I think the fact that trepanation is not mentioned in the Edwin Smith
Papyrus speaks against the so-called medical usages of it by ancients and I
think that makes it more likely to have been used to enhance psychic
awareness as in the case of the Merovingian King Dagobert. I do know that
letting pressure off the skull by drilling into it was in use by the Inca
and still is in Africa. Trepanation is not a simple hole in the skull.
"According to Breasted, the Edwin Smith Papyrus is a copy of an ancient
composite manuscript which contained, in addition to the original author's
text (3000-2500 B.C.), a commentary added a few hundred years later in the
form of 69 explanatory notes (glosses). It contains 48 systematically
arranged case histories, beginning with injuries of the head and proceeding
downward to the thorax and spine, where the document unfortunately breaks
off. These cases are typical rather than individual, and each presentation
of a case is divided into title, examination, diagnosis, and treatment.
There is a definite differentiation between rational surgical treatments and
the much less employed medico-magical measures. Significantly, trepanation
is not mentioned."