Spaceflight-Associated Brain White Matter Microstructural Changes and Intracranial Fluid Redistribution.

Area of Science:

• Neuroscience
• Space Medicine
• Radiology

Background:

• Spaceflight is known to cause transient balance declines and brain morphologic changes.
• The specific effects of spaceflight on brain white matter, particularly after accounting for fluid shifts, remain under-examined.

Purpose of the Study:

• To map intracranial free water (FW) shifts induced by spaceflight.
• To evaluate changes in brain white matter diffusion measures in astronauts post-flight.

Main Methods:

• Retrospective analysis of diffusion magnetic resonance imaging (dMRI) data from 15 astronauts (pre- and post-flight).
• Analysis of brain FW and white matter diffusion metrics, corrected for FW.
• Assessment of balance using computerized dynamic posturography to correlate with brain changes.

Main Results:

• Significant, widespread increases in frontal, temporal, and occipital lobe FW (2.5%-4.0%) and decreases in the posterior vertex were observed.
• White matter changes (0.75%-1.25%) occurred in the superior/inferior longitudinal fasciculi, corticospinal tract, and cerebellar peduncles.
• Mission duration correlated with cerebellar white matter changes; superior longitudinal fasciculus changes correlated with balance decline.

Conclusions:

• Spaceflight induces significant free water redistribution and white matter alterations in the astronaut brain.
• Observed white matter changes are more pronounced than those typically seen with aging.
• Further research is needed to understand recovery timelines and behavioral impacts of these spaceflight-induced brain modifications.