Heart rate and respiration influence on macroscopic blood and CSF flows

Abstract

Background Changes in blood volume in the intracranial arteries and the resulting oscillations of brain parenchyma have been presumed as main initiating factors of cerebrospinal fluid (CSF) pulsations. However, respiration has been recently supposed to influence CSF dynamics via thoracic pressure changes. Purpose To measure blood and CSF cervical flow and quantify the contribution of cardiac and respiratory cycles on the subsequent signal evolution. Material and Methods Sixteen volunteers were enrolled. All participant underwent two-dimensional fast field echo echo planar imaging (FFE-EPI). Regions of interest were placed on internal carotids, jugular veins, and rachidian canal to extract temporal profiles. Spectral analysis was performed to extract respiratory and cardiac frequencies. The contribution of respiration and cardiac activity was assessed to signal evolution by applying a multiple linear model. Results Mean respiratory frequency was 14.6 ± 3.9 cycles per min and mean heart rate was 66.8 ± 9 cycles per min. Cardiac contribution was higher than breathing for internal carotids, explaining 74.68% and 10.27% of the signal variance, respectively. For the jugular veins, respiratory component was higher than the cardiac one contributing 44.28% and 6.53% of the signal variance, respectively. For CSF, breathing and cardiac component contributed less than half of signal variance (12.61% and 23.23%, respectively). Conclusion Respiration and cardiac activity both influence fluid flow at the cervical level. Arterial inflow is driven by the cardiac pool whereas venous blood aspiration seems more due to thoracic pressure changes. CSF dynamics acts as a buffer between these two blood compartments.

Phase contrast MRI measurements of net cerebrospinal fluid flow through the cerebral aqueduct are confounded by respiration

“…Takizawa et al investigated the relative contributions of the cardiac and respiratory cycles to CSF velocity and CSF displacement, and showed that the contribution of the respiratory cycle to CSF velocity in the aqueduct is smaller compared with the cardiac cycle, but that the resulting total displacement through the aqueduct is larger than the displacements induced by the cardiac cycle. Daouk et al investigated blood and CSF flows using signal intensity changes, and found that arterial blood flow is influenced mostly by the cardiac cycle, while venous blood flow is influenced mostly by the respiratory cycle. CSF appeared to act as a buffer between the arterial and venous blood compartments.…”

Non-invasive assessment of pulsatile intracranial pressure with phase-contrast magnetic resonance imaging

“…Finally, but not least, recent studies have demonstrated respiration to have a major influence on CSF flow [ 33 , 34 ]. With cardiac gated PC-MRI, which can be considered to represent current state-of-the-art methodology in PC-MRI based measurements of intracranial and intraspinal CSF flow quantification, only cardiac beat induced CSF flow is detected.…”

Changing the Currently Held Concept of Cerebrospinal Fluid Dynamics Based on Shared Findings of Cerebrospinal Fluid Motion in the Cranial Cavity Using Various Types of Magnetic Resonance Imaging Techniques

“…These results are consistent with those of other studies that have used EPI and showed that respiration and cardiac pulsation both affect CSF movement at the cervical level. 66,67)…”