Comparison of Different CSF Sampling Sites on External Ventricular Drains

Inclusion Criteria: * Patients with an EVD in place regardless of the underlying pathology. * Written informed consent to participate in the study must be obtained from the subject. If the subject is not capable of self-consent, all efforts will be made to locate a legally acceptable representative to act on behalf of the subject. When the patient is considered capable to consent but physically unable to sign an informed consent form and a representative is not available an impartial witness can attend the informed consent process. \- Males and females of all ages, including children and pregnant females Exclusion Criteria: * Patients in whom the removal of the drain is planned within 48 hours, before routine sampling, will be excluded.