Cerebrospinal Fluid Temporal Dynamic Characterization in the Spinal Subarachnoid Space Using 2D Phase Contrast MRI

Cerebrospinal fluid (CSF) is critical for metabolic clearance and brain protection. The slow biphasic movement of CSF in the spinal subarachnoid space (SAS) creates complex flow patterns; however, current research of bulk flow in the SAS is limited to the cervical spine. This in vivo imaging study characterizes the temporal dynamics of CSF flow along the entire spinal canal (SC) to inform intrathecal (IT) drug delivery. CSF flow in the SAS was measured in 7 healthy subjects using sagittal and axial 2D phase contrast MRI acquisitions in a Siemens 3T scanner at Purdue University. Cranio-caudal velocities were calculated with 50 timeframes per cardiac cycle using retrospective ECG gating. Pulse wave velocity (PWV) was estimated as the slope of the linear regression between distance along the SAS and delay in wave-foot arrival time. CSF flow metrics (average and peak velocities, flow rate, stroke volume) were calculated at 8 transverse locations from cervical to lumbar spine. The mean PWV for the entire SC was 4.27 ± 1.56 m/s. Mixed-effects regression showed a significant decline in stroke volume and quadratic change in peak velocity along the SAS, indicating the attenuation of CSF flow towards the lumbar spine. Mean flow rate and net stroke volume analysis showed a small net cranial flow despite overall oscillatory motion. Results provide insight into temporal CSF dynamics in the SAS to inform computational modeling for IT drug delivery.