Space motion sickness: A common neurovestibular dysfunction in microgravity (original) (raw)
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Neurological conditions caused by microgravity
São Paulo Medical Journal, 2021
Background: Since Space Tourism is closer to reality, a review of the most prevalent neurological pathologies in microgravity is needed. Objective: Review major neurological afflictions in astronauts. Methods: Research into bibliographic reviews at PubMed, using the descriptors “astronauts” and “neurological disorders” Results: Several neurological alterations, such as ataxy, intracranial hypertension (ICH), neuromuscular disorders, ocular disturbances and changes in cognitive functions were assigned to a microgravity environment. Astronauts returning from space presented ICH; being the main pathophysiology hypothesis referred to a change in the liquor dynamics as a result of venous drainage obstruction and hematoencephalic barrier. Also, gravity doesn’t act on the neurovestibular system during space flights. This phenomenon can lead to Space Motion Sickness, situation in which astronauts report balance, coordination and sight disturbances, as well as movement illusions. A subset of...
Intravestibular Balance and Motion Sickness
Aerospace medicine and human performance, 2018
A theory is presented to explain the major findings regarding motion sickness and to synthetize current theories concerning its etiology. The theory proposes that an imbalance in the output of the two major organs of the labyrinthfavoring the semicircular canals over the otolith organs-is responsible for most instances of motion sickness as experienced in terrestrial and microgravity environments. METHODS: Strengths and limitations of current theories are first outlined before the different roles of the canals and otoliths in the genesis of motion sickness symptoms are described. RESULTS: The proposed theory is shown to explain a large number of findings and integrate current theories. DISCUSSION: The role of vestibular imbalance in motion sickness may be a consequence of the more general differences between the canals and otoliths in autonomic control.
The effect of spaceflight and microgravity on the human brain
Journal of Neurology
Microgravity, confinement, isolation, and immobilization are just some of the features astronauts have to cope with during space missions. Consequently, long-duration space travel can have detrimental effects on human physiology. Although research has focused on the cardiovascular and musculoskeletal system in particular, the exact impact of spaceflight on the human central nervous system remains to be determined. Previous studies have reported psychological problems, cephalic fluid shifts, neurovestibular problems, and cognitive alterations, but there is paucity in the knowledge of the underlying neural substrates. Previous space analogue studies and preliminary spaceflight studies have shown an involvement of the cerebellum, cortical sensorimotor, and somatosensory areas and the vestibular pathways. Extending this knowledge is crucial, especially in view of long-duration interplanetary missions (e.g., Mars missions) and space tourism. In addition, the acquired insight could be relevant for vestibular patients, patients with neurodegenerative disorders, as well as the elderly population, coping with multisensory deficit syndromes, immobilization, and inactivity. Keywords Human spaceflight Á Microgravity Á Brain Á Central nervous system Á Dry immersion Á Bed rest Á Parabolic flight Á MRI Á EEG Á Neuroplasticity
Hippokratia, 2008
Severe and prolonged unmitigated SAS and SMS related symptoms have been thoroughly described in Astronauts during adaptation periods for orbital flight and post orbital flight. It has recently been shown that there is a strong correlation between these symptoms most often suffered by astronauts to that of the symptoms of patients suffering from Postural Deficiency Syndrome (PDS) on Earth that have been successfully assessed, diagnosed and treated. International peer-reviewed literature identifies PDS as a trauma induced medical condition which originates from central neural dysregulation of sensory-motor and cognitive controls; these dysfunctions can be accurately identified, measured, and monitored via a specific ocular-vestibular-postural monitoring system along with relevant clinical data. This higher level of understanding is necessary in order to reach the next stage of success for humans living and working in Space. Central sensory-motor and cognitive controls dysfunction unde...
Intracranial Effects of Microgravity: A Prospective Longitudinal MRI Study
Radiology, 2020
A pproximately 60% of the crew members of the International Space Station have reported altered visual acuity after long-duration exposure to microgravity (1). Postflight evaluation has shown variable degrees and combinations of optic disc edema, retinal nerve fiber layer thickening, retinal hemorrhage, cotton wool spots, posterior globe flattening, and choroidal folds (1). Lacking a terrestrially based clinical correlate, this medical condition is generically referred to by the National Aeronautics and Space Administration (NASA) as the spaceflight-associated neuro-ocular syndrome. The discovery of spaceflight-associated neuro-ocular syndrome has inevitably raised concerns for the long-term health of astronauts on extended-duration interplanetary travel. MRI findings in postflight astronauts, in whom similarities to idiopathic intracranial hypertension such as posterior globe flattening are found, have implicated elevated intracranial pressure (ICP) as a hypothesized mechanism of spaceflight-associated neuro-ocular syndrome (2,3). However, contrary to expectations, ICP measured in volunteers during brief microgravity exposures in aerial parabolic flight was not elevated (ICP, 13 mm Hg), but instead remained between the supine (ICP, 15 mm Hg) and 90° upright (ICP, 4 mm Hg) baseline values (4). It has been suggested that the inherent absence of postural ICP variability in microgravity could expose astronauts to increased mean diurnal ICP because of the inability to intermittently lower ICP by upright positioning that depends on a gravitational environment (4). This is potentially problematic because chronic supine-like ICP, without intermittent decompression, simulated by 30 days of strict head-down-tilt bedrest, is associated with optic nerve edema in otherwise healthy adults (5). Although an unremitting mild increase in the mean diurnal ICP may play a role in the development of spaceflight-associated neuro-ocular syndrome, a potential
Effects of Microgravity on Human Physiology
Beyond LEO - Human Health Issues for Deep Space Exploration [Working Title]
The effects of microgravity conditions on neurovestibular, cardiovascular, musculoskeletal, bone metabolic, and hemato-immunological systems are described. We discuss "space motion sickness," sensorimotor coordination disorders, cardiovascular deconditioning, muscular atrophy, bone loss, and anemia/ immunodeficiency, including their causes and mechanisms. In addition to the previously described deconditioning, new problems related to microgravity, spaceflight-associated neuro-ocular syndrome (SANS), and structural changes of the brain by magnetic resonance imaging (MRI) are also explained. Our proposed countermeasure, artificial gravity produced by a short-arm centrifuge with ergometric exercise, is also described in detail, and we confirmed this system to be effective in preventing the abovementioned deconditioning caused by microgravity exposure.
Posture, locomotion, spatial orientation, and motion sickness as a function of space flight
Brain Research Reviews, 1998
This article summarizes a variety of newly published findings obtained by the Neuroscience Laboratory, Johnson Space Center, and attempts to place this work within a historical framework of previous results on posture, locomotion, motion sickness, and perceptual responses that have been observed in conjunction with space flight. In this context, we have taken the view that correct transduction and integration of signals from all sensory systems is essential to maintaining stable vision, postural and locomotor control, and eye-hand coordination as components of spatial orientation. The plasticity of the human central nervous system allows individuals to adapt to altered stimulus conditions encountered in a microgravity environment. However, until some level of adaptation is achieved, astronauts and cosmonauts often experience space motion sickness, disturbances in motion control and eye-hand coordination, unstable vision, and illusory motion of the self, the visual scene, or both. Many of the same types of disturbances encountered in space flight reappear immediately after crew members return to earth. The magnitude of these neurosensory, sensory-motor and perceptual disturbances, and the time needed to recover from them, tend to vary as a function of mission duration and the space travelers prior experience with the stimulus rearrangement of space flight. To adequately chart the development of neurosensory changes associated with space flight, we recommend development of enhanced eye movement systems and body position measurement. We also advocate the use of a human small radius centrifuge as both a research tool and as a means of providing on-orbit countermeasures that will lessen the impact of living for long periods of time with out exposure to altering gravito-inertial forces. q
Artificial gravity : neurovestibular adaptation to incremental exposure to centrifugation
2004
In order to counteract the debilitating effects of the space environment on the human body, short‐radius intermittent centrifugation is investigated as a possible means to expose astro‐ nauts to artificial gravity. Whereas AG is efficient in providing stimuli for muscles, bones and cardiovascular system, short‐radius centrifugation elicits discomfort and illusory sensa‐ tions of motion if particular head movements are made while spinning. Past research has shown that human beings can adapt to these sensations and undergo various stimuli with‐ out the disturbing effects of motion sickness, sensations of tumbling and inappropriate eye movements. However, current protocols for adaptation basically consist in repeated expo‐ sure to the discomfort. This solution is not satisfactory because the drop‐out rate oscillates between 30 and 50%. Since it is not acceptable to spend days of training on astronauts who, in the end, because of this training, could become unsuitable for flight, it is ...