Artificial gravity: an effective countermeasure for microgravity-induced headward fluid shift?

Long-duration spaceflight is associated with pathophysiological changes in the intracranial compartment hypothetically linked to microgravity-induced headward fluid shift. This study aimed to determine whether daily artificial gravity (AG) sessions can mitigate these effects, supporting its application as a countermeasure to spaceflight. Twenty-four healthy adult volunteers (16 men) were exposed to 60 days of 6° head-down tilt bed rest (HDTBR) as a ground-based analog of chronic headward fluid shift.

Retrorectal Hernia: A Rare Cause of Constipation Diagnosed on Magnetic Resonance (MR) Defecography.

Retrorectal herniation of the sigmoid colon is a rare condition characterized by the protrusion of a segment of the colon into the pre-sacral space and posterior to the rectum. This herniation occurs through a defect in the peritoneum, which may have developed secondary to congenital mechanisms, surgery, trauma, or inflammatory processes. Here, a case of retrorectal herniation of the sigmoid colon in an elderly female patient presenting with constipation is reported, with a review of the literature.

Incidental Detection of a Rare Pediatric High-Grade Fibrosarcoma in a Post-traumatic Setting: The Conundrum of Intra-Abdominal Hematoma versus Neoplasia.

Infantile fibrosarcoma (IF) is a rare malignant fibroblastic tumor that affects infants and young children, occurring most commonly in the extremities. Here, we present a 14-year-old patient with an abdominal mass incidentally detected after a blunt injury to the abdomen. The initial trauma protocol CT revealed a high attenuation mesenteric lesion in the left central abdomen suggestive of mesenteric hematoma.

Functional assessment of the dural lymphatic vessels using dynamic contrast MRI in multiple sclerosis.

Background And Purpose: The discovery of glymphatic function in the human brain has generated interest in waste clearance mechanisms in neurological disorders such as multiple sclerosis (MS). However, noninvasive in vivo functional assessment is currently lacking. This work studies the feasibility of a novel intravenous dynamic contrast MRI method to assess the dural lymphatics, a purported pathway contributing to glymphatic clearance.

Optic nerve sheath diameter and spaceflight: defining shortcomings and future directions.

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.

Cerebrovascular Effects of Lower Body Negative Pressure at 3T MRI: Implications for Long-Duration Space Travel.

Background: Optic disc edema develops in most astronauts during long-duration spaceflight. It is hypothesized to result from weightlessness-induced venous congestion of the head and neck and is an unresolved health risk of space travel.

Purpose: Determine if short-term application of lower body negative pressure (LBNP) could reduce internal jugular vein (IJV) expansion associated with the supine posture without negatively impacting cerebral perfusion or causing IJV flow stasis.

Heparin for Vertebral Intraluminal Thrombus Causing Retroperitoneal Hemorrhage from Occult Renal Angiomyolipoma.

Stroke is a common cause of mortality and serious long-term disability worldwide. In the acute setting, current American Heart Association/American Stroke Association guidelines do not recommend routine anticoagulation for the management of acute ischemic strokes. However, short-term use of unfractionated heparin (UFH) in select subpopulations has demonstrated improved outcomes.

Association of Structural Changes in the Brain and Retina After Long-Duration Spaceflight.

Importance: Long-duration spaceflight induces structural changes in the brain and eye. Identification of an association between cerebral and ocular changes could help determine if there are common or independent causes and inform targeted prevention strategies or treatments.

Objective: To determine if there is an association between quantitative changes in intracranial compartment volumes and peripapillary total retinal thickness after spaceflight.

Changes in the Optic Nerve Head and Choroid Over 1 Year of Spaceflight.

Importance: While 6-month data are available regarding spaceflight-associated neuro-ocular syndrome, manned missions for 1 year and beyond are planned, warranting evaluation for spaceflight-associated neuro-ocular syndrome beyond 6 months.

Objective: To determine if the manifestation of spaceflight-associated neuro-ocular syndrome worsens during International Space Station missions exceeding the present 4- to 6-month duration.

Design, Setting, And Participants: The One-Year Mission Study used quantitative imaging modalities to investigate changes in ocular structure in 2 crew members who completed a 1-year-long spaceflight mission.

Persistent Globe Flattening in Astronauts following Long-Duration Spaceflight.

Posterior globe flattening has been well-documented in astronauts both during and after long-duration space flight (LDSF) and has been observed as early as 10 days into a mission on the International Space Station. Globe flattening (GF) is thought to be caused by the disc centred anterior forces created by elevated volume and/or pressure within the optic nerve sheath (ONS). This might be the result of increased intracranial pressure, increased intraorbital ONS pressure from compartmentalisation or a combination of these mechanisms.

Intracranial Effects of Microgravity: A Prospective Longitudinal MRI Study.

Background Astronauts on long-duration spaceflight missions may develop changes in ocular structure and function, which can persist for years after the return to normal gravity. Chronic exposure to elevated intracranial pressure during spaceflight is hypothesized to be a contributing factor, however, the etiologic causes remain unknown. Purpose To investigate the intracranial effects of microgravity by measuring combined changes in intracranial volumetric parameters, pituitary morphologic structure, and aqueductal cerebrospinal fluid (CSF) hydrodynamics relative to spaceflight and to establish a comprehensive model of recovery after return to Earth.

Association of Long-Duration Spaceflight With Anterior and Posterior Ocular Structure Changes in Astronauts and Their Recovery.

Importance: During long-duration spaceflights, nearly all astronauts exhibit some change in ocular structure within the spectrum of spaceflight-associated neuro-ocular syndrome.

Objective: To quantitatively determine in a prospective study whether changes in ocular structures hypothesized to be associated with the development of spaceflight-associated neuro-ocular syndrome occur during 6-month missions on board the International Space Station (ISS).

Design, Setting, And Participants: The Ocular Health ISS Study of astronauts is a longitudinal prospective cohort study that uses objective quantitative imaging modalities.

Longitudinal Analysis of Quantitative Brain MRI in Astronauts Following Microgravity Exposure.

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.

Post-Traumatic Stress Symptoms after Pediatric Injury: Relation to Pre-Frontal Limbic Circuitry.

Pre-frontal limbic circuitry is vulnerable to effects of stress and injury. We examined microstructure of pre-frontal limbic circuitry after traumatic brain injury (TBI) or extracranial injury (EI) and its relation to post-traumatic stress symptoms (PTSS). Participants aged 8 to 15 years who sustained mild to severe TBI ( = 53) or EI ( = 26) in motor vehicle incidents were compared with healthy children ( = 38) in a prospective longitudinal study.

Diffusion Tensor Imaging of the Superior Thalamic Radiation and Cerebrospinal Fluid Distribution in Idiopathic Normal Pressure Hydrocephalus.

Background And Purpose: Ventricular enlargement in elderly raises a challenging differential diagnosis to physicians. While Alzheimer's disease is the most common form of dementia, idiopathic normal pressure hydrocephalus (iNPH) constitutes a potentially reversible syndrome. iNPH has a unique pathophysiology pertaining to cerebrospinal fluid (CSF) dynamics and periventricular white matter.

Brain Quantitative MRI Metrics in Astronauts as a Unique Professional Group.

Background And Purpose: As part of its technological sophistication, the International Space Station (ISS) Program operates a robust medical surveillance schedule for its rotating 6-person crew to control the known health risks and to address knowledge gaps related to human health in space flight environment. Recent evidence on visual impairment in a subset of ISS crew has renewed the interest in the effects of long-duration space flight on the central nervous system (CNS). Through retrospective analysis in a sample of 10 healthy astronauts, we demonstrate the utility of multimodal quantitative magnetic resonance imaging (qMRI) with diffusion tensor imaging (DTI)-based customized brain templates to examine the structural attributes of various CNS compartments in this occupational group.

Acute Swine Model for Assessing Biocompatibility of Biomedical Interface Materials.

We established an acute animal model for early, straightforward, and reproducible assessment of a biocompatible material interface. Bilateral femoral artery-to-vein shunts were created in 12 pigs: two tubes per shunt, the left two coated and the right two uncoated. We evaluated two groups: uncontrolled flow (UF; shunt flow unregulated) and controlled flow (CF; shunt flow ∼50 mL/min).

MRI-derived diffusion parameters in the human optic nerve and its surrounding sheath during head-down tilt.

More than half of astronauts present with significant neuro-ophthalmic findings during 6-month missions onboard the International Space Station. Although the underlying cause of this Microgravity Ocular Syndrome is currently unknown, alterations in cerebrospinal fluid dynamics within the optic nerve sheath may play a role. In the presented study, diffusion tensor imaging was used to assess changes in diffusivity of the optic nerve and its surrounding sheath during head-down tilt, a ground-based model of microgravity.

Quantitative MRI volumetry, diffusivity, cerebrovascular flow, and cranial hydrodynamics during head-down tilt and hypercapnia: the SPACECOT study.

To improve the pathophysiological understanding of visual changes observed in astronauts, we aimed to use quantitative MRI to measure anatomic and physiological responses during a ground-based spaceflight analog (head-down tilt, HDT) combined with increased ambient carbon dioxide (CO). Six healthy, male subjects participated in the double-blinded, randomized crossover design study with two conditions: 26.5 h of -12° HDT with ambient air and with 0.

Longitudinal diffusion tensor imaging after pediatric traumatic brain injury: Impact of age at injury and time since injury on pathway integrity.

Following pediatric traumatic brain injury (TBI), longitudinal diffusion tensor imaging may characterize alterations in initial recovery and subsequent trajectory of white matter development. Our primary aim examined effects of age at injury and time since injury on pathway microstructure in children ages 6-15 scanned 3 and 24 months after TBI. Microstructural values generated using tract-based spatial statistics extracted from core association, limbic, and projection pathways were analyzed using general linear mixed models.

Plasticity of Interhemispheric Temporal Lobe White Matter Pathways Due to Early Disruption of Corpus Callosum Development in Spina Bifida.

Spina bifida myelomeningocele (SBM) is commonly associated with anomalous development of the corpus callosum (CC) because of congenital partial hypogenesis and hydrocephalus-related hypoplasia. It represents a model disorder to examine the effects of early disruption of CC neurodevelopment and the plasticity of interhemispheric white matter connections. Diffusion tensor imaging was acquired on 76 individuals with SBM and 27 typically developing individuals, aged 8-36 years.