Quantification of arterial, venous, and cerebrospinal fluid flow dynamics by magnetic resonance imaging under simulated micro-gravity conditions: a prospective cohort study

• Type of Material: Article
• Authors: Arslan M. Zahid, Emory University; Bryn Martin, University of Idaho; Stephanie Collins, Emory University; John Oshinski, Emory University; Christopher Ethier, Emory University
• Language: English
• Date: 2021-02-12
• Publisher: BMC Publishing
• Publication Version: Final Published Version
• Copyright Statement: © The Author(s) 2021.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1186/s12987-021-00238-3
• Title of Journal or Parent Work: Fluids and Barriers of the CNS
• Volume: 18
• Issue: 1
• Start Page: 8
• End Page: 8
• Grant/Funding Information: This work was funded by Georgia CTSA Grants TL1TR002382 and UL1TR002378, NASA grant NNX16AT06G, and the Georgia Research Alliance (CRE).
• Keywords: Neurosciences; Science & Technology; Spaceflight‐ Life Sciences & Biomedicine; Neurosciences & Neurology; cerebrospinal fluid dynamics; down tilt; associated neuro‐ Head‐ ocular syndrome; Arterial; venous; Simulated microgravity
• Research Categories: Health Sciences, Radiology; Biology, Neuroscience; Engineering, Biomedical

Abstract

Background Astronauts undergoing long-duration spaceflight are exposed to numerous health risks, including Spaceflight-Associated Neuro-Ocular Syndrome (SANS), a spectrum of ophthalmic changes that can result in permanent loss of visual acuity. The etiology of SANS is not well understood but is thought to involve changes in cerebrovascular flow dynamics in response to microgravity. There is a paucity of knowledge in this area; in particular, cerebrospinal fluid (CSF) flow dynamics have not been well characterized under microgravity conditions. Our study was designed to determine the effect of simulated microgravity (head-down tilt [HDT]) on cerebrovascular flow dynamics. We hypothesized that microgravity conditions simulated by acute HDT would result in increases in CSF pulsatile flow. Methods In a prospective cohort study, we measured flow in major cerebral arteries, veins, and CSF spaces in fifteen healthy volunteers using phase contrast magnetic resonance (PCMR) before and during 15° HDT. Results We found a decrease in all CSF flow variables [systolic peak flow (p = 0.009), and peak-to-peak pulse amplitude (p = 0.001)]. Cerebral arterial average flow (p = 0.04), systolic peak flow (p = 0.04), and peak-to-peak pulse amplitude (p = 0.02) all also significantly decreased. We additionally found a decrease in average cerebral arterial flow (p = 0.040). Finally, a significant increase in cerebral venous cross-sectional area under HDT (p = 0.005) was also observed. Conclusions These results collectively demonstrate that acute application of −15° HDT caused a reduction in CSF flow variables (systolic peak flow and peak-to-peak pulse amplitude) which, when coupled with a decrease in average cerebral arterial flow, systolic peak flow, and peak-to-peak pulse amplitude, is consistent with a decrease in cardiac-related pulsatile CSF flow. These results suggest that decreases in cerebral arterial inflow were the principal drivers of decreases in CSF pulsatile flow.