DropkickMurphy
Contributor
Wow, whats the odds of such a thing happening and the person even surviving, he certainly got lucky there! I hope that it has no lasting effects on the guy!
Actually, for non-gunshot wound penetrating trauma to the head, the rate of survival is remarkably high. Remember that most of what really does damage in the case of a gunshot is the shockwave surrounding the bullet as it passes through soft tissue (and brain is about as soft as it gets). That isn't present in the case of stabbings to the head, impaled objects, etc. During my tenure in health care and emergency services I have personally seen four cases- one arrow, a stabbing, an industrial accident involving a flying piece of metal and a piece of wood associated with tornadic winds to be precise- where this has happened and the person survived. In all of them, the person was conscious and talking afterward. Google Phineas Gage for the ultimate example of what a person can take in terms of penetrating head injury and still survive (although Gage had serious personality changes after his injury).
Judging by the rather odd angle of the CT image that was provided with the spear impalement story, I am almost willing to bet it did not actually enter his brain but perhaps lodged in the outer table of his skull and sinuses or it may have just pushed his frontal lobes out of the way as it came in. The brain is somewhat compressible within certain limits. Too much compression from swelling, blood accumulating, etc and you start to squeeze the bottom of the brain out the bottom of the skull where the spinal cord exits; this is called herniation for those who are playing along at home and is one of the more common things that kill people dying of head injuries and other related problems. However, sometimes on a rare occasion the brain being soft and kind of malleable is what saves someone from death or an even worse fate.
Still, that would hurt like hell, but it's not nearly as bad as "He was shot in the head with a speargun" makes it sound at first blush. The primary concerns with something like this occurring underwater in a marine environment is the secondary infections that can happen. Ocean water contains some pretty nasty bacteria that just LOVE open wounds.