Effects of Repetitive Sub-concussive Mild Traumatic Brain Injury
Approximately 67,000 high school football players are clinically diagnosed with a concussion each year, and it is estimated that the equivalence goes undiagnosed. With concussion awareness dramatically increasing, attention has also shifted in a new direction with brain injury. Recent evidence suggests that athletes sustain many head hits that occur in football and other contact sports in which symptoms of a concussion do not develop, yet there are visible signs of neurological dysfunction. These deficits may go unnoticed by medical professionals, coaches, and even the players themselves. Investigation of high school football teams has found the average player to sustain about 652 impacts in a 14-week season. The cumulative impact burden over the course of an athlete’s career may be just as detrimental to the individual’s mental health as the accumulation of clinically diagnosed concussions. The effects of repetitive sub-concussive head injuries shown in high school and collegiate athletes are supported in rat models of repetitive mild traumatic brain injury (mTBI). Such findings have also been demonstrated through examining the neurological performance and health in the presence of head collision events in high school football players, using longitudinal measures of collision events (the HIT System), neurocognitive testing (ImPACT), assessment of blood-brain barrier disruption (BBBD), and functional magnetic resonance imaging MRI (fMRI). The following review provides an organized overview of some of the major evidence supporting the concept of sub-concussion.