Burr hole

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 trypanon, 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. [Source: Wikipedia ]