LMU physicians have shown that widespread changes in the relative tissue volumes of the brains of cosmonauts who have spent long periods of time in the weightlessness of outer space can still be detected more than 6 months after their return to Earth.

Spending long periods in space not only leads to muscle atrophy and reductions in bone density, it also has lasting effects on the brain. However, little is known about how different tissues of the brain react to exposure to microgravity, and it remains unclear whether and to what extent the neuroanatomical changes so far observed persist following return to normal gravity.

Initiated and guided by a team of neuroscientists (headed by Prof. Floris L. Wuyts) based at the University of Antwerp, and in close cooperation with Russian colleagues, LMU neurologist Professor Peter zu Eulenburg has completed the first long-term study in Russian cosmonauts.

In this study, which appears in the New England Journal of Medicine, they show that differential changes in the three main tissue volumes of the brain remain detectable for at least half a year after the end of their last mission. The study was carried out on ten cosmonauts, each of whom had spent an average of 189 days on board the International Space Station (ISS). The authors used magnetic resonance tomography (MRT) to image the brains of the subjects both before and shortly after the conclusion of their long-term missions. In addition, seven members of the cohort were re-examined seven months after their return from space.

This is actually the first study in which it has been possible to objectively quantify changes in brain structures following a space mission also including an extended follow-up period.

Taken together, our results point to prolonged changes in the pattern of cerebrospinal fluid circulation over a period of at least seven months following the return to Earth. However, whether or not the extensive alterations shown in the grey and the white matter lead to any changes in cognition remains unclear at present.
LMU neurologist Professor Peter zu Eulenburg

So far the only clinical indication for detrimental effects is a reduction in visual acuity that was demonstrated in several long-term space travellers. These changes may very well be attributable to the increased pressure exerted by the cerebrospinal fluid on the retina and the optic nerve. The governing cause for the widespread structural changes in the brain following long spaceflights might lie in minimal pressure changes within the body’s various water columns under conditions of microgravity that have a cumulative effect over time.

According to the authors, to minimize the risks associated with long-term missions and to characterize any clinical significance of their structural findings, further studies using a wider range of diagnostic methods are deemed essential.

 

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