Research has shown long-duration spaceflight missions impact the vision of astronauts. Now a new study, published today in the journal Radiology, shows extended time in space also alters brain and pituitary structure.
“We hypothesized from previous MRI studies of the eye that elevated intracranial pressure during spaceflight could potentially contribute to the changes in vision for astronauts, and we wanted to document if there were any changes in the brain that could support this theory,” said Larry Kramer, MD, professor of diagnostic and interventional imaging at McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth) and lead author of the study.
To study these effects and establish a preflight baseline, researchers completed a brain MRI on 11 astronauts, including 10 men and one woman, before they traveled to space. Upon their return to Earth, astronauts were scanned within several days of landing, and then again at various time points up to one year postflight.
MRI results showed that microgravity exposure in long-duration spaceflights caused expansions in the astronauts’ brain and cerebrospinal fluid (CSF) volumes, which could potentially elevate intracranial pressure. CSF is the fluid that flows in and around the hollow spaces of the brain and spinal cord.
“The bulk of this expansion is due to white matter and lateral ventricular enlargement. At the one-year postflight mark, these volumes remained elevated, suggesting permanent change in brain structure,” he said.
The tests also showed that the majority of the astronauts developed deformation of the pituitary gland, which is a pea-sized body attached to the base of the brain that is essential in controlling growth, development, and the functioning of the other endocrine glands in the body.
“In a previous retrospective study, we could see that the pituitary gland was abnormal postflight, but this time around we were able to carefully compare preflight and postflight MRI studies and confirm a causal relationship to spaceflight. This was an important finding since acquired deformation of the pituitary gland provided us with indirect evidence of elevated levels of intracranial pressure during spaceflight,” he said.
Kramer and his team are currently working to expand on this research in hopes that their findings can be applicable to non-astronauts.
“There are patients, typically elderly, having what is referred to as normal pressure hydrocephalus, which is characterized by enlarged ventricles. However, the cause is unknown. Concentrating our research effort into why the astronauts’ ventricles are enlarging in microgravity could also improve our understanding of mechanisms involved in normal pressure hydrocephalus,” Kramer said.
Kramer, in collaboration with other national and international research teams, is also studying artificial gravity and lower body negative pressure as a potential countermeasure to the intracranial effects of microgravity.
Co-authors from UTHealth were Khader Hasan, PhD, and Roy Riascos, MD. Other co-authors were Michael B. Stenger, PhD, with NASA Johnson Space Center; Ashot Sargsyan, MD, Steven S. Laurie, PhD, Karina Marshall-Goebel, PhD, and Brandon R. Macias, PhD, with KBR; Christian Otto, MD, MMSc, from Memorial Sloan-Kettering Cancer Center; and Robert J. Ploutz-Snyder, PhD, PStat, with the University of Michigan.
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