Coupled pulsatile vascular and paravascular fluid dynamics in the human brain

Area of Science:

• Neuroimaging
• Cerebrovascular Dynamics
• Cerebrospinal Fluid Flow

Background:

• Cerebral homeostasis relies on blood flow driven by cardiac pulsation.
• Paravascular cerebrospinal fluid (pCSF) flow, crucial for waste removal, is suspected to be driven by arterial pulsations.
• The precise relationship between vascular and pCSF dynamics in humans is not well understood.

Purpose of the Study:

• To develop and validate a non-invasive neuroimaging approach to investigate the coupling between pulsatile vascular and pCSF dynamics.
• To compare this coupling in younger and older adults.
• To assess the reproducibility of the developed method.

Main Methods:

• Utilized resting-state functional MRI (fMRI) and dynamic diffusion-weighted imaging (dynDWI), retrospectively cardiac-aligned.
• Measured time between peaks (∆TTP) in fMRI and dynDWI waveforms to represent cerebral hemodynamics and pCSF motion.
• Calculated waveform correlation after peak alignment to quantify coupling, comparing results between age groups and across imaging protocols.

Main Results:

• Cerebral hemodynamic changes consistently preceded pCSF motion.
• Younger adults exhibited a significantly shorter ∆TTP compared to older adults.
• High correlation at aligned peaks, indicating robust coupling, did not differ significantly between age groups and was reproducible across protocols.

Conclusions:

• A novel non-invasive technique was established to evaluate vascular and paravascular fluid dynamics.
• Findings demonstrate a consistent and robust cardiac pulsation-driven coupling between cerebral hemodynamics and pCSF dynamics.
• This coupling is present in both younger and older adults, suggesting preserved function with age.