Fig 1.
Single cardiac-induced ICP wave.
One single ICP wave is illustrated with its individual parameters. We measured pressure in mm Hg; with a heart rate of 60, the duration of a single wave is about 1 second. The mean ICP wave amplitude (MWA) is determined as the average of amplitudes from single ICP waves during consecutive 6-second time intervals.
Fig 2.
(A) Level of PC-MRI acquisitions. PC-MRI was performed perpendicular to the cervical spinal canal at level C2, which is typically the closest level to the intracranial compartment where the assumption of the spinal canal as a rigid, cylindrical tube can be made when estimating MRI-dP. (B) ROI outlining. The subarachnoid space was manually defined from phase images with a region of interest (ROI).
Fig 3.
The PC-MRI derived pulse pressure gradient (MRI-dP).
MRI-dP is calculated as the difference between the maximum and minimum pressure gradient within the cycle.
Table 1.
Demographic information about patients and healthy controls.
Fig 4.
Trend plots of (a) MWA (6.6±1.8 mmHg), (b) mean ICP (2.8±4.8 mmHg), and (c) HR (76.2±13.7 beats/min) for patient 20, who underwent prolonged invasive monitoring, illustrating the variation in the ICP-derived parameters over time. In (d) is shown one individual cardiac-beat induced ICP wave with its amplitude (dP) and rise time (RT).
Table 2.
Summary of ICP data from iNPH patients.
Table 3.
PC-MRI data from patients and healthy controls (median with range).
Fig 5.
The association between MRI-dP and standardized over-night, invasive monitoring (11 p.m. to 7 a.m.) of (a) pulsatile ICP (MWA) and (b) static ICP (mean ICP).The Pearson correlation coefficient (R) and significance level are presented for each plot.
Fig 6.
MRI-dP and pulsatile ICP (MWA) thresholds for shunting in iNPH.
The MRI-dP values are shown for iNPH patients with preoperative MWA values either above (n = 16) or below (n = 6) the thresholds used for selection of patients for shunting, and also for the healthy reference subjects. There were no significant differences between groups (P>0.44).
Fig 7.
HR from PC-MRI and ICP monitoring.
(a) The association between MRI-derived HR and ICP-derived HR, Pearson correlation coefficient (R) and significance level. (b) Bland-Altman plot of all MRI- and ICP-derived HR observations. The line in the middle is the mean difference (2.3 beats/min) and the upper and lower lines represent mean+2SD (standard deviations; 15.0 beats/min) and mean– 2SD (-10.4 beats/min), respectively.
Fig 8.
Heterogeneity of CSF flow velocities.
Patient 4, demonstrating spatial variations in flow velocity within the ROI at one time step (t = 0.70 s). The color bar represents velocities in cm/s.