Glymphatic Pathway in Brain Imaging: Evaluation of MRI Findings

To investigate the contrast enhancement in different brain compartments. Until recently, it had been assumed that Gadolinium-based contrast agents do not cross the blood-brain barrier, but delayed imaging revealed signal increase in a number of compartments in the CSF (the perilymph of the inner ear, the internal auditory canal, the Meckel's cave, the suprasellar cistern, the ambient cistern and anterior eye compartment). These findings suggested, that Gadolinium-based contrast agents (GBCA) penetrate into the CSF through the choroid plexus and the aqueous chamber of the eye. MRI has provided the evidence of presence of meningeal lymphatic vessels in human and non-human primates for central nervous system waste clearance. It has been demonstrated that heavily T2-weighted fluid-attenuated inversion recovery (hT2w-FLAIR) MRI detects even very low concentrations of GBCA in the CSF.

The aim of our study is to find specific enhancement patterns in various cerebral compartments in correlation with specific diseases and procedures such as radiation, surgery and drug application in delayed gadolinium imaging. Only patients with a clinical indication for GBCA will be included in this prospective study. Before enrollment, each patient will have provided written informed consent of participation and publication prior to inclusion to the observational study. The scan will be performed as baseline before intravenous contrast administration of a single dose of gadoteric acid 20 minutes and 120 minutes after contrast administration. Whole-brain image stacks will be analyzed on patient basis. Regions of interest for signal intensity measurements will be drawn in various cerebral fluid spaces, the size of the region of interest will depend on the target structure. The following structures should be measured: lateral and central aqueous chamber and vitreous body of the eye, distal optic nerve sheath, Meckel's cave, lateral ventricles and basal cisterns.

Data will be expressed as mean values +/- one-fold standard deviation (SD). The normality of data distribution will be assessed using Levene's test. Data showing a Gaussian distribution will be evaluated by an analysis of variances (ANOVA) with a post-hoc analysis. Estimated sample size is around 30 patients in the control and the experimental group. Cases with missing or unavailable data will be excluded.