Although it’s been 56 years since Russian cosmonaut Yuri Gagarin became the first man in space, humanity is still far from becoming a spacefaring species. We’ve never set foot farther out than the moon, and there are still many challenges which we must overcome. One important obstacle is the effect of space travel on the human body. Studies have documented various physiological and genetic changes in the bodies of astronauts stationed on the International Space Station such as altered vision or muscle atrophy. One new study suggests that spending a prolonged time in space also significantly alters the brain’s structure which explains why some astronauts experience unusual symptoms upon returning to Earth.

Credit: Boeing/NASA.

Researchers at the Medical University of South Carolina (MUSC) led by Donna Roberts, an associate professor of radiology, investigated the brain anatomy of astronauts who had returned from spaceflight. Roberts has been closely working with NASA to study the health effects of long-duration spaceflights since the early 1990s.

Altered vision and increased pressure inside the head are among the physiological changes both men and women experience following space flight. These symptoms have been lumped together by NASA under visual impairment intracranial pressure syndrome, or VIIP syndrome for short. Scientists hypothesized that at least one of the causes for VIIP syndrome could be related to the redistribution of body fluid toward the head due to microgravity exposure.

To get to the bottom of things, Roberts and colleagues used magnetic resonance imaging (MRI) to scan the brains of 34 astronauts before and after they spent time in space. Sixteen of the participants had been part of long-duration missions aboard the International Space Station (six-months in microgravity, on average) while the other eighteen were part of short-duration missions aboard space shuttle flights (two weeks, on average).

“We know these long-duration flights take a big toll on the astronauts and cosmonauts; however, we don’t know if the adverse effects on the body continue to progress or if they stabilize after some time in space,” Roberts said in a press release. “These are the questions that we are interested in addressing, especially what happens to the human brain and brain function?”

Upon returning from space, the brains of astronauts who had stayed on the ISS for a long time shifted upward in their skulls. Specifically, the gyri and sulci, the bumps and depressions in the brain that give it its folded appearance, crowded at the top of the skull. There was also evidence of a narrowing of the space between the top of the brain and the inner table of the skull. This space is filled with cerebrospinal fluid (CSF), which is a clear, colorless liquid that surrounds the brain and the spinal cord, providing a mechanical barrier against shock.

None of the astronauts on short-duration missions exhibited such significant changes to brain structure. Three astronauts were diagnosed with VIIP syndrome when they got home to Earth, and all three experienced a narrowing of the central sulcus.

Researchers think that the obstruction of CSF flow increases the pressure in the skull causing optic-nerve swelling, eventually leading to poor vision as reported by astronauts.

A and B are before and after brain scan images for long-term spaceflight astronauts. C and D are for short-term spaceflight. Credit: NEJM.

The changes observed by the researchers may explain set of unusual symptoms experienced by astronauts upon returning home. With these new findings, the study could help NASA take preventive measures and plan ahead for long-duration space exploration.

Scientists say that since there is no longer the force of gravity pulling the brain down, the brain moves upward. The altered structure could potentially impact cognition, though there’s no evidence of such effects yet.

More studies such as this are needed for scientists to understand the full scope of consequences microgravity has on the human body. For instance, it’s not clear whether or not these changes are permanent or irreversible.

“We have known for years that microgravity affects the body in numerous ways,” said Michael Antonucci, also at MUSC and co-author of the new study published in the New England Journal of Medicine. 

“However, this study represents the most comprehensive assessment of the impact of prolonged space travel on the brain. The changes we have seen may explain unusual symptoms experienced by returning space station astronauts and help identify key issues in the planning of longer-duration space exploration, including missions to Mars.”