Trepanation is the act of drilling a hole in one's head for no (legitimate) medical reason. Practitioners believe that trepanation can work all kinds of miracles, opening up a "third eye", getting to a higher state of consciousness, letting the brain "breathe" or "pulsate" or allowing the demons to leave the patient's skull. Needless to say, this puts it squarely in the realm of alternative medicine. It is believed to be one of the oldest surgical practices in existence as several neolithic skulls have been found with evidence for this being done; some fossil skulls indicate that the patient managed to survive the procedure. Nobody knows why the ancients did such things, however, the fact that our ancestors did trepanate themselves is taken by modern followers of the practice as justification for doing it in the present.
These days, demonic possession is generally referred to as mental illness (denialism notwithstanding) and witch doctors are now called psychiatrists. Instead of drilling holes in the skulls, their preferred methods now include the administering of drugs and other evidence-based therapies.
There is a reason that the skull does not have a hole at the place you plan to drill; its job is to protect the brain from harm. You already have the eyesocket and the holes to connect your spinal cord with the rest of your body and your brain does not benefit from making new holes by growing a new major nerve out of that hole. Needless to say this is a risky procedure. First, no medical doctor will be willing to do this to you, hence, people who trepanate themselves often use things like dental drills or even power tools. Furthermore, there is only a small amount of space between the skull and the brain itself, so the margin of error between a "third eye" and a lobotomy is very small. Finally, if it does not heal properly the brain could be exposed to infections.
 Before you pounce...
There is actually a legitimate medical reason for drilling a hole in the skull, but there is no way our ancestors could have known about it without CT scans. Sometimes when the body sustains a severe blow to the head the brain will begin to swell which builds pressure on the brain, further damaging it. Hence, doctors in an emergency room will sometimes drill holes into the head in order to relieve the pressure and in some cases a metal plate will be attached to the skull to help it heal. Portions of the skull may also be removed for the purpose of brain biopsy or other procedure.
 See also
- A Hole In The Head Documentary about trepanation. WARNING: contains some brutal closeup footage of trepanation in action. Not for the faint of heart.
- ↑ Well, putting everything aside, one does need as much space as an eye socket to put in an extra eye.
- ↑ How did the demon get in anyways? It's not like the demon needed a new hole to get in, so why would it need a new hole to get out?
- ↑ Unless you believe the content of the novel Romance of the Three Kingdoms is based on actual historical events, which then you will believe that a medical practitioner can determine what's wrong with the patient's brain by talking to the patient, in addition to the pulses at the wrist of the patient. But that's for tumor removal through opening the skull, instead of simply drilling a hole.