Puncture of the ventricular system is one of the most frequently performed neurosurgical interventions. This procedure is commonly performed in order to treat and/or measure pathologically elevated intracranial pressure. Therefore a safe and fast surgical procedure is needed.Currently the "landmark-based" placement of intraventricular catheters is the gold standard. Nonetheless it is known that more than 60% of the catheters are not placed accurately performing "landmark-based" procedures. When the catheter is not placed accurately multiple punctures may be required. Incorrectly placed intraventricular catheters may lead to undesirable side effects like catheter dysfunction,in which case a correction of the catheter position or a even a new puncture will be required. These corrections increase the risk of intracerebral hemorrhages, infections or secondary brain injuries. In this study, the investigators will prospectively investigate whether ultrasound guidance increases the number of well-placed ventricular catheters and reduces the number of undesirable side effects. In this study the correct catheter position is defined when the catheter tip is located in the lateral ventricle (ipsilateral to the burrhole) anterior of the foramen of Monro. Catheter tip position will be assessed by cranial computer tomography after the operation. The CT scans will be evaluated by an independent expert rater, blinded for the procedure type. These incorrectly placed intraventricular catheters may lead to undesirable side effects, like catheter dysfunction wherefore a correction of the catheter position or a even a new puncture has to be done. These corrections increase the risk of intracerebral hemorrhages, infections or secondary brain damages.