Olfactory function and cognition in relapsing–remitting and secondary-progressive multiple sclerosis

Vitamin D levels and olfactory dysfunction in multiple sclerosis patients

OBJECTIVE

The objective was to explore the possible relationship between the serum vitamin D level and olfactory impairment in a population of multiple sclerosis (MS) patients in Guizhou, China.

METHODS

We included 25 patients with MS and 18 healthy controls (HCs) who were recruited from the Affiliated Hospital of Guizhou Medical University from February 2021 to September 2021. The University of Pennsylvania Smell Identification Test (UPSIT) was used to test the patients' sense of smell, and the level of serum 25-hydroxyethylene polyprotein D was measured.

RESULTS

Serum vitamin D levels and UPSIT scores were significantly different between the MS group and the control group (both p < 0.001). Moreover, a significant positive correlation emerged between vitamin D levels and UPSIT scores in MS patients (r = 0.537, p = 0.021).

CONCLUSIONS

The serum vitamin D level may be involved in the regulation of olfactory dysfunction in MS patients in Guizhou, China.

Evaluation of the NIH Toolbox Odor Identification Test across normal cognition, amnestic mild cognitive impairment, and dementia due to Alzheimer's disease

INTRODUCTION

Olfactory decline is associated with cognitive decline in aging, amnestic mild cognitive impairment (aMCI), and amnestic dementia associated with Alzheimer's disease neuropathology (ADd). The National Institutes of Health Toolbox Odor Identification Test (NIHTB-OIT) may distinguish between these clinical categories.

METHODS

We compared NIHTB-OIT scores across normal cognition (NC), aMCI, and ADd participants (N = 389, ≥65 years) and between participants positive versus negative for AD biomarkers and the APOE ε4 allele.

RESULTS

NIHTB-OIT scores decreased with age (p < 0.001) and were lower for aMCI (p < 0.001) and ADd (p < 0.001) compared to NC participants, correcting for age and sex. The NIHTB-OIT detects aMCI (ADd) versus NC participants with 49.4% (56.5%) sensitivity and 88.8% (89.5%) specificity. NIHTB-OIT scores were lower for participants with positive AD biomarkers (p < 0.005), but did not differ based on the APOE ε4 allele (p > 0.05).

DISCUSSION

The NIHTB-OIT distinguishes clinically aMCI and ADd participants from NC participants.

HIGHLIGHTS

National Institutes of Health Toolbox Odor Identification Test (NIHTB-OIT) discriminated normal controls from mild cognitive impairment. NIHTB-OIT discriminated normal controls from Alzheimer's disease dementia. Rate of olfactory decline with age was similar across all diagnostic categories. NIHTB-OIT scores were lower in participants with positive Alzheimer's biomarker tests. NIHTB-OIT scores did not differ based on APOE genotype.

Olfactory function in Susac syndrome

OBJECTIVES

Susac syndrome is a rare autoimmune endotheliopathy involving the brain, retina, and inner ear. Olfactory dysfunction is a common early manifestation of several central nervous system diseases, including neurodegenerative diseases and autoimmune-mediated diseases such as Multiple Sclerosis. While the literature is abundant about the Susac syndrome classic triad of encephalopathy, branch retinal artery occlusion, and low-frequency sensorineural hearing loss, little is known about the extent of olfactory sense involvement.

METHODS

Using the Sniffin' Sticks test, this study evaluated olfactory function (identification and threshold) in ten recovering Susac syndrome patients under our clinic surveillance with a median of 3.1 (SD=1.53) years post-disease onset.

RESULTS

olfactory assessment by threshold and odor identification were within the normal range. No differences between recovering Susac syndrome patients to standard norms of odor identification and threshold were found.

CONCLUSIONS

Our findings do not support olfactory dysfunction in Susac syndrome and thereby, do not support olfactory assessment as a reliable biomarker for this condition.

The effects of cognition, quality of life, and fatigue on olfactory function in patients with multiple sclerosis

AIM

The frequency of olfactory dysfunction in patients with Multiple Sclerosis (MS) has revealed very different results in studies. Some studies have shown that olfactory dysfunction may be associated with cognitive impairment and poor quality of life. In these studies, different odor tests and cognitive tests were used and different results were obtained.

MATERIALS AND METHODS

Forty literate patients over the age of 18 and 24 healthy volunteers of similar age and education were included in the study. Sniffin' Sticks Odor Test, California Verbal Learning Test II, Symbol Digit Modalities Test, Revised Brief Visuospatial Memory Test, Trail-Making Test, Quality of Life Short Form-36, Fatigue Impact Scale, Beck Depression Inventory, and Beck Anxiety Inventory were applied to the individuals.

RESULTS

Olfactory dysfunction was detected in 50 % of the patients. High disability rate, low cognitive functions, low quality of life, and fatigue were identified as the factors affecting olfactory function negatively. Odor discrimination and identification abilities were associated with disability level and cognitive functions, whereas quality of life was linked to odor threshold scores. The olfactory function and cognitive abilities of patients with progressive MS (n = 5) were worse than those of patients with relapsing remitting MS (n = 35).

CONCLUSION

Olfactory dysfunction is common in patients with MS and is associated with disability and quality of life. Olfactory function can be used in the follow-up of patients and olfactory dysfunction deserves further study as a metric that might emerge as a biomarker.

Olfactory Dysfunction Reflects Disease Progression in Japanese Patients with Multiple Sclerosis

Objective Olfactory dysfunction is an important clinical feature in patients with multiple sclerosis (MS). The incidence and extent of olfactory dysfunction are reportedly higher in secondary progressive (SP) MS than in relapsing and remitting (RR) MS. We investigated the use of olfactory dysfunction for evaluating the disease status of Japanese patients with MS. Methods Olfactory identification was evaluated using the Odor Stick Identification Test for the Japanese (OSIT-J) in patients with RRMS (n=40) and SPMS (n=11) and compared the findings with those of healthy controls (n=40). Patients with RRMS for more than 10 years (L-RRMS, n=10) were included in the RRMS group. The cognitive function was evaluated using the Japanese version of the Wechsler Adult Intelligence Scale, 3rd edition. The third ventricle width (3rd VW) was measured as a marker of central brain atrophy using magnetic resonance imaging. Results SPMS patients had significantly lower OSIT-J scores than RRMS and L-RRMS patients. More SPMS patients had OSIT-J scores below the lower limit of the normal score (LLN) than RRMS patients. The LLN effectively discriminated between RRMS and SPMS (sensitivity 70%, specificity 91.5%, area under the curve 0.933, 95% confidence interval 0.874-1.000). Patients with SPMS had a significantly lower processing speed and larger 3rd VW than those with RRMS or L-RRMS. Conclusion The olfactory dysfunction was worse, along with cognitive impairment and brain atrophy, in SPMS patients than in RRMS patients, independent of disease duration, in our Japanese population. This directly reflected the disease progression and may have been able to distinguish SPMS from RRMS, independent of ethnic and cultural background.

Olfactory dysfunction is common in classical infratentorial superficial siderosis of the central nervous system

Background

Established features of classical infratentorial superficial siderosis (iSS) include hearing loss, impaired balance, myelopathy and, less commonly, cognitive compromise. Olfactory function may be affected but dedicated studies are lacking. This study aimed to assess the prevalence of olfactory dysfunction in iSS and correlate it with auditory and cognitive functions.

Methods

Ten participants with iSS completed the University of Pennsylvania Smell Identification Test (UPSIT). The scores were compared with population norms; regression analysis was performed to evaluate associations between the scores and hearing thresholds (3-frequency average, 3FA) or the number of cognitive domains impaired. Imaging was reviewed for haemosiderin distribution and to exclude other causes of olfactory and hearing dysfunction.

Results

Eight of ten participants were male; the mean (standard deviation, SD) age was 52.5 (14.5) years. Olfactory hypofunction was identified in all participants and in six (60%) was moderate or completely absent. The mean UPSIT score of 25.5 (7.8) was significantly worse than population norms (difference in means − 10.0; 95% CI − 15.6 to − 4.4). Linear regression identified an association between UPSIT and hearing thresholds (R = 0.75; p = 0.013). The score decreases by 0.157 units (95% CI − 0.31 to − 0.002; p = 0.048) per unit increase in 3FA, after adjusting for hearing loss risk factors. There was no statistically significant association between UPSIT and cognitive function (R = 0.383; p = 0.397).

Conclusion

We report a high prevalence of olfactory dysfunction in iSS, the severity of which correlated with hearing loss. Olfaction appears to be a core feature of the iSS clinical syndrome that should be assessed routinely.

Olfaction and Executive Cognitive Performance: A Systematic Review

Objective tests of olfaction are widely available to aid in the assessment of olfaction. Their clearest role is in the characterization of olfactory changes, either reported by or suspected in a patient. There is a rapidly growing literature concerned with the association of olfactory changes with certain neuropsychiatric conditions and the use of olfactory testing to supplement conventional assessments in clinical and research practice is evolving. Neural pathways important for olfactory processing overlap extensively with pathways important for cognitive functioning, and especially those important for executive functioning, many of which are concentrated in the frontal lobes. Previous work has identified associations between performance on certain olfactory tests (most frequently olfactory identification) and executive functioning and behavioral measures (e.g. of impulsivity). More recently, similar associations have also been identified in non-clinical samples, raising new questions as to the utility of olfactory test scores as proxy measures for non-olfactory phenomena. In this systemic review, we sought to identify studies, both clinical and non-clinical, that investigated the associations of olfaction with performance on tasks sensitive to frontal lobe functioning. Our search criteria led to the identification of 70 studies published in English. We examined in detail and tabulated the data from these studies, highlighted each study's key findings, and critically evaluated these studies. We use the results of this review to reflect on some of the current and future challenges concerning the use of olfactory testing in clinical neuropsychiatric practice and research and speculate on the potential benefits of administering phonemic fluency in combination with olfactory testing to enhance its predictive value.

Olfactory dysfunction in patients with multiple sclerosis; A systematic review and meta-analysis

Background

The importance and prevalence of olfactory dysfunction is recently gaining attention in patients with multiple sclerosis (MS) as a result of their chronic inflammatory disease, yet different prevalence rates are reported for it. Therefore, we have designed this systematic review to estimate the pooled prevalence of olfactory dysfunction in patients with MS. To our knowledge, this is the first systematic review and meta-analysis on the prevalence of olfactory dysfunction in MS patients.

Methods

We searched PubMed, Scopus, EMBASE, Web of Science, ProQuest, and gray literature including references from the identified studies, review studies, and conference abstracts which were published up to January 2021. Articles that were relevant to our topic and could provide information regarding the prevalence of olfactory dysfunction, or the scores of smell threshold, discrimination, or identification (TDI) among MS patients and healthy individuals were included. The pooled prevalence was calculated using a random-effects model and a funnel plot and Egger’s regression test were used to see publication bias.

Results

The literature search found 1630 articles. After eliminating duplicates, 897 articles remained. Two conference abstracts were included for final analysis. A total of 1099 MS cases and 299 MS patients with olfactory dysfunction were included in the analysis. The pooled prevalence of olfactory dysfunction in the included studies was 27.2%. Also, the overall TDI score in MS patients was lower than that in the control group, and the level of Threshold, Discrimination, and Identification per se were lower in MS compared with control respectively.

Conclusion

The results of this systematic review show that the prevalence of olfactory dysfunction in MS patients is high and more attention needs to be drawn to this aspect of MS.

International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

Mapping the Microstructure and Striae of the Human Olfactory Tract with Diffusion MRI

The human sense of smell plays an important role in appetite and food intake, detecting environmental threats, social interactions, and memory processing. However, little is known about the neural circuity supporting its function. The olfactory tracts project from the olfactory bulb along the base of the frontal cortex, branching into several striae to meet diverse cortical regions. Historically, using diffusion magnetic resonance imaging (dMRI) to reconstruct the human olfactory tracts has been prevented by susceptibility and motion artifacts. Here, we used a dMRI method with readout segmentation of long variable echo-trains (RESOLVE) to minimize image distortions and characterize the human olfactory tracts in vivo We collected high-resolution dMRI data from 25 healthy human participants (12 male and 13 female) and performed probabilistic tractography using constrained spherical deconvolution (CSD). At the individual subject level, we identified the lateral, medial, and intermediate striae with their respective cortical connections to the piriform cortex and amygdala (AMY), olfactory tubercle (OT), and anterior olfactory nucleus (AON). We combined individual results across subjects to create a normalized, probabilistic atlas of the olfactory tracts. We then investigated the relationship between olfactory perceptual scores and measures of white matter integrity, including mean diffusivity (MD). Importantly, we found that olfactory tract MD negatively correlated with odor discrimination performance. In summary, our results provide a detailed characterization of the connectivity of the human olfactory tracts and demonstrate an association between their structural integrity and olfactory perceptual function.SIGNIFICANCE STATEMENT This study provides the first detailed in vivo description of the cortical connectivity of the three olfactory tract striae in the human brain, using diffusion magnetic resonance imaging (dMRI). Additionally, we show that tract microstructure correlates with performance on an odor discrimination task, suggesting a link between the structural integrity of the olfactory tracts and odor perception. Lastly, we generated a normalized probabilistic atlas of the olfactory tracts that may be used in future research to study its integrity in health and disease.

Clinical and Paraclinical Biomarkers and the Hitches to Assess Conversion to Secondary Progressive Multiple Sclerosis: A Systematic Review

Conversion to secondary progressive (SP) course is the decisive factor for long-term prognosis in relapsing multiple sclerosis (MS), generally considered the clinical equivalent of progressive MS-associated neuroaxonal degeneration. Evidence is accumulating that both inflammation and neurodegeneration are present along a continuum of pathologic processes in all phases of MS. While inflammation is the prominent feature in early stages, its quality changes and relative importance to disease course decreases while neurodegenerative processes prevail with ongoing disease. Consequently, anti-inflammatory disease-modifying therapies successfully used in relapsing MS are ineffective in SPMS, whereas specific treatment for the latter is increasingly a focus of MS research. Therefore, the prevention, but also the (anticipatory) diagnosis of SPMS, is of crucial importance. The problem is that currently SPMS diagnosis is exclusively based on retrospectively assessing the increase of overt physical disability usually over the past 6–12 months. This inevitably results in a delay of diagnosis of up to 3 years resulting in periods of uncertainty and, thus, making early therapy adaptation to prevent SPMS conversion impossible. Hence, there is an urgent need for reliable and objective biomarkers to prospectively predict and define SPMS conversion. Here, we review current evidence on clinical parameters, magnetic resonance imaging and optical coherence tomography measures, and serum and cerebrospinal fluid biomarkers in the context of MS-associated neurodegeneration and SPMS conversion. Ultimately, we discuss the necessity of multimodal approaches in order to approach objective definition and prediction of conversion to SPMS.

Remifentanil reduces glutamate toxicity in rat olfactory bulb neurons in culture

Background

Opioids are widely used as an analgesic drug in the surgical setting. Remifentanil is an ultra-short acting opioid with selective affinity to the mu (μ) receptor, and also exhibits GABA agonist effects. The aim of this study was study of the neurotoxic or neuroprotective effect of different doses of remifentanil in glutamate-induced toxicity in olfactory neuron cell culture.

Materials and methods

Olfactory neurons were obtained from newborn Sprague Dawley rat pups. Glutamate 10^-5 mM was added to all culture dishes, except for the negative control group. Remifentanil was added at three different doses for 24 hours, after which evaluation was performed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Total Antioxidant Capacity (TAC), Total Oxidant Status (TOS), and Annexin V.

Results

The highest and lowest viability values were obtained from the low and high remifentanil doses at approximately 91% and 75%, respectively. TAC and TOS were correlated with the MTT results. TAC, TOS and MTT most closely approximated to the sham group values in the remifentanil 0.02 mM group.

Conclusions

Our results suggest that remifentanil has the potential to reduce glutamate toxicity and to increase cell viability in cultured neuron from the rat olfactory bulb.

Olfactory Dysfunction and Cognition in Radiologically Isolated Syndrome and Relapsing-Remitting Multiple Sclerosis

BACKGROUND

Multiple Sclerosis (MS) is a neuroinflammatory, neurodegenerative, demyelinating disease that causes cognitive, olfactory, and other neurological dysfunctions. Radiologically Isolated Syndrome (RIS), in which only radiological findings are monitored, is accepted as the preclinical stage of demyelinating disease and is considered an important period for disease pathology. Therefore, in this study, we aimed to evaluate the olfactory and cognitive functions and their clinical correlation in RIS and Relapsing-Remitting MS (RRMS) patients and a healthy control group.

METHODS

Our study included 10 RRMS patients, 10 RIS patients, and 10 healthy controls. We conducted an olfactor evaluation via the "Sniffin' Sticks" test. The subjects underwent a neuropsychometric test battery to evaluate cognitive functions, including memory, visuospatial, and executive functions. Depression was evaluated using the Beck depression scale. Fatigue and daily life activity were evaluated using the Fatigue Severity Scale (FSS) and the 36-Item Short Form Survey (SF-36), respectively. Disability assessment was done with the Expanded Disability Status Scale (EDSS).

RESULTS

RRMS and RIS patients' olfactory test scores were significantly different from those in the control group (p < 0.05). There was a significant difference between the odor threshold scores of patients in the RRMS and RIS groups. There was a significant correlation between memory-oriented cognitive tests and olfactory tests in the RRMS and RIS groups.

CONCLUSION

Olfactory dysfunction can be seen in RIS patients, like in RRMS patients. Cognitive and olfactory dysfunction may be together a sign of degeneration in demyelinating diseases.

Neurocognitive impairment and social cognition in multiple sclerosis

PURPOSE/AIM OF THE STUDY

The impairment of neurocognitive functions occurs in all subtypes of multiple sclerosis, even from the earliest stages of the disease. Commonly reported manifestations of cognitive impairment include deficits in attention, conceptual reasoning, processing efficiency, information processing speed, memory (episodic and working), verbal fluency (language), and executive functions. Multiple sclerosis patients also suffer from social cognition impairment, which affects their social functioning. The objective of the current paper is to assess the effect of neurocognitive impairment and its potential correlation with social cognition performance and impairment in multiple sclerosis patients.

MATERIALS AND METHODS

An overview of the available-to-date literature on neurocognitive impairment and social cognition performance in multiple sclerosis patients by disease subtype was performed.

RESULTS

It is not clear if social cognition impairment occurs independently or secondarily to neurocognitive impairment. There are associations of variable strengths between neurocognitive and social cognition deficits and their neural basis is increasingly investigated.

CONCLUSIONS

The prompt detection of neurocognitive predictors of social cognition impairment that may be applicable to all multiple sclerosis subtypes and intervention are crucial to prevent further neural and social cognition decline in multiple sclerosis patients.

Olfactory Dysfunction in Patients With Relapsing-Remitting Multiple Sclerosis Treated With Disease-Modifying Therapies

BACKGROUND

Olfactory dysfunction evaluated with time-consuming tests was more common in patients with multiple sclerosis (MS) than in controls and correlated with neurological deficit. The aim of the present study was to compare olfactory function between patients with relapsing-remitting MS (RRMS) and controls with short and simple screening tool-the Sniffin' Sticks Identification Test (SSIT)-and search for its association with clinical and radiological features of the disease.

METHODS

The study included 30 controls and 30 patients with RRMS treated with disease-modifying therapies-injectables (interferon β or glatiramer acetate, N = 18) and oral drugs (dimethyl fumarate or fingolimod, N = 12). Hyposmia was defined as a score of 6 points or fewer in the SSIT olfactory test. The data concerning number of previous relapses, disability in Expanded Disability Status Scale (EDSS), and recent brain magnetic resonance imaging (MRI) scan were collected. Moreover, thalamic volume and third ventricle width were recorded in every patient. Additionally, cognition and fatigue in patients were evaluated 24 months after olfactory assessment with the Symbol Digit Modalities Test (SDMT) and Fatigue Scale for Motor and Cognitive Functions (FSMC), respectively.

RESULTS

Patients with RRMS had a higher risk of hyposmia than controls (66.7% vs 36.7%, OR = 1.82, 95% CI, 1.10-3.67, P = .02). Neither inflammatory (number of previous relapses or new brain MRI lesions) nor neurodegenerative (EDSS, SDMT, and FSMC scores; thalamic volume; third ventricle width) MS features did not correlate with SSIT score (P > .05). In patients treated with oral drugs, olfactory dysfunction correlated with FSMC cognitive subscale (r = -0.90, P = .006).

CONCLUSIONS

Olfactory dysfunction is nearly twice as common in RRMS as in controls and correlates with fatigue level in patients treated with dimethyl fumarate or fingolimod.

Smell as a clinical-marker for functional limitations in multiple sclerosis: A pilot study

BACKGROUND

Olfactory dysfunction is a common symptom of multiple sclerosis (MS). The questions of whether and to what degree olfactory dysfunction can serve as a clinical marker of MS disability (i.e. cognitive impairments and functional limitations) are not yet answered. The current study aimed to explore associations between olfactory function (i.e. smell identification) with cognitive capacities, functional performance and quality of life (QOL) in persons with MS.

METHODS

Olfactory function was measured by the University of Pennsylvania Smell Identification Test (UPSIT). Functional ability was assessed by the Actual Reality^TM (AR) task. QOL was assessed by the Multiple Sclerosis Quality of Life-54 (MSQOL-54). Cognition was assessed by the Brief International Cognitive Assessment for MS (BICAMS) in 23 MS patients and 15 matched healthy controls.

RESULTS

MS patients had lower UPSIT scores than healthy controls. Worse UPSIT scores were associated with reduced performances on the BICAMS and AR task as well as lower MSQOL-54 scores. Specifically, UPSIT scores were related to MSQOL-54 scores independent of BICAMS composite scores, while the relationship between UPSIT score and AR performance was mediated by BICAMS composite score.

CONCLUSION

This study confirms previous studies which concluded that olfactory function is impaired in MS. Furthermore, olfactory dysfunction is related to limitations in activity performance and QOL. Taken together with previous studies, olfactory function may be considered as a clinical marker related to MS disability. Longitudinal studies are needed to confirm these results.

Prognostic value of odor identification impairment in multiple sclerosis: 10-Years follow-up

BACKGROUND

Olfactory dysfunction has been linked to clinical severity variables in multiple MS populations. Though, its prognostic value is still unknown.

OBJECTIVE

The aim of this study was to explore the long-term outcome associated with Brief-Smell Identification Test (B-SIT) performance in a cohort of MS patients.

METHODS

A retrospective review of the clinical records was conducted in 149 patients who participated in a previous study, with a median follow-up of 121 months. Demographic and clinical data regarding the last clinical appointment with EDSS measurement were collected. Multiple Sclerosis Severity Scale (MSSS) and Age-Related Multiple Sclerosis Severity (ARMSS) scores were calculated. Date of the last clinical contact or death was recorded.

RESULTS

Among MS patients with progressive clinical course (n = 33), those with impaired B-SIT at baseline had greater change per month during follow-up (as measured by increases in MSSS and ARMSS scores) and a higher hazard of death. No significant associations were found among patients with relapsing and remitting MS (n = 116).

CONCLUSIONS

The study results demonstrate that odor identification impairment has prognostic value in progressive MS, suggesting that a brief odor identification measure can be a marker of neurodegeneration in progressive MS.

Harmonization of real-world studies in multiple sclerosis: Retrospective analysis from the rirems group

BACKGROUND

Worldwide multiple sclerosis (MS) centers have coordinated their efforts to use data acquired in clinical practice for real-world observational studies. In this retrospective study, we aim to harmonize outcome measures, and to evaluate their heterogeneity within the Rising Italian Researchers in MS (RIReMS) study group.

METHODS

RIReMS members filled in a structured questionnaire evaluating the use of different outcome measures in clinical practice. Thereafter, thirty-four already-published papers from RIReMS centers were used for heterogeneity analyses, using the DerSimonian and Laird random-effects method to compute the between-study variance (τ²).

RESULTS

Based on questionnaire results, we defined basic modules for diagnosis and follow-up, consisting of outcome measures recorded by all participating centers at the time of diagnosis, and, then, at least annually; we also defined more detailed/optional modules, with outcome measures recorded less frequently and/or in the presence of specific clinical indications. Looking at heterogeneity, we found 5-year variance in age at onset (ES=27.34; 95%CI=26.18, 28.49; p<0.01; τ²=4.76), and 7% in female percent (ES=66.42; 95%CI=63.08, 69.76; p<0.01; τ²=7.15). EDSS variance was 0.2 in studies including patients with average age <36.1 years (ES=1.96; 95%CI=1.69, 2.24; p<0.01; τ²=0.19), or from 36.8 to 41.1 years (ES=2.70; 95%CI=2.39, 3.01; p<0.01; τ²=0.18), but increased to 3 in studies including patients aged >41.4 years (ES=4.37; 95%CI=3.40, 5.35; p<0.01; τ²=2.96). The lowest variance of relapse rate was found in studies with follow-up duration ≤2 years (ES=9.07; 95%CI=5.21, 12.93; p = 0.02; τ²=5.53), whilst the lowest variance in EDSS progression was found in studies with follow-up duration >2 years (ES=5.41; 95%CI=3.22, 7.60; p = 0.02; τ²=1.00).

DISCUSSION

We suggest common sets of biomarkers to be acquired in clinical practice, that can be used for research purposes. Also, we provide researchers with specific indications for improving inclusion criteria and data analysis, ultimately allowing data harmonization and high-quality collaborative studies.

Particles Containing Cells as a Strategy to Promote Remyelination in Patients With Multiple Sclerosis

The repair of demyelinated lesions is a key objective in multiple sclerosis research. Remyelination fundamentally depends on oligodendrocyte progenitor cells (OPC) reaching the lesion; this is influenced by numerous factors including age, disease progression time, inflammatory activity, and the pool of OPCs available, whether they be NG2 cells or cells derived from neural stem cells. Administering OPCs has been proposed as a potential cell therapy; however, these cells can only be administered directly. This article discusses the potential administration of OPCs encapsulated within hydrogel particles composed of biocompatible biomaterials, via the nose-to-brain pathway. We also discuss conditions for the indication of this therapy, and such related issues as the influence on endogenous remyelination, migration of OPCs to demyelinated areas, and the immune response, given the autoimmune nature of multiple sclerosis. Chitosan and derivatives constitute the most promising biomaterial for this purpose, although these issues must be addressed. In conclusion, this line of research may yield an alternative to the remyelinating drugs currently being studied.

Anosmia in COVID-19: Mechanisms and Significance

The global pandemic of coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 remains a challenge for prevention due to asymptomatic or paucisymptomatic patients. Anecdotal and preliminary evidence from multiple institutions shows that these patients present with a sudden onset of anosmia without rhinitis. We aim to review the pathophysiology of anosmia related to viral upper respiratory infections and the prognostic implications. Current evidence suggests that SARS-CoV-2-related anosmia may be a new viral syndrome specific to COVID-19 and can be mediated by intranasal inoculation of SARS-CoV-2 into the olfactory neural circuitry. The clinical course of neuroinvasion of SARS-CoV-2 is yet unclear, however an extended follow up of these patients to assess for neurological sequelae including encephalitis, cerebrovascular accidents and long-term neurodegenerative risk may be indicated.