Increased risk of acute kidney injury in the first part of an ultra-trail-Implications for abandonment.

Acute kidneys injuries (AKIs) have been described in marathon and trail running. The currently available data allows assessment of before/after comparisons but does not allow an analysis of what happens during the race. A multidisciplinary assessment protocol was performed during the first trail of Clécy (Normandy France) in November 2021. This allowed an initial assay to be carried out, then at the end of each of the 6 loops of 26 km, and finally after 24 h of recovery. The race extends over 156 km in hilly terrain and 6000 m of elevation gain (D+). The level of impairment according to the RIFLE classification was defined for each runner at each assay. Fifty-five runners were at the start, and the per protocol analysis involved 36 runners (27 men and 9 women, 26 finishers). Fifteen (41.7%) of the riders presented at least one result corresponding to a "RIFLE risk" level. After 24 h of rest, only one runner still had a "RIFLE Risk". The distance around the marathon seems to be the moment of greatest risk. For the first time, we find an association between this renal risk and the probability of abandonment. Many runners are vulnerable to kidney damage during long-duration exercise, which is why it's important to limit risk situations, such as the use of potentially toxic drugs or hydration disorders. The consumption of NSAIDs (nonsteroidal anti-inflammatory drugs) before or during an ultra-distance race should therefore be prohibited. Attention should be paid to hydration disorders.

Glycaemic Effects of a 156-km Ultra-trail Race in Athletes: An Observational Field Study.

BACKGROUND: Ultra-trail running races pose appreciable physiological challenges, particularly for glucose metabolism. Previous studies that yielded divergent results only measured glycaemia at isolated times. OBJECTIVES: We aimed to explore the impact of an ultra-endurance race on continuously measured glycaemia and to understand potential physiological mechanisms, as well as the consequences for performance and behavioural alertness. METHODS: Fifty-five athletes (78% men, 43.7 ± 9.6 years) ran a 156-km ultra-trail race (six 26-km laps, total elevation 6000 m). Participants wore a masked continuous glucose monitoring sensor from the day before the race until 10 days post-race. Blood was taken at rest, during refuelling stops after each lap, and after 24-h recovery. Running intensity (% heart rate reserve), performance (lap times), psychological stress, and behavioural alertness were explored. Linear mixed models and logistic regressions were carried out. RESULTS: No higher risk of hypo- or hyperglycaemia was observed during the exercise phases of the race (i.e. excluding stops for scientific measurements and refuelling) compared with resting values. Laps comprising a greater proportion of time spent at maximal aerobic intensity were nevertheless associated with more time > 180 mg/dL (P = 0.021). A major risk of hyperglycaemia appeared during the 48-h post-race period compared with pre-race (P < 0.05), with 31.9% of the participants spending time with values > 180 mg/dL during recovery versus 5.5% during resting. Changes in circulating insulin, cortisol, and free fatty acids followed profiles comparable with those usually observed during traditional aerobic exercise. However, creatine phosphokinase, and to a lesser extent lactate dehydrogenase, increased exponentially during the race (P < 0.001) and remained high at 24-h post-race (P < 0.001; respectively 43.6 and 1.8 times higher vs. resting). Glycaemic metrics did not influence physical performance or behavioural alertness. CONCLUSION: Ultra-endurance athletes were exposed to hyperglycaemia during the 48-h post-race period, possibly linked to muscle damage and inflammation. Strategies to mitigate muscle damage or subsequent inflammation before or after ultra-trail races could limit recovery hyperglycaemia and hence its related adverse health consequences. TRIAL REGISTRATION NUMBER: NCT05538442 2022-09-21 retrospectively registered.

Statistical Associations between Vestibular Pathologies and Hypothyroidism: A Retrospective Study.

The association between vestibular pathologies and thyroid hormone disorders has been known for several decades. However, very little information is available on the types of vestibular symptoms that may be affected by altered thyroid hormone levels. The aim of this study was to provide patient data in order to identify statistical associations between vestibular pathologies and thyroid hormone disorders. A retrospective review of the records of 422 patients seen for physiotherapy treatment of vertigo was carried out. Statistical analysis of the data was performed using logistic regression, providing Chi2 and Odds Ratio statistics. Our results show that hypothyroidism statistically significantly increases the expression of certain symptoms, such as vestibular instability and gait disorders, in vestibular pathologies such as Menière's disease or central vertigo. By analyzing patient data, our study provides new evidence of dependence between altered thyroid status and the expression of vestibular pathologies.

Use of video-electroencephalography as a first-line examination in veterinary neurology: development and standardization of electroencephalography in unsedated dogs and cats.

Objective: To assess the feasibility and validate the use of video-electroencephalography (EEG) in conscious dogs and cats and to propose guidelines of routine EEG in veterinary clinical practice. Design: Prospective clinical study. Data: One hundred and fifty EEG recordings were carried out to validate the clinical adding-value, reproducibility, and guidelines on 140 owned animals. One hundred and one EEGs were performed on dogs and 49 on cats. Procedures: We compared recordings performed with 8 EEG unwired stud Ag/AgCl electrodes held by elastic straps and 8 EEG wired cup Ag electrodes held by a tailor-made manufactured headset combined with a wired video-EEG device. Electrodes placement was determined according to previously published animal EEG protocols. Physiological sensors, such as electrocardiography, electromyography, and respiratory sensors were added. Stimulation protocols were tested. Quality and interpretability were evaluated. Results: Headsets and recording procedures appeared suitable for all skull shapes and sizes. Video-EEG recordings were successfully performed without tranquilization or anesthesia except for 9 animals. Median EEG recordings time was 40 min. Impedance remained below 20 kΩ in 99% of dog EEGs and 98% of cat EEGs. Isosynchrony was reported in 6% of the channels. Seventy-five percent of dog EEGs and 83% of cat EEGs were readable for more than 50% (to 100%) of their duration. Successful discrimination of vigilance states from rhythm analysis (wakefulness, drowsiness, and sleepiness) was possible in 99% of dog EEGs and 91% of cat EEGs. Photic driving responses during photic stimulations were observed in 11% of dog EEGs and 85% of cat EEGs. Electroencephalography recordings were directly informative in 32% of the examinations: in 25% EEG abnormalities were associated with clinical signs and 7% concerned EEG abnormalities without clinical symptoms during recording. Thirteen percent of dogs subjected to photic stimulation exhibited epileptic anomalies. Among 9 EEGs with other history-based stimulations, three displayed epileptic graphoelements. Conclusions: We have developed a standardized unanesthetized video-EEG procedure easily performed and reproducible in dogs and cats. Qualitative and quantitative technical and medical criteria were evaluated and were in accordance with human EEG recommendations. Moreover, we have demonstrated its relevance and accuracy for diagnostic purposes, providing further arguments for the use of EEG as a first-line neurological functional exploration test.

Evaluation of taVNS for extreme environments: an exploration study of health benefits and stress operationality.

Introduction: Long-duration space missions will be a real challenge for maintaining astronauts' adaptability. Research on transcutaneous vagus nerve stimulation (taVNS) is expanding rapidly, and its modalities constitute a major research challenge. A growing number of reviews stress the need to validate biomarkers for monitoring effects to enhance our understanding of the processes by which taVNS acts. Heart rate variability (HRV) appears to be a relevant candidate that informs on the autonomic nervous system (ANS). This is a promising technique to minimize the pathogenic effects of such large-scale missions and thus might be a relevant countermeasure. This study aimed to investigate the impact of taVNS on cognitive, psychological, and physiological functioning, including ANS functioning, and the benefits of increasing the number of taVNS sessions. Method: A total of 44 healthy participants were randomly assigned to one of the two cross-over protocols: a single session protocol (one taVNS and one sham simulation) or a repeated session protocol (three taVNS and three sham simulations). Cognitive, psychological, and physiological measures were performed before (pre) and after (post) each intervention. Sleep monitoring was only recorded before the first and after the last intervention in each protocol. For the repeated session protocol only, participants were allocated to two groups according to their parasympathetic activation gain during the three interventions: high parasympathetic delta (HPd) and low parasympathetic delta (LPd). Results: Participants in the repeated session protocol increased their HRV, cognitive performance, and sleep efficiency. In particular, taVNS induced higher parasympathetic activation and cardiac flexibility compared to the sham simulation in the repeated session protocol. Nevertheless, the perception of stress may indicate a nocebo effect of the repeated session. The HPd profile had higher interoceptive awareness, HRV highlighted by non-linear measures, and cognitive performance, but presented a decrease in some indicators of sleep efficiency compared to the LPd profile. Conclusion: taVNS seems to induce positive health outcomes, especially when the stimulation is repeated three times per week. Our findings highlight the benefits of parasympathetic activation during taVNS on psychophysiological and cognitive functioning. Further research is needed to validate these results on a large sample, using longitudinal measures over several months. This intervention appears promising as a countermeasure to extreme missions and occupations.

Chronic Vestibular Hypofunction Is Associated with Impaired Sleep: Results from the DizzyReg Patient Registry.

Temporary or permanent vestibular hypofunction has been hypothesized to affect circadian rhythm, sleep, and thermoregulation. Chronic or long-term vestibular disorders such as unilateral vestibular hypofunction may have an even greater negative impact on sleep quality than acute vestibular problems. This study examines self-reported sleep quality, as assessed by the Pittsburgh Sleep Quality Index (PSQI), and its association with vestibular symptom duration in a group of patients with vestibular disorders. We used data from the cross-sectional DizzyReg patient registry of the German Center for Vertigo and Balance Disorders outpatient clinic. Vestibular diagnoses were ascertained based on the International Classification of Vestibular Disorders. A total of 137 patients were included (60% female, mean age 55.4 years, standard deviation, SD, 16.7). The mean PSQI total score was 6.3 (SD = 3.2), with 51% reporting overall poor sleep quality. Patients who had vertigo for two years or longer reported significantly poorer global sleep quality (63% vs. 37%, p = 0.021) and significantly more difficulties with sleep latency (79% vs. 56%, p = 0.013) and sleep efficiency (56% vs. 34%, p = 0.022). The association of poor sleep quality with a longer duration of vertigo remained significant after multivariable adjustment. Further research should investigate the interaction of vestibular disorders, sleep, and their potential mechanisms.

Ultrasound assessments of organs and blood vessels before and after 40 days isolation in a cavern (deep time experiment 2021).

Introduction: Spaceflight simulation studies like confinement in small volume habitat with limited physical activity have reported even after 60 days an abnormal arterial wall adaptation with increase thickness or stiffness. The purpose of the current study was to determine the effects on blood vessel and organ structure of 40 days of isolation in a huge habitat with intensive physical activity. Method: Data were collected from 14 individuals (7 male) who isolated in a cavern for 40-days while performing normal daily activities without time references. Ultrasound assessments were performed pre- and post-isolation using a teleoperated system with eight different acoustic windows to obtain 19 measurements on 12 different organ/vascular structures which included the common carotid artery, femoral artery, tibial artery, jugular vein, portal vein, bile duct, kidney, pancreas, abdominal aorta, cervical and lumbar vertebral distance, and Achilles tendon. Results: Common carotid artery measures, including the intima media thickness, stiffness index, and the index of reflectivity measured from the radiofrequency signal, were not changed with isolation. Similarly, no differences were found for femoral artery measurements or measurements of any of the other organs/vessels assessed. There were no sex differences for any of the assessments. Discussion: Results from this study indicate a lack of physiological effects of 40-days of isolation in a cavern, contrary to what observed in previous 60 days confinement. This suggests a potential protective effect of sustained physical activity, or reduced environmental stress inside the huge volume of the confined facility.

Vestibular Disorders and Hormonal Dysregulations: State of the Art and Clinical Perspectives.

The interaction between endocrine and vestibular systems remains poorly documented so far, despite numerous observations in humans and animals revealing direct links between the two systems. For example, dizziness or vestibular instabilities often accompany the menstrual cycle and are highly associated with the pre-menopause period, while sex hormones, together with their specific receptors, are expressed at key places of the vestibular sensory network. Similarly, other hormones may be associated with vestibular disorders either as causal/inductive factors or as correlates of the pathology. This review was carried out according to the PRISMA method, covering the last two decades and using the MEDLINE and COCHRANE databases in order to identify studies associating the terms vestibular system and/or vestibular pathologies and hormones. Our literature search identified 646 articles, 67 of which referred directly to vestibular dysfunction associated with hormonal variations. While we noted specific hormonal profiles depending on the pathology considered, very few clinical studies attempted to establish a direct link between the expression of the vestibular syndrome and the level of circulating hormones. This review also proposes different approaches to shed new light on the link between hormones and vestibular disorders, and to improve both the diagnosis and the therapeutic management of dizzy patients.

Vertigoheel improves central vestibular compensation after unilateral peripheral vestibulopathy in rats.

The aim of this study was to assess the effect of Vertigoheel on central vestibular compensation and cognitive deficits in rats subjected to peripheral vestibular loss. Young adult male Long Evans rats were subjected to bilateral vestibular insults through irreversible sequential ototoxic destructions of the vestibular sensory organs. Vestibular syndrome characteristics were monitored at several time points over days and weeks following the sequential insults, using a combination of behavioral assessment paradigms allowing appreciation of patterns of change in static and dynamic deficits, together with spatial navigation, learning, and memory processes. Vertigoheel administered intraperitoneally significantly improved maximum body velocity and not moving time relative to its vehicle control on days 2 and 3 and on day 2, respectively, after unilateral vestibular lesion (UVL). It also significantly improved postural control relative to its vehicle 1 day after UVL. Conversely, Vertigoheel did not display any significant effect vs. vehicle on the severity of the syndrome, nor on the time course of other examined parameters, such as distance moved, mean body velocity, meander, and rearing. Spatial cognition testing using Y- and T-maze and eight-radial arm maze did not show any statistically significant difference between Vertigoheel and vehicle groups. However, Vertigoheel potentially enhanced the speed of learning in sham animals. Evaluating Vertigoheel's effect on thigmotaxis during the open-field video tracking test revealed no significant difference between Vertigoheel and its vehicle control groups suggesting that Vertigoheel does not seem to induce sedative or anxiolytic effects that could negatively affect vestibular and memory function. Present observations reveal that Vertigoheel improves central vestibular compensation following the unilateral peripheral vestibular loss as demonstrated by improvement of specific symptoms.

Study of the Kinetics of the Determinants of Performance During a Mountain Ultramarathon: Multidisciplinary Protocol of the First Trail Scientifique de Clécy 2021.

BACKGROUND: The growing interest of the scientific community in trail running has highlighted the acute effects of practice at the time of these races on isolated aspects of physiological and structural systems; biological, physiological, cognitive, and muscular functions; and the psychological state of athletes. However, no integrative study has been conducted under these conditions with so many participants and monitoring of pre-, per-, and postrace variables for up to 10 days over a distance close to 100 miles. OBJECTIVE: The aim of this study was to evaluate the kinetics of the performance parameters during a 156 km trail run and 6000 m of elevation gain in pre-, per-, and postrace conditions. The general hypothesis is based on significant alterations in the psychological, physiological, mechanical, biological, and cognitive parameters. METHODS: The Trail Scientifique de Clécy took place on November 11, 2021. This prospective experimental study provides a comprehensive exploration of the constraints and adaptations of psychophysiological and sociological variables assessed in real race conditions during a trail running of 156 km on hilly ground and 6000 m of elevation gain (D+). The study protocol allowed for repeatability of study measurements under the same experimental conditions during the race, with the race being divided into 6 identical loops of 26 km and 1000 m D+. Measurements were conducted the day before and the morning of the race, at the end of each lap, after a pit stop, and up to 10 days after the race. A total of 55 participants were included, 43 (78%) men and 12 (22%) women, who were experienced in ultra-trail-running events and with no contraindications to the practice of this sport. RESULTS: The launch of the study was authorized on October 26, 2021, under the trial number 21-0166 after a favorable opinion from the Comité de Protection des Personnes Ouest III (21.09.61/SIRIPH 2G 21.01586.000009). Of the 55 runners enrolled, 41 (75%) completed the race and 14 (25%) dropped out for various reasons, including gastric problems, hypothermia, fatigue, and musculoskeletal injuries. All the measurements for each team were completed in full. The race times (ie, excluding the measurements) ranged from 17.8206 hours for the first runner to 35.9225 hours for the last runner. The average time to complete all measurements for each lap was 64 (SD 3) minutes. CONCLUSIONS: The Trail Scientifique de Clécy, by its protocol, allowed for a multidisciplinary approach to the discipline. This approach will allow for the explanation of the studied parameters in relation to each other and observation of the systems of dependence and independence. The initial results are expected in June 2022. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR1-10.2196/38027.

Hormones and Vestibular Disorders: The Quest for Biomarkers.

The vestibular system exerts control over various functions through neural pathways that are not yet fully mapped. Functional dysregulations or tissue lesions at different levels of the peripheral and the central vestibular networks can alter these different functions, causing a wide variety of symptoms, ranging from posturo-locomotor alterations to psychiatric syndromes such as PPPD, including the deregulation of the main biological functions. These different symptoms differ by their expression kinetics (they each appear and regress with their own kinetics) by the targets affected (muscles, organs, and brain areas) and by the sensitivity specific to each individual. Vestibular pathologies thus cover a mosaic of distinct effects, and they involve various effectors-which constitute the many markers of their different types and stages. It is therefore crucial, to predict the onset of a vertigo syndrome, to follow its temporal course, or to monitor the impact of therapeutic approaches, and to have specific and reliable biomarkers. Hormonal variations are among the possible sources of biomarkers for neurotology. We know that specific hormonal profiles can promote the appearance of vestibular disorders. We also know that the expression of vertigo syndrome is accompanied by measurable hormonal variations. The link between endocrine deregulation and vestibular alterations therefore no longer needs to be proven. However, there are still few data on their precise correlations with the vertigo syndrome. This study was undertaken with the aim to deliver an extensive review of the hormonal alterations linked to vestibular disorders. A review of the literature covering the last two decades was carried out using the MEDLINE and COCHRANE databases in order to identify studies associating the terms vestibular system or vestibular pathologies and hormones. Bibliographic data provides several outcomes in terms of therapeutic innovation in the diagnosis and therapeutic follow-up of vestibular pathologies.

Navigation strategies in patients with vestibular loss tested in a virtual reality T-maze.

During navigation, humans mainly rely on egocentric and allocentric spatial strategies, two different frames of reference working together to build a coherent representation of the environment. Spatial memory deficits during navigation have been repeatedly reported in patients with vestibular disorders. However, little is known about how vestibular disorders can change the use of spatial navigation strategies. Here, we used a new reverse T-maze paradigm in virtual reality to explore whether vestibular loss specifically modifies the use of egocentric or allocentric spatial strategies in patients with unilateral (n = 23) and bilateral (n = 23) vestibular loss compared to healthy volunteers (n = 23) matched for age, sex and education level. Results showed that the odds of selecting and using a specific strategy in the T-maze were significantly reduced in both unilateral and bilateral vestibular loss. An exploratory analysis suggests that only right vestibular loss decreased the odds of adopting a spatial strategy, indicating an asymmetry of vestibular functions. When considering patients who used strategies to navigate, we observed that a bilateral vestibular loss reduced the odds to use an allocentric strategy, whereas a unilateral vestibular loss decreased the odds to use an egocentric strategy. Age was significantly associated with an overall lower chance to adopt a navigation strategy and, more specifically, with a decrease in the odds of using an allocentric strategy. We did not observe any sex difference in the ability to select and use a specific navigation strategy. Findings are discussed in light of previous studies on visuo-spatial abilities and studies of vestibulo-hippocampal interactions in peripheral vestibular disorders. We discuss the potential impact of the history of the disease (chronic stage in patients with a bilateral vestibulopathy vs. subacute stage in patients with a unilateral vestibular loss), of hearing impairment and non-specific attentional deficits in patients with vestibular disorders.

4 Day in dry immersion reproduces partially the aging effect on the arteries as observed during 6 month spaceflight or confinement.

The objectives of this study were to determine whether 4 days of dry immersion (DI) induced similar arterial aging as spaceflight and to test the impact of thigh cuffs. Eighteen subjects underwent DI; nine wore thigh cuffs. Cardiac and arterial targets were assessed by ultrasound. No significant differences were found between the groups. The left ventricle volume, stroke volume (SV), and ejection fraction decreased with DI (p < 0.001). Carotid distensibility reduced (p < 0.05), carotid to femoral arterial tree became stiffer in 33% of the subjects, and femoral artery intima media thickness increased (p < 0.05). A reduction in plasma volume is likely to have caused the observed cardiac changes, whereas the arterial wall changes are probably best explained by hypokinesia and/or environmental stress. These changes are similar but lower in amplitude than those observed in spaceflight and mimic the natural aging effect on earth. The daytime-worn thigh cuffs had no acute or chronic impact on these arterial-focused measurements.

Motion Sickness Lessons from the Southern Ocean.

BACKGROUND: The objectives were to assess the prevalence, severity, and medication taken, and to look for predictive factors in order to better identify characteristics of passengers at risk of motion sickness during transport from Hobart in Tasmania to the French polar stations in Antarctica. METHODS: There were 239 passengers who were surveyed over 4 yr with 4 round trips per year using the Motion Sickness Susceptibility Questionnaire (MSSQ), Simulator Sickness Questionnaire (SSQ), state-trait anxiety test (STAI-Trait and STAI-State), and general parameters (age, gender, number of trips, jet-lag, direction of the trip), medication, calculation of the distance of each passengers cabin to the center of gravity (CoG). RESULTS: While the passengers had a low intrinsic sensitivity to motion sickness (MSSQ), 94 reported at least one SSQ symptom of motion sickness, and 38 vomited. Five associated factors were discovered: greater initial sensitivity (MSSQ), anticipation of being ill, younger age, higher level of anxiety at midtrip, and greater distance from the CoG. Of the passengers, there were 54 who took anti-motion sickness medication at different times of the trip, however, these passengers experienced more nausea. This could be due to self-selection since they were more sensitive to motion sickness. CONCLUSION: We identified three predictive factors of motion sickness (greater intrinsic susceptibility, younger age, and greater cabin distance from the CoG). For preventive purposes, two associated factors of MS (anticipation of being ill, MSSQ score) were determined to classify three groups of risk of MS to improve passenger care during the trip. Besnard S, Bois J, Hitier M, Vogt J, Laforet P, Golding JF. Motion sickness lessons from the Southern Ocean. Aerosp Med Hum Perform. 2021; 92(9):720727.

Impaired Attentional Processing During Parabolic Flight.

Previous studies suggest that altered gravity levels during parabolic flight maneuvers affect spatial updating. Little is known about the impact of the experimental setting and psychological stressors associated with parabolic flight experiments on attentional processes. To address this gap, we investigated the level of alertness, selective and sustained attention in 1 and 0 g using a Go/No-Go Continuous Performance Task. We also identified several parameters associated with the experimental set-up of a parabolic flight that could be expected to affect attentional processing. These included the use of scopolamine, sleep quality prior to the flight day, participant's stress level as well as mood and anxiety state before and after the parabolic flight. We observed a deterioration in attentional processing prior to the first parabola that was further aggravated in weightlessness and returned to baseline after the last parabola. Reaction Time, Hit and False Alarm Rate were moderately correlated with self-reported anxiety state, but not cortisol levels or emotional states. The use of scopolamine had minor effects on Reaction Time. Our results confirm previous studies reporting impairments of cognitive performance in 0 g, and highlight important aspects that should be considered for the design of behavioral research experiments in future parabolic flight campaigns.

Stratification of hippocampal electrophysiological activation evoked by selective electrical stimulation of different angular and linear acceleration sensors in the rat peripheral vestibular system.

It has become well established that vestibular information is important for hippocampal function and spatial memory. However, as yet, relatively little is known about how different kinds of vestibular information are 'represented' in different parts of the hippocampus. This study used selective electrical stimulation of each of the 5 vestibular sensors (the horizontal (HC), anterior (AC) and posterior (PC) semi-circular canals, and the utricle and saccule) in the rat and recorded local field potentials (LFPs) across the hippocampus, using a 16 electrode microarray. We found that stimulation of any vestibular sensor in the left labyrinth evoked triphasic LFPs in both hippocampi, although it was clear that, in general, the amplitudes were greater for the right, contralateral side. This was particularly true for Phase 1 for the HC, AC, utricle and saccule, Phase 2 for the HC, PC, utricle and saccule, and Phase 3 for the AC, PC and saccule. Overall, our results suggest that vestibular input to the hippocampus is bilateral, preferentially contralateral, but highly stratified in that stimulation of the same vestibular sensor results in activation of different specific areas of the hippocampus, with different LFP amplitudes and latencies. This suggests the possibility that different regions of the hippocampus use different kinds of vestibular information for different purposes and that there may be a high degree of redundancy in the representation of vestibular input, perhaps ensuring that the hippocampus is more robust to the partial loss of vestibular information.

Electroencephalographic Abnormalites in SARS-CoV-2 Patients.

Viral infection with SARS-CoV-2 has a neurological tropism that may induce an encephalopathy. In this context, electroencephalographic exploration (EEG) is indicated as a diagnostic argument correlated with lumbar puncture, biology, and imaging. We performed a retrospective analysis of 42 patients explored by EEG and infected by COVID-19, according to the EEG abnormalities and clinical signs that motivated the examination. Confusion and epileptic seizures were the most common clinical indications, with 64% of the patients displaying these symptoms. The EEG was altered in 85% of the cases of confusion, in 57% of the cases of epileptic symptoms (general or focal seizure or prolonged loss of contact) and 20% of the cases of malaise or brief loss of consciousness. Nine EEG (21%) were in favor of an encephalopathy, two had de novo alterations in persistent consciousness and two had alterations in general states of confusion; one was very agitated and without history of epilepsy and combined eyelids clonia while a second one exhibited unconsciousness with left hemicorpus clonus. Two were being investigated for delayed awakening without sedation for more than 24 h. All of these patients were diagnosed COVID-19, some of them with associated mild to severe respiratory disorders. This work shows the interest of the EEG in exploring COVID-19 patients suffering from neurological or general symptoms looking for cerebral alteration.

Thigh Cuff Effects on Venous Flow Redistribution During 4 Days in Dry Immersion.

PURPOSE: The objective was to quantify the venous redistribution during a 4-d dry immersion (DI) and evaluate the effect of thigh cuffs.METHODS: The study included nine control (Co) and nine subjects wearing thigh cuffs during the daytime (CU). Ultrasound measures were performed Pre-DI, on day 4 AM (D4 AM) and D4 PM: left ventricle stroke volume and ejection fraction (SV, EF), jugular vein volume (JVvol), portal vein diameter (PV), and middle cerebral vein velocity (MCVv). An additional measure of JVvol was performed on Day 1 after 2 h in DI.RESULTS: After 2 h in DI, JVvol increased significantly from Pre in both groups, but increased more in the Co compared to the CU subjects (Co: 0.27 0.15 cm³ to 0.94 0.22 cm³; CU: 0.32 0.13 cm³ to 0.64 0.32 cm³). At D4 AM, SV and EF decreased from Pre (SV: 111 23 cm³ to 93 24 cm³; EF: 0.66 0.07 to 0.62 0.07). JVvol was slightly increased (Co: 0.47 0.22 cm³ CU: 0.35 014 cm³). MCVv and PV remained unchanged from Pre-DI. No difference was found between the two groups for any of the parameters measured. From D4 AM to PM, no significant change was observed for any parameter.CONCLUSION: The results confirm that DI induces, during the first 2-3 h, a significant cephalic fluid shift as observed in spaceflight. During this early phase, the thigh cuffs reduced the amplitude of the fluid shift toward the head, but after 4 d in DI there was only a slight memory (residual) effect of DI on the jugular volume and no residual effect of the thigh cuffs.Arbeille P, Greaves D, Guillon L, Besnard S. Thigh cuff effects on venous flow redistribution during 4 days in dry immersion. Aerosp Med Hum Perform. 2020; 91(9):697702.

Vestibular Modulation of Long-Term Potentiation and NMDA Receptor Expression in the Hippocampus.

Loss of vestibular function is known to cause spatial memory deficits and hippocampal dysfunction, in terms of impaired place cell firing and abnormal theta rhythm. Based on these results, it has been of interest to determine whether vestibular loss also affects the development and maintenance of long-term potentiation (LTP) in the hippocampus. This article summarizes and critically reviews the studies of hippocampal LTP following a vestibular loss and its relationship to NMDA receptor expression, that have been published to date. Although the available in vitro studies indicate that unilateral vestibular loss (UVL) results in reduced hippocampal field potentials in CA1 and the dentate gyrus (DG), the in vivo studies involving bilateral vestibular loss (BVL) do not. This may be due to the differences between UVL and BVL or it could be a result of in vitro/in vivo differences. One in vitro study reported a decrease in LTP in hippocampal slices following UVL; however, the two available in vivo studies have reported different results: either no effect or an increase in EPSP/Population Spike (ES) potentiation. This discrepancy may be due to the different high-frequency stimulation (HFS) paradigms used to induce LTP. The increased ES potentiation following BVL may be related to an increase in synaptic NMDA receptors, possibly increasing the flow of vestibular input coming into CA1, with a loss of selectivity. This might cause increased excitability and synaptic noise, which might lead to a degradation of spatial learning and memory.

The effects of selective electrical stimulation of the rat cochlea on hippocampal field potentials.

The hippocampus is a brain structure well known for its importance to spatial learning and memory. As such it is assumed to use multisensory integration in order to generate mathematical maps of the spatial environment. Auditory inputs to the hippocampus have been described to a limited extent. Although it has been demonstrated that natural auditory stimulation can evoke local field potentials (LFPs) and single neuron responses in the hippocampus, and that noise trauma and tinnitus can cause maladaptive hippocampal plasticity, to the best of our knowledge no one has selectively, electrically stimulated the cochlea and recorded electrophysiological responses in the hippocampus. Here, we used unilateral electrical cochlear stimulation in rats while recording LFPs in the hippocampus bilaterally, with a multi-electrode array. We observed triphasic LFP responses bilaterally from unilateral stimulation, but with larger amplitudes on the contralateral side, especially for Phase 1 and 3 of the LFP, for which the latencies were also longer. The latencies under urethane anaesthesia were consistent with auditory information from the cochlea travelling across approximately 6-7 synapses. These data demonstrate that the cochlea contributes a powerful auditory input to the hippocampus, which is also lateralized, and may have implications for spatial cognition in cochlear implant patients.