Astronauts risk their lives to expand our knowledge of outer space. As we travel further into the universe, our astronauts should be in tip-top shape for any challenge that comes their way. However, a growing concern among astronauts is the increased incidence of vision problems after returning from space travel. To find the source of this problem, researchers from Texas, New York, and Michigan collaborated with NASA to study if the lack of gravity in space negatively affects the brain. Their findings were published in the Radiology journal.
In this study, the researchers used an MRI machine, a medical device that scans the brain and takes pictures of it using magnetic fields. They took pictures of the brains of 11 astronauts who volunteered for the study. Of these 11 astronauts, 5 had previously traveled and 6 had no spaceflight experience. The average exposure to microgravity was around 171 days. Brain scans were taken before astronauts left for a space mission, and they were taken again at several time points after their return. Brain scans were conducted 1 day, 1 month, 3 months, 6 months, and 1 year after astronauts returned from space travel.
Results showed changes in the cerebrospinal fluid of astronauts. Cerebrospinal fluid is a clear liquid that protects our brain and spinal cord by absorbing shock. Imagine trying to punch someone underwater. Unless you’re a professional underwater boxer, you’ll probably be slower and weaker as the water is absorbing most of the punch. Similarly, when a person is hit in the head, cerebrospinal fluid cushions the blow and minimizes any serious damage to the brain.
Long-term exposure to the low gravity of space increased the volume of cerebrospinal fluid in astronauts’ brains. In addition, cerebrospinal fluid volume continued to stay high one year after space travel, suggesting that microgravity caused long-term brain changes.
This additional amount of cerebrospinal fluid may seem like a good thing, but it can actually lead to increased pressure on the brain called intracranial pressure. Returning to our water analogy, if you decided to swim towards the bottom of the ocean, there would be lots of water. This would create high amounts of water pressure that pushes down on your body. Likewise, when there is too much cerebrospinal fluid, the liquid puts severe pressure on our brain. Because intracranial pressure is pushing down on many brain areas, it can lead to headaches, blurred vision, altered levels of consciousness, and vomiting without nausea.
MRI scans also showed bigger brains in astronauts. The increased size was the result of structural changes in the ventricles and white matter of the brain. The ventricles are the sites where cerebrospinal fluid is produced, which can explain the increased cerebrospinal fluid volume. White matter serves as the brain’s highway system, as brain cells use it to send high-speed messages to other areas. According to the researchers, their results are consistent with previous spaceflight research that found small increases in white matter size. However, they conclude that this is the first time a study shows a large increase in white matter after 1 year in space.
Brain scans also showed that long space flights affected another brain region, the pituitary gland. Prolonged exposure to microgravity led to a structural deformity in this pea-sized gland. The pituitary gland may be small, but it is nicknamed “the master gland” because it regulates our hormones. According to the researchers, this is further evidence of increased fluid buildup as pituitary gland defects have been linked to increased pressure in the brain.
The researchers suggest that the increased brain pressure may also be pushing on brain parts like the optic nerve, which could explain the vision problems some astronauts experience after space travel. While the underlying driver in these changes remain unknown, they note that the brain changes in astronauts are similar to a condition called hydrocephalus. Hydrocephalus occurs when there is too much cerebrospinal fluid in the brain, which causes increased pressure and extensive brain damage. Because of their similarities, these scientists conclude that studying patients with hydrocephalus may help to explain and eventually treat astronauts’ increased ventricle size and white matter.