Trephination is a surgical procedure in which a circular part of the skull is carved away leaving a hole in the skull. This was the first known surgical practice and evidence of it has been found as early as the Neolithic period (10,000 BC-3,000 BC). It is theorized that early cultures used trephination to release spirits from a person or as a cure for convulsions and headaches. Ancient Egyptians also used to medical procedure and used the bone pieces in ceremonies. It is still used today to relieve brain hematoma but is typically called a craniotomy by modern doctors.