A Military-Relevant Model of Closed Concussive Head Injury: Longitudinal Studies Characterizing and Validating Single and Repetitive mTBI

Abstract : Because of sports injuries, automobile accidents, falls, etc., and with the escalation of the use of improvised explosion devices (IEDs) by our enemies as witnessed in the most recent military conflicts in Iraq and Afghanistan, there has been an increased awareness of closed head concussions, also commonly referred to as the mild TBI (mTBI) injury. The prevalence of this type of closed head brain injury, estimated as afflicting over 300,000 deployed soldiers or approximately 30% of all deployed troops, has distinguished it as the signature injury of these military conflicts. Despite the enormity of this medical problem, and recognition of the importance for the need to quickly and accurately diagnose the event in the face of a limited clinical presentation (i.e. no obvious wounds to the head), objective diagnostic tools and knowledge about what occurs in the brain following this type of injury are limited. Of equal concern is our lack of understanding the impact of multiple concussions on the brain and its consequences on the long term health of individuals. In order to address this problem, the WRAIR projectile concussive impact (PCI) model was developed under directive of the Combat Casualty Care Research Program (CCCRP). Provided in this Year 2 Annual Report are the results of our Phase I studies focused on characterizing the neuropathologic, molecular and neurobehavioral changes following a single concussive impact (PCI) injury. Additionally, this Report also includes data comparing the effects of a single concussive impact to repeated concussive impacts using the PCI model. Phase I studies have been completed and these results set the foundation for Phase II studies designed to evaluate the effects of repeated concussions that occur prior to and after the resolution of the healing profile for a single concussion.