After dura opening, once the appropriate trajectory is chosen, the catheter is inserted according to the precalculated insertion angle. After tactile feedback of entering the ventricle, the stylet is removed. Cerebrospinal fluid (CSF) drainage ensures that the ventricular catheter is sufficiently in place. Catheters deemed to be suboptimally placed are repositioned when necessary. We rely on length markings on the ventricular catheter and, when possible, flow through the distal catheter to ensure the catheter has not been moved after fixation on the skin and is continuing to provide a conduit for CSF. The remainder of the possibly following shunt procedure or connection to a Ommaya reservoir was performed with standard techniques.