The study consists of two additional ultrasonographic examinations . The standard treatment of patients undergoing clamping of EVD/LD is not affected by the study. The first ultrasonographic examination is performed in parallel to the baseline CT scan (either immediately before or after the CT scan) before clamping of the EVD/LD. The second ultrasound is made 24 hours after clamping of the EVD/LD in parallel to the follow-up CT Scan (either immediately before or after the CT scan). The examinations will be made bedside in the supine position on the ward where the patient is treated.