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Concussion grading systems are sets of criteria used in sports medicine to determine the severity, or grade, of a concussion, the mildest form of traumatic brain injury. At least 16 such systems exist,〔 〕 and there is little agreement among professionals about which is the best to use.〔 〕 Several of the systems use loss of consciousness and amnesia as the primary determinants of the severity of the concussion.〔 The systems are widely used to determine when it is safe to allow an athlete to return to competition. Concern exists that multiple concussions received in a short time may present an added danger, since an initial concussion may leave the brain in a vulnerable state for a time. Injured athletes are prohibited from returning to play before they are symptom-free during rest and exertion and their neuropsychological tests are normal again, in order to avoid a risk of cumulative effects such as decline in mental function and second-impact syndrome, which may occur on very rare occasions after a concussion that occurs before the symptoms from another concussion have resolved. It is estimated that over 40% of high school athletes return to action prematurely〔(Concussions Extra Dangerous to Teen Brains, CNN, 4 February 2010 )〕 and over 40,000 youth concussions occur annually.〔(Heading Off Sports Injuries, Newsweek, 5 Feb 2010 )〕 Concussions account for nearly 10% of sport injuries, and are the second leading cause of brain injury for young people ages 15–24.〔(High School Athletes Face Serious Concussion Risks, USA Today, 4 May 2009 )〕 Three grading systems are followed most widely: the first by neurosurgeon Robert Cantu, another by the Colorado Medical Society, and a third by the American Academy of Neurology.〔 〕 The Cantu system has become somewhat outdated. ==American Academy of Neurology guidelines== The guidelines devised in 1997 by the American Academy of Neurology (AAN) were based on those formulated by the Colorado Medical Society.,〔 〕 however, in 2013 the AAN published a revised set of guidelines that moved away from concussion grading, emphasizing more detailed neurological assessment prior to return to play.〔Giza CC, Kutcher JS, Ashwal S, et al. Summary of evidence-based guideline update: evaluation and management of concussion in sports: report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology 2013;80(24):2250–7. 〕 The guidelines emphasized that younger patients should be managed more conservatively and that risk of recurrent concussion was highest within 10 days following the initial injury. Risk of concussion was also stratified by sport, training time, and player Body Mass Index. The guideline also called into question the existence of the "second impact syndrome," proposing instead that athletes with a previous concussion may be more vulnerable to severe injury due to decreased reaction time and coordination, symptoms of the initial injury. 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「Concussion grading systems」の詳細全文を読む スポンサード リンク
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