Stovitz, Steven D.Weseman, Jonathan D.Hooks, Matthew C.Schmidt, Robert J.Koffel, Jonathan B.Patricios, Jonathan Speridon2017-03-012017-01Stovitz, SD, Weseman, JD, Hooks, MC, Schmidt, RJ, Koffel, JB & Patricios, JS 2017, 'What definition is used to describe second impact syndrome in sports? A systematic and critical review', Current Sports Medicine Reports, vol. 16, no. 1, pp. 50-55.1537-890X (print)1537-8918 (online)10.1249/JSR.0000000000000326http://hdl.handle.net/2263/59206Concern about what has been termed, “second impact syndrome” (SIS) is a major factor determining return-to-play decisions after concussion. However, definitions of SIS vary. We used Scopus to conduct a systematic review and categorize the definitions used to describe SIS. Of the 91 sources identified, 79 (87%) clearly specified that SIS involved either cerebral edema or death after a concussion when a prior concussion had not resolved. Twelve articles (13%) could be interpreted as merely the events of two consecutive concussions. Among the articles that listed mortality rates, nearly all (33/35, 94%) said the rate of death was “high” (e.g., 50% to 100%). Our review found that most articles define SIS as a syndrome requiring catastrophic brain injury after consecutive concussive episodes. Given that it is unclear how common it is to have a second concussion while not fully recovered from a first concussion, the actual mortality rate of SIS is unknown.en© 2017 by the American College of Sports Medicine. This is a non-final version of an article published in final form in Current Sports Medicine Reports, vol. 16, no. 1, pp. 50-55, 2017. doi : 10.1249/JSR.0000000000000326.SportsDefinitionSecond impact syndrome (SIS)ConcussionReturn-to-play decisionsPostprint Article