The invention concerns a cranial drill system(100, 200, 300, 400) comprising one or more surgical drill elements (102, 202, 302, 402) for drilling into the brain. The invention also concerns a cranial drilling system (1200, 1300) comprising a surgical drill element for drilling into the skull (110, 210, 310, 410, 1210, 1310) and an element (102, 202, 302, 402, 1202, 1302) for penetrating the dura. The surgical drill element (310, 1310) may comprise a profile that forms an opening (153, 1153) in the skull (151, 1151) having a narrower diameter portion (153a, 1153a) and a wider diameter portion and the piercing element (302, 1302) may be arranged to be a close fit in the narrower diameter portion (153a, 1153a) of the opening. The invention also concerns a cranial drill system comprising a guiding element (210, 1210) to be located in a hole (153, 1153) formed through the skull (151, 1151) and a piercing element (202, 1202) for piercing the dura. The guiding element (210, 1210) may have a passageway or channel (220, 1220) therein for receiving the piercing element (202, 1202) such that the piercing element (202, 202) is movable relative to the guide element (210, 1210) to pierce the dura.
