Fig. 4

The pressure-gradient within the cerebral aqueduct correlates with several independent measures of CSF tracer movement and CSF flow. There was a significant positive correlation between the pressure-gradient (dP) and tracer enrichment within 3rd ventricle after 6 h (a; n = 74) and 24 h (b; n = 80), and tracer enrichment within lateral ventricles after 6 h (c; n = 74) and 24 h (d; n = 80). The pressure gradient (dP) also correlated positively with the total flow per cycle in the cerebral aqueduct (e; n = 85), the absolute net flow per cycle in the cerebral aqueduct (f; n = 85), and with the average overnight mean ICP wave amplitude indicative of the intracranial compliance (g; n = 50), whereas no correlated was found with static ICP (mean ICP, h; n = 48). Each plot shows the fit line with Pearson correlation coefficients and significance levels