SECOND IMPACT SYNDROME [ back to Glossary Index ]
Second Impact Syndrome refers to two different TBI related phenomena. One of them is the catastrophic effect of a second concussion before symptoms from the first concussion have fully resolved. Chicago neurologist James Kelly developed guidelines for management of sports concussions, which were published by the American Academy of Neurology in March 1997, after studying the deaths of highs school and college athletes who suffered two "mild" concussions close in time. The underlying mechanism has been identified as "vascular dysregulation" with explosive cerebral edema leading to death. Anyone who has recently suffered a concussion, even a mild one characterized by dazing or confusion without loss of consciousness, should rest, see a doctor and avoid contact sports until released by a neurologist. The other phenomenon referenced by second impact syndrome is the geometric increase in the risk of new concussions after each one. After the initial concussion, the risk of having a second increases by a factor of 3. After the second, the risk of having a third increases by a factor of 8.  The underlying mechanism has to do with impaired judgment, delayed perception and reaction time and impulsiveness.