What is trepanning?
Trepanning, also known as trepanation, trephination, trephining, or making a burr hole (the verb trepan derives from Old French from Medieval Latin trepanum from Greek trúpanon, literally "borer, auger") is a surgical intervention in which a hole is drilled or scraped into the human skull. The intentional perforation of the cranium exposes the dura mater to treat health problems related to intracranial diseases or release pressured blood buildup from an injury. It may also refer to any "burr" hole created through other body surfaces, including nail beds. A trephine is an instrument used for cutting out a round piece of skull bone to relieve pressure beneath a surface.