|
Second-impact syndrome (SIS) occurs when the brain swells rapidly, and catastrophically, after a person suffers a second concussion before symptoms from an earlier one have subsided. This second blow may occur minutes, days or weeks after an initial concussion,〔 and even the mildest grade of concussion can lead to SIS.〔 The condition is often fatal, and almost everyone who is not killed is severely disabled. The cause of SIS is uncertain, but it is thought that the brain's arterioles lose their ability to regulate their diameter, and therefore lose control over cerebral blood flow, causing massive cerebral edema.〔 Most cases of SIS have occurred in young people, who are thought to be particularly vulnerable. In order to prevent SIS, guidelines have been established to prohibit athletes from returning to a game prematurely. For example, professionals recommend that athletes not return to play before symptoms of an initial head injury have resolved. Due to the very small number of recorded cases of SIS, there is doubt about whether it is a valid diagnosis. However, the syndrome is recognized by physicians.〔 〕 ==Epidemiology== Though the incidence of second impact syndrome is unknown,〔 the condition is rare; very few cases have been confirmed in medical literature.〔 In the 13 year period from 1980–1993, 35 American football related cases of SIS were recorded, but only 17 of these were confirmed by necropsy or surgery and magnetic resonance imaging to be due to SIS, and 18 cases were found to be probably SIS-related.〔 Additionally, the initial trauma commonly goes unreported, adding to the confusion about how often the syndrome occurs.〔 By one estimate, the syndrome kills four to six people under the age of 18 per year.〔Bach G (2007), "(Heads up )". ''SportingKid Magazine''. National Alliance for Youth Sports. Scientific Advisory Services, Ltd. Retrieved on 2007-12-30.〕 According to the Centers for Disease Control, about 1.5 people die each year from concussion in the US; in most of these cases, the person had received another concussion previously.〔Neurosurgery Today (November 2005). (Concussion ). Neurosurgerytoday.org. Retrieved on 2008-01-02.〕 In part due to the poor documentation of the initial injury and continuing symptoms in recorded cases,〔 some professionals think that the condition is over-diagnosed,〔 and some doubt the validity of the diagnosis altogether.〔 〕 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「Second-impact syndrome」の詳細全文を読む スポンサード リンク
|