Quantitative Evaluation of Low-Frequency Oscillation in Blood and CSF Flow and its Changes from Eye Open to Eye Closed

Motivation: Low-frequency oscillations (LFO) are a key driver of brain waste clearance, yet their role in CSF has only been qualitatively assessed using fMRI, lacking quantitative evaluation. Goal(s): To quantitatively evaluate LFO in blood and CSF flows and study changes with drowsiness. Approach: Arterial, venous, and CSF flow at the cervical level (C2/C3) were measured using real-time phase-contrast MRI, with measurements once with the eye open and once after a 30-minute eye closure. Band power from LFO, respiration, and cardiac pulsations were analyzed. Results: LFO shows an increase from awake to drowsy in all fluid compartments, despite contributing small to overall oscillations. Impact: Cervical CSF flow shows LFO at 3%, below respiration (13%) and cardiac (84%), contrasting with LFO>cardiac at the fourth ventricle in fMRI. The consistent LFO increase from alert to drowsy suggests a role in enhancing fluid clearance during sleep.