Figure 1: Data acquisition by phase-contrast magnetic resonance imaging: the selected acquisition planes were perpendicular to the presumed flow direction. Sections through the aqueduct of Sylvius and the C2-C3 subarachnoid space (C2-C3) were used for cerebrospinal fluid flow measurement (a). Examples of phase contrast images at the Sylvian aqueduct and the cervical subarachnoid spaces are shown in images (b) and (c).