The invention concerns a cranial drill system comprising one or more surgical drill elements for drilling into the brain. The invention also concerns a cranial drilling system comprising a surgical drill element for drilling into the skull and an element for penetrating the dura. The surgical drill element may comprise a profile that forms an opening in the skull having a narrower diameter portion and a wider diameter portion and the piercing element may be arranged to be a close fit in the narrower diameter portion of the opening. The invention also concerns a cranial drill system comprising a guiding element to be located in a hole formed through the skull and a piercing element for piercing the dura. The guiding element may have a passageway or channel therein for receiving the piercing element such that the piercing element is movable relative to the guide element to pierce the dura.
