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Diffuse axonal injury (DAI) is a brain injury in which damage in the form of extensive lesions in white matter tracts occurs over a widespread area. DAI is one of the most common and devastating types of traumatic brain injury,〔Iwata A., Stys P.K., Wolf J.A., Chen X.H., Taylor, A.G., Meaney D.F., and Smith D.H. (2004). (Traumatic axonal injury induces proteolytic cleavage of the voltage-gated sodium channels modulated by tetrodotoxin and protease inhibitors ). ''The Journal of Neuroscience''. 24 (19): 4605—4613.〕 and is a major cause of unconsciousness and persistent vegetative state after head trauma.〔Wasserman J. and Koenigsberg R.A. (2007). (Diffuse axonal injury ). Emedicine.com. Retrieved on 2008-01-26.〕 It occurs in about half of all cases of severe head trauma. The outcome is frequently coma, with over 90% of patients with severe DAI never regaining consciousness.〔 Those who do wake up often remain significantly impaired.〔Vinas F.C. and Pilitsis J. (2006). (Penetrating head trauma ). Emedicine.com. Retrieved on 2008-01-14.〕 DAI can occur in every degree of severity from very mild or moderate to very severe.〔Vik A., Kvistad, K.A., Skandsen, T. & Ingebritsen, T. (2006). Diffus aksonal skade ved hodetraume. Tiddskr. ''Nor. Lægeforen''. 126: 2940-44.〕〔Smith, D.H. and Meaney D.F. (2000). (Axonal damage in traumatic brain injury ). ''The Neuroscientist''. 6 (6): 483—495.〕 Concussion may be a milder type of diffuse axonal injury. ==Mechanism== Unlike brain trauma that occurs due to direct impact and deformation of the brain, DAI is the result of traumatic shearing forces that occur when the head is rapidly accelerated or decelerated, as may occur in auto accidents, falls, and assaults.〔Wolf J.A., Stys P.K., Lusardi T., Meaney D., and Smith, D.H. (2001). (Traumatic axonal injury induces calcium influx modulated by tetrodotoxin-sensitive sodium channels ). ''Journal of Neuroscience''. 21 (6): 1923–1930 〕 It usually results from rotational forces or severe deceleration.〔Sanders M.J. and McKenna K. 2001. ''Mosby’s Paramedic Textbook'', 2nd revised Ed. Chapter 22, "Head and Facial Trauma." Mosby.〕〔Shepherd S. 2004. (Head Trauma ). Emedicine.com. Retrieved on 2008-01-17.〕 Vehicle accidents are the most frequent cause of DAI; it can also occur as the result of child abuse〔 such as in shaken baby syndrome.〔Smith D. and Greenwald B. 2003.( Management and staging of traumatic brain injury ). Emedicine.com. Retrieved through web archive on 17 January 2008.〕 The major cause of damage in DAI is the disruption of axons, the neural processes that allow one neuron to communicate with another. Tracts of axons, which appear white due to myelination, are referred to as white matter. Acceleration causes shearing injury: damage inflicted as tissue slides over other tissue. When the brain is accelerated, parts of differing densities and distances from the axis of rotation slide over each other, stretching axons that traverse junctions between areas of different density, especially at junctions between white and grey matter.〔 Two thirds of DAI lesions occur in areas where grey and white matter meet.〔 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「Diffuse axonal injury」の詳細全文を読む スポンサード リンク
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