Current and Emerging MR Imaging Techniques for the Diagnosis and Management of CSF Flow Disorders: A Review of Phase-Contrast and Time–Spatial Labeling Inversion Pulse

Abstract

SUMMARY: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. ABBREVIATIONS:CSP ϭ cavum septi pellucidi; NPH ϭ normal pressure hydrocephalus; PC ϭ phase-contrast; Time-SLIP ϭ time-spatial labeling inversion pulse;

An update on research priorities in hydrocephalus: overview of the third National Institutes of Health-sponsored symposium “Opportunities for Hydrocephalus Research: Pathways to Better Outcomes”

“…Phase-contrast MRI can quantify aqueductal CSF flow and, along with other imaging correlates such as CSF flow voids, can predict shunt responsiveness in NPH. 8,14,134 What is often missing in development and validation of diagnostic and prognostic imaging techniques is the link between these techniques and the underlying mechanisms responsible for any imaging changes. Various MRI techniques, such as phase-contrast MRI, DTI, and elastography, hold great promise in identifying hydrocephalus pathophysiology, guiding clinical management, and developing alternative therapies.…”

“…5,56,108,123,134 Appropriate sample size has been a major issue, with 50% of general surgical trials being underpowered. 31,107 Within surgical specialties, RCTs are less common because of the surgical research culture, the difficulty of conducting surgical RCTs, limited RCT expertise among surgeons, limited infrastructure, and limited funding.…”

Advanced Neuroimaging Techniques in Pediatric Hydrocephalus

“…The newer hydrodynamic theory divides hydrocephalus into acute and chronic or communicating hydrocephalus, and states that these latter entities occur due to an increase in pulse pressure in brain capillaries and decreased intracranial compliance, which in turn maintains ventricular enlargement [29,30] . Over the last few decades, flow-sensitive imaging such as PC-MRI has emerged as an important tool in the assessment of communicating hydrocephalus, particularly in attempts to determine the functionality of operative interventions, such as the placement of a ventriculoperitoneal shunt or ETV [28,31] .…”

“…PC-MRI is a noninvasive technique that allows for the observation of CSF flow velocity and its directionality during a single cardiac cycle by utilizing a specially designed flow-sensitive gradient echo (GRE) sequence. When used in combination, 3D-CISS and PC-MRI can provide a wealth of information about the anatomy of the CSF pathways, the directionality of flow, areas of obstruction or concern, and potential operative targets for intervention [18,27,28] .…”

“…Since the introduction of PC-MRI, a wave of other MR modalities or pulse sequences have been studied for the evaluation of CSF in pathophysiological conditions with some success, including, but not limited to, PC balanced 439 steady-state free precession [36] , 3D MR velocity mapping [37] , time-spatial labeling inversion pulse, and arterial spin labeling [28,36] , as well as 3D-sampling perfection with application-optimized contrast [38,39] . Overall, the various MR techniques developed within the last 2 decades have been an invaluable resource for noninvasive study of intracranial pulsatility in hydrocephalus.…”