Athletes with no clinical sign of concussion still show functional and cognitive impairment
Even though there has been considerable attention put on sports-related brain injury recently, undiagnosed brain injuries are still putting athletes back on the field too soon.
In one recent study comparing football players without a diagnosed concussion to football players with a diagnosed concussion, researchers found some who had no clinical signs of injury, but showed signs of impairment both in neuropsychological testing and from a functional MRI.
Additionally, both the type of cognitive impairment and the location of brain impairment were related to visual working memory-that is, the ability to keep in mind what you've recently seen. The most commonly damaged brain area was the dorsolateral prefrontal cortex (located on the top front of skull), where-not surprisingly-helmet-to-helmet contact is often made.
Talavage TM, Nauman EA, Breedlove EL, et al. Functionally-detected cognitive impairment in high school football players without clinically-diagnosed concussion. Journal of Neurotrauma. (October 2010).