Introduction: The ability to establish patency of cerebral spinal fluid (CSF) flow between adjacent central nervous system (CNS) compartments is of importance in the diagnosis and treatment of patients with CSF flow obstruction in various areas. The method described was originally derived from arterial spin labeling (ASL) of blood flowing in vessels. This technique, referred to as time-spatial labeling inversion pulse (time-SLIP), was further modified to non-invasively visualize CSF pulsatile and turbulent flow between two regions of interest.
Methods: The presence of CSF flow was examined at the foramen Magnum (FMag), the aqueduct of Sylvius (AS), the foramen of Magendie (FMgd), the floor of the third ventricle (3rd V), and at the foramen of Monro (FM). The studies were compared with clinical information and classified as true positive, true negative, false positive, and false negative based on expectation of patency.
Results: A total of 83 studies were done on 51 patients. Among positive readings of the FMag, AS, 3rd V, and FM, 49/49, 40/40, 15/15, and 9/9 were true, while 3/5, 20/30, 2/5, and 0/2 negative readings were true, respectively. The sensitivity and specificity percentages of the technique at the FMag, AS, 3rd V, and FM were, respectively, 96, 100; 80, 100; 83, 100, and 82, undefined. Negative likelihood ratios for these sites were, respectively, 0.04, 0.20, 0.17, and undefined.
Conclusions: Establishing qualitative patency between adjacent CSF compartments using MRI is possible with a modified ASL technique. The freely selectable tag allows CSF flow to be visualized in any direction or location. This technique can be used post-endoscopic third ventriculostomy to evaluate the patency of the fenestration in addition to evaluating pre- and postoperative craniocervical decompression changes to CSF flow. This technique has excellent (above 80%) sensitivity, specificity, and negative likelihood ratio at all sites studied.
Patient Care: If clinicians are able to implement this low-cost MRI modification in their hospital or clinical setting, they will be able to locate with greater confidence the potential site of a patient's CSF flow obstruction or disruption. Clinicians may use this knowledge to guide decision making on treatments such as shunt installation or revision. Moreover, surgeons will be able to evaluate the success of treatments such as ventricular or cystic fenestrations, or posterior fossa decompressions with greater confidence.
Learning Objectives: By the conclusion of this session, participants should be able to:
1. Discern the qualitative difference between this modified ASL technique and T2 imaging or phase contrast imaging.
2. Understand the basic scientific principles of this modified ASL technique.
3. Evaluate the collaborative workflow necessary to implement this imaging technique at his or her respective academic institution.
4.Cite the sensitivity and specificity values of this technique at all the tagging locations.
References: 1. Yamada, S., Tsuchiya, K., Bradley, W. G., Law, M., Winkler, M. L., Borzage, M. T., ... & McComb, J. G. (2015). 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. American Journal of Neuroradiology, 36(4), 623-630.
2.Yamada, S. (2015). Physiological variability in CSF motion using magnetic resonance time spatial labeling inversion pulse (Time-SLIP)-real time imaging. Fluids and Barriers of the CNS, 12(Suppl 1), O27.
3.Yamada, S., Goto, T., & McComb, J. G. (2013). Use of a spin-labeled cerebrospinal fluid magnetic resonance imaging technique to demonstrate successful endoscopic fenestration of an enlarging symptomatic cavum septi pellucidi. World neurosurgery, 80(3), 436-e15.