Dynamic MRI of Fluid and Solute Transportation across the Arachnoid Barrier in the Human Meninges.

Abstract

Background The dura mater has a permeable vasculature similar to that of peripheral organs, and is separated from the brain, which is enclosed within the arachnoid barrier. Fluid and solute transport across the arachnoid barrier between the subarachnoid space (SAS) and dura is crucial for brain waste clearance and immune surveillance, but few neuroimaging approaches can capture this dynamic process. Purpose To establish a clinically feasible intravenous gadolinium-based contrast agent (GBCA)-based MRI approach for assessing fluid and solute transport across the arachnoid barrier. Materials and Methods This prospective study was conducted from September 2023 to September 2024 in healthy participants. High-resolution structural MRI was used to identify subregions in the meninges. Dynamic dual spin-echo perfusion (DDSEP) MRI was performed to track GBCA distribution in blood and cerebrospinal fluid (CSF) simultaneously. The spatiotemporal characteristics of fluid and solute transportation across the arachnoid barrier were examined by analyzing GBCA-induced signal intensity changes in the fluid outside (dura) and inside (SAS) the arachnoid barrier in the meninges around the superior sagittal sinus (SSS) and bridging veins (BVs). Mann-Whitney <i>U</i> tests were used for group comparisons. Results Twenty healthy participants (mean age, 30 years ± 7 [SD]; 12 men) were included. GBCA enhancement was detected in subregions of the meninges on structural MRI scans, including the periosteal and meningeal layers, but enhancement from blood and CSF could not be separated. Using DDSEP MRI, GBCA-induced blood signal intensity changes were detected in the dura within 10 seconds following intravenous administration. GBCA-induced CSF signal intensity changes were detected in the dura and SAS approximately 20-40 seconds after intravenous administration. The time courses showed a delayed mean time to onset of GBCA-induced CSF signal intensity changes in the SAS around BVs compared with the SAS around the SSS (45.6 seconds ± 18.2 vs 18.4 seconds ± 4.6; <i>P</i> = .047). Conclusion Dynamic fluid and solute transportation across the arachnoid barrier in the meninges of healthy participants was measured by tracking intravenous GBCA entering CSF from dural blood vessels using DDSEP MRI. © RSNA, 2026 <i>Supplemental material is available for this article.</i>