NASA astronauts have experienced altered vision and increased intracranial pressure (VIIP) during flight aboard the International Space Station. The VIIP syndrome is thought to result from the redistribution of body fluid toward the head during long-term microgravity exposure; however, the exact cause is unknown.
In the November 2, 2017, issue of the New England Journal of Medicine (doi: 10.1056/NEJMoa1705129), Donna R. Roberts, M.D., associate professor in the Department of Radiology and Radiological Sciences, reported the findings of a study comparing brain MRI scans from NASA’s Lifetime Surveillance of Astronaut Health program for two groups of astronauts: 16 astronauts who had been in space short-term aboard the space shuttle and 18 astronauts who had been in space for longer periods of time, typically three months, aboard the International Space Station.
Roberts’ team evaluated the cerebrospinal fluid (CSF) spaces at the top of the brain and CSF-filled structures, called ventricles, located at the center of the brain. The team also paired the preflight and postflight MRI cine clips from high-resolution 3-D imaging of 12 astronauts from long-duration flights and six astronauts from short-duration flights and looked for any displacement in brain structure.
Study results confirmed a narrowing of the brain’s central sulcus, a groove in the cortex near the top of the brain that separates the parietal and frontal lobes, in 94 percent of long-duration flight astronauts and 18.8 percent of the short-duration flight astronauts. Among the long-duration flight astronauts only, cine clips also showed an upward shift of the brain and narrowing of the CSF spaces at the top of the brain.
These findings suggest that significant changes in brain structure occur during long-duration space flight and that symptoms of VIIP syndrome would be expected to worsen the longer an astronaut stays in space. The parts of the brain that are most affected — the frontal and parietal lobes — control movement of the body and higher executive function.
With NASA’s Mars expedition mission set to launch in 2033, it is urgent for researchers such as Roberts to continue to collect data about astronauts and understand the basics of human space physiology.