Effects of Spaceflight on Astronaut Brain Structure as Indicated on MRI

Roberts, Donna R.; Albrecht, Moritz H.; Collins, Heather; Asemani, Davud; Chatterjee, Arindam; Spampinato, Maria Vittoria; Zhu, Xiaolong; Chimowitz, Marc I.; Antonucci, Michael U.

doi:10.1056/nejmoa1705129

Cited by 246 publications

(234 citation statements)

References 15 publications

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“…Our results revealed a small, but a trend of increase in ventricular volume similar to that previously published in astronauts . A terrestrial‐based microgravity analogue study using the head‐down‐tilt bed rest model has similarly shown that an increase in ventricular volume can even occur within 24 hours of induced head‐ward fluid shift from the lower extremities .…”

Section: Discussionsupporting

confidence: 88%

“…Alternatively, given previously shown changes of the anterior optic system in microgravity, our findings may be ascribed to possible degeneration of the optic radiation and associate visual cortices secondary to changes of the optic nerve.…”

Section: Discussionmentioning

confidence: 52%

“…Previous studies, using high‐resolution MRIs of the orbits have described a spectrum of findings, including distention and tortuosity of the optic nerve sheaths, optic nerve thickening, globe flattening, and optic nerve protrusion suggesting imaging characteristics similar with those in idiopathic intracranial hypertension . Subsequent MRI studies focusing on the intracranial compartment have also documented narrowing of the central sulcus, an upward shift of the brain, lateral ventricular enlargement, and narrowing of cerebral spinal fluid (CSF) spaces following long‐term exposure to microgravity . The preponderance of cases have raised new health concerns for long‐duration human space missions and warranted further study …”

Section: Introductionmentioning

confidence: 99%

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Longitudinal Analysis of Quantitative Brain MRI in Astronauts Following Microgravity Exposure

Riascos

Kamali

Hakimelahi

et al. 2019

Journal of Neuroimaging

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BACKGROUND AND PURPOSE Assessment of the effects of microgravity on astronauts’ brains using microstructural measures by utilizing quantitative MRI, before and after spaceflight would help understand the structural changes. METHODS Quantitative MRI data sets in 19 astronauts were acquired before and after space missions. Both diffusion tensor metrics and volumetric measures were analyzed in the brain regions involved in the visual function. RESULTS The fractional anisotropy was reduced in the right posterior thalamic radiations (P = .0009) and remained significant after a false discovery rate (FDR) correction (P = .03). A trend of increase in the mean diffusivities of different subregions of the occipital cortex on the right side, including calcarine, middle occipital, inferior occipital, and fusiform gyri, was noted and became insignificant after FDR correction. Similarly, there was a trend of cortical thinning involving the right occipital lobe and bilateral fusiform gyri, volume reduction of the left thalamus, and increase in lateral ventricular volume in the postflight scans. CONCLUSION Gray and white matter alterations are detected by quantitative MRI before and after space flight. Our findings may be used to understand the neuroanatomical mechanisms of possible brain dysfunction or neuroplasticity in microgravity condition in the future studies.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 52%

Section: Introductionmentioning

confidence: 99%

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Longitudinal Analysis of Quantitative Brain MRI in Astronauts Following Microgravity Exposure

Riascos

Kamali

Hakimelahi

et al. 2019

Journal of Neuroimaging

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“…; Roberts et al . ). Because SANS appears to be closely related to this headward fluid shift and failure to unload the brain during the day, countermeasures should focus on reversing the fluid shift and reintroducing intracranial pressure and fluid variability.…”

Section: Discussionmentioning

confidence: 97%

Lower body negative pressure to safely reduce intracranial pressure

Petersen

Lawley

Lilja-Cyron

et al. 2018

The Journal of Physiology

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Key points During long‐term missions, some astronauts experience structural and functional changes of the eyes and brain which resemble signs/symptoms experienced by patients with intracranial hypertension. Weightlessness prevents the normal cerebral volume and pressure ‘unloading’ associated with upright postures on Earth, which may be part of the cerebral and ocular pathophysiology. By placing the lower body in a negative pressure device (LBNP) that pulls fluid away from cranial compartments, we simulated effects of gravity and significantly lowered pressure within the brain parenchyma and ventricle compartments. Application of incremental LBNP demonstrated a non‐linear dose–response curve, suggesting 20 mmHg LBNP as the optimal level for reducing pressure in the brain without impairing cerebral perfusion pressure. This non‐invasive method of reducing pressure in the brain holds potential as a countermeasure in space as well as having treatment potential for patients on Earth with traumatic brain injury or other pathology leading to intracranial hypertension. Abstract Patients with elevated intracranial pressure (ICP) exhibit neuro‐ocular symptoms including headache, papilloedema and loss of vision. Some of these symptoms are also present in astronauts during and after prolonged space‐flight where lack of gravitational stress prevents daily lowering of ICP associated with upright posture. Lower body negative pressure (LBNP) simulates the effects of gravity by displacing fluid caudally and we hypothesized that LBNP would lower ICP without compromising cerebral perfusion. Ten cerebrally intact volunteers were included: six ambulatory neurosurgical patients with parenchymal ICP‐sensors and four former cancer patients with Ommaya‐reservoirs to the frontal horn of a lateral ventricle. We applied LBNP while recording ICP and blood pressure while supine, and during simulated intracranial hypertension by 15° head‐down tilt. LBNP from 0 to 50 mmHg at increments of 10 mmHg lowered ICP in a non‐linear dose‐dependent fashion; when supine (n = 10), ICP was decreased from 15 ± 2 mmHg to 14 ± 4, 12 ± 5, 11 ± 4, 10 ± 3 and 9 ± 4 mmHg, respectively (P < 0.0001). Cerebral perfusion pressure (CPP), calculated as mean arterial blood pressure at midbrain level minus ICP, was unchanged (from 70 ± 12 mmHg to 67 ± 9, 69 ± 10, 70 ± 12, 72 ± 13 and 74 ± 15 mmHg; P = 0.02). A 15° head‐down tilt (n = 6) increased ICP to 26 ± 4 mmHg, while application of LBNP lowered ICP (to 21 ± 4, 20 ± 4, 18 ± 4, 17 ± 4 and 17 ± 4 mmHg; P < 0.0001) and increased CPP (P < 0.01). An LBNP of 20 mmHg may be the optimal level to lower ICP without impairing CPP to counteract spaceflight‐associated neuro‐ocular syndrome in astronauts. Furthermore, LBNP holds clinical potential as a safe, non‐invasive method for lowering ICP and improving CPP for patients with pathologically elevated ICP on Earth.

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“…I en studie som nylig er publisert i New England Journal of Medicine, ble hjernene til 34 astronauter undersøkt med MR-undersøkelse før og etter tokt i verdensrommet (1). Halvparten av astronautene hadde oppholdt seg på den internasjonale romstasjonen i om lag seks måneder, mens resten hadde vaert på kortvarige tokt i verdensrommet på ca.…”

Section: Illustrasjonsfoto: Science Photo Library/ntb Scanpixunclassified

Vektløshet gir forandringer i hjernen

Haga¹

2018

Tidsskriftet

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TidsskriftetAstronauter som oppholder seg lenge i verdensrommet, kommer hjem med en hjerne som ser litt annerledes ut. Illustrasjonsfoto: Science Photo Library/NTB ScanpixI en studie som nylig er publisert i New England Journal of Medicine, ble hjernene til 34 astronauter undersøkt med MR-undersøkelse før og etter tokt i verdensrommet (1). Halvparten av astronautene hadde oppholdt seg på den internasjonale romstasjonen i om lag seks måneder, mens resten hadde vaert på kortvarige tokt i verdensrommet på ca. 14 dager.Det ble påvist strukturelle forandringer i hjernen ved MR-undersøkelse hos nesten alle astronautene med langvarige opphold i rommet, bl.a. kranial forskyvning av hjernevevet og en avsmalning av sentralfuren. Forfatterne argumenterer for at obstruksjon av venesinuser eller av araknoidale granulasjoner kan ha påvirket sirkulasjon av cerebrospinalvaeske hos astronautene. Til sammenligning kom astronautene, som hadde vaert på kortvarige opphold i rommet, tilbake til jorden stort sett uten påvisbare hjerneforandringer.-Denne studien belyser mekanismer bak økt intrakranialt trykk hos astronauter etter lengre tids opphold i verdensrommet, sier Rolf Salvesen, avdelingsoverlege ved Nevrologisk avdeling, Nordlandssykehuset, og professor ved Universitetet i Tromsø -Norges arktiske universitet. -Funnene er konsistente, men det er en svakhet at undersøkelsene før tokt var

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Effects of Spaceflight on Astronaut Brain Structure as Indicated on MRI

Cited by 246 publications

References 15 publications

Longitudinal Analysis of Quantitative Brain MRI in Astronauts Following Microgravity Exposure

Longitudinal Analysis of Quantitative Brain MRI in Astronauts Following Microgravity Exposure

Lower body negative pressure to safely reduce intracranial pressure

Vektløshet gir forandringer i hjernen

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