Spaceflight-induced changes in white matter hyperintensity burden in astronauts.

Area of Science:

• Neuroimaging
• Space Medicine
• Astronaut Health

Background:

• Spaceflight induces physiological changes, including fluid shifts.
• Understanding brain alterations in microgravity is crucial for astronaut health.
• White matter hyperintensities (WMH) are markers of brain aging and disease.

Purpose of the Study:

• To evaluate the impact of weightlessness on white matter hyperintensity (WMH) burden in astronauts.
• To determine the roles of cerebrospinal fluid (CSF) and vascular fluid in these WMH changes.
• To compare effects between short-duration and long-duration space missions.

Main Methods:

• Analysis of pre- and post-flight brain MRI scans from 17 astronauts (10 ISS, 7 Shuttle).
• Automated quantification of WMH, CSF, and brain tissue volumes using FLAIR and T1-weighted imaging.
• Assessment of reversibility in a subcohort of 5 long-duration astronauts with follow-up scans.

Main Results:

• Long-duration missions showed significant increases in periventricular WMH and ventricular CSF volumes.
• No significant changes in deep WMH or brain tissue volumes were observed in either cohort.
• Increased periventricular WMH volume correlated with increased ventricular CSF volume (ρ = 0.63, p = 0.008).

Conclusions:

• Long-duration microgravity exposure is associated with increased periventricular WMH in astronauts.
• This WMH increase is linked to elevated ventricular CSF volume, particularly in ISS astronauts.
• Deep white matter WMH volumes remained unchanged, unlike findings in high-altitude pilots.