NASA has long understood that abnormal amounts of cerebrospinal fluid accumulate deep in the brains of astronauts exposed to microgravity. In 1983, the space agency received a patent for a “ventricular catheter” designed to be inserted into the brains of astronauts, to relieve the pressure.
And since then, the space agency has funded research into the problem. A new study has found that astronauts in space for six or more months develop the worst hydrocephalus, meaning they had the most enlarged ventricles, the reservoirs for spinal fluid nestled deep in the brain. After the initial six months, the effect seemed to plateau and stayed there for a long time, even after the men and women returned to earth gravity.
The new study found that it appeared to take at least three years for the pressure to equalize. And if an astronaut returned to space with partially recovered ventricles, the person returned to the old plateau, starting the recovery process all over again.
Research sometimes refers to this problem as hydrocephalus associated with long-term spaceflight (HALS) or, spaceflight associated neuro-ocular syndrome (SANS), since the astronauts often develop vision problems.
Generally speaking, hydrocephalus is a serious condition that can result in long-lasting harm to the brain and a number of short-term symptoms, including walking difficulties, memory problems, headaches, nausea, seizures and the aforementioned vision problems.
While some babies are born with the condition, adults can develop it, too. Brain tumors, meningitis, spina bifida – or, as research has found, extended trips to the International Space Station can create the condition.
Private space operator SpaceX plans to take a first step toward managing HALS later this year, when it launches the five-day Polaris Dawn mission, which will orbit Earth at a record distance for a crewed vessel. The pilot, Scott Poteet, will wear a spinal catheter that will measure his spinal fluid pressure throughout the mission, while the whole crew will wear special contact lenses to measure their intraocular pressure.
NASA will continue to monitor the issue as it sends astronauts to the moon as part of the Artemis program and, as may happen in the next decade, the great distance to Mars.
The new study relied on MRI scans of 30 astronauts taken over several years, and it added to a growing collection of research investigating HALS. The studies have concluded that lack of gravity causes the brain to drift upward, leading to a number of changes.
For one, gray matter volume increases on top of the brain and decreases along the base. The effect was greatest on six-month voyages, but there was no plateau: The growth was even greater on one-year trips to the ISS.
Fluid presses into the ventricles, swelling them by 11 to 25 percent. While ventricles normally enlarge with age, the astronauts’ rate was much higher. (Researchers still aren’t sure if this swelling is an adaptive response to dysfunction in the brain or the dysfunction itself.)
Following spaceflight, fluid pressure moves from the top of the brain back down to its base. Gray matter shifts downward, as well, from the top of the brain.
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