What definition is used to describe second impact syndrome in sports? A systematic and critical review

Steven D Stovitz, Jonathan D. Weseman, Matthew C. Hooks, Robert J. Schmidt, Jonathan B. Koffel, Jon S. Patricios

Research output: Contribution to journalReview article

7 Scopus citations


Concern 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.

Original languageEnglish (US)
Pages (from-to)50-55
Number of pages6
JournalCurrent sports medicine reports
Issue number1
StatePublished - Jan 1 2017


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