1
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Xie Y, Fu Y, Shao Y, Qu L, Yang J, Yang C, Zhou K, Li K, Xu Z, Xu D, Cao K, Tian N, Lv K, Wang L, Wang Y, Wang N, Li Y. Quantitative ultrasound image assessment of the optic nerve subarachnoid space during 90-day head-down tilt bed rest. NPJ Microgravity 2024; 10:9. [PMID: 38233425 PMCID: PMC10794463 DOI: 10.1038/s41526-024-00347-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 01/03/2024] [Indexed: 01/19/2024] Open
Abstract
The elevation in the optic nerve sheath (ONS) pressure (ONSP) due to microgravity-induced headward fluid shift is the primary hypothesized contributor to SANS. This longitudinal study aims to quantify the axial plane of the optic nerve subarachnoid space area (ONSSA), which is filled with cerebrospinal fluid (CSF) and expands with elevated ONSP during and after head-down tilt (HDT) bed rest (BR). 36 healthy male volunteers (72 eyes) underwent a 90-day strict 6° HDT BR. Without obtaining the pre-HDT data, measurements were performed on days 30, 60, and 90 during HDT and at 6 recovery time points extended to 180-days (R + 180) in a supine position. Portable B-scan ultrasound was performed using the 12 MHz linear array probe binocularly. The measurements of the ONS and the calculation of the ONSSA were performed with ImageJ 1.51 analysis software by two experienced observers in a masked manner. Compared to R + 180, the ONSSA on HDT30, HDT60, and HDT90 exhibited a consistently significant distention of 0.44 mm2 (95% CI: 0.13 to 0.76 mm2, P = 0.001), 0.45 mm2 (95% CI: 0.15 to 0.75 mm2, P = 0.001), and 0.46 mm2 (95% CI: 0.15 to 0.76 mm2, P < 0.001), respectively, and recovered immediately after HDT on R + 2. Such small changes in the ONSSA were below the lateral resolution limit of ultrasound (0.4 mm) and may not be clinically relevant, possibly due to ONS hysteresis causing persistent ONS distension. Future research can explore advanced quantitative portable ultrasound-based techniques and establish comparisons containing the pre-HDT measurements to deepen our understanding of SANS.
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Affiliation(s)
- Yuan Xie
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China
| | - Yingdi Fu
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Yaqi Shao
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Lina Qu
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Jiangang Yang
- Xi'an No.1 Hospital; Shanxi Institute of Ophthalmology; Shanxi Key Laboratory of Ophthalmology; Clinical Research Center for Ophthalmology Diseases of Shanxi Province; the First Affiliated Hospital of Northwestern University, Xi'an, 710002, Shanxi Province, China
| | - Chengjia Yang
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Kun Zhou
- Xi'an No.1 Hospital; Shanxi Institute of Ophthalmology; Shanxi Key Laboratory of Ophthalmology; Clinical Research Center for Ophthalmology Diseases of Shanxi Province; the First Affiliated Hospital of Northwestern University, Xi'an, 710002, Shanxi Province, China
| | - Kai Li
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Zi Xu
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Dong Xu
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Kai Cao
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Ning Tian
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China
| | - Ke Lv
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Linjie Wang
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Yaping Wang
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China
| | - Ningli Wang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.
- Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100005, China.
| | - Yinghui Li
- China Astronaut Research and Training Center, State Key Lab of Space Medicine Fundamentals and Application, No. 26 Beiqing Road, Haidian District, Beijing, 100094, China.
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2
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Milner DC, Subramanian PS. Insights into spaceflight-associated neuro-ocular syndrome with review of intraocular and orbital findings. Curr Opin Ophthalmol 2023; 34:493-499. [PMID: 37729662 DOI: 10.1097/icu.0000000000001000] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
PURPOSE OF REVIEW Spaceflight-associated neuro-ocular syndrome (SANS) remains a phenomenological term, and advances in ophthalmic imaging as well as new insights from ground-based experiments have given support to new theories of how SANS develops and what may be done to counter it. RECENT FINDINGS SANS has been postulated to arise from elevated intracranial pressure (ICP) during long-duration spaceflight (LDSF). However, recent work has shown that acute microgravity exposure does not increase ICP, and the effect of cephalad fluid shifts on ICP in microgravity remain unknown. In addition, structural imaging of the retina and optic nerve show changes after LDSF that are distinct from findings in terrestrial patients with elevated ICP. Since astronauts have not reported symptoms that would be expected with chronic ICP elevation, new theories that orbital and/or intracranial venous pressure may be the primary contributors to the development of SANS. SUMMARY Research has been filling knowledge gaps that exist regarding the cause(s) of SANS, and these advances are crucial steps in the effort to design countermeasures that will be required before human deep space exploration missions can be undertaken.
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Affiliation(s)
- Dallin C Milner
- Sue Anschutz-Rodgers University of Colorado Eye Center and Department of Ophthalmology
| | - Prem S Subramanian
- Sue Anschutz-Rodgers University of Colorado Eye Center and Department of Ophthalmology
- Department of Neurology
- Department of Neurosurgery, University of Colorado School of Medicine, Aurora, Colorado
- Department of Surgery (Division of Ophthalmology), Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
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3
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Grigoryan EN. Impact of Microgravity and Other Spaceflight Factors on Retina of Vertebrates and Humans In Vivo and In Vitro. Life (Basel) 2023; 13:1263. [PMID: 37374046 DOI: 10.3390/life13061263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 05/20/2023] [Accepted: 05/25/2023] [Indexed: 06/29/2023] Open
Abstract
Spaceflight (SF) increases the risk of developmental, regenerative, and physiological disorders in animals and humans. Astronauts, besides bone loss, muscle atrophy, and cardiovascular and immune system alterations, undergo ocular disorders affecting posterior eye tissues, including the retina. Few studies revealed abnormalities in the development and changes in the regeneration of eye tissues in lower vertebrates after SF and simulated microgravity. Under microgravity conditions, mammals show disturbances in the retinal vascular system and increased risk of oxidative stress that can lead to cell death in the retina. Animal studies provided evidence of gene expression changes associated with cellular stress, inflammation, and aberrant signaling pathways. Experiments using retinal cells in microgravity-modeling systems in vitro additionally indicated micro-g-induced changes at the molecular level. Here, we provide an overview of the literature and the authors' own data to assess the predictive value of structural and functional alterations for developing countermeasures and mitigating the SF effects on the human retina. Further emphasis is given to the importance of animal studies on the retina and other eye tissues in vivo and retinal cells in vitro aboard spacecraft for understanding alterations in the vertebrate visual system in response to stress caused by gravity variations.
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Affiliation(s)
- Eleonora N Grigoryan
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, 119334 Moscow, Russia
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4
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Fall DA, Lee AG, Bershad EM, Kramer LA, Mader TH, Clark JB, Hirzallah MI. Optic nerve sheath diameter and spaceflight: defining shortcomings and future directions. NPJ Microgravity 2022; 8:42. [PMID: 36202836 PMCID: PMC9537149 DOI: 10.1038/s41526-022-00228-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/12/2022] [Indexed: 11/24/2022] Open
Abstract
Neuro-ocular changes during long-duration space flight are known as spaceflight-associated neuro-ocular syndrome (SANS). The ability to detect, monitor, and prevent SANS is a priority of current space medicine research efforts. Optic nerve sheath diameter (ONSD) measurement has been used both terrestrially and in microgravity as a proxy for measurements of elevated intracranial pressure. ONSD shows promise as a potential method of identifying and quantitating neuro-ocular changes during space flight. This review examines 13 studies measuring ONSD and its relationship to microgravity exposure or ground-based analogs, including head-down tilt, dry immersion, or animal models. The goal of this correspondence is to describe heterogeneity in the use of ONSD in the current SANS literature and make recommendations to reduce heterogeneity in future studies through standardization of imaging modalities, measurement techniques, and other aspects of study design.
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Affiliation(s)
- Dylan A Fall
- Baylor College of Medicine and The Center for Space Medicine, Houston, TX, USA
| | - Andrew G Lee
- Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX, USA.,Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, USA.,Department of Ophthalmology, Weill Cornell Medicine, New York, NY, USA.,Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, USA.,University of Texas MD Anderson Cancer Center, Houston, TX, USA.,Texas A and M College of Medicine, Bryan, TX, USA
| | - Eric M Bershad
- Baylor College of Medicine and The Center for Space Medicine, Houston, TX, USA.,Department of Neurology, Baylor College of Medicine, Houston, TX, USA
| | - Larry A Kramer
- Department of Diagnostic and Interventional Imaging, University of Texas Health Science Center, Houston, USA
| | | | - Jonathan B Clark
- Baylor College of Medicine and The Center for Space Medicine, Houston, TX, USA
| | - Mohammad I Hirzallah
- Baylor College of Medicine and The Center for Space Medicine, Houston, TX, USA. .,Department of Neurology, Baylor College of Medicine, Houston, TX, USA.
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5
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Li S, Song Q, Wu B, Kan G, Wang F, Yang J, Zhu S. Structural damage to the rat eye following long-term simulated weightlessness. Exp Eye Res 2022; 223:109200. [PMID: 35932903 DOI: 10.1016/j.exer.2022.109200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Revised: 06/14/2022] [Accepted: 07/18/2022] [Indexed: 11/29/2022]
Abstract
To better perform space missions and develop human spaceflights, the eye health of astronauts is receiving increasing attention from researchers. In this study, we used prolonged tail suspension to simulate microgravity cephalad fluid shift in space to observe intraocular pressure (IOP) changes, retinal structure, and optic nerve damage in rats. We observed significant choroidal thickening and optic nerve demyelination lesions in the rats in each experimental group. At the cellular level, retinal ganglion cells (RGCs) survival was significantly reduced, optic nerve oligodendrocytes were reduced, and apoptotic factors and microglia-mediated inflammation-related factors were detected in both the retina and optic nerve. The severity of these changes increased with increasing tails suspension time. In conclusion, simulated long-term microgravity can lead to slight intraocular pressure fluctuations, choroidal thickening, reduced RGCs survival, and optic nerve demyelination in rats.
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Affiliation(s)
- Siqi Li
- Eye School of Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan, 610036, China
| | - Qiuyi Song
- Eye School of Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan, 610036, China
| | - Bin Wu
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Guanghan Kan
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Fei Wang
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, 100094, China
| | - Jiawei Yang
- Eye School of Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan, 610036, China; Key Laboratory of Sichuan Province Ophthalmopathy Prevention & Cure and Visual Function Protection, Chengdu, Sichuan, 610075, China.
| | - Siquan Zhu
- Eye School of Chengdu University of Traditional Chinese Medicine, Chengdu, Sichuan, 610036, China; Department of Ophthalmology, Beijing Anzhen Hospital, Capital Medical University, Beijing, 100029, China.
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6
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A perspective on spaceflight associated neuro-ocular syndrome causation secondary to elevated venous sinus pressure. NPJ Microgravity 2022; 8:3. [PMID: 35169156 PMCID: PMC8847421 DOI: 10.1038/s41526-022-00188-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 01/21/2022] [Indexed: 11/17/2022] Open
Abstract
Spaceflight associated neuro-ocular syndrome (SANS) alters the vision of astronauts during long-duration spaceflights. There is controversy regarding SANS being similar to patients with idiopathic intracranial hypertension (IIH). IIH has been shown to be due to an elevation in venous sinus pressure. The literature suggests an increase in jugular vein pressure secondary to a headward shift of fluid occurs in SANS but this may not be enough to significantly alter the intracranial pressure (ICP). The literature regarding cardiac output and cerebral blood flow (CBF) in long-duration spaceflight is contradictory, however, more recent data suggests increased flow. Recent modelling has shown that an increase in CBF can significantly increase sinus pressure. The purpose of the present paper is to review the SANS vascular dynamics literature and through mathematical modelling suggest the possible underlying cause of SANS as an elevation in venous sinus pressure, secondary to the redistribution of fluids towards the head, together with a significant increase in pressure drop across the venous system related to the CBF.
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7
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Carlstrom LP, Eltanahy A, Perry A, Rabinstein AA, Elder BD, Morris JM, Meyer FB, Graffeo CS, Lundgaard I, Burns TC. A clinical primer for the glymphatic system. Brain 2021; 145:843-857. [PMID: 34888633 DOI: 10.1093/brain/awab428] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 11/02/2021] [Accepted: 11/07/2021] [Indexed: 11/14/2022] Open
Abstract
The complex and dynamic system of fluid flow through the perivascular and interstitial spaces of the central nervous system has new-found implications for neurological diseases. Cerebrospinal fluid movement throughout the CNS parenchyma is more dynamic than could be explained via passive diffusion mechanisms alone. Indeed, a semi-structured glial-lymphatic (glymphatic) system of astrocyte-supported extracellular perivascular channels serves to directionally channel extracellular fluid, clearing metabolites and peptides to optimize neurologic function. Clinical studies of the glymphatic network has to date proven challenging, with most data gleaned from rodent models and post-mortem investigations. However, increasing evidence suggests that disordered glymphatic function contributes to the pathophysiology of CNS aging, neurodegenerative disease, and CNS injuries, as well as normal pressure hydrocephalus. Unlocking such pathophysiology could provide important avenues toward novel therapeutics. We here provide a multidisciplinary overview of glymphatics and critically review accumulating evidence regarding its structure, function, and hypothesized relevance to neurological disease. We highlight emerging technologies of relevance to the longitudinal evaluation of glymphatic function in health and disease. Finally, we discuss the translational opportunities and challenges of studying glymphatic science.
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Affiliation(s)
- Lucas P Carlstrom
- Departments of Neurologic Surgery, Mayo Clinic, Rochester, MN 55905 USA
| | - Ahmed Eltanahy
- Departments of Neurologic Surgery, Mayo Clinic, Rochester, MN 55905 USA
| | - Avital Perry
- Departments of Neurologic Surgery, Mayo Clinic, Rochester, MN 55905 USA
| | | | - Benjamin D Elder
- Departments of Neurologic Surgery, Mayo Clinic, Rochester, MN 55905 USA
| | | | - Fredric B Meyer
- Departments of Neurologic Surgery, Mayo Clinic, Rochester, MN 55905 USA
| | | | - Iben Lundgaard
- Departments of Experimental Medical Science, Lund University, Lund 228 11 Sweden.,Wallenberg Center for Molecular Medicine, Lund University, Lund 228 11 Sweden
| | - Terry C Burns
- Departments of Neurologic Surgery, Mayo Clinic, Rochester, MN 55905 USA
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8
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Kermorgant M, Sadegh A, Geeraerts T, Varenne F, Liberto J, Roubelat FP, Bataille N, Bareille MP, Beck A, Godard B, Golemis A, Nasr N, Arvanitis DN, Hélissen O, Senard JM, Pavy-Le Traon A, Soler V. Effects of Venoconstrictive Thigh Cuffs on Dry Immersion-Induced Ophthalmological Changes. Front Physiol 2021; 12:692361. [PMID: 34335300 PMCID: PMC8317025 DOI: 10.3389/fphys.2021.692361] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 06/10/2021] [Indexed: 11/13/2022] Open
Abstract
Neuro-ophthalmological changes named spaceflight associated neuro-ocular syndrome (SANS) reported after spaceflights are important medical issues. Dry immersion (DI), an analog to microgravity, rapidly induces a centralization of body fluids, immobilization, and hypokinesia similar to that observed during spaceflight. The main objectives of the present study were 2-fold: (1) to assess the neuro-ophthalmological impact during 5 days of DI and (2) to determine the effects of venoconstrictive thigh cuffs (VTC), used as a countermeasure to limit headward fluid shift, on DI-induced ophthalmological adaptations. Eighteen healthy male subjects underwent 5 days of DI with or without VTC countermeasures. The subjects were randomly assigned into two groups of 9: a control and cuffs group. Retinal and optic nerve thickness were assessed with spectral-domain optical coherence tomography (OCT). Optic nerve sheath diameter (ONSD) was measured by ocular ultrasonography and used to assess indirect changes in intracranial pressure (ICP). Intraocular pressure (IOP) was assessed by applanation tonometry. A higher thickness of the retinal nerve fiber layer (RNFL) in the temporal quadrant was observed after DI. ONSD increased significantly during DI and remained higher during the recovery phase. IOP did not significantly change during and after DI. VTC tended to limit the ONSD enlargement but not the higher thickness of an RNFL induced by DI. These findings suggest that 5 days of DI induced significant ophthalmological changes. VTC were found to dampen the ONSD enlargement induced by DI.
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Affiliation(s)
- Marc Kermorgant
- INSERM DR Midi-Pyrénées Limousin, Institute of Cardiovascular and Metabolic Diseases (I2MC) UMR1297, University Hospital of Toulouse, Toulouse, France
| | - Ayria Sadegh
- Department of Ophthalmology, University Hospital of Toulouse, Toulouse, France
| | - Thomas Geeraerts
- Department of Anaesthesiology and Critical Care, University Hospital of Toulouse, Toulouse, France
| | - Fanny Varenne
- Department of Ophthalmology, University Hospital of Toulouse, Toulouse, France
| | - Jérémy Liberto
- Department of Ophthalmology, University Hospital of Toulouse, Toulouse, France
| | | | - Noémie Bataille
- Department of Ophthalmology, University Hospital of Toulouse, Toulouse, France
| | | | - Arnaud Beck
- Institute for Space Medicine and Physiology (MEDES), Toulouse, France
| | - Brigitte Godard
- Institute for Space Medicine and Physiology (MEDES), Toulouse, France
| | - Adrianos Golemis
- Institute for Space Medicine and Physiology (MEDES), Toulouse, France
| | - Nathalie Nasr
- INSERM DR Midi-Pyrénées Limousin, Institute of Cardiovascular and Metabolic Diseases (I2MC) UMR1297, University Hospital of Toulouse, Toulouse, France.,Department of Neurology, University Hospital of Toulouse, Toulouse, France
| | - Dina N Arvanitis
- INSERM DR Midi-Pyrénées Limousin, Institute of Cardiovascular and Metabolic Diseases (I2MC) UMR1297, University Hospital of Toulouse, Toulouse, France
| | - Ophélie Hélissen
- INSERM DR Midi-Pyrénées Limousin, Institute of Cardiovascular and Metabolic Diseases (I2MC) UMR1297, University Hospital of Toulouse, Toulouse, France
| | - Jean-Michel Senard
- INSERM DR Midi-Pyrénées Limousin, Institute of Cardiovascular and Metabolic Diseases (I2MC) UMR1297, University Hospital of Toulouse, Toulouse, France.,Department of Clinical Pharmacology, University Hospital of Toulouse, Toulouse, France
| | - Anne Pavy-Le Traon
- INSERM DR Midi-Pyrénées Limousin, Institute of Cardiovascular and Metabolic Diseases (I2MC) UMR1297, University Hospital of Toulouse, Toulouse, France.,Department of Neurology, University Hospital of Toulouse, Toulouse, France
| | - Vincent Soler
- Department of Ophthalmology, University Hospital of Toulouse, Toulouse, France
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9
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Sater SH, Sass AM, Seiner A, Natividad GC, Shrestha D, Fu AQ, Oshinski JN, Ethier CR, Martin BA. MRI-based quantification of ophthalmic changes in healthy volunteers during acute 15° head-down tilt as an analogue to microgravity. J R Soc Interface 2021; 18:20200920. [PMID: 33906382 DOI: 10.1098/rsif.2020.0920] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Spaceflight is known to cause ophthalmic changes in a condition known as spaceflight-associated neuro-ocular syndrome (SANS). It is hypothesized that SANS is caused by cephalad fluid shifts and potentially mild elevation of intracranial pressure (ICP) in microgravity. Head-down tilt (HDT) studies are a ground-based spaceflight analogue to create cephalad fluid shifts. Here, we developed non-invasive magnetic resonance imaging (MRI)-based techniques to quantify ophthalmic structural changes under acute 15° HDT. We specifically quantified: (i) change in optic nerve sheath (ONS) and optic nerve (ON) cross-sectional area, (ii) change in ON deviation, an indicator of ON tortuosity, (iii) change in vitreous chamber depth, and (iv) an estimated ONS Young's modulus. Under acute HDT, ONS cross-sectional area increased by 4.04 mm2 (95% CI 2.88-5.21 mm2, p < 0. 000), while ON cross-sectional area remained nearly unchanged (95% CI -0.12 to 0.43 mm2, p = 0.271). ON deviation increased under HDT by 0.20 mm (95% CI 0.08-0.33 mm, p = 0.002). Vitreous chamber depth decreased under HDT by -0.11 mm (95% CI -0.21 to -0.03 mm, p = 0.009). ONS Young's modulus was estimated to be 85.0 kPa. We observed a significant effect of sex and BMI on ONS parameters, of interest since they are known risk factors for idiopathic intracranial hypertension. The tools developed herein will be useful for future analyses of ON changes in various conditions.
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Affiliation(s)
- Stuart H Sater
- Alcyone Therapeutics Inc., Lowell, MA 01852, USA.,Department of Chemical and Biological Engineering, University of Idaho, 875 Perimeter Drive, MC1122, Moscow, ID 83844-1122, USA
| | - Austin M Sass
- Department of Chemical and Biological Engineering, University of Idaho, 875 Perimeter Drive, MC1122, Moscow, ID 83844-1122, USA
| | - Akari Seiner
- Department of Chemical and Biological Engineering, University of Idaho, 875 Perimeter Drive, MC1122, Moscow, ID 83844-1122, USA
| | - Gabryel Conley Natividad
- Department of Chemical and Biological Engineering, University of Idaho, 875 Perimeter Drive, MC1122, Moscow, ID 83844-1122, USA
| | - Dev Shrestha
- Department of Chemical and Biological Engineering, University of Idaho, 875 Perimeter Drive, MC1122, Moscow, ID 83844-1122, USA
| | - Audrey Q Fu
- Department of Mathematics and Statistical Science, Institute of Bioinformatics and Evolutionary Studies, Institute for Modeling Collaboration and Innovation, University of Idaho, 875 Perimeter Drive, MC1122, Moscow, ID 83844-1122, USA
| | - John N Oshinski
- Department of Radiology and Imaging Sciences, Emory University, Atlanta, GA, USA.,Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Bryn A Martin
- Alcyone Therapeutics Inc., Lowell, MA 01852, USA.,Department of Chemical and Biological Engineering, University of Idaho, 875 Perimeter Drive, MC1122, Moscow, ID 83844-1122, USA
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10
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The glymphatic pathway in the optic nerve: did astronauts already reveal signs of its existence? NPJ Microgravity 2021; 7:14. [PMID: 33875668 PMCID: PMC8055966 DOI: 10.1038/s41526-021-00142-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 03/17/2021] [Indexed: 11/08/2022] Open
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11
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Sater SH, Sass AM, Rohr JJ, Marshall-Goebel K, Ploutz-Snyder RJ, Ethier CR, Stenger MB, Kramer LA, Martin BA, Macias BR. Automated MRI-based quantification of posterior ocular globe flattening and recovery after long-duration spaceflight. Eye (Lond) 2021; 35:1869-1878. [PMID: 33514895 PMCID: PMC8225832 DOI: 10.1038/s41433-021-01408-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 01/13/2021] [Accepted: 01/14/2021] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND/OBJECTIVES Spaceflight associated neuro-ocular syndrome (SANS), a health risk related to long-duration spaceflight, is hypothesized to result from a headward fluid shift that occurs with the loss of hydrostatic pressure gradients in weightlessness. Shifts in the vascular and cerebrospinal fluid compartments alter the mechanical forces at the posterior eye and lead to flattening of the posterior ocular globe. The goal of the present study was to develop a method to quantify globe flattening observed by magnetic resonance imaging after spaceflight. SUBJECTS/METHODS Volumetric displacement of the posterior globe was quantified in 10 astronauts at 5 time points after spaceflight missions of ~6 months. RESULTS Mean globe volumetric displacement was 9.88 mm3 (95% CI 4.56-15.19 mm3, p < 0.001) on the first day of assessment after the mission (R[return]+ 1 day); 9.00 mm3 (95% CI 3.73-14.27 mm3, p = 0.001) at R + 30 days; 6.53 mm3 (95% CI 1.24-11.83 mm3, p < 0.05) at R + 90 days; 4.45 mm3 (95% CI -0.96 to 9.86 mm3, p = 0.12) at R + 180 days; and 7.21 mm3 (95% CI 1.82-12.60 mm3, p < 0.01) at R + 360 days. CONCLUSIONS There was a consistent inward displacement of the globe at the optic nerve, which had only partially resolved 1 year after landing. More pronounced globe flattening has been observed in previous studies of astronauts; however, those observations lacked quantitative measures and were subjective in nature. The novel automated method described here allows for detailed quantification of structural changes in the posterior globe that may lead to an improved understanding of SANS.
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Affiliation(s)
- Stuart H Sater
- Alcyone Therapeutics Inc., Lowell, MA, USA.,Neurophysiological Imaging and Modeling Laboratory, University of Idaho, Moscow, ID, USA
| | - Austin M Sass
- Neurophysiological Imaging and Modeling Laboratory, University of Idaho, Moscow, ID, USA
| | - Jesse J Rohr
- Neurophysiological Imaging and Modeling Laboratory, University of Idaho, Moscow, ID, USA
| | | | - Robert J Ploutz-Snyder
- Applied Biostatistics Laboratory, School of Nursing, University of Michigan, Ann Arbor, MI, USA
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Michael B Stenger
- Cardiovascular and Vision Laboratory, Johnson Space Center, National Aeronautics and Space Administration, Houston, TX, USA
| | - Larry A Kramer
- Department of Diagnostic and Interventional Imaging, University of Texas Health Science Center at Houston, McGovern Medical School, Houston, TX, USA
| | - Bryn A Martin
- Alcyone Therapeutics Inc., Lowell, MA, USA. .,Neurophysiological Imaging and Modeling Laboratory, University of Idaho, Moscow, ID, USA.
| | - Brandon R Macias
- Cardiovascular and Vision Laboratory, Johnson Space Center, National Aeronautics and Space Administration, Houston, TX, USA
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