Brain trauma can occur during an auto collision when the head hits the windshield or steering wheel. The skull does not have to have been penetrated or fractured for a TBI to occur. The impact involved in an auto collision can cause the soft brain to strike the hard bone of the skull. This occurs because the impact causes the head, which had previously been in motion, to come to an abrupt stop. The brain continues its forward movement, and impacts the interior of the skull. This impact can cause bruising of the brain and/or a brain hemorrhage (bleeding) which in most cases is not visible at the time of injury.
Blunt trauma is another mechanism of injury during a car accident. This occurs when a moving head slams against a hard object such as the windshield. Often, upon impact with the hard object, and open head wound will be visible. This can also occur if the car occupant is ejected at impact.