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Intention tremor, also known as cerebellar tremor, is a dyskinetic disorder characterized by a broad, coarse, and low frequency (below 5 Hz) tremor. The amplitude of an intention tremor increases as an extremity approaches the endpoint of deliberate and visually guided movement (hence the name intention tremor). An intention tremor is usually perpendicular to the direction of movement. When experiencing an intention tremor, one often overshoots or undershoots their target, a condition known as dysmetria.〔() Seeberger, Lauren. "Cerebellar Tremor-Definition and Treatment." The Colorado Neurological Institute Review. Fall 2005.〕〔() National Institute of Neurological Disorders and Stroke. “Tremor Fact Sheet.” Jan 2011. National Institutes of Health.〕 Intention tremor is the result of dysfunction of the cerebellum, particularly on the same side as the tremor in the lateral zone, which controls visually guided movements. Depending on the location of cerebellar damage, these tremors can be either unilateral or bilateral.〔 A variety of causes have been discovered to date, including damage or degradation of the cerebellum due to neurodegenerative diseases, trauma, tumor, stroke, or toxicity. There is currently no established pharmacological treatment; however, some success has been seen using treatments designed for essential tremors.〔 ==Causes== Intention tremors are common among individuals with multiple sclerosis (MS). One common symptom of multiple sclerosis is ataxia, a lack of coordinated muscle movement caused by cerebellar lesions characteristic of multiple sclerosis. The disease often destroys physical and cognitive function of individuals. Intention tremors can be a first sign of multiple sclerosis, since loss or deterioration of motor function and sensitivity are often one of the first symptoms of cerebellar lesions.〔 Intention tremors have a variety of other recorded causes as well. These include a variety of neurological disorders, such as stroke, alcoholism, alcohol withdrawal, peripheral neuropathy, Wilson's disease, Creutzfeldt–Jakob disease, Guillain–Barré syndrome and fragile X syndrome, as well as brain tumors, low blood sugar, hyperthyroidism, hypoparathyroidism, insulinoma, normal aging, and traumatic brain injury.〔〔() Hoch, Daniel MD. “Tremor.” Updated 6/15/2010. U.S. National Library of Medicine.〕〔() Hagerman, Paul, Hagerman, Randi. “Fragile X-Associated Tremor/Ataxia Syndrome-An Older Face of the Fragile X Gene.” 2007. In ''Nature Clinical Practice Neurology''. Nature Publishing Group.〕〔() Eidelberg, David, Pourfar, Michael. "Tremor." 2007. In ''The Merck Manuals'' Online Medical Library.〕 Holmes tremor, a rubral or midbrain tremor, is another form of tremor that includes intention tremors, among other symptoms. This disease affects the proximal muscles of the head, shoulders, and neck. Tremors of this disease occur at frequencies of 2–4 Hz or more.〔() "Postischemic Holmes Tremor Investigated by FDG- and H2 O-PET." Jan Kassubek, G. Bernhard Landwehrmeyer, Carl H. Lücking, Freimut D. Juengling. The Journal of Radiology, June 2003〕 Intention tremor is also known to be associated with infections, West Nile virus, rubella, H. influenza, rabies, and varicella.〔 A variety of poisons have been shown to cause intention tremor, including mercury, methyl bromide, and phosphine.〔〔() “Epidemiological Notes and Reports Elemental Mercury Poisoning in a Household – Ohio 1989.” 1990. In ''Morbidity and Mortality Weekly Report''. Centers for Disease Control and Prevention.〕〔() “Medical Management Guidelines for Acute Chemical Exposures.” 1992. U.S Department of Human Health Services.〕 In addition, vitamin deficiencies have been linked to intention tremor, especially deficiency in vitamin E. Pharmacological agents such as anti-arrhythmic drugs, anti-epileptic agents, benzodiazepine, cyclosporine, lithium, neuroleptics, and stimulants have been known to cause intention tremor.〔 Some ordinary activities including ingesting too much caffeine, cigarettes, and alcohol, along with stress, anxiety, fear, anger and fatigue have also been shown to cause intention tremor by negatively affecting the cerebellum, brainstem, or thalamus, as discussed in mechanisms.〔 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「intention tremor」の詳細全文を読む スポンサード リンク
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