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Updated: Mar 9, 2026
Objectively Assessing Sports Concussion Utilizing Visual Evoked Potentials
Published on: April 27, 2021
What Definition Is Used to Describe Second Impact Syndrome in Sports? A Systematic and Critical Review
Steven D Stovitz1, Jonathan D Weseman, Matthew C Hooks
11Department of Family Medicine and Community Health, University of Minnesota, Minneapolis, MN; 2University of Minnesota Medical School, Minneapolis, MN; 3Bio-Medical Library, University of Minnesota, Minneapolis, MN; 4Section of Sports Medicine, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa; and 5Department of Emergency Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
Abstract:
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.
