A Projectile Concussive Impact Model Produces Neuroinflammation in Both Mild and Moderate-Severe Traumatic Brain Injury

Traumatic brain injury (TBI) is as a major cause of death and disability experienced by nearly 3 million people annually resulting from falls, vehicular accidents, or from being struck by or against an object. While TBIs can range in severity, the majority of injuries are considered to be mild. However, TBI of any severity has the potential to have long-lasting neurological effects including headaches, cognitive/memory impairments, mood dysfunction, and fatigue as a result of neuronal damage and neuroinflammation. The goal of the study was to evaluate the neuroinflammatory and neuronal damage outcomes associated with mild or moderate-severe TBI via the modification of an established closed-head injury model of TBI by varying the material of the projectile. Rats that received TBI using a stainless steel projectile exhibited outcomes strongly correlated to moderate-severe TBI, such as prolonged unconsciousness, impaired neurobehavior, increased risk for hematoma and death, as well as significant neuronal degeneration and neuroinflammation throughout the cortex, hippocampus, thalamus, and cerebellum. In contrast, rats that received TBI with an aluminum projectile exhibited characteristics more congruous with mild TBI, such as a trend for longer periods of unconscious in the absence of neurobehavioral deficits, a lack of neurodegeneration and mild neuroinflammation. Our results indicate that different levels of behavioral, neuroinflammatory, and damage outcomes are associated with differing levels of TBI severity.