How our fluids react under microgravity would explain the expansion of brain volume and the deformation of the pituitary gland seen in some astronauts.
A study by American researchers published last Tuesday (14) in the scientific journal Radiology suggests that long-term space travel can cause changes in brain volume and deformation of the pituitary gland, an endocrine gland, in astronauts.
The research was conducted because more than half of the crew of the International Space Station (ISS) reported changes in vision after prolonged exposure to the microgravity of space. The post-flight evaluation revealed swelling of the optic nerve, retinal hemorrhage and other ocular structural changes.
Scientists have hypothesized that this is because space does not have the pressure necessary to generate hydrostatic balance, that is, the fluids in our body are not distributed in an ideal and balanced way.
“When you’re in microgravity, fluid such as your venous blood no longer pools toward your lower extremities but redistributes headward,” said the study’s lead author, Larry A. Kramer, MD, of the Texas Health Science Center at Houston. “That movement of fluid toward your head may be one of the mechanisms causing changes we are observing in the eye and intracranial compartment.”
The team carried out brain magnetic resonance imaging on 11 astronauts before they traveled to the ISS. Then they underwent the same exam one day after their return, and at various intervals throughout the following year. The results showed that exposure to long-term microgravity caused expansion in brain volumes.
In addition, there was also an increase in the velocity of cerebrospinal fluid flowing through a small channel that connects the four fluid-filled cavities in the center of the brain, which can cause trouble walking, problems with bladder control and dementia. However, to date, these symptoms have not been reported in astronauts after space travel.
Magnetic resonance imaging also showed changes in the pituitary gland, also called the “master gland”, which governs the function of many other glands in the body. “We found that the pituitary gland loses height and is smaller postflight than it was preflight,” said Kramer.
Scientists are studying ways to counter the effects of microgravity. One option under consideration is the creation of artificial gravity, using a large centrifuge that can rotate people in a sitting or prone position. The use of negative pressure on the lower extremities of the body as a way to counteract the effects of microgravity is also under investigation.