nih.gov/health/hearing/Pages/tinnitus.aspx )〕 Most of the time, it comes on gradually.〔 In some people, the sound causes depression, anxiety or interferes with concentration.〔 Tinnitus is not a disease but a symptom that can result from a number of underlying causes. One of the most common causes is noise-induced hearing loss. Other causes include: ear infections, disease of the heart or blood vessels, Meniere's disease, brain tumors, exposure to certain medications, a previous head injury and earwax.〔 It is more common in those with depression.〔 The diagnosis is usually based on the person's description. Occasionally, the sound may be heard by someone else using a stethoscope: in which case, it is known as objective tinnitus. A number of questionnaires exist that assess how much tinnitus is interfering with a person's life.〔 People should have an audiogram and neurological exam as part of the diagnosis.〔〔 If certain problems are found, medical imaging such as with MRI may be recommended. Those who have tinnitus that occurs with the same rhythm as their heartbeat also need further testing.〔 Prevention involves avoiding loud noise.〔 If there is an underlying cause, treating it may lead to improvements.〔 Otherwise, typically, management involves talk therapy.〔 Sound generators or hearing aids may help some.〔 As of 2013, there are no effective medications. It is common, affecting about 10-15% of people. Most, however, tolerate it well with its being a significant problem in only 1-2% of people. The word tinnitus is from the Latin ''tinnīre'' which means "to ring".〔 ==Signs and symptoms== 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, electric buzzing, hissing, humming, tinging or whistling sound or as ticking, clicking, roaring, "crickets" or "tree frogs" or "locusts (cicadas)", tunes, songs, beeping, sizzling, sounds that slightly resemble human voices or even a pure steady tone like that heard during a hearing test and, in some cases, pressure changes from the interior ear.〔(【引用サイトリンク】title=Information and resources: Tinnitus: About tinnitus: What is tinnitus )〕 It has also been described as a "whooshing" sound because of acute muscle spasms, as of wind or waves. Tinnitus can be intermittent or it can be continuous: in the latter case, it can be the cause of great distress. In some individuals, the intensity can be changed by shoulder, head, tongue, jaw or eye movements. Most people with tinnitus have some degree of hearing loss: they are often unable to clearly hear external sounds that occur within the same range of frequencies as their "phantom sounds". This has led to the suggestion that one cause of tinnitus might be a homeostatic response of central dorsal cochlear nucleus auditory neurons that makes them hyperactive in compensation to auditory input loss. The sound perceived may range from a quiet background noise to one that can be heard even over loud external sounds. The specific type of tinnitus called pulsatile tinnitus is characterized by hearing the sounds of one's own pulse or muscle contractions, which is typically a result of sounds that have been created from the movement of muscles near to one's ear, changes within the canal of one's ear or issues related to blood flow of the neck or face. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Tinnitus」の詳細全文を読む スポンサード リンク
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