It's probably a funny depiction of trepination, right?

The drilling, sawing or scraping of holes in the skull is one of the earliest medical procedures we have evidence for. It relieves pressure and brain swelling. As gruesome as it sounds, it was quite survivable and people survived multiple trepinations deep into prehistory.

Once you get hospitals in the medieval period the survival rate drops - don't be in a room of sick people when your skull has a hole in it.