Researchers from the University of Antwerp in Belgium have found that the fluid surrounding the brain, known as craniospinal fluid, redistributes in the skull during spaceflight. While the redistributed fluid doesn't seem to disrupt pressure inside the skull, nor circulation of the craniospinal fluid, its redistribution may be the reason why some crewmembers experience blurry vision during and after spaceflight.
For the study, the researchers studied the brains of 11 cosmonauts before their spaceflights, nine days after landing back on Earth, and six to seven months later. To analyze how their brains changed during spaceflight, they used a kind of MRI scan that involved taking a series of diffusion MRI (dMRI) images.
In the end, the researchers found that during spaceflight, the fluid around the brain and spine moves differently in space to how it moves on Earth. In particular, they found that cosmonauts who spent six months in the International Space Station tended to have more of the fluid in the lower region of the brain than in the top region. This is likely to have happened as spaceflight causes the brain to shift upwards in the skull. Follow-up scans, however, show that these effects reverse once arriving back on Earth.
The study also confirmed earlier studies' findings- showing that the open structures found inside the brain where cerebrospinal fluid is produced (the ventricles) dilate when in space. The new work also found that although the ventricles reduced in size between post-flight exams and 7-month follow-up exams, they still contained more cerebrospinal fluid than before they were in space.
The researchers behind the study say that using different MRI techniques in the future could help scientists understand more about how the brain operates in space, as well as whether spaceflight causes any structural changes to the organ.