A needle or puncture guard that has inherent probe directing features for use in an in-line configured shunt valve is provided. The guard comprises a base member configured for mounting within the domed reservoir of the shunt valve, and a guide wall seated on the base member. The guide wall is defined by a top wall, an inner side wall, and an opposed outer side wall. The inner side wall has an indented section with an aperture extending through the indented section. The inner side wall can be concavely curved, while the indented section has a curvature that directs instruments that are pressed against the guide wall towards the aperture. A method for performing catheter revisions on a shunt system having a guard within the shunt valve is provided as well. Also provided is a method for placement of an intracranial pressure sensor percutaneously into a ventricular catheter for determining intracranial pressure.