Spatiotemporal Characteristics of Cerebrospinal Fluid Flow Across the Craniospinal Axis Using Cine Phase-Contrast MRI: A Ventral-Dorsal Dual-Region Flow Pattern in the Spinal Subarachnoid Space

Background: Cerebrospinal fluid (CSF) circulation is important for maintaining homeostasis of the central nervous system. Previous studies have largely focused on the ventricular system, the craniocervical junction, or local spinal segments, leaving the overall and spatially heterogeneous characteristics of CSF flow across the craniospinal axis insufficiently characterized. The spinal subarachnoid space (SAS) is often treated as a homogeneous annular compartment surrounding the spinal cord, an approach that may obscure directional differences among its internal regions. Methods: This single-center, exploratory, prospective imaging study enrolled 15 healthy volunteers. All participants underwent 3.0-T electrocardiography-gated two-dimensional cine phase-contrast magnetic resonance imaging (Cine PC-MRI) and high-resolution T2-weighted imaging. CSF was evaluated at the level of the cerebral aqueduct outlet/fourth-ventricle inlet, C1-C2, C5-C6, T5-T6, L1-L2, and the lumbar cistern. Region-of-interest (ROI)-based quantitative analysis using Q-Flow software recorded mean velocity, absolute peak velocity, and directional peak velocity. Results: Multiplanar Cine PC-MRI showed that CSF phase signals within the spinal SAS were not uniformly distributed but formed two principal flow regions, ventral and dorsal. Mean velocity and absolute peak velocity were similar between the ventral and dorsal regions, whereas directional peak velocity differed (1.50 +/- 2.98 cm/s vs. -0.38 +/- 3.23 cm/s, P = 0.036). High-resolution T2-weighted imaging showed denticulate ligaments, nerve roots, and associated fibrous connective tissue in the lateral transition zones between the two regions. Conclusions: In healthy adults, CSF flow in the spinal SAS was not synchronous motion within a single homogeneous compartment; rather, it showed longitudinal oscillatory flow in ventral and dorsal regions coupled to the cardiac cycle. These findings provide preliminary in vivo evidence for studies of CSF hydrodynamics across the craniospinal axis and an imaging basis for investigating CSF circulation disturbances in conditions such as hydrocephalus, Chiari malformation, syringomyelia, and arachnoid adhesions.