If we define a direct fatality as one occurring directly from participation in the skills of a sport as opposed to an indirect fatality, which is one caused by systemic failure as a result of exertion while participating in a sport, head injury is the most frequent direct cause of death in sport.<sup>16Mueller F.O., Blyth C.S. Survey of catastrophic football injuries: 1977–1983 Physician and Sportsmedicine 1985 ;  13 : 75

Cliccare qui per andare alla sezione Riferimenti</sup> Furthermore, injury to the head takes on a singular importance when we realize the brain is neither capable of regeneration nor, unlike many other body parts and organs, of transplantation. Every effort must be made to protect the athlete's head as injury can lead to dementia, epilepsy, paralysis, and death.

Over the last 20 years there has been a dramatic decrease in the most serious head injuries—especially the incidence of subdural hematoma—due to multiple factors including rule changes, such as outlawing spear tackling and butt blocking in American football, equipment standards, better conditioning of the neck, and improved on-field medical care.

During this same time period, and especially within the last 5 years, there has been a dramatic increase in the literature citations of the second-impact syndrome (SIS) with 17 of 24 citations coming between 1992 and the present. We have no reason, however, to assume the incidence of SIS has increased as the number of cases seen annually in football has remained at one or two. Rather, we believe this condition is better recognized and reported by sports medicine professionals today.

Recognition of a head injury is easy if the athlete has lost consciousness. It is much more difficult to recognize the far more frequent head injuries in which there is no loss of consciousness but rather only a transient loss of alertness. More than 90% of all cerebral concussions fall into this most mild category where there has not been a loss of consciousness but rather only a brief period of post-traumatic amnesia or loss of mental alertness.<sup>3Cantu R.C. Guidelines for return to contact sports after a cerebral concussion Physician and Sportsmedicine 1986 ;  14 : 10

Cliccare qui per andare alla sezione Riferimenti, 4Cantu R.C. Minor head injuries in sports Adolescent Medicine: State of the Art Reviews Philadelphia: Hanley&Belfus (1991). 

Cliccare qui per andare alla sezione Riferimenti</sup> Because the dreaded SIS can occur after a grade 1 concussion, just as it can after more serious head injuries, it becomes very important to recognize all grades of concussion.<sup>3Cantu R.C. Guidelines for return to contact sports after a cerebral concussion Physician and Sportsmedicine 1986 ;  14 : 10

Cliccare qui per andare alla sezione Riferimenti, 6Cantu R.C., Voy R. Second impact syndrome a risk in any contact sport Physician and Sportsmedicine 1995 ;  23 : 27

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