The effect of prolonged spaceflight on cerebrospinal fluid and perivascular spaces of astronauts and cosmonauts

Abstract

Long-duration spaceflight induces changes to the brain and cerebrospinal fluid compartments and visual acuity problems known as spaceflight-associated neuro-ocular syndrome (SANS). The clinical relevance of these changes and whether they equally affect crews of different space agencies remain unknown. We used MRI to analyze the alterations occurring in the perivascular spaces (PVS) in NASA and European Space Agency astronauts and Roscosmos cosmonauts after a 6-mo spaceflight on the International Space Station (ISS). We found increased volume of basal ganglia PVS and white matter PVS (WM-PVS) after spaceflight, which was more prominent in the NASA crew than the Roscosmos crew. Moreover, both crews demonstrated a similar degree of lateral ventricle enlargement and decreased subarachnoid space at the vertex, which was correlated with WM-PVS enlargement. As all crews experienced the same environment aboard the ISS, the differences in WM-PVS enlargement may have been due to, among other factors, differences in the use of countermeasures and high-resistive exercise regimes, which can influence brain fluid redistribution. Moreover, NASA astronauts who developed SANS had greater pre- and postflight WM-PVS volumes than those unaffected. These results provide evidence for a potential link between WM-PVS fluid and SANS.

Keywords: brain; microgravity; perivascular space; spaceflight; spaceflight-associated neuroocular syndrome.

Fig. 1.

Controls on Earth do not show significant changes in PVS, VSA, or LV volumes after a 1-y follow-up (A–D). After long-duration spaceflight on the ISS, we observed a significant increase in PVS and LV and a decrease in VSA volumes (E–H). Short-duration spaceflight on the space shuttle was not associated with significant changes in PVS, VSA, or LV volumes (I–L). Examples of 3D masks (cyan) of WM-PVS, BG-PVS, VSA, and LV before and after long-duration spaceflight on the ISS (M). The postflight changes in PVS, but not in VSA and LV, were significantly higher in NASA astronauts than ROS cosmonauts (N). All data represent mean ± SEM. Paired (A–L) or independent samples t tests (N). *P ≤ 0.01; **P < 0.001.

Fig. 2.

Preflight and postflight WM-PVS volumes (A) were significantly higher in NASA astronauts who developed SANS than those unaffected. A significant PVS (A and B) and LV (D) enlargement and VSA reduction (C) were observed in both groups (post hoc comparisons, mixed model ANOVA). The spaceflight-associated PVS dilation (E and F) and VSA reduction (G) were not significantly different between the groups, but a significantly greater LV enlargement (H) was observed in the non-SANS group (time by SANS interaction, mixed model ANOVA). Data represent mean ± SEM. *P < 0.05; **P ≤ 0.001.