<unk>  are sets of criteria used in sports medicine to determine the severity, or grade, of a<unk> , the mildest form of traumatic brain injury. At least 16 such<unk>  exist, and there is little agreement among professionals about which is the best to use. Several of the<unk>  use loss of consciousness and amnesia as the primary determinants of the severity of the<unk> . The<unk>  are widely used to determine when it is safe to allow an athlete to return to competition. Concern exists that multiple<unk> s received in a short time may present an added danger, since an initial<unk>  may leave the brain in a vulnerable state for a time. Injured athletes are prohibited from returning to play before they are symptom-free during rest and exertion and their neuropsychological tests are normal again, in order to avoid a risk of cumulative effects such as decline in mental function and second-impact syndrome, which may occur on very rare occasions after a<unk>  that occurs before the symptoms from another<unk>  have resolved. It is estimated that over 40% of high school athletes return to action prematurely and over 40,000 youth<unk> s occur annually.<unk> s account for nearly 10% of sport injuries, and are the second leading cause of brain injury for young people ages 15–24. Three<unk><unk>  are followed most widely: the first by neurosurgeon Robert Cantu, another by the Colorado Medical Society, and a third by the American Academy of Neurology. The Cantu<unk> has become somewhat outdated.
Concussion grading systems
Blantyre coma scale
Transactions of the American Neurological Association
Schmidt sting pain index
Pain scale
Fares Scale of Injuries due to Cluster Munitions
Figure rating scale
Pain ladder