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Roberts DR, Tidwell J, Taylor JA. Reply. AJNR Am J Neuroradiol 2024; 45:E7. [PMID: 38724192 DOI: 10.3174/ajnr.a8279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2024]
Affiliation(s)
- Donna R Roberts
- Department of Radiology and Radiological ScienceMedical University of South CarolinaCharleston, South CarolinaInternational Space Station National LaboratoryMelbourne, Florida
| | - Joe Tidwell
- Department of Radiology and Radiological ScienceMedical University of South CarolinaCharleston, South Carolina
| | - J Andrew Taylor
- Department of Radiology and Radiological ScienceMedical University of South CarolinaCharleston, South Carolina
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2
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Bateman GA, Bateman AR. A perspective on the evidence for glymphatic obstruction in spaceflight associated neuro-ocular syndrome and fatigue. NPJ Microgravity 2024; 10:23. [PMID: 38418508 PMCID: PMC10901896 DOI: 10.1038/s41526-024-00365-9] [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: 11/29/2023] [Accepted: 02/12/2024] [Indexed: 03/01/2024] Open
Abstract
Spaceflight associated neuro-ocular syndrome (SANS) alters the vision of astronauts during long-duration spaceflights. Previously, the current authors have discussed the similarities and differences between SANS and idiopathic intracranial hypertension to try to elucidate a possible pathophysiology. Recently, a theory has been advanced that SANS may occur secondary to failure of the glymphatic system caused by venous dilatation within the brain and optic nerves. There is recent evidence to suggest glymphatic obstruction occurs in childhood hydrocephalus, multiple sclerosis and syringomyelia due to venous outflow dilatation similar to that proposed in SANS. The purpose of the current paper is to discuss the similarities and differences between the known CSF and venous pathophysiology in SANS with these other terrestrial diseases, to see if they can shed any further light on the underlying cause of this microgravity-induced disease.
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Affiliation(s)
- Grant Alexander Bateman
- Department of Medical Imaging, John Hunter Hospital, Newcastle, NSW, Australia.
- Newcastle University Faculty of Health, Callaghan Campus, Newcastle, NSW, Australia.
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Li Z, Wu J, Zhao T, Wei Y, Xu Y, Liu Z, Li X, Chen X. Microglial activation in spaceflight and microgravity: potential risk of cognitive dysfunction and poor neural health. Front Cell Neurosci 2024; 18:1296205. [PMID: 38425432 PMCID: PMC10902453 DOI: 10.3389/fncel.2024.1296205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 01/29/2024] [Indexed: 03/02/2024] Open
Abstract
Due to the increased crewed spaceflights in recent years, it is vital to understand how the space environment affects human health. A lack of gravitational force is known to risk multiple physiological functions of astronauts, particularly damage to the central nervous system (CNS). As innate immune cells of the CNS, microglia can transition from a quiescent state to a pathological state, releasing pro-inflammatory cytokines that contribute to neuroinflammation. There are reports indicating that microglia can be activated by simulating microgravity or exposure to galactic cosmic rays (GCR). Consequently, microglia may play a role in the development of neuroinflammation during spaceflight. Prolonged spaceflight sessions raise concerns about the chronic activation of microglia, which could give rise to various neurological disorders, posing concealed risks to the neural health of astronauts. This review summarizes the risks associated with neural health owing to microglial activation and explores the stressors that trigger microglial activation in the space environment. These stressors include GCR, microgravity, and exposure to isolation and stress. Of particular focus is the activation of microglia under microgravity conditions, along with the proposal of a potential mechanism.
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Affiliation(s)
- Zihan Li
- Beijing International Science and Technology Cooperation Base for Antiviral Drugs, College of Chemistry and Life Science, Beijing University of Technology, Beijing, China
| | - Jiarui Wu
- Beijing International Science and Technology Cooperation Base for Antiviral Drugs, College of Chemistry and Life Science, Beijing University of Technology, Beijing, China
| | - Tianyuan Zhao
- Beijing International Science and Technology Cooperation Base for Antiviral Drugs, College of Chemistry and Life Science, Beijing University of Technology, Beijing, China
| | - Yiyun Wei
- Beijing International Science and Technology Cooperation Base for Antiviral Drugs, College of Chemistry and Life Science, Beijing University of Technology, Beijing, China
| | - Yajing Xu
- Beijing International Science and Technology Cooperation Base for Antiviral Drugs, College of Chemistry and Life Science, Beijing University of Technology, Beijing, China
| | - Zongjian Liu
- Department of Rehabilitation, Beijing Rehabilitation Hospital, Capital Medical University, Beijing, China
| | - Xiaoqiong Li
- School of Life Sciences, Beijing Institute of Technology, Beijing, China
| | - Xuechai Chen
- Beijing International Science and Technology Cooperation Base for Antiviral Drugs, College of Chemistry and Life Science, Beijing University of Technology, Beijing, China
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Caddy HT, Kelsey LJ, Parker LP, Green DJ, Doyle BJ. Modelling large scale artery haemodynamics from the heart to the eye in response to simulated microgravity. NPJ Microgravity 2024; 10:7. [PMID: 38218868 PMCID: PMC10787773 DOI: 10.1038/s41526-024-00348-w] [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: 05/24/2023] [Accepted: 01/03/2024] [Indexed: 01/15/2024] Open
Abstract
We investigated variations in haemodynamics in response to simulated microgravity across a semi-subject-specific three-dimensional (3D) continuous arterial network connecting the heart to the eye using computational fluid dynamics (CFD) simulations. Using this model we simulated pulsatile blood flow in an upright Earth gravity case and a simulated microgravity case. Under simulated microgravity, regional time-averaged wall shear stress (TAWSS) increased and oscillatory shear index (OSI) decreased in upper body arteries, whilst the opposite was observed in the lower body. Between cases, uniform changes in TAWSS and OSI were found in the retina across diameters. This work demonstrates that 3D CFD simulations can be performed across continuously connected networks of small and large arteries. Simulated results exhibited similarities to low dimensional spaceflight simulations and measured data-specifically that blood flow and shear stress decrease towards the lower limbs and increase towards the cerebrovasculature and eyes in response to simulated microgravity, relative to an upright position in Earth gravity.
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Affiliation(s)
- Harrison T Caddy
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, WA, Australia
- School of Human Sciences (Exercise and Sport Sciences), The University of Western Australia, Perth, WA, Australia
| | - Lachlan J Kelsey
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, WA, Australia
- School of Engineering, The University of Western Australia, Perth, WA, Australia
| | - Louis P Parker
- FLOW, Department of Engineering Mechanics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Daniel J Green
- School of Human Sciences (Exercise and Sport Sciences), The University of Western Australia, Perth, WA, Australia
| | - Barry J Doyle
- Vascular Engineering Laboratory, Harry Perkins Institute of Medical Research, Queen Elizabeth II Medical Centre, Nedlands, Australia and the UWA Centre for Medical Research, The University of Western Australia, Perth, WA, Australia.
- School of Engineering, The University of Western Australia, Perth, WA, Australia.
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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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Tidwell JB, Taylor JA, Collins HR, Chamberlin JH, Barisano G, Sepehrband F, Turner MD, Gauthier G, Mulder ER, Gerlach DA, Roberts DR. Longitudinal Changes in Cerebral Perfusion, Perivascular Space Volume, and Ventricular Volume in a Healthy Cohort Undergoing a Spaceflight Analog. AJNR Am J Neuroradiol 2023; 44:1026-1031. [PMID: 37562828 PMCID: PMC10494950 DOI: 10.3174/ajnr.a7949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 06/25/2023] [Indexed: 08/12/2023]
Abstract
BACKGROUND AND PURPOSE A global decrease in brain perfusion has recently been reported during exposure to a ground-based spaceflight analog. Considering that CSF and glymphatic flow are hypothesized to be propelled by arterial pulsations, it is unknown whether a change in perfusion would impact these CSF compartments. The aim of the current study was to evaluate the relationship among changes in cerebral perfusion, ventricular volume, and perivascular space volume before, during, and after a spaceflight analog. MATERIALS AND METHODS Eleven healthy participants underwent 30 days of bed rest at 6° head-down tilt with 0.5% atmospheric CO2 as a spaceflight analog. For each participant, 6 MR imaging brain scans, including perfusion and anatomic-weighted T1 sequences, were obtained before, during, and after the analog period. Global perfusion, ventricular volume, and perivascular space volume time courses were constructed and evaluated with repeated measures ANOVAs. RESULTS Global perfusion followed a divergent time trajectory from ventricular and perivascular space volume, with perfusion decreasing during the analog, whereas ventricular and perivascular space volume increased (P < .001). These patterns subsequently reversed during the 2-week recovery period. CONCLUSIONS The patterns of change in brain physiology observed in healthy participants suggest a relationship between cerebral perfusion and CSF homeostasis. Further study is warranted to determine whether a causal relationship exists and whether similar neurophysiologic responses occur during spaceflight.
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Affiliation(s)
- J B Tidwell
- From the Department of Radiology and Radiological Science (J.B.T., J.A.T., H.R.C., J.H.C., M.D.T., G.G., D.R.R.), Medical University of South Carolina; Charleston, South Carolina
| | - J A Taylor
- From the Department of Radiology and Radiological Science (J.B.T., J.A.T., H.R.C., J.H.C., M.D.T., G.G., D.R.R.), Medical University of South Carolina; Charleston, South Carolina
| | - H R Collins
- From the Department of Radiology and Radiological Science (J.B.T., J.A.T., H.R.C., J.H.C., M.D.T., G.G., D.R.R.), Medical University of South Carolina; Charleston, South Carolina
| | - J H Chamberlin
- From the Department of Radiology and Radiological Science (J.B.T., J.A.T., H.R.C., J.H.C., M.D.T., G.G., D.R.R.), Medical University of South Carolina; Charleston, South Carolina
| | - G Barisano
- Laboratory of Neuroimaging (F.S.), University of Southern California, Los Angeles, California
| | - F Sepehrband
- Department of Neurosurgery (G.B.), Stanford University, Stanford, California
| | - M D Turner
- From the Department of Radiology and Radiological Science (J.B.T., J.A.T., H.R.C., J.H.C., M.D.T., G.G., D.R.R.), Medical University of South Carolina; Charleston, South Carolina
| | - G Gauthier
- From the Department of Radiology and Radiological Science (J.B.T., J.A.T., H.R.C., J.H.C., M.D.T., G.G., D.R.R.), Medical University of South Carolina; Charleston, South Carolina
| | - E R Mulder
- Department of Neurosurgery (G.B.), Stanford University, Stanford, California
| | - D A Gerlach
- Department of Neurosurgery (G.B.), Stanford University, Stanford, California
| | - D R Roberts
- From the Department of Radiology and Radiological Science (J.B.T., J.A.T., H.R.C., J.H.C., M.D.T., G.G., D.R.R.), Medical University of South Carolina; Charleston, South Carolina
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Boschert AL, Gauger P, Bach A, Gerlach D, Johannes B, Jordan J, Li Z, Elmenhorst D, Bauer A, Marshall-Goebel K, Tank J, Zange J, Rittweger J. External to internal cranial perfusion shifts during simulated weightlessness: Results from a randomized cross-over trial. NPJ Microgravity 2023; 9:25. [PMID: 36977696 PMCID: PMC10050182 DOI: 10.1038/s41526-023-00267-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 03/13/2023] [Indexed: 03/30/2023] Open
Abstract
The exact pathophysiology of the spaceflight-associated neuro-ocular syndrome (SANS) has so far not been completely elucidated. In this study we assessed the effect of acute head-down tilt position on the mean flow of the intra- and extracranial vessels. Our results suggest a shift from the external to the internal system that might play an important role in the pathomechanism of SANS.
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Affiliation(s)
- Alessa L Boschert
- Department of Muscle and Bone Metabolism, German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany.
- Institute of Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany.
| | - Peter Gauger
- Department of Cardiovascular Aerospace Medicine, German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
| | - Anja Bach
- Department of Cardiovascular Aerospace Medicine, German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
| | - Darius Gerlach
- Department of Cardiovascular Aerospace Medicine, German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
| | - Bernd Johannes
- Department of Muscle and Bone Metabolism, German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
| | - Jens Jordan
- Institute of Aerospace Medicine, German Aerospace Center (DLR) and Chair of Aerospace Medicine, Cologne, Germany
| | - Zhili Li
- State Key Laboratory of Space Medicine Fundamentals and Application, China Astronaut Research and Training Center, Beijing, China
| | - David Elmenhorst
- Forschungszentrum Jülich, Institute of Neuroscience and Medicine (INM-2), Jülich, Germany
| | - Andreas Bauer
- Forschungszentrum Jülich, Institute of Neuroscience and Medicine (INM-2), Jülich, Germany
| | | | - Jens Tank
- Department of Cardiovascular Aerospace Medicine, German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
| | - Jochen Zange
- Department of Muscle and Bone Metabolism, German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
| | - Jörn Rittweger
- Department of Muscle and Bone Metabolism, German Aerospace Center (DLR), Institute of Aerospace Medicine, Cologne, Germany
- Department of Pediatrics and Adolescent Medicine, University of Cologne, Cologne, Germany
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Pessa JE. Identification of a novel path for cerebrospinal fluid (CSF) drainage of the human brain. PLoS One 2023; 18:e0285269. [PMID: 37141309 PMCID: PMC10159342 DOI: 10.1371/journal.pone.0285269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 04/18/2023] [Indexed: 05/06/2023] Open
Abstract
How cerebrospinal fluid (CSF) drains from the human brain is of paramount importance to cerebral health and physiology. Obstructed CSF drainage results in increased intra-cranial pressure and a predictable cascade of events including dilated cerebral ventricles and ultimately cell death. The current and accepted model of CSF drainage in humans suggests CSF drains from the subarachnoid space into the sagittal sinus vein. Here we identify a new structure in the sagittal sinus of the human brain by anatomic cadaver dissection. The CSF canalicular system is a series of channels on either side of the sagittal sinus vein that communicate with subarachnoid cerebrospinal fluid via Virchow-Robin spaces. Fluorescent injection confirms that these channels are patent and that flow occurs independent of the venous system. Fluoroscopy identified flow from the sagittal sinus to the cranial base. We verify our previous identification of CSF channels in the neck that travel from the cranial base to the subclavian vein. Together, this information suggests a novel path for CSF drainage of the human brain that may represent the primary route for CSF recirculation. These findings have implications for basic anatomy, surgery, and neuroscience, and highlight the continued importance of gross anatomy to medical research and discovery.
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Affiliation(s)
- Joel E Pessa
- Private Practice, Arlington, Massachusetts, United States of America
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Seidler RD, Stern C, Basner M, Stahn AC, Wuyts FL, zu Eulenburg P. Future research directions to identify risks and mitigation strategies for neurostructural, ocular, and behavioral changes induced by human spaceflight: A NASA-ESA expert group consensus report. Front Neural Circuits 2022; 16:876789. [PMID: 35991346 PMCID: PMC9387435 DOI: 10.3389/fncir.2022.876789] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 06/27/2022] [Indexed: 11/13/2022] Open
Abstract
A team of experts on the effects of the spaceflight environment on the brain and eye (SANS: Spaceflight-Associated Neuro-ocular Syndrome) was convened by NASA and ESA to (1) review spaceflight-associated structural and functional changes of the human brain and eye, and any interactions between the two; and (2) identify critical future research directions in this area to help characterize the risk and identify possible countermeasures and strategies to mitigate the spaceflight-induced brain and eye alterations. The experts identified 14 critical future research directions that would substantially advance our knowledge of the effects of spending prolonged periods of time in the spaceflight environment on SANS, as well as brain structure and function. They used a paired comparison approach to rank the relative importance of these 14 recommendations, which are discussed in detail in the main report and are summarized briefly below.
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Affiliation(s)
- Rachael D. Seidler
- Department of Applied Physiology & Kinesiology, Health and Human Performance, University of Florida, Gainesville, FL, United States
| | - Claudia Stern
- Department of Clinical Aerospace Medicine, German Aerospace Center (DLR) and ISS Operations and Astronauts Group, European Astronaut Centre, European Space Agency (ESA), Cologne, Germany
- *Correspondence: Claudia Stern,
| | - Mathias Basner
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Alexander C. Stahn
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Floris L. Wuyts
- Department of Physics, University of Antwerp, Antwerp, Belgium
- Laboratory for Equilibrium Investigations and Aerospace (LEIA), Antwerp, Belgium
| | - Peter zu Eulenburg
- German Vertigo and Balance Center, University Hospital, Ludwig-Maximilians-Universität München (LMU), Munich, Germany
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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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