A cranial anchor system configured to attach to an opening in a cranium includes an anchor member. The anchor member has a middle anchor portion and a lower anchor portion coupled to and disposed in a downward direction relative to the middle anchor portion. The lower anchor portion has a plurality of contact members, each of which have a leg that extends at least partially in the downward direction, a tab connected to the leg, and a rib disposed between the leg and the tab. The system further includes an outer sheath and an inner sheath disposed within the outer sheath and slidable relative to the outer sheath.