Abstract
This article provides an overview of phase-contrast and time-spatial labeling inversion pulse MR imaging techniques to assess CSF movement in the CNS under normal and pathophysiologic situations. Phase-contrast can quantitatively measure stroke volume in selected regions, notably the aqueduct of Sylvius, synchronized to the heartbeat. Judicious fine-tuning of the technique is needed to achieve maximal temporal resolution, and it has limited visualization of CSF motion in many CNS regions. Phase-contrast is frequently used to evaluate those patients with suspected normal pressure hydrocephalus and a Chiari I malformation. Correlation with successful treatment outcome has been problematic. Time-spatial labeling inversion pulse, with a high signal-to-noise ratio, assesses linear and turbulent motion of CSF anywhere in the CNS. Time-spatial labeling inversion pulse can qualitatively visualize whether CSF flows between 2 compartments and determine whether there is flow through the aqueduct of Sylvius or a new surgically created stoma. Cine images reveal CSF linear and turbulent flow patterns.
Highlights
Following surgical fenestration of the cavum septi pellucidi (CSP), MR imaging with Time-SLIP demonstrated decreased ventricular and CSP size and the presence of CSF flowing between the third ventricle and the CSP, which coincided with resolution of this patient’s symptoms
The higher intrinsic SNR and temporal resolution of Time-SLIP make it possible to visualize CSF movement in response to respiration and how the CSF flow patterns are altered by the depth of the respiratory effort
The typical CSF flow pathway that has been described in textbooks is much different from that observed noninvasively with Time-SLIP,[45] even in the normal, nonhydrocephalic brain
Summary
ABBREVIATIONS: CSP ϭ cavum septi pellucidi; NPH ϭ normal pressure hydrocephalus; PC ϭ phase-contrast; Time-SLIP ϭ time–spatial labeling inversion pulse; Venc ϭ velocity-encoding value In the pulsatile models of hydrocephalus, a “waterhammer” effect is hypothesized, in which large undampened pulsations produce increased pressure gradients and asymmetric pulsation distributions lead to ventricular dilation.[34,35] Enlarged pulse-wave amplitudes of CSF movement in patients with NPH have been observed and measured with MR imaging for a number of years.[1,36] This effort has attempted to improve our understanding of hydrocephalus.[14,15,36] it has failed to correctly identify those patients who would benefit from CSF diversion.
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