Brain injuries vary in severity, but they all have one thing in common, which is lingering effects that may last for weeks, months, or years after the accident.Concussion: A concussion is caused by the rapid movement of the brain within the skull, most often as a result of an impact or a blow to the head. This movement may result in chemical and structural changes within the brain. There are different grades of concussions, ranging from those that involve no loss of consciousness to those where there is a prolonged period of unconsciousness. If not treated immediately, any concussion can result in lasting damage, including post-concussion syndrome and a potentially deadly condition known as second impact syndrome.Contusion: A contusion involves actual bruising and/or tissue damage to the brain. During a car accident, a contusion can result when the brain impacts the interior of the skull. This can cause internal bleeding. Because the brain is completely enclosed within the skull, bleeding can cause pressure to build leading to serious damage.Diffuse axonal injury: Diffuse axonal injury (DAI) occurs when connective neurological structures within the brain tear, as the brain moves rapidly within the skull during a collision. DAI is an extremely serious injury that can lead to a coma and persistent vegetative state.Coup-Contrecoup: Similar to DAI, this injury is caused by the movement of the brain within the skull during impact. Coup-contrecoup involves two brain injuries: one when the brain impacts the front of the skull (such as in a head-on collision) and another when the brain moves back and impacts the rear of the skull.