A support and guide device (1) for a surgical instrument, in particular for neurosurgery, comprises a base body (6), extending substantially along and about an axis (A) and provided with a fastening system (7) for fastening the device (1) to a bone, a guide rod (8) having a channel (47) for receiving in use a surgical instrument, and a ball joint (9) which joins the guide rod (8) to the base body (6) the fastening system (7) is an expansion fastening system, comprising fastening elements (12), connected to a central element (11) by means of hinge portions (25) which allow the fastening elements (12) to flex with respect to the axis (A) and with respect to the central element (11) and adjusting screws (37) that act on the fastening elements (12) for flexing and therefore expanding the fastening elements (12).
