Thermoregulation in multiple sclerosis

Trends in mortality due to multiple sclerosis in the United States: A retrospective analysis from 1999 to 2020

BACKGROUND

Multiple sclerosis (MS) is a neuroinflammatory condition with a prevalence of about 309.2 per 100,000 people in the United States. We aim to identify MS-related mortality trends in the USA from 1999 to 2020, stratified by age, sex, race, and geography, and its correlation with sunlight.

METHODS

Death certificates from the CDC-WONDER database were examined for adults aged ≥25 years. Crude rates (CR) and age-adjusted mortality rates (AAMRs) per 1,000,000 persons and annual percent change (APC) were calculated. We also retrieved data for daily sunlight from 1999 to 2011.

RESULTS

From 1999 to 2020, a total of 121,694 deaths occurred due to MS. The AAMR rose from 23.6 in 1999 to 29.7 in 2020 (APC 0.65), with a stable trend till 2018 (APC -0.22) followed by an abrupt increase towards 2020 (APC 9.27). Women had higher AAMR than men. Non-Hispanic (NH) Whites exhibited the highest AAMR (28.5), followed by NH Blacks (25.9), NH American Indians/Alaska Natives (9.6), Hispanics or Latino (6.8), and NH Asian or Pacific Islanders (1.9). AAMRs also varied substantially by region (Midwest: 32.4; Northeast: 26.9; West: 26.2; South: 19.4). States with the highest AAMRs were Montana, Wyoming, Colorado, and Oregon. The states with lower daily sunlight had higher AAMRs (r = -0.559, p = 0.000). AAMRs were comparable in urban (25) and rural (26.3) areas. Most deaths occurred in medical facilities (33.92 %) and nursing homes / long-term care (30.80 %), followed by home (27.79 %), and hospice (4.06 %). Adults ≥ 65 years depicted the highest mortality rates (CR 64.4) while adults aged 25 to 44 years showed the lowest rates (CR 4.6).

CONCLUSION

We found an overall stable trend in MS-related mortality rates in the US till 2018 with a sharp increase thereafter. We observed highest mortality among women and NH White adults, among residents of Midwest and Northeast regions, and among adults ≥ 65 years. Higher disease burden in recent years calls for devising timely policies focused on these high-risk populations.

Acute Clinical Events Identified as Relapses With Stable Magnetic Resonance Imaging in Multiple Sclerosis

Importance

Understanding the association between clinically defined relapses and radiological activity in multiple sclerosis (MS) is essential for patient treatment and therapeutic development.

Objective

To investigate clinical events identified as relapses but not associated with new T2 lesions or gadolinium-enhanced T1 lesions on brain and spinal cord magnetic resonance imaging (MRI).

Design, Setting, and Participants

This multicenter observational cohort study was conducted between January 2015 and June 2023. Data were extracted on June 8, 2023, from the French MS registry. All clinical events reported as relapses in patients with relapsing-remitting MS were included if brain and spinal cord MRI was performed within 12 and 24 months before the event, respectively, and 50 days thereafter with gadolinium injection.

Exposures

Events were classified as relapses with active MRI (RAM) if a new T2 lesion or gadolinium-enhanced T1 lesion appeared on brain or spinal cord MRI or as acute clinical events with stable MRI (ACES) otherwise.

Main Outcomes and Measures

Factors associated with ACES were investigated; patients with ACES and RAM were compared regarding Expanded Disability Status Scale (EDSS) course, relapse rate, confirmed disability accrual (CDA), relapse-associated worsening (RAW), progression independent of relapse activity (PIRA), and transition to secondary progressive (SP) MS, and ACES and RAM rates under each disease-modifying therapy (DMT) were estimated.

Results

Among 31 885 clinical events, 637 in 608 patients (493 [77.4%] female; mean [SD] age, 35.8 [10.7] years) were included. ACES accounted for 166 (26.1%) events and were more likely in patients receiving highly effective DMTs, those with longer disease duration (odds ratio [OR], 1.04; 95% CI, 1.01-1.07), or those presenting with fatigue (OR, 2.14; 95% CI, 1.15-3.96). ACES were associated with significant EDSS score increases, lower than those found for RAM. Before the index event, patients with ACES experienced significantly higher rates of relapse (relative rate [RR], 1.21; 95% CI, 1.01-1.46), CDA (hazard ratio [HR], 1.54; 95% CI, 1.13-2.11), and RAW (HR, 1.72; 95% CI, 1.20-2.45). Patients with ACES were at significantly greater risk of SP transition (HR, 2.58; 95% CI, 1.02-6.51). Although RAM rate decreased with DMTs according to their expected efficacy, ACES rate was stable across DMTs.

Conclusions and Relevance

The findings in this study introduce the concept of ACES in MS, which accounted for one-fourth of clinical events identified as relapses.

Sleeping for One Week on a Temperature-Controlled Mattress Cover Improves Sleep and Cardiovascular Recovery

Body temperature should be tightly regulated for optimal sleep. However, various extrinsic and intrinsic factors can alter body temperature during sleep. In a free-living study, we examined how sleep and cardiovascular health metrics were affected by sleeping for one week with (Pod ON) vs. without (Pod OFF), an active temperature-controlled mattress cover (the Eight Sleep Pod). A total of 54 subjects wore a home sleep test device (HST) for eight nights: four nights each with Pod ON and OFF (>300 total HST nights). Nightly sleeping heart rate (HR) and heart rate variability (HRV) were collected. Compared to Pod OFF, men and women sleeping at cooler temperatures in the first half of the night significantly improved deep (+14 min; +22% mean change; p = 0.003) and REM (+9 min; +25% mean change; p = 0.033) sleep, respectively. Men sleeping at warm temperatures in the second half of the night significantly improved light sleep (+23 min; +19% mean change; p = 0.023). Overall, sleeping HR (-2% mean change) and HRV (+7% mean change) significantly improved with Pod ON (p < 0.01). To our knowledge, this is the first study to show a continuously temperature-regulated bed surface can (1) significantly modify time spent in specific sleep stages in certain parts of the night, and (2) enhance cardiovascular recovery during sleep.

Whole-Body Cryostimulation in Multiple Sclerosis: A Scoping Review

Multiple sclerosis (MS) is the most common cause of non-traumatic long-term disability in young adults. Whole-body cryostimulation (WBC) is a cold-based physical therapy known to induce physiological exercise-mimicking changes in the cardiovascular, neuromuscular, immune, and endocrine systems and to influence functional and psychological parameters by exposing the human body to cryogenic temperatures (≤-110 °C) for 2-3 min. The purpose of this scoping review is to present an overall view on the potential role of WBC as an adjuvant therapy in the treatment of MS. PubMed, ScienceDirect, Embase, and Web of Science were searched up to 30 November 2023, and a total of 13 articles were included. WBC may have beneficial antioxidant effects as a short-term adjuvant treatment in MS. There were no significant changes in antioxidant enzymes, nitric oxide levels, metalloproteinase levels, blood counts, rheology, and biochemistry. WBC can lead to a reduction in fatigue and an improvement in functional status, with a significant effect on both mental and physical well-being. There were no reported adverse effects. The results suggest that WBC may complement therapeutic options for patients with MS, as the effects of cryogenic cold stimulation have been shown to activate antioxidant processes and improve functional status, mood, anxiety, and fatigue.

Understanding the spectrum of non-motor symptoms in multiple sclerosis: insights from animal models

Multiple sclerosis is a chronic autoimmune disease of the central nervous system and is generally considered to be a non-traumatic, physically debilitating neurological disorder. In addition to experiencing motor disability, patients with multiple sclerosis also experience a variety of non-motor symptoms, including cognitive deficits, anxiety, depression, sensory impairments, and pain. However, the pathogenesis and treatment of such non-motor symptoms in multiple sclerosis are still under research. Preclinical studies for multiple sclerosis benefit from the use of disease-appropriate animal models, including experimental autoimmune encephalomyelitis. Prior to understanding the pathophysiology and developing treatments for non-motor symptoms, it is critical to characterize the animal model in terms of its ability to replicate certain non-motor features of multiple sclerosis. As such, no single animal model can mimic the entire spectrum of symptoms. This review focuses on the non-motor symptoms that have been investigated in animal models of multiple sclerosis as well as possible underlying mechanisms. Further, we highlighted gaps in the literature to explain the non-motor aspects of multiple sclerosis in experimental animal models, which will serve as the basis for future studies.

The Finger Dexterity Test: Validation study of a smartphone-based manual dexterity assessment

BACKGROUND

The Nine-Hole Peg Test (9HPT) is the golden standard to measure manual dexterity in people with multiple sclerosis (MS). However, administration requires trained personnel and dedicated time during a clinical visit.

OBJECTIVES

The objective of this study is to validate a smartphone-based test for remote manual dexterity assessment, the icompanion Finger Dexterity Test (FDT), to be included into the icompanion application.

METHODS

A total of 65 MS and 81 healthy subjects were tested, and 20 healthy subjects were retested 2 weeks later.

RESULTS

The FDT significantly correlated with the 9HPT (dominant: ρ = 0.62, p < 0.001; non-dominant: ρ = 0.52, p < 0.001). MS subjects had significantly higher FDT scores than healthy subjects (dominant: p = 0.015; non-dominant: p = 0.013), which was not the case for the 9HPT. A significant correlation with age (dominant: ρ = 0.46, p < 0.001; non-dominant: ρ = 0.40, p = 0.002), Expanded Disability Status Scale (EDSS, dominant: ρ = 0.36, p = 0.005; non-dominant: ρ = 0.31, p = 0.024), and disease duration for the non-dominant hand (ρ = 0.31, p = 0.016) was observed. There was a good test-retest reliability in healthy subjects (dominant: r = 0.69, p = 0.001; non-dominant: r = 0.87, p < 0.001).

CONCLUSIONS

The icompanion FDT shows a moderate-to-good concurrent validity and test-retest reliability, differentiates between the MS subjects and healthy controls, and correlates with clinical parameters. This test can be implemented into routine MS care for remote follow-up of manual dexterity.

Individual perception of environmental factors that influence lower limbs spasticity in inherited spastic paraparesis

BACKGROUND

Phenotypic variability is a consistent finding in neurogenetics and therefore applicable to hereditary spastic paraparesis. Identifying reasons for this variability is a challenge. We hypothesized that, in addition to genetic modifiers, extrinsic factors influence variability.

OBJECTIVES

Our aim was to describe the clinical variability in hereditary spastic paraparesis from the person's perspective. Our goals were to identify individual and environmental factors that influence muscle tone disorders and derive interventions which could improve spasticity.

METHODS

This study was based on self-assessments with questions on nominal and ordinal scales completed by participants with hereditary spastic paraparesis. A questionnaire was completed either in-person in the clinic or electronically via lay organization websites.

RESULTS

Among the 325 responders, most had SPG4/SPAST (n = 182, 56%) with a mean age at onset of 31.7 (SD 16.7) years and a mean disease duration of 23 (SD 13.6) years at the time of participation. The 2 factors identified as improving spasticity for > 50% of the responders were physiotherapy (193/325, 59%), and superficial warming (172/308, 55%). Half of the responders (n = 164, 50%) performed physical activity at least once a month and up to once a week. Participants who reported physiotherapy as effective were significantly more satisfied with ≥ 3 sessions per week. Psychologically stressful situations (246/319, 77%) and cold temperatures (202/319, 63%) exacerbated spasticity for most participants.

CONCLUSION

Participants perceived that physiotherapy reduced spasticity and that the impact of physiotherapy on spasticity was much greater than other medical interventions. Therefore, people should be encouraged to practice physical activity at least 3 times per week. This study reported participants' opinions: in hereditary spastic paraparesis only functional treatments exist, therefore the participant's expertise is of particular importance.

Autonomic nervous system disorders in multiple sclerosis

Multiple sclerosis (MS) is a chronic progressive demyelinating disease of the central nervous system (CNS), which also affects the autonomic nervous system (ANS). Manifestations of MS in the ANS include urological, sexual, gastrointestinal, cardiovascular, and thermoregulatory disorders as well as increased fatigue. These problems are common yet are often underestimated due to the non-specificity of the symptoms and the limited evaluation of the ANS in the usual clinical practice. Most of these symptoms seem to be related to localized lesions in the CNS. However, the mechanisms by which these disorders are caused in MS have not been fully investigated, thus preventing any focused etiological treatment. The most common disorders of the ANS in MS represent a challenge for clinicians due to the variability of the clinical picture and our minimal data on their diagnosis and treatment. Early diagnosis and initiation of individualized treatment regimens, often in need of multiple approaches, seem to yield the best results in managing ANS dysfunction in MS patients.

Body temperatures, thermal comfort, and neuropsychological responses to air temperatures ranging between 12°C and 39°C in people with Multiple Sclerosis

The negative effects of thermal stress on Multiple Sclerosis (MS)' symptoms have long been known. However, the underlying mechanisms of MS heat and cold intolerance remain unclear. The aim of this study was to evaluate body temperatures, thermal comfort, and neuropsychological responses to air temperatures between 12 to 39°C in people with MS compared to healthy controls (CTR). Twelve MS (5 males/7 females; age: 48.3±10.8 years; EDSS range: 1-7) and 11 CTR participants (4 males /7 females; age: 47.5±11.3 years) underwent two 50-min trials in a climatic chamber. Air temperature was ramped from 24°C to either 39°C (HEAT) or 12°C (COLD) and we continuously monitored participants' mean skin (T_sk) and rectal temperatures (T_rec), heart rate and mean arterial pressure. We recorded participants' self-reported thermal sensation and comfort, mental and physical fatigue, and we assessed their cognitive performance (information processing). Changes in mean T_sk and T_rec did not differ between MS and CTR neither during HEAT nor COLD. However, at the end of the HEAT trial, 83% of MS participants and 36% of CTR participants reported being "uncomfortable". Furthermore, self-reports of mental and physical fatigue increased significantly in MS but not CTR (p<0.05), during both HEAT and COLD. Information processing was lower in MS vs. CTR (p<0.05); yet this cognitive impairment was not exacerbated by HEAT nor COLD (p>0.05). Our findings indicate that neuropsychological factors (i.e. discomfort and fatigue) could contribute to MS heat and cold intolerance in the absence of deficits in the control of body temperature.

Multiple sclerosis-related heat sensitivity linked to absence of DMT prescription and subjective hand impairment but not autonomic or corticospinal dysfunction

OBJECTIVES

Heat sensitivity (HS) describes a temporary worsening of multiple sclerosis (MS) symptoms with increased body temperature. The pathophysiology may relate to central nervous system conduction deficits and autonomic dysfunction. We conducted deep clinical phenotyping of a cohort of persons with MS to identify predictors of HS.

METHODS

We recruited 59 MS participants with HS or No HS. Participants self-reported symptom severity (Hospital Anxiety and Depression Scale, Multiple Sclerosis Impact Scale, and fatigue visual analog scale) and underwent maximal exercise and transcranial magnetic stimulation testing to characterize autonomic and corticospinal function. We examined associations with HS using binomial logistic regression.

RESULTS

People with HS (36/59) had significantly greater disability, depression, fatigue, and physical and psychological functional effects of MS. They also had significantly lower corticospinal excitability but not conduction. After controlling for disease-modifying therapy (DMT), disability, and disease type, self-reported difficulty using hands in everyday tasks was significantly associated with a large increase in the odds of HS. Autonomic and corticospinal dysfunction were not associated with HS. Lack of DMT use alone was also associated with a large increase in the odds of HS.

DISCUSSION

Following a comprehensive assessment of plausible contributors to HS, HS was most strongly associated with lack of a DMT prescription and self-reported hand dysfunction. Surprisingly, objective measurement of autonomic and corticospinal integrity did not contribute to HS.

Clinical-Radiological Mismatch in Multiple Sclerosis Patients during Acute Relapse: Discrepancy between Clinical Symptoms and Active, Topographically Fitting MRI Lesions

BACKGROUND

Relapses in multiple sclerosis (MS) patients are usually defined as subacute clinical symptoms that last for at least 24 h. To validate a clinical relapse on magnetic resonance imaging (MRI), an anatomically fitting lesion with gadolinium enhancement in the central nervous system (CNS) would be mandatory. The aim of this study was to validate clinical relapses in regard to the concomitant detection of active, anatomically fitting MRI lesions.

METHODS

We performed a retrospective analysis of 199 MS patients with acute relapse who had received an MRI scan before the initiation of methylprednisolone (MPS) therapy. Clinical data and MRIs were systematically reanalyzed by correlating clinical symptoms with their anatomical representation in the CNS. Patients were then categorized into subgroups with a clinical-radiological match (group 1) or clinical-radiological mismatch (group 2) between symptoms and active, topographically fitting lesions and further analyzed in regard to clinical characteristics.

RESULTS

In 43% of our patients, we observed a clinical-radiological mismatch (group 2). Further analysis of patient characteristics showed that these patients were significantly older at the time of relapse. MS patients in group 2 also showed a significantly longer disease duration and significantly more previous relapses when compared to group 1. Comparing symptom clusters, the appearance of motor dysfunction during the current relapse was significantly more frequent in group 2 than in group 1. The overall dose of MPS treatment was significantly lower in group 2 than in group 1 with a similar treatment response in both groups.

CONCLUSIONS

The substantial clinical-radiological mismatch during acute relapse in our study could be explained by several factors, including a psychosomatic component or disturbance of network connectivity. Alternatively, secondary progression or a diffuse neuro-inflammatory process might cause clinical symptoms, especially in older patients with a longer disease duration. As a consequence, treatment of clinical relapses and the definition of breakthrough disease should be reconsidered in regard to combined clinical and MRI criteria and/or additional biomarkers. Further studies are necessary to address the contribution of diffuse neuro-inflammation to the clinical presentation of symptoms.

Thermophysiological aspects of wearable robotics: Challenges and opportunities

Technological advancements in the last two decades have enabled development of a variety of mechanically supporting wearable robots (i.e. exoskeletons) that are transitioning to practice in medical and industrial settings. The feedback from industry and recent controlled studies is highlighting thermal discomfort as a major reason for the disuse of the devices and a substantial barrier to their long-term adoption. Furthermore, a brief overview of the devices and their intended applications reveals that many of the potential users are likely to face thermal comfort issues because of either high exertion or medically related high heat sensitivity. The aim of this review is to discuss these emerging thermal challenges and opportunities surrounding wearable robots. This review discusses mechanisms, potential solutions, and a platform for systematically measuring heat transfer inhibition caused by wearing of an exoskeleton. Lastly, the potential for substantial metabolic rate reduction provided by exoskeletons to reduce worker thermal strain in warm-to-hot conditions is also considered.

Thermoregulatory dynamics reveal sex-specific inflammatory responses to experimental autoimmune encephalomyelitis in mice: Implications for multiple sclerosis-induced fatigue in females

The course of multiple sclerosis (MS) is characterized by striking sex differences in symptoms such as fatigue and impaired thermal regulation, which are associated with aggravated systemic pro-inflammatory processes. The purpose of this study was to replicate these symptoms in experimental autoimmune encephalomyelitis (EAE) in C57BL/6 mice in the quest to advance the preclinical study of non-motor symptoms of MS. Male and female C57BL/6 mice exposed to a mild form of EAE were evaluated for the progression of clinical, behavioural, thermal, and inflammatory processes. We show higher susceptibility in females to EAE than males based on greater clinical score and cumulative disease index (CDI), fatigue-like and anxiety-like behaviours. Accordingly, infrared (IR) thermography indicated higher cutaneous temperatures in females from post-induction days 12-23. Females also responded to EAE with greater splenic and adrenal gland weights than males as well as sex-specific changes in pro- and anti-inflammatory cytokines. These findings provide the first evidence of a sex-specific thermal response to immune-mediated demyelination, thus proposing a non-invasive assessment approach of the psychophysiological dynamics in EAE mice. The results are discussed in relation to the thermoregulatory correlates of fatigue and how endogenously elevated body temperature without direct heat exposure may be linked to psychomotor inhibition in patients with MS.

The pathophysiology of motor fatigue and fatigability in multiple sclerosis

Multiple Sclerosis (MS) is a heterogeneous immune mediated disease of the central nervous system (CNS). Fatigue is one of the most common and disabling symptom of MS. It interferes with daily activities on the level of cognition and motor endurance. Motor fatigue can either result from lesions in cortical networks or motor pathways (“primary fatigue”) or it may be a consequence of detraining with subsequent adaptions of muscle and autonomic function. Programmed exercise interventions are used frequently to increase physical fitness in MS-patients. Studies investigating the effects of training on aerobic capacity, objective endurance and perceived fatigability have yielded heterogenous results, most likely due to the heterogeneity of interventions and patients, but probably also due to the non-uniform pathophysiology of fatigability among MS-patients. The aim of this review is to summarize the current knowledge on the pathophysiology of motor fatigability with special reference to the basic exercise physiology that underlies our understanding of both pathogenesis and treatment interventions.

Toxic Air Pollutants and Their Effect on Multiple Sclerosis: A Review Study

Toxic air pollutants are one of the main factors that have the effect of synergism to increase the incidence of multiple sclerosis (MS). This review aims to investigate the effects of toxic air pollutants on the occurrence of multiple sclerosis (MS). A narrative review of the literature was done from 2000 to 2022 based on various databases such as Google Scholar, Web of Science, Springer, PubMed, and Science Direct. In this study, according to the databases, three hundred and sixty articles were retrieved. Of these, 28 studies were screened after review and 14 full-text articles entered into the analysis process. Finally, 9 articles were selected in this study. According to the finding of this study, toxic air pollutants including polycyclic aromatic hydrocarbons (PAHs), heavy metals (HM), volatile organic compounds (VOCs), particulate matter (PM), and gases are the main agents that cause the development and spread of chronic diseases such as respiratory and cardiovascular diseases, chronic obstructive pulmonary disease (COPD), and multiple sclerosis. The result of this study showed that the main sources of emission of toxic air pollutants include industries, cars, power plants, and the excessive consumption of fossil fuels. In general, the inhalation of high concentration of toxic air pollutants can increase the risk of chronic diseases and multiple sclerosis.

Acute Thermoregulatory and Cardiovascular Response to Submaximal Exercise in People With Multiple Sclerosis

Background

Heat sensitivity occurs in a high percentage of people with multiple sclerosis (PwMS), in response to environmental or exercise-induced increase in body temperature. However, the kinetic and magnitude of adaptation of the internal load and of the core body temperature (CBT) to a submaximal continuous exercise has been poorly addressed in PwMS; this may be relevant for the brief exercise bouts usually occurring in normal daily life. The aim of this work was to evaluate whether multiple sclerosis influences the acute adaptation of the internal load, the CBT and the perceptual load in response to a constant submaximal work step.

Methods

CBT has been continuously monitored (0.5 Hz) by a validated wearable heat-flux sensor and electrocardiography was recorded (250 Hz) by a wearable device during a standard 6-minute walk test (6MWT) in 14 PwMS (EDSS, 4.7 ± 1.2; disease duration: 13.0 ± 10.2 years; m ± SD) and 14 age, sex and BMI-matched healthy subjects (HS). The rate of perceived exertion (RPE) of the lower limbs was assessed during the 6MWT by the Borg scale (6-20).

Results

As expected, PwMS walked a significantly shorter distance (361 ± 98 m) than the HS group (613 ± 62 m, p<0.001 vs PwMS). However, the kinetics of adaptation of CBT and the magnitude of CBT change from baseline did not differ between groups. Similarly, heart rate (HR) kinetics and HR change from baseline were comparable between groups during the 6MWT. Finally, lower limbs RPE gradually increased during the exercise test, but without significant differences between groups.

Conclusion

The internal load, the metabolic heat production, and the perceptive load due to a standard submaximal walking exercise seems to be preserved in PwMS, suggesting a comparable acute heat production and dissipation during exercise. Therefore, it is unlikely that the different distance achieved during the 6MWT may be caused by altered thermoregulatory responses to exercise. Rather, this appears to be a consequence of the known increased energy cost of locomotion in PwMS.

The importance of body core temperature evaluation in balneotherapy

It is not wrong to say that there are no application standards or best practices in balneotherapy considering traditional applications. There is not enough information about how changes in body temperature, duration, and frequency of exposure to heat affect therapeutic outcomes of balneotherapeutic applications. Body core temperature (BCT) is probably the best parameter for expressing the heat load of the body and can be used to describe the causal relationship between heat exposure and its effects. There are several reasons to take BCT changes into account; for example, it can be used for individualized treatment planning, defining the consequences of thermal effects, developing disease-specific approaches, avoiding adverse effects, and designing clinical trials. The reasons why BCT changes should be considered instead of conventional measures will be discussed while explaining the effects of balneotherapy in this article, along with a discussion of BCT measurement in balneotherapy practice.

Thermal dysregulation in patients with multiple sclerosis during SARS-CoV-2 infection. The potential therapeutic role of exercise

Thermoregulation is a homeostatic mechanism that is disrupted in some neurological diseases. Patients with multiple sclerosis (MS) are susceptible to increases in body temperature, especially with more severe neurological signs. This condition can become intolerable when these patients suffer febrile infections such as coronavirus disease-2019 (COVID-19). We review the mechanisms of hyperthermia in patients with MS, and they may encounter when infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Finally, the thermoregulatory role and relevant adaptation to regular physical exercise are summarized.

Physiological Considerations to Support Podium Performance in Para-Athletes

The twenty-first century has seen an increase in para-sport participation and the number of research publications on para-sport and the para-athlete. Unfortunately, the majority of publications are case reports/case series or study single impairment types in isolation. Indeed, an overview of how each International Paralympic Committee classifiable impairment type impact athlete physiology, health, and performance has not been forthcoming in the literature. This can make it challenging for practitioners to appropriately support para-athletes and implement evidence-based research in their daily practice. Moreover, the lack of a cohesive publication that reviews all classifiable impairment types through a physiological lens can make it challenging for researchers new to the field to gain an understanding of unique physiological challenges facing para-athletes and to appreciate the nuances of how various impairment types differentially impact para-athlete physiology. As such, the purpose of this review is to (1) summarize how International Paralympic Committee classifiable impairments alter the normal physiological responses to exercise; (2) provide an overview of "quick win" physiological interventions targeted toward specific para-athlete populations; (3) discuss unique practical considerations for the para-sport practitioner; (4) discuss research gaps and highlight areas for future research and innovation, and (5) provide suggestions for knowledge translation and knowledge sharing strategies to advance the field of para-sport research and its application by para-sport practitioners.

Voluntary Cooling during Exercise Is Augmented in People with Multiple Sclerosis Who Experience Heat Sensitivity

INTRODUCTION

We tested the hypothesis that people with multiple sclerosis (MS) who experience heat sensitivity voluntarily engage in cool-seeking behavior during exercise to a greater extent than healthy controls.

METHODS

In a 27.0°C ± 0.2°C, 41% ± 2% RH environment, seven participants with relapsing-remitting MS who exhibited heat sensitivity and seven healthy controls completed two randomized trials cycling for 40 min (EX) at 3.5 W·kg-1 metabolic heat production, followed by 30 min recovery (REC). In one trial, participants were restricted from engaging in cooling (CON). In the other trial, participants voluntarily pressed a button to receive 2 min of ~2°C water perfusing a top (COOL). Mean skin and core temperatures and mean skin wettedness were recorded continuously. Total time in cooling provided an index of cool-seeking behavior. RPE, total symptom scores (MS only), and subjective fatigue (MS only) were recorded every 10 min.

RESULTS

Core temperature (+0.5°C ± 0.1°C) and skin wettedness (+0.53 ± 0.02 a.u.) increased but were not different between groups or trials at end exercise (P = 0.196) or end recovery (P = 0.342). Mean skin temperature was reduced in COOL compared with CON at end exercise (P ≤ 0.002), with no differences between groups (P ≥ 0.532). MS spent more total time in cooling during EX (MS, 13 ± 3 min; healthy, 7 ± 4 min; P < 0.001) but not REC (MS, 2 ± 1 min; healthy, 0 ± 1 min; P = 0.496). RPE was greater at end exercise in MS (P = 0.001). Total symptom scores increased during exercise (P = 0.005) but was not different between trials (P = 0.321), whereas subjective fatigue was not attenuated in the cooling trial (P = 0.065).

CONCLUSION

Voluntary cooling is augmented in MS but does not consistently mitigate perceptions of heat-related symptoms or subjective fatigue.

Distinguishing between Fatigue and Fatigability in Multiple Sclerosis

Fatigue is one of the most common debilitating symptoms reported by persons with multiple sclerosis (MS). It reflects feelings of tiredness, lack of energy, low motivation, and difficulty in concentrating. It can be measured at a specific instant in time as a perception that arises from interoceptive networks involved in the regulation of homeostasis. Such ratings indicate the state level of fatigue and likely reflect an inability to correct deviations from a balanced homeostatic state. In contrast, the trait level of fatigue is quantified in terms of work capacity (fatigability), which can be either estimated (perceived fatigability) or measured (objective fatigability). Clinically, fatigue is most often quantified with questionnaires that require respondents to estimate their past capacity to perform several cognitive, physical, and psychosocial tasks. These retrospective estimates provide a measure of perceived fatigability. In contrast, the change in an outcome variable during the actual performance of a task provides an objective measure of fatigability. Perceived and objective fatigability do not assess the same underlying construct. Persons with MS who report elevated trait levels of fatigue exhibit deficits in interoceptive networks (insula and dorsal anterior cingulate cortex), including increased functional connectivity during challenging tasks. The state and trait levels of fatigue reported by an individual can be modulated by reward and pain pathways. Understanding the distinction between fatigue and fatigability is critical for the development of effective strategies to reduce the burden of the symptom for individuals with MS.

State and trait of finger tapping performance in multiple sclerosis

Finger tapping tests have been shown feasible to assess motor performance in multiple sclerosis (MS) and were observed to be strongly associated with the estimated clinical severity of the disease. Therefore, tapping tests could be an adequate tool to assess disease status in MS. In this study we examined potential influencing factors on a maximum tapping task with the whole upper-limb for 10 s in 40 MS patients using linear mixed effects modelling. Patients were tested in three sessions with two trials per body-side per session over the course of 4–27 days of inpatient rehabilitation. Tested factors were the expanded disability scale (EDSS) score, laterality of MS, age, sex, hand dominance, time of day, session, trial (first or second), time between sessions, and the reported day form. A second model used these factors to examine the self-reported day form of patients. Linear mixed effects modelling indicated the tapping test to have a good inter-trial (proportional variance < 0.01) and inter-session reliability (non-significant; when controlling for time between sessions), an influence of hand-dominance (proportional variance 0.08), to be strongly associated with the EDSS (eta² = 0.22, interaction with laterality of MS eta² = 0.12) and to be not associated with the reported day form. The model explained 87% (p < 0.01) of variance in tapping performance. Lastly, we were able to observe a positive effect of neurologic inpatient rehabilitation on task performance obvious from a significant effect of the time between sessions (eta² = 0.007; longer time spans between sessions were associated with higher increments in performance). Day form was only impacted by EDSS and the time of the day (p < 0.01, R² = 0.57, eta²_TIME = 0.017, eta²_EDSS = 01.19). We conclude that the tapping test is a reliable and valid assessment tool for MS.

Hot weather and heat extremes: health risks

Hot ambient conditions and associated heat stress can increase mortality and morbidity, as well as increase adverse pregnancy outcomes and negatively affect mental health. High heat stress can also reduce physical work capacity and motor-cognitive performances, with consequences for productivity, and increase the risk of occupational health problems. Almost half of the global population and more than 1 billion workers are exposed to high heat episodes and about a third of all exposed workers have negative health effects. However, excess deaths and many heat-related health risks are preventable, with appropriate heat action plans involving behavioural strategies and biophysical solutions. Extreme heat events are becoming permanent features of summer seasons worldwide, causing many excess deaths. Heat-related morbidity and mortality are projected to increase further as climate change progresses, with greater risk associated with higher degrees of global warming. Particularly in tropical regions, increased warming might mean that physiological limits related to heat tolerance (survival) will be reached regularly and more often in coming decades. Climate change is interacting with other trends, such as population growth and ageing, urbanisation, and socioeconomic development, that can either exacerbate or ameliorate heat-related hazards. Urban temperatures are further enhanced by anthropogenic heat from vehicular transport and heat waste from buildings. Although there is some evidence of adaptation to increasing temperatures in high-income countries, projections of a hotter future suggest that without investment in research and risk management actions, heat-related morbidity and mortality are likely to increase.

Sports Dietitians Australia Position Statement: Nutrition for Exercise in Hot Environments

It is the position of Sports Dietitians Australia (SDA) that exercise in hot and/or humid environments, or with significant clothing and/or equipment that prevents body heat loss (i.e., exertional heat stress), provides significant challenges to an athlete's nutritional status, health, and performance. Exertional heat stress, especially when prolonged, can perturb thermoregulatory, cardiovascular, and gastrointestinal systems. Heat acclimation or acclimatization provides beneficial adaptations and should be undertaken where possible. Athletes should aim to begin exercise euhydrated. Furthermore, preexercise hyperhydration may be desirable in some scenarios and can be achieved through acute sodium or glycerol loading protocols. The assessment of fluid balance during exercise, together with gastrointestinal tolerance to fluid intake, and the appropriateness of thirst responses provide valuable information to inform fluid replacement strategies that should be integrated with event fuel requirements. Such strategies should also consider fluid availability and opportunities to drink, to prevent significant under- or overconsumption during exercise. Postexercise beverage choices can be influenced by the required timeframe for return to euhydration and co-ingestion of meals and snacks. Ingested beverage temperature can influence core temperature, with cold/icy beverages of potential use before and during exertional heat stress, while use of menthol can alter thermal sensation. Practical challenges in supporting athletes in teams and traveling for competition require careful planning. Finally, specific athletic population groups have unique nutritional needs in the context of exertional heat stress (i.e., youth, endurance/ultra-endurance athletes, and para-sport athletes), and specific adjustments to nutrition strategies should be made for these population groups.

Heat Exposure and Multiple Sclerosis-A Regional and Temporal Analysis

Multiple sclerosis (MS) is a neurological disorder that progressively distorts the myelination of axons within the central nervous system (CNS). Increased core body temperature or metabolism as a result of exercise are common causes of short-term exacerbations of neurological symptoms in MS. About 60–80% of patients with MS experience a worsening of their symptoms when exposed to heat. In comparison, less data are available on the relationship between ambient meteorological conditions (e.g., temperature and relative humidity (RH)) and fluctuations in such variables in relation to MS symptoms. Thus, this study examined associations between time-lagged exposure to meteorological conditions and risk of a clinic visit due to MS among US veterans between 2010 and 2013. This study leveraged data from the Veterans Affairs (VA) and National Climactic Data Center (NCDC) for the continental US, partitioned into eight climate zones. We used a case crossover design to assess the risk of a MS clinic visit with respect to several meteorological conditions. Location-specific time-lagged daily (ambient) exposure to temperature, RH, and temperature variations (standard deviation (SD) of temperature) were computed (up to 30 days) for each case (i.e., day of MS visit) and control (a randomly assigned date ± 90–270 days prior to visit). Statistical analyses were conducted to examine independent associations between the selected meteorological conditions and risk of MS visits at the national and regional levels. A total of 533,066 patient visits received a MS diagnosis (International Classifications of Diseases (ICD)-9 code = 340). The Northeast (NE) and Upper Midwest (UMW) regions reported the highest frequency of clinic visits due to MS. Clinic visits were 9% more likely to occur in the spring, summer, and fall months (March–October) than in the winter (OR = 1.089; 95% CI = 1.076–1.103; p < 0.01). In the univariate analyses, the SD of temperature, temperature, and temperature–RH interaction were positively associated with an elevated risk of a MS clinic visit, while the RH was negatively associated with the risk for a clinic visit. In multivariate analyses, the strongest association of a MS clinic visit was observed with the SD of the temperature (OR = 1.012; 95% CI 1.008–1.017; p < 0.01). These associations between MS clinic visits and meteorological conditions varied across climate regions, with the strongest associations being observed in the LMW, UMW, DSW, and NE zones. The SD of the temperature was again the strongest associated predictor when examined regionally. Temperature variations and temperature–RH interactions (a proxy of the heat index) showed significant associations with MS clinic visits. These associations varied across climate regions when examined geographically. Our findings have implications for the management of MS in severe or recurrent cases, especially considering the impending changes in the daily temperature variations and intensity of the heatwaves expected with the intensification of global warming.

[Differential diagnostics of autoimmune inflammatory spinal cord diseases]

Myelitis is an acute or subacute inflammatory syndrome of the spinal cord. Myelopathy, often used as a synonym and presenting with similar symptoms in clinical practice, can be caused by numerous, not primarily inflammatory etiologies and might also show a progressive disease course. Within the last decade the spectrum of autoimmune myelitis was significantly broadened as was the spectrum of diagnostic methods. Apart from the characteristic example of multiple sclerosis with short-length myelitis and neuromyelitis optica spectrum disorders with longitudinally extensive transverse myelitis, multiple rare but important differential diagnoses should also be considered. Magnetic resonance imaging and laboratory analyses of serum antibodies and cerebrospinal fluid are the most important diagnostic methods and are fundamental for rapid treatment decisions, subsequently with better prognosis. This article reviews representative diseases within the spectrum of autoimmune spinal cord diseases and their differential diagnoses.

Anomalously warm weather and acute care visits in patients with multiple sclerosis: A retrospective study of privately insured individuals in the US

BACKGROUND

As the global climate changes in response to anthropogenic greenhouse gas emissions, weather and temperature are expected to become increasingly variable. Although heat sensitivity is a recognized clinical feature of multiple sclerosis (MS), a chronic demyelinating disorder of the central nervous system, few studies have examined the implications of climate change for patients with this disease.

METHODS AND FINDINGS

We conducted a retrospective cohort study of individuals with MS ages 18-64 years in a nationwide United States patient-level commercial and Medicare Advantage claims database from 2003 to 2017. We defined anomalously warm weather as any month in which local average temperatures exceeded the long-term average by ≥1.5°C. We estimated the association between anomalously warm weather and MS-related inpatient, outpatient, and emergency department visits using generalized log-linear models. From 75,395,334 individuals, we identified 106,225 with MS. The majority were women (76.6%) aged 36-55 years (59.0%). Anomalously warm weather was associated with increased risk for emergency department visits (risk ratio [RR] = 1.043, 95% CI: 1.025-1.063) and inpatient visits (RR = 1.032, 95% CI: 1.010-1.054). There was limited evidence of an association between anomalously warm weather and MS-related outpatient visits (RR = 1.010, 95% CI: 1.005-1.015). Estimates were similar for men and women, strongest among older individuals, and exhibited substantial variation by season, region, and climate zone. Limitations of the present study include the absence of key individual-level measures of socioeconomic position (i.e., race/ethnicity, occupational status, and housing quality) that may determine where individuals live-and therefore the extent of their exposure to anomalously warm weather-as well as their propensity to seek treatment for neurologic symptoms.

CONCLUSIONS

Our findings suggest that as global temperatures rise, individuals with MS may represent a particularly susceptible subpopulation, a finding with implications for both healthcare providers and systems.

Central neuropathic pain in multiple sclerosis is associated with impaired innocuous thermal pathways and neuronal hyperexcitability

OBJECTIVE

About a third of patients with multiple sclerosis (MS) suffer from chronic and excruciating central neuropathic pain (CNP). The mechanism underlying CNP in MS is not clear, since previous studies are scarce and their results are inconsistent. Our aim was to determine whether CNP in MS is associated with impairment of the spinothalamic-thalamocortical pathways (STTCs) and/or increased excitability of the pain system.

DESIGN

Cross sectional study.

SETTING

General hospital.

SUBJECTS

47 MS patients with CNP, 42 MS patients without CNP, and 32 healthy controls.

METHODS

Sensory testing included the measurement of temperature, pain, and touch thresholds and the thermal grill illusion (TGI) for evaluating STTCs function, and hyperpathia and allodynia as indicators of hyperexcitability. CNP was characterized using interviews and questionnaires.

RESULTS

The CNP group had higher cold and warm thresholds (p < 0.01), as well as higher TGI perception thresholds (p < 0.05), especially in painful body regions compared to controls, whereas touch and pain thresholds values were normal. The CNP group also had a significantly greater prevalence of hyperpathia and allodynia. Regression analysis revealed that whereas presence of CNP was associated with a higher cold threshold, CNP intensity, and the number of painful body regions were associated with allodynia and hyperpathia, respectively.

CONCLUSIONS

CNP in MS is characterized by a specific impairment of STTC function; the innocuous thermal pathways, and by pain hyperexcitability. Whereas CNP presence is associated with STTC impairment, its severity and extent are associated with pain hyperexcitability. Interventions that reduce excitability level may therefore mitigate CNP severity.

Probing the Brain-Body Connection Using Transcranial Magnetic Stimulation (TMS): Validating a Promising Tool to Provide Biomarkers of Neuroplasticity and Central Nervous System Function

Transcranial magnetic stimulation (TMS) is a non-invasive method used to investigate neurophysiological integrity of the human neuromotor system. We describe in detail, the methodology of a single pulse TMS protocol that was performed in a large cohort of people (n = 110) with multiple sclerosis (MS). The aim was to establish and validate a core-set of TMS variables that predicted typical MS clinical outcomes: walking speed, hand dexterity, fatigue, and cognitive processing speed. We provide a brief and simple methodological pipeline to examine excitatory and inhibitory corticospinal mechanisms in MS that map to clinical status. Delayed and longer ipsilateral silent period (a measure of transcallosal inhibition; the influence of one brain hemisphere's activity over the other), longer cortical silent period (suggestive of greater corticospinal inhibition via GABA) and higher resting motor threshold (lower corticospinal excitability) most strongly related to clinical outcomes, especially when measured in the hemisphere corresponding to the weaker hand. Greater interhemispheric asymmetry (imbalance between hemispheres) correlated with poorer performance in the greatest number of clinical outcomes. We also show, not surprisingly, that TMS variables related more strongly to motor outcomes than non-motor outcomes. As it was validated in a large sample of patients with varying severities of central nervous system dysfunction, the protocol described herein can be used by investigators and clinicians alike to investigate the role of TMS as a biomarker in MS and other central nervous system disorders.

Early Treatment Initiation With Oral Prednisolone for Relapse Prevention Alleviates Depression and Fatigue in Aquaporin-4-Positive Neuromyelitis optica Spectrum Disorder

Background:Neuromyelitis optica spectrum disorder (NMOSD) is a relapsing autoimmune-related neurological disorder of the central nervous system. Most patients with NMOSD have serum anti-aquaporin-4 immunoglobulin G antibodies (AQP4-IgG). In addition to optic neuritis and myelitis, other insidious symptoms such as depressive state and chronic fatigue in NMOSD are gradually being recognized.

Methods: To elucidate the impact of low- to medium-dose oral prednisolone (PSL) as a relapse prevention therapy for psychiatric disturbances and chronic fatigue in NMOSD, we evaluated clinical data from 39 patients with AQP4-IgG-positive NMOSD, along with the details of present and cumulative oral PSL dosage.

Results: Thirty-six of the 39 patients were treated with low- to medium-dose oral PSL, and the mean and standard deviation of the present daily dose of oral PSL were 7.9 ± 4.0 mg/day. None of the patients were treated with a daily PSL dose of >15 mg. As a result, the disease duration and the untreated period before starting oral PSL showed weak to moderate correlations with the subsequent severities of psychiatric disturbance and fatigue level. Meanwhile, none of the other treatment-related variables evaluated, such as the present oral PSL daily dose, cumulative PSL dose, months of oral PSL administration, previous courses of steroid pulse therapy, and coadministered immunosuppressants, were correlated with these insidious symptoms.

Conclusion: Our results suggest that the use of long-term low- to medium-dose oral PSL ≤15 mg daily for relapse prevention in AQP4-IgG-positive NMOSD would not aggravate the psychiatric and fatigue conditions. On the contrary, early initiation of oral PSL for relapse prevention, together with significantly decreased relapse rate, alleviated the subsequent depressive state and fatigue from the disease.

Evaluating the Utility of Smartphone-Based Sensor Assessments in Persons With Multiple Sclerosis in the Real-World Using an App (elevateMS): Observational, Prospective Pilot Digital Health Study

Background

Multiple sclerosis (MS) is a chronic neurodegenerative disease. Current monitoring practices predominantly rely on brief and infrequent assessments, which may not be representative of the real-world patient experience. Smartphone technology provides an opportunity to assess people’s daily-lived experience of MS on a frequent, regular basis outside of episodic clinical evaluations.

Objective

The objectives of this study were to evaluate the feasibility and utility of capturing real-world MS-related health data remotely using a smartphone app, “elevateMS,” to investigate the associations between self-reported MS severity and sensor-based active functional tests measurements, and the impact of local weather conditions on disease burden.

Methods

This was a 12-week, observational, digital health study involving 3 cohorts: self-referred participants who reported an MS diagnosis, clinic-referred participants with neurologist-confirmed MS, and participants without MS (controls). Participants downloaded the elevateMS app and completed baseline assessments, including self-reported physical ability (Patient-Determined Disease Steps [PDDS]), as well as longitudinal assessments of quality of life (Quality of Life in Neurological Disorders [Neuro-QoL] Cognitive, Upper Extremity, and Lower Extremity Function) and daily health (MS symptoms, triggers, health, mobility, pain). Participants also completed functional tests (finger-tapping, walk and balance, voice-based Digit Symbol Substitution Test [DSST], and finger-to-nose) as an independent assessment of MS-related cognition and motor activity. Local weather data were collected each time participants completed an active task. Associations between self-reported baseline/longitudinal assessments, functional tests, and weather were evaluated using linear (for cross-sectional data) and mixed-effects (for longitudinal data) regression models.

Results

A total of 660 individuals enrolled in the study; 31 withdrew, 495 had MS (n=359 self-referred, n=136 clinic-referred), and 134 were controls. Participation was highest in clinic-referred versus self-referred participants (median retention: 25.5 vs 7.0 days). The top 5 most common MS symptoms, reported at least once by participants with MS, were fatigue (310/495, 62.6%), weakness (222/495, 44.8%), memory/attention issues (209/495, 42.2%), and difficulty walking (205/495, 41.4%), and the most common triggers were high ambient temperature (259/495, 52.3%), stress (250/495, 50.5%), and late bedtime (221/495, 44.6%). Baseline PDDS was significantly associated with functional test performance in participants with MS (mixed model–based estimate of most significant feature across functional tests [β]: finger-tapping: β=–43.64, P<.001; DSST: β=–5.47, P=.005; walk and balance: β=–.39, P=.001; finger-to-nose: β=.01, P=.01). Longitudinal Neuro-QoL scores were also significantly associated with functional tests (finger-tapping with Upper Extremity Function: β=.40, P<.001; walk and balance with Lower Extremity Function: β=–99.18, P=.02; DSST with Cognitive Function: β=1.60, P=.03). Finally, local temperature was significantly associated with participants’ test performance (finger-tapping: β=–.14, P<.001; DSST: β=–.06, P=.009; finger-to-nose: β=–53.88, P<.001).

Conclusions

The elevateMS study app captured the real-world experience of MS, characterized some MS symptoms, and assessed the impact of environmental factors on symptom severity. Our study provides further evidence that supports smartphone app use to monitor MS with both active assessments and patient-reported measures of disease burden. App-based tracking may provide unique and timely real-world data for clinicians and patients, resulting in improved disease insights and management.

The diversity of neuronal phenotypes in rodent and human autonomic ganglia

Selective sympathetic and parasympathetic pathways that act on target organs represent the terminal actors in the neurobiology of homeostasis and often become compromised during a range of neurodegenerative and traumatic disorders. Here, we delineate several neurotransmitter and neuromodulator phenotypes found in diverse parasympathetic and sympathetic ganglia in humans and rodent species. The comparative approach reveals evolutionarily conserved and non-conserved phenotypic marker constellations. A developmental analysis examining the acquisition of selected neurotransmitter properties has provided a detailed, but still incomplete, understanding of the origins of a set of noradrenergic and cholinergic sympathetic neuron populations, found in the cervical and trunk region. A corresponding analysis examining cholinergic and nitrergic parasympathetic neurons in the head, and a range of pelvic neuron populations, with noradrenergic, cholinergic, nitrergic, and mixed transmitter phenotypes, remains open. Of particular interest are the molecular mechanisms and nuclear processes that are responsible for the correlated expression of the various genes required to achieve the noradrenergic phenotype, the segregation of cholinergic locus gene expression, and the regulation of genes that are necessary to generate a nitrergic phenotype. Unraveling the neuron population-specific expression of adhesion molecules, which are involved in axonal outgrowth, pathway selection, and synaptic organization, will advance the study of target-selective autonomic pathway generation.

Multiple sclerosis-related fatigue: the role of impaired corticospinal responses and heightened exercise fatigability

It is unclear whether motor fatigability and perceived fatigue share a common pathophysiology in people with multiple sclerosis (PwMS). This cross-sectional investigation explored the relationship between the mechanisms of motor fatigability from cycling and fatigue severity in PwMS. Thirteen highly fatigued (HF) and thirteen nonfatigued (LF) PwMS and thirteen healthy controls (CON) completed a step test until volitional exhaustion on an innovative cycle ergometer. Neuromuscular evaluations involving femoral nerve electrical stimulation and transcranial magnetic stimulation were performed every 3 min throughout cycling. One-way ANOVA at baseline and exhaustion uncovered evidence of consistently smaller motor evoked potential (MEP) amplitudes (P = 0.011) and prolonged MEP latencies (P = 0.041) in HF as well as a greater decline in maximal voluntary contraction force (HF: 63 ± 13%; LF: 75 ± 13%; CON: 73 ± 11% of pre; P = 0.037) and potentiated twitch force (HF: 35 ± 13%; LF: 50 ± 16%; CON: 47 ± 17% of pre; P = 0.049) in HF at volitional exhaustion. Hierarchical regression determined that fatigue severity on the Fatigue Severity Scale was predicted by prolonged MEP latencies (change in r² = 0.389), elevated peripheral muscle fatigability (change in r² = 0.183), and depressive symptoms (change in r² = 0.213). These findings indicate that MS-related fatigue is distinguished by disrupted corticospinal responsiveness, which could suggest progressive pathology, but fatigability from whole body exercise and depressive symptoms also influence perceptions of fatigue in PwMS.NEW & NOTEWORTHY The etiology of fatigability from whole body exercise was examined for the first time to accurately elucidate the relationship between fatigue and fatigability in multiple sclerosis (MS). Compromised corticospinal responsiveness predicted fatigue severity, providing a novel, objective indicator of fatigue in MS. Although the impaired corticomotor transmission did not aggravate muscle activation in this group of people with multiple sclerosis (PwMS) of lower disability, heightened muscle fatigability was seen to contribute to perceptions of fatigue in PwMS.

The effects of temperature on the biophysical properties of optic nerve F-fibres

In multiple sclerosis, exacerbation of symptoms with rising body temperature is associated with impulse conduction failure. The mechanism is not fully understood. Remarkably, normal optic nerve axons also show temperature dependent effects, with a fall in excitability with warming. Here we show two properties of optic nerve axons, accommodation and inward rectification (I_h), respond to temperature changes in a manner consistent with a temperature dependent membrane potential. As we could find no evidence for the functional expression of K_V7.2 in the axons, using the K⁺ channel blocker tetraethylammonium ions, we suggest this may explain the membrane potential lability. In order to understand how the axonal membrane potential may show temperature dependence, we have developed a hypothesis involving the electroneutral movement of Na⁺ ions across the axon membrane, that increases with increasing temperature with an appropriate Q₁₀. Part, but probably not all, of the electroneutral Na⁺ movement is eliminated by removing extracellular Cl⁻ or exposure to bumetanide, consistent with the involvement of the transporter NKCC1. Numerical simulation suggests a change in membrane potential of − 15–20 mV mimics altering temperature between room and physiological in the largest axons.

Association between diurnal temperature range and emergency department visits for multiple sclerosis: A time-stratified case-crossover study

Although multiple sclerosis (MS) has been the leading cause of neurologically-induced disability in young adults, risk factors for the relapse and acute aggravation of MS remain unclear. A few studies have suggested a possible role of temperature changes on the relapse and acute aggravation of MS. We investigated the association between short-term exposure to wide diurnal temperature ranges (DTRs) and acute exacerbation of MS requiring an emergency department (ED) visit. A total of 1265 patients visited EDs for acute aggravation of MS as the primary disease in Seoul between 2008 and 2014 from the national emergency database. We conducted a conditional logistic regression analysis of the time-stratified case-crossover design to compare DTRs on the ED visit days for MS and those on control days matched according to the day of the week, month, and year. We examined possible associations with other temperature-related variables (ambient temperature, between-day temperature change, and sunlight hours). Short-term exposure to wide DTRs immediately increased the risk of ED visits for MS. Especially, 2-day average (lag0-1) DTR levels on the day of and one day prior to ED visits exhibited the strongest association (an 8.81% [95% CI: 3.46%-14.44%] change in the odds ratio per 1 °C increase in the DTR). Other temperature-related variables were not associated with MS aggravation. Our results suggest that exposure to wider DTR may increase the risk of acute exacerbation of MS. Given the increasing societal burden of MS and the increasing temperature variability due to climate change, further studies are required.

Exercise in the management of multiple sclerosis relapses: current evidence and future perspectives

Relapses are a common feature of multiple sclerosis; however, recovery from relapses is often incomplete, with up to half of people experiencing residual disabilities postrelapse. Therefore, treatments are required to promote recovery of function and reduce the extent of residual disabilities postrelapse. Accordingly, this Perspective article explores the role of exercise in relapse management. Current evidence from two studies suggests that exercise in combination with steroid therapy improves disability and quality of life postrelapse, and may be more beneficial in promoting relapse recovery than steroid therapy alone. However, given the small number of studies and methodological limitations, further studies are required to understand the effects of exercise in relapse management and the mechanism through which exercise influences relapse recovery.

A multi-scalar climatological analysis in preparation for extreme heat at the Tokyo 2020 Olympic and Paralympic Games

Extreme heat can be harmful to human health and negatively affect athletic performance. The Tokyo Olympic and Paralympic Games are predicted to be the most oppressively hot Olympics on record. An interdisciplinary multi-scale perspective is provided concerning extreme heat in Tokyo-from planetary atmospheric dynamics, including El Niño Southern Oscillation (ENSO), to fine-scale urban temperatures-as relevant for heat preparedness efforts by sport, time of day, and venue. We utilize stochastic methods to link daytime average wet bulb globe temperature (WBGT) levels in Tokyo in August (from meteorological reanalysis data) with large-scale atmospheric dynamics and regional flows from 1981 to 2016. Further, we employ a mesonet of Tokyo weather stations (2009-2018) to interpolate the spatiotemporal variability in near-surface air temperatures at outdoor venues. Using principal component analysis, two planetary (ENSO) regions in the Pacific Ocean explain 70% of the variance in Tokyo's August daytime WBGT across 35 years, varying by 3.95°C WGBT from the coolest to warmest quartile. The 10-year average daytime and maximum intra-urban air temperatures vary minimally across Tokyo (<1.2°C and 1.7°C, respectively), and less between venues (0.6-0.7°C), with numerous events planned for the hottest daytime period (1200-1500 hr). For instance, 45% and 38% of the Olympic and Paralympic road cycling events (long duration and intense) occur midday. Climatologically, Tokyo will present oppressive weather conditions, and March-May 2020 is the critical observation period to predict potential anomalous late-summer WBGT in Tokyo. Proactive climate assessment of expected conditions can be leveraged for heat preparedness across the Game's period.

Comfortable walking speed and energy cost of locomotion in patients with multiple sclerosis

Comfortable walking speed and energy cost of walking are physiological markers of metabolic activity during gait. People with multiple sclerosis are characterized by altered gait biomechanics and energetics, related to the degree of disability and spasticity, which lead to an increased energy cost of walking. Several studies concerning the energy cost of walking in multiple sclerosis have been published. Nevertheless, differences in protocols and characteristics of the sample have led to different outcomes. The aim of the present meta-analysis is to summarize results from studies with specific inclusion characteristics, and to present data about the comfortable walking speed and the energy cost of walking at that speed. Moreover, a detailed discussion of the potential mechanisms involved in the altered metabolic activity during exercise was included. A total of 19 studies were considered, 12 of which were also part of the quantitative analysis. Despite the strict selection process, high between-group heterogeneity was found for both outcomes. Nevertheless, the overall results suggest a pooled mean comfortable walking speed of 1.12 m/s (95% CI 1.05-1.18) and energy cost of 0.19 mLO₂/kg/m (95% CI 0.17-0.21). These findings support the results of previous studies suggesting that energy cost of walking may be increased by 2-3 times compared to healthy controls (HC), and encourage the use of this marker in association with other parameters of the disease.

Effects of Wrist Cooling on Recovery From Exercise-Induced Heat Stress With Firefighting Personal Protective Equipment

OBJECTIVE

To determine the effects of wrist cooling on recovery from exercise-induced heat stress (EIHS) from wearing firefighting personal protective equipment (PPE) and self-contained breathing apparatus.

METHODS

Using a single-blind, counterbalanced, crossover-design, in 11 healthy men, we measured heart rate (HR), HR variability (HRV), core temperature (TCore), thermal strain (TS), and fatigue at rest, during 30-minute of exercise in PPE+SCBA, and during recovery while wearing a wrist cooling band (control[off] vs cool[on]).

RESULTS

No differences were observed between trials at baseline or during exercise, in HR, TCore, TS, or fatigue. Time to 50% and recovery were not different between trials. Upon recovery, TCore was lower, while HR, fatigue, HRV, and TS were relatively indifferent with cooling.

CONCLUSION

Wrist cooling after EIHS only modestly enhanced recovery, questioning its implementation during on-scene rehabilitation of firefighters.

Wilhelm Uhthoff and Uhthoff's phenomenon

Wilhelm Uhthoff, known for his contributions to both neurology and neuro-ophthalmology, was a German ophthalmologist who specialized in neurologic disorders. The eponym "Uhthoff's phenomenon" was first used to describe the reversible, transient blurring of vision in patients with multiple sclerosis during exercise. Subsequently, it was discovered that this neurologic sign not only was triggered by physical exertion but also by other homeostatic disruptions such as hot baths, menstruation, and high external temperatures. Here, we take a look at the life and career of Wilhelm Uhthoff and discuss the basis behind this phenomenon.

Apurinic endonuclease-1 preserves neural genome integrity to maintain homeostasis and thermoregulation and prevent brain tumors

Frequent oxidative modification of the neural genome is a by-product of the high oxygen consumption of the nervous system. Rapid correction of oxidative DNA lesions is essential, as genome stability is a paramount determinant of neural homeostasis. Apurinic/apyrimidinic endonuclease 1 (APE1; also known as "APEX1" or "REF1") is a key enzyme for the repair of oxidative DNA damage, although the specific role(s) for this enzyme in the development and maintenance of the nervous system is largely unknown. Here, using conditional inactivation of murine Ape1, we identify critical roles for this protein in the brain selectively after birth, coinciding with tissue oxygenation shifting from a placental supply to respiration. While mice lacking APE1 throughout neurogenesis were viable with little discernible phenotype at birth, rapid and pronounced brain-wide degenerative changes associated with DNA damage were observed immediately after birth leading to early death. Unexpectedly, Ape1 ^Nes-cre mice appeared hypothermic with persistent shivering associated with the loss of thermoregulatory serotonergic neurons. We found that APE1 is critical for the selective regulation of Fos1-induced hippocampal immediate early gene expression. Finally, loss of APE1 in combination with p53 inactivation resulted in a profound susceptibility to brain tumors, including medulloblastoma and glioblastoma, implicating oxidative DNA lesions as an etiologic agent in these diseases. Our study reveals APE1 as a major suppressor of deleterious oxidative DNA damage and uncovers specific and broad pathogenic consequences of respiratory oxygenation in the postnatal nervous system.

Burn injury and multiple sclerosis: A retrospective case-control study

OBJECTIVES

The purpose of this study was to determine whether having a previous diagnosis of multiple sclerosis (MS) changed acute care needs in burn-injured patients.

METHODS

This was a retrospective case-control study that included adult (aged ≥18years) patients with an acute burn injury. Control patients were matched with eleven patients with a history of MS at a 4:1 ratio. Outcomes included fluid resuscitation volumes, temperature, heart rate, mean arterial pressure, in-hospital complications, and hospital length of stay (LOS).

RESULTS

There were fifty-five patients included and of those, eleven had a documented history of MS. Fluid resuscitation volumes, temperature, heart rate, and mean arterial pressure were similar between groups during the resuscitation period (p>0.05). LOS was similar between both groups (12, IQR: 2-17 vs. median 16, IQR: 12-21; p=0.090). However, when normalized to % TBSA burn, patients with MS had a significantly higher median LOS/% TBSA burned (1.2, IQR: 0.7-2.0 vs. 2.1, IQR: 1.1-7.1; p=0.031).

CONCLUSIONS

Patients with concurrent burn injuries and MS have a significantly longer LOS/% TBSA burn suggesting that more time is required to heal their wounds. Surprisingly, there were no other significant differences in the after the burn acute phase between these two cohorts.

The motivation to behaviorally thermoregulate during passive heat exposure in humans is dependent on the magnitude of increases in skin temperature

We tested the hypothesis that the motivation to behaviorally thermoregulate in humans is dependent on the magnitude of changes in mean skin temperature. Ten healthy subjects (22 ± 3 y, 5 females) underwent 60 min of seated rest in a 32±1 °C or 42±1 °C environment (20% relative humidity). Trials were completed in a counterbalanced order. The motivation to behaviorally thermoregulate was measured using an operant behavior task on a fixed ratio schedule, in which subjects received thermal reinforcement after clicking a button 100 times. The reinforcer was 30 s of cooling on the dorsal aspect of the neck. The motivation to behave was defined as the cumulative number of button clicks over time and behavioral thermoregulation was defined as the change in neck skin temperature. Mean skin temperature was higher throughout the 42 °C versus the 32 °C trial (at 60 min: 36.3±0.5 °C vs. 34.5±0.5 °C, P < .01) and core temperature became higher in this trial 40 min into heat exposure (at 60 min: 37.2±0.2 °C vs. 37.1±0.1 °C, P ≤ .04), but did not differ from pre- heat exposure (P = .81). Neck skin temperature was lower in the 42 °C compared to the 32 °C trial starting at 30 min (33.7±0.8 °C vs. 35.3±0.5°C, P < .01), which was maintained thereafter (P ≤ .04). Cumulative responding for thermal reinforcement was greater in the 42 °C trial compared to the 32 °C trial at 20 min (180±155 clicks vs. 0±0 clicks, P < .01), which persisted thereafter (P < .01). These data indicate that the motivation to behaviorally thermoregulate during passive heat exposure in humans is dependent on the magnitude of increases in skin temperature.

Temperature sensitivity in multiple sclerosis: An overview of its impact on sensory and cognitive symptoms

Multiple sclerosis (MS) is an autoimmune neurodegenerative disease characterized by demyelination of the central nervous system (CNS). The exact cause of MS is still unknown; yet its incidence and prevalence rates are growing worldwide, making MS a significant public health challenge. The heterogeneous distribution of demyelination within and between MS patients translates in a complex and varied array of autonomic, motor, sensory and cognitive symptoms. Yet a unique aspect of MS is the highly prevalent (60-80%) temperature sensitivity of its sufferers, where neurological symptoms are temporarily exacerbated by environmental- or exercise-induced increases (or decreases) in body temperature. MS temperature sensitivity is primarily driven by temperature-dependent slowing or blocking of neural conduction within the CNS due to changes in internal (core) temperature; yet changes in skin temperature could also contribute to symptom exacerbation (e.g. during sunlight and warm ambient exposure). The impact of temperature sensitivity, and particularly of increases in core temperature, on autonomic (e.g. thermoregulatory/cardiovascular function) and motor symptoms (e.g. fatigue) is well described. However, less attention has been given to how increases (and decreases) in core and skin temperature affect sensory and cognitive symptoms. Furthermore, it remains uncertain whether changes in skin temperature alone could also trigger worsening of symptoms. Here we review the impact of temperature sensitivity on MS sensory and cognitive function and discuss additional factors (e.g. changes in skin temperature) that potentially contribute to temperature-induced worsening of symptoms in the absence of alteration in core temperature.