Figure 1.

Sequential events of primary injury in TBI. Initial impact is usually by directing trauma to the head either open or closed head injury. This trauma will cause mechanical damage to neurons, axons, glia, and blood vessels by shearing, tearing, or stretching. Blood vessel ruptures cause hemorrhage. Even in unruptured blood vessels, BBB permeability increases resulting in edema. Hemorrhage and edema often lead to intracranial hypertension. Following hemorrhage, ischemia could occur in brain tissue. TBI-caused cell damage induces macrophage and lymphocytes migrant to the injury site releasing inflammatory mediators that triggers a cascade of events towards necrosis and/or apoptosis. Necrosis and/or apoptosis also can be a consequence of hemorrhage and ischemia.