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A tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving oscillations or twitching movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Most tremors occur in the hands. In some people, a tremor is a symptom of another neurological disorder. A very common tremor is the chattering of teeth, usually induced by cold temperatures or by fear. ==Causes== Tremor can be a symptom associated with disorders in those parts of the brain that control muscles throughout the body or in particular areas, such as the hands. Neurological disorders or conditions that can produce tremor including multiple sclerosis, stroke, traumatic brain injury, chronic kidney disease and a number of neurodegenerative diseases that damage or destroy parts of the brainstem or the cerebellum, Parkinson's disease being the one most often associated with tremor. Other causes include the use of drugs (such as amphetamines, cocaine, caffeine, corticosteroids, SSRI), alcohol, mercury poisoning; or the withdrawal of drugs such as alcohol or benzodiazepine. Tremors can also be seen in infants with phenylketonuria (PKU), overactive thyroid or liver failure. Tremors can be an indication of hypoglycemia, along with palpitations, sweating and anxiety. Tremor can also be caused from lack of sleep, lack of vitamins, or increased stress. Deficiencies of magnesium and thiamine have also been known to cause tremor or shaking, which resolves when the deficiency is corrected. See magnesium in biology. Some forms of tremor are inherited and run in families, while others have no known cause. Tremors can also be caused by some spider bites, e.g. the redback spider of Australia. Characteristics may include a rhythmic shaking in the hands, arms, head, legs, or trunk; shaky voice; and problems holding things such as a fork or pen. Some tremors may be triggered by or become exacerbated during times of stress or strong emotion, when the individual is physically exhausted, or during certain postures or movements. Tremor may occur at any age but is most common in middle-age and older persons. It may be occasional, temporary, or occur intermittently. Tremor affects men and women equally. 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「tremor」の詳細全文を読む スポンサード リンク
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