Head injuries may result from any accident in which the head is struck, shaken or penetrated with an object. No matter how hard you strike your head, brain injuries may occur, even if the blow was only small. In many cases injuries may be quite minor, such as concussion, a relatively common brain injury with short-term symptoms, where no lasting damage is caused. Other more serious injuries may occur with harder blows to the head or shaking, even if the skull is not broken. Where other areas of the body would bruise when bumped, the brain may swell a little. Even a small amount of swelling will however increase the pressure in the skull, which may in turn put pressure onto some of the blood vessels and prevent oxygen from flowing. This is known medically as "compression" and can lead small areas of the brain dying from oxygen starvation, which in turn leads to permanent brain injuries. Similarly, if the brain is penetrated by any object, this may also lead to long-lasting brain injury, possibly resulting in permanent disability.