Neural activity induces repeatable subarachnoid CSF flow responses with coherent spatial pathways: a concurrent 4D CSF flow and BOLD fMRI study

Motivation: How neural activity influences subarachnoid-CSF flow remains poorly understood. Goal(s): To investigate subarachnoid-CSF flow responses to neural-activity-induced hemodynamic responses, including temporal properties, test-retest repeatability, and spatial patterns. Approach: We employed our newly developed slow-flow-sensitized EPTI sequence which provides concurrent 4D-CSF-flowmetry and BOLD-fMRI, to map visual-task-induced subarachnoid-CSF flow. We conducted slow-flow phantom experiments for validation, and performed in-vivo test-retest experiments across runs/subjects. Results: The slow-flow phantom measurement agrees well with true flow rates. In-vivo experiments show strong neural-activation-evoked subarachnoid-CSF flow that is highly correlated with dBOLD/dt, and directional spatial flow-patterns around cortex with coherence pathways aligning with anatomical curvature, which are also highly reproducible. Impact: We demonstrate that neural-activation-related hemodynamic responses induce significant directional subarachnoid-CSF flow. Test-retest experiments showed that the spatial patterns and flow pathways are reproducible across runs and subjects. These findings suggest that brain activity can effectively modulate subarachnoid-CSF flow.