A traumatic brain injury occurs when the brain sustains a traumatic injury due to an outside physical force. Most often a traumatic brain injury is caused by a severe car accident or a motorcycle accident where the individual is ejected from the vehicle or bike. Other instances that can cause a traumatic brain injury would be a sports injury or a bad fall. A traumatic brain injury happens when a sudden trauma forces the head forward or sideways with extreme force causing the brain to smash into the skull. This movement of the brain can lead to internal tears and even bleeding.