Abstract
Traumatic brain injury (TBI) is a public health problem of great concern, because it affects more than 2 million individuals each year. TBI occurs as a result of motor vehicle crashes, falls, and sports-related events. Biomechanical mechanisms occurring at the time of the injury initiate primary and secondary injuries that evolve over several days. In this article the relationship between an blunt injury event and the subsequent damage produced is addressed. Mechanisms of brain injury from biomechanics to cellular pathobiology are presented. Primary and secondary injuries are differentiated, and specific focal and diffuse clinical syndromes are described. Cellular mechanisms responsible for injury are also addressed, because they provide the unifying concepts across the many clinical syndromes so often discussed separately in reviews of traumatic brain injury.