Bingo! It was almost exactly 50 years ago the Mr Knight of blessed memory - world’s best elementary school science teacher, pbuh, told us that the Egyptians did trepanning - taking out a chunk of broken skull so it wouldn’t impinge on the brain ... and that people survived it.
The Neanderthals did trepanning, so did the ancient Peruvians, the Babylonians, and the ancient Celts.
Prehistoric skulls have been found in Germany not only with lovely neat round holes cut in them, but regrowth of the bone to fill the hole . . . which shows that the patients actually SURVIVED the operation.
They may have been trying to let "evil spirits" out, but in the case of a traumatic head injury it was the right thing to do.