Complex sentence: A concussion is the most common type of traumatic brain injury which can be caused by directly damage to the head, gunshot wounds, violent shaking of the head, or force from a whiplash type injury.
Split into simpler sentences: A concussion is the most common type of traumatic brain injury. It can be caused by direct damage to the head, gunshot wounds, violent shaking of the head, or force from a whiplash type injury.