Trepanation (also known as trepanning, trephination, trephining or burr hole) is surgery in which a hole is rilled or scraped into the skull, thus exposing the dura mater in order to treat health problems related to intracranial diseases, though in the modern era it is used only to treat epidural and subdural hematomas and for surgical access for certain other neurosurgical procedures, such as intracranial pressure monitoring.