CSF Biomarkers in COVID-19 Associated Encephalopathy and Encephalitis Predict Long-Term Outcome

Blood neurofilament light chain and S100B as biomarkers of neurological involvement and functional prognosis in COVID-19: a multicenter study

BACKGROUND AND AIM

COVID-19 is associated with neurological complications, termed neuro-COVID, affecting patient outcomes. We aimed to evaluate the association between serum neurofilament light chain (NfL) and S100B biomarkers with the presence of neurological manifestations and functional prognosis in COVID-19 patients.

METHODS

A multicenter prospective cohort study was conducted in three hospitals in the Emilia-Romagna region, Italy, from March 2020 to April 2022. Hospitalized patients with PCR-confirmed COVID-19 were enrolled. Serum S100B and NfL levels were measured in the acute or subacute phase after admission. Diagnostic accuracy was assessed using receiver operating characteristic (ROC) analyses. Statistical analyses were performed to evaluate the association between biomarkers, clinical/laboratory variables, and prognosis, specifically focusing on worsening of the modified Rankin Scale (mRS) from admission to discharge.

RESULTS

A total of 279 patients (153 males, median age 76.7 years) were included. Among them, 69 (24.7%) developed neuro-COVID. Serum NfL levels were significantly higher in the neuro-COVID group (median 110 vs 68.3; p = 0.035) and correlated with severe encephalopathy and extracranial neurologic manifestations. The ROC analysis showed low accuracy in the discrimination between the two groups for both NfL and S100B. Key predictors of worsening mRS included mechanical ventilation (OR = 9.56, 95% CI = 1.67-54.75; p = 0.011), severe encephalopathy (OR = 5.10, 95% CI = 1.58-16.19; p = 0.006), and elevated S100B levels (OR = 2.62, 95% CI = 1.10-6.46; p = 0.037).

CONCLUSIONS

Serum NfL and S100B biomarkers were not accurate in discriminating neuro-COVID patients, however NfL levels were associated with severe and extracranial neuro-COVID, while S100B with functional outcomes, potentially informing clinical management.

Central and peripheral kynurenine pathway metabolites in COVID-19: Implications for neurological and immunological responses

Long-term symptoms such as pain, fatigue, and cognitive impairments are commonly observed in individuals affected by coronavirus disease 2019 (COVID-19). Metabolites of the kynurenine pathway have been proposed to account for cognitive impairment in COVID-19 patients. Here, cerebrospinal fluid (CSF) and plasma levels of kynurenine pathway metabolites in 53 COVID-19 patients and 12 non-inflammatory neurological disease controls in Sweden were measured with an ultra-performance liquid chromatography-tandem mass spectrometry system (UPLC-MS/MS) and correlated with immunological markers and neurological markers. Single cell transcriptomic data from a previous study of 130 COVID-19 patients was used to investigate the expression of key genes in the kynurenine pathway. The present study reveals that the neuroactive kynurenine pathway metabolites quinolinic acid (QUIN) and kynurenic acid (KYNA) are increased in CSF in patients with acute COVID-19. In addition, CSF levels of kynurenine, ratio of kynurenine/tryptophan (rKT) and QUIN correlate with neurodegenerative markers. Furthermore, tryptophan is significantly decreased in plasma but not in the CSF. In addition, the kynurenine pathway is strongly activated in the plasma and correlates with the peripheral immunological marker neopterin. Single-cell transcriptomics revealed upregulated gene expressions of the rate-limiting enzyme indoleamine 2,3- dioxygenase1 (IDO1) in CD14+ and CD16+ monocytes that correlated with type II-interferon response exclusively in COVID-19 patients. In summary, our study confirms significant activation of the peripheral kynurenine pathway in patients with acute COVID-19 and, notably, this is the first study to identify elevated levels of kynurenine metabolites in the central nervous system associated with the disease. Our findings suggest that peripheral inflammation, potentially linked to overexpression of IDO1 in monocytes, activates the kynurenine pathway. Increased plasma kynurenine, crossing the blood-brain barrier, serves as a source for elevated brain KYNA and neurotoxic QUIN. We conclude that blocking peripheral-to-central kynurenine transport could be a promising strategy to protect against neurotoxic effects of QUIN in COVID-19 patients.

Autoantibodies as potential prognostic factors for clinical outcomes related to COVID-19: a systematic review of inception prospective cohort studies with GRADE recommendations

This systematic review of inception prospective cohort studies aimed to investigate whether autoantibodies are potential prognostic factors for short- and long-term clinical outcomes of COVID-19. Searches were conducted in MEDLINE, EMBASE, AMED, GLOBAL HEALTH, and COCHRANE databases from 2019 to 2022. When possible, meta-analysis was conducted, otherwise findings from individual studies were reported using odds ratios (OR) with 95% confidence intervals (CI). Quality of evidence was summarized using the GRADE criteria. We identified 2292 references, 18 inception prospective cohort studies (3178 patients) were included in the systematic review, and 12 studies reached criteria for meta-analysis. Studies achieved, in general, low to moderate risk of bias. Moderate quality of evidence showed that anti-interferon (IFN) was associated with increased risk of severity (OR=7.75; CI=1.79-33.61) and mechanical ventilation (OR=4.19; CI=2.06-8.53), but not with COVID-19 mortality (OR=1.68; CI=0.63-4.44). Antiphospholipids were not associated with COVID-19 mortality (OR=1.42; CI=0.85-2.37; P=0.18; I2=3.21) nor with thrombosis risk (OR=1.41; CI: 0.71-2.8; P=0.33). Antinuclear antibody level was not associated with risk of mortality or severity (risk for mortality: OR=3.8; CI=0.78-18.6; P=0.1; I2: 32.3; severity: OR=1.74; CI=0.96-3.16; P=0.07). Evidence currently available is insufficient for a quantitative analysis of autoantibodies association with long COVID-19. Anti-IFN measurement should be considered in COVID-19 follow-up. In a population-based rational, optimized vaccination strategies should be considered for individuals with anti-IFN antibodies since it could represent a risk for a worse prognosis. High-quality prospective studies for short- and long-term disease effects and autoantibody evaluation are still needed.

Acute and long-term effects of COVID-19 on brain and mental health: A narrative review

BACKGROUND

COVID infection has been associated with long term sequalae (Long COVID) which include neurological and behavioral effects in thousands of patients, but the etiology and scope of symptoms is not well understood. This paper reviews long term sequelae of COVID on brain and mental health in patients with the Long COVID syndrome.

METHODS

This was a literature review which queried databases for Pubmed, Psychinfo, and Medline for the following topics for January 1, 2020-July 15, 2023: Long COVID, PASC, brain, brain imaging, neurological, neurobiology, mental health, anxiety, depression.

RESULTS

Tens of thousands of patients have developed Long COVID, with the most common neurobehavioral symptoms anosmia (loss of smell) and fatigue. Anxiety and mood disorders are elevated and seen in about 25% of Long COVID patients. Neuropsychological testing studies show a correlation between symptom severity and cognitive dysfunction, while brain imaging studies show global decreases in gray matter and alterations in olfactory and other brain areas.

CONCLUSIONS

Studies to date show an increase in neurobehavioral disturbances in patients with Long COVID. Future research is needed to determine mechanisms.

Persistence of Long COVID Symptoms Two Years After SARS-CoV-2 Infection: A Prospective Longitudinal Cohort Study

BACKGROUND/OBJECTIVES

Millions of individuals worldwide continue to experience symptoms following SARS-CoV-2 infection. This study aimed to assess the prevalence and phenotype of multi-system symptoms attributed to Long COVID-including fatigue, pain, cognitive-emotional disturbances, headache, cardiopulmonary issues, and alterations in taste and smell-that have persisted for at least two years after acute infection, which we define as "persistent Long COVID". Additionally, the study aimed to identify clinical features and blood biomarkers associated with persistent Long COVID symptoms.

METHODS

We sent a detailed long COVID symptoms questionnaire to an existing cohort of 1258 vaccinated adults (age 18-79 years) who had mild infection (e.g., non-hospitalized) SARS-CoV-2 Delta variant 2 years earlier. These individuals had comprehensive datasets, including blood samples, available for further analysis. We estimated prevalence of persistent long COVID two years post-infection using weighted adjustment (Horvitz-Thompson estimator) to overcome reporting bias. Multivariable logistic regression models were used to determine association of clinical features and blood biomarkers (pre-infection SARS-CoV-2 RBD-IgG, SARS-CoV-2 neutralizing antibodies, and pre-infection and post-infection neurofilament light) with prevalence of persistent long COVID.

RESULTS

N = 323 participants responded to the survey, of whom N = 74 (23%) reported at least one long COVID symptom that had persisted for two years after the acute infection. Weighted prevalence of persistent long COVID symptoms was 21.5% (95% CI = 16.7-26.3%). Female gender, smoking, and severity of acute COVID-19 infection were significantly associated with persistent Long COVID. The blood biomarkers assessed were not significantly associated with persistent Long COVID.

CONCLUSIONS

Among vaccinated adults two years after mild infection with Delta variant SARS-CoV-2, persistent symptoms attributed to Long COVID are extremely common, certain subgroups are at higher risk, and further research into biological mechanisms and potential treatment targets is needed.

Increased occurrence of microstate class B as the independent risk factor for persistent psychiatric symptoms related to omicron infection

OBJECTIVE

This study aimed to investigate the EEG microstate characteristics in patients with persistent Omicron-related Psychiatric Symptoms (ORPS) as well as their correlations with the severity of ORPS.

METHODS

This study included 31 patients with ORPS, and they were divided into remission group (n=19) and non-remission group (n=12) according to the decrease of Brief Psychiatric Rating Scale (BPRS) at discharge. Multivariate logistic models were applied to analyze the risk features associated with non-remission of ORPS at discharge, and the Spearman rank correlation was adopted to analyze the correlation between the occurrence of microstate class B and BPRS score at admission.

RESULTS

The analysis revealed that an increased occurrence of EEG microstate class B was significantly associated with a higher likelihood of non-remission of ORPS at discharge (p < 0.05). Furthermore, a moderate positive correlation was observed between the occurrence of microstate class B and BPRS scores at admission (r = 0.390, p = 0.030), indicating that patients with more frequent microstate class B tended to exhibit more severe psychiatric symptoms at onset.

CONCLUSIONS

The findings suggest that an increased occurrence of EEG microstate class B is an independent risk factor for non-remission of ORPS at discharge. Additionally, the positive correlation between microstate class B and BPRS scores underscores the potential of microstate class B as a biomarker for the severity of psychiatric symptoms in ORPS patients.

SIGNIFICANCE

Identifying the increased occurrence of microstate class B at admission could serve as a novel marker for early assessment of ORPS severity and prognostic evaluation.

Effect of a biomimetic pathogen adsorbing device on inflammatory biomarkers in COVID-19 patients

INTRODUCTION

The Seraph 100 Microbind Affinity blood filter eliminate bacteria, viruses, fungi and toxins from blood stream.

METHODS

This is a prospective multicenter observational biomarker trial in PCR-positive SARS-CoV-2 patients with acute respiratory failure. Biomarkers were sequentially tested at three time points.

RESULTS

Forty-two patients with SARS-CoV-2 detected by PCR with acute respiratory failure were included. When receiving hemoperfusion treatment, 27 (64%) patients were on mechanical ventilation, 41 (98%) patients were treated in the ICU. The 3-month survival was 52%. After one hemoperfusion treatment cycle, D-dimer (p = 0.014), hemoglobin (p = 0.003) and LDH (p = 0.001) concentrations were significantly reduced 4 days after treatment. From the multiplex assay IL-1b, CXCL8/ IL-8, IL-10, IL-13, IL-15, CCL11/Eotaxin, G-CSF, and CXCL10/IP-10 were significantly reduced 1 h after treatment, however not 4 days later.

CONCLUSION

Hemoperfusion with Seraph 100 Microbind Affinity Filter in patients with severe COVID-19 can transiently reduce several inflammatory biomarkers in the blood.

Positive 14-3-3 protein in cerebrospinal fluid followed by poppy-induced delayed post-hypoxic leukoencephalopathy: A case report

Background

Delayed post-hypoxic leukoencephalopathy (DPHL) is characterized by a biphasic clinical course, with complete recovery from coma to a fully conscious state lasting one to four weeks (lucid interval), followed by abrupt neurological deterioration as an indirect consequence of hypoxic events like carbon monoxide poisoning and narcotic drug overdose. To our best knowledge, there are no documented cases in literature of choreoathetosis and dementia following poppy-induced DPHL with 14-3-3 protein in cerebrospinal fluid (CSF).

Case presentation

We report the case of a 70-year-old female who underwent cardiopulmonary resuscitation (CPR) due to overdose of homemade refined opium poppy paste two weeks prior to presentation. She presented a progressive cognitive decline, along with the development of apraxia and choreic movement affecting her tongue and bilateral upper and lower extremities. During the symptomatic phase, brain magnetic resonance imaging (MRI) showed bilateral symmetrical hyperintense signals mostly in central frontal, temporal, and parieto-occipital lobes in the diffusion weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) sequences which are the characteristic findings of DPHL. CSF routine analysis, as well as toxicology screening, autoimmune and paraneoplastic encephalitis panels were negative, but the presence of 14-3-3 protein in the CSF was detected. With steroid therapy, hyperbaric oxygen therapy and symptomatic treatment, she experienced gradual improvement in cognition, motivation, and psychomotor function.

Conclusion

DPHL represents a distinct form of encephalopathy characterized by unique clinical course and imaging features. It is the first report of DPHL with positive 14-3-3 protein in CSF. The potential of 14-3-3 protein as a biomarker for diagnosing DPHL and its ability to predict disease severity and prognosis warrants further research.

Cerebellitis following COVID-19 infection: A case-based systematic review and pooled analysis

Background

The COVID-19 pandemic has been linked to neurological complications, including Cerebellitis. This study aims to investigate the clinical features, and consequences of Cerebellitis following COVID-19 infection, informing medical management strategies.

Methods

A systematic search was conducted through PubMed, Web of Science, Embase, ProQuest, and Cochrane databases from January 2018 to September 12, 2023, on cases post-COVID-19. Demographics, clinical characteristics, and diagnostic techniques were analyzed using descriptive statistics. Chi-Square tests assessed associations between diagnoses and treatments, with visualizations including heatmaps and scatter plots.

Results

After the final Screening, the analysis of 18 cases revealed Cerebellitis post-COVID-19 spanned 9 countries, predominantly from the USA (27.8 %), with a mean patient age of 40.1 years (±24.6). Males comprised 94.4 % of cases. Common underlying conditions included hypertension (22.2 %) and diabetes (11.1 %). Neurological symptoms presented on average 15.15 ± 12.7 days post-COVID-19 infection. A moderate negative correlation (r = -0.358) was observed between age and symptom onset. Blood and CSF biomarkers showed weak correlations with symptom onset intervals. Treatment efficacy varied, with most cases achieving symptom-free outcomes. The Chi-Square test for diagnosis-treatment associations yielded a p-value of 0.089, and for follow-up outcomes, a p-value of 0.283, indicating no significant statistical associations.

Conclusion

This systematic review highlights increased reports of Cerebellitis in males in their fourth decade of life, with the highest comorbidities being vascular diseases. Marker assessments show a decrease in CSF protein in half of patients, along with complete recovery following combination treatment with antivirals and steroids in acute Cerebellitis.

SARS-CoV-2 infects neurons, astrocytes, choroid plexus epithelial cells and pericytes of the human central nervous system in vitro

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection is associated with neurological sequelae including haemorrhage, thrombosis and ischaemic necrosis and encephalitis. However, the mechanism by which this occurs is unclear. Neurological disease associated with COVID-19 has been proposed to occur following direct infection of the central nervous system and/or indirectly by local or systemic immune activation. We evaluated the expression of angiotensin-converting enzyme-2 and transmembrane protease, serine 2 (TMPRSS2) in brain tissue from five healthy human donors and observed low-level expression of these proteins in cells morphologically consistent with astrocytes, neurons and choroidal ependymal cells within the frontal cortex and medulla oblongata. Primary human astrocytes, neurons, choroid plexus epithelial cells and pericytes supported productive SARS-CoV-2 infection with ancestral, Alpha, Delta and Omicron variants. Infected cells supported the full viral life cycle, releasing infectious virus particles. In contrast, primary brain microvascular endothelial cells and microglia were refractory to SARS-CoV-2 infection. These data support a model whereby SARS-CoV-2 can infect human brain cells, and the mechanism of viral entry warrants further investigation.

Cognitive profile, neuroimaging and fluid biomarkers in post-acute COVID-19 syndrome

We aimed to characterize the cognitive profile of post-acute COVID-19 syndrome (PACS) patients with cognitive complaints, exploring the influence of biological and psychological factors. Participants with confirmed SARS-CoV-2 infection and cognitive complaints ≥ 8 weeks post-acute phase were included. A comprehensive neuropsychological battery (NPS) and health questionnaires were administered at inclusion and at 1, 3 and 6 months. Blood samples were collected at each visit, MRI scan at baseline and at 6 months, and, optionally, cerebrospinal fluid. Cognitive features were analyzed in relation to clinical, neuroimaging, and biochemical markers at inclusion and follow-up. Forty-nine participants, with a mean time from symptom onset of 10.4 months, showed attention-executive function (69%) and verbal memory (39%) impairment. Apathy (64%), moderate-severe anxiety (57%), and severe fatigue (35%) were prevalent. Visual memory (8%) correlated with total gray matter (GM) and subcortical GM volume. Neuronal damage and inflammation markers were within normal limits. Over time, cognitive test scores, depression, apathy, anxiety scores, MRI indexes, and fluid biomarkers remained stable, although fewer participants (50% vs. 75.5%; p = 0.012) exhibited abnormal cognitive evaluations at follow-up. Altered attention/executive and verbal memory, common in PACS, persisted in most subjects without association with structural abnormalities, elevated cytokines, or neuronal damage markers.

High Levels of NfL, GFAP, TAU, and UCH-L1 as Potential Predictor Biomarkers of Severity and Lethality in Acute COVID-19

Few studies showed that neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), total tubulin-associated unit (TAU), and ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1) may be related to neurological manifestations and severity during and after SARS-CoV-2 infection. The objective of this work was to investigate the relationship among nervous system biomarkers (NfL, TAU, GFAP, and UCH-L1), biochemical parameters, and viral loads with heterogeneous outcomes in a cohort of severe COVID-19 patients admitted in Intensive Care Unit (ICU) of a university hospital. For that, 108 subjects were recruited within the first 5 days at ICU. In parallel, 16 mild COVID-19 patients were enrolled. Severe COVID-19 group was divided between "deceased" and "survivor." All subjects were positive for SARS-CoV-2 detection. NfL, total TAU, GFAP, and UCH-L1 quantification in plasma was performed using SIMOA SR-X platform. Of 108 severe patients, 36 (33.33%) presented neurological manifestation and 41 (37.96%) died. All four biomarkers - GFAP, NfL, TAU, and UCH-L1 - were significantly higher among deceased patients in comparison to survivors (p < 0.05). Analyzing biochemical biomarkers, higher Peak Serum Ferritin, D-Dimer Peak, Gamma-glutamyltransferase, and C-Reactive Protein levels were related to death (p < 0.0001). In multivariate analysis, GFAP, NfL, TAU, UCH-L1, and Peak Serum Ferritin levels were correlated to death. Regarding SARS-CoV-2 viral load, no statistical difference was observed for any group. Thus, Ferritin, NFL, GFAP, TAU, and UCH-L1 are early biomarkers of severity and lethality of SARS-COV-2 infection and may be important tools for therapeutic decision-making in the acute phase of disease.

Diagnostic markers of acute encephalitis syndrome and COVID-associated multisystem inflammatory syndrome in children from Southern India

Acute encephalitis syndrome (AES) in children poses a significant public health challenge in India. This study aims to explore the utility of host inflammatory mediators and neurofilament (NfL) levels in distinguishing etiologies, assessing disease severity, and predicting outcomes in AES. We assessed 12 mediators in serum (n = 58) and 11 in cerebrospinal fluid (CSF) (n = 42) from 62 children with AES due to scrub typhus, viral etiologies, and COVID-associated multisystem inflammatory syndrome (MIS-C) in Southern India. Additionally, NfL levels in serum (n = 20) and CSF (n = 18) were examined. Clinical data, including Glasgow coma scale (GCS) and Liverpool outcome scores, were recorded. Examining serum and CSF markers in the three AES etiology groups revealed notable distinctions, with scrub typhus differing significantly from viral and MIS-C causes. Viral causes had elevated serum CCL11 and CCL2 compared with scrub typhus, while MIS-C cases showed higher HGF levels than scrub typhus. However, CSF analysis showed a distinct pattern with the scrub typhus group exhibiting elevated levels of IL-1RA, IL-1β, and TNF compared with MIS-C, and lower CCL2 levels compared with the viral group. Modeling the characteristic features, we identified that age ≥3 years with serum CCL11 < 180 pg/mL effectively distinguished scrub typhus from other AES causes. Elevated serum CCL11, HGF, and IL-6:IL-10 ratio were associated with poor outcomes (p = 0.038, 0.005, 0.02). Positive CSF and serum NfL correlation, and negative GCS and serum NfL correlation were observed. Median NfL levels were higher in children with abnormal admission GCS and poor outcomes. Measuring immune mediators and brain injury markers in AES provides valuable diagnostic insights, with the potential to facilitate rapid diagnosis and prognosis. The correlation between CSF and serum NfL, along with distinctive serum cytokine profiles across various etiologies, indicates the adequacy of blood samples alone for assessment and monitoring. The association of elevated levels of CCL11, HGF, and an increased IL-6:IL-10 ratio with adverse outcomes suggests promising avenues for therapeutic exploration, warranting further investigation.

Viral Infections, Are They a Trigger and Risk Factor of Alzheimer's Disease?

Alzheimer's Disease (AD), a progressive and debilitating condition, is reported to be the most common type of dementia, with at least 55 million people believed to be currently affected. Many causation hypotheses of AD exist, yet the intriguing link between viral infection and its possible contribution to the known etiology of AD has become an attractive focal point of research for the field and a challenging study task. In this review, we will explore the historical perspective and milestones that led the field to investigate the viral connection to AD. Specifically, several viruses such as Herpes Simplex Virus 1 (HSV-1), Zika virus (ZIKV), and severe cute respiratory syndrome coronavirus 2 (SARS-CoV-2), along with several others mentioned, include the various viruses presently considered within the field. We delve into the strong evidence implicating these viruses in the development of AD such as the lytic replication and axonal transport of HSV-1, the various mechanisms of ZIKV neurotropism through the human protein Musashi-1 (MSI1), and the spread of SARS-CoV-2 through the transfer of the virus through the BBB endothelial cells to glial cells and then to neurons via transsynaptic transfer. We will also explore beyond these mere associations by carefully analyzing the potential mechanisms by which these viruses may contribute to AD pathology. This includes but is not limited to direct neuronal infections, the dysregulation of immune responses, and the impact on protein processing (Aβ42 and hyperphosphorylated tau). Controversies and challenges of the virus-AD relationship emerge as we tease out these potential mechanisms. Looking forward, we emphasize future directions, such as distinct questions and proposed experimentations to explore, that the field should take to tackle the remaining unanswered questions and the glaring research gaps that persist. Overall, this review aims to provide a comprehensive survey of the past, present, and future of the potential link between viral infections and their association with AD development while encouraging further discussion.

Brain Pathology in COVID-19: Clinical Manifestations and Potential Mechanisms

Neurological manifestations of coronavirus disease 2019 (COVID-19) are less noticeable than the respiratory symptoms, but they may be associated with disability and mortality in COVID-19. Even though Omicron caused less severe disease than Delta, the incidence of neurological manifestations is similar. More than 30% of patients experienced "brain fog", delirium, stroke, and cognitive impairment, and over half of these patients presented abnormal neuroimaging outcomes. In this review, we summarize current advances in the clinical findings of neurological manifestations in COVID-19 patients and compare them with those in patients with influenza infection. We also illustrate the structure and cellular invasion mechanisms of SARS-CoV-2 and describe the pathway for central SARS-CoV-2 invasion. In addition, we discuss direct damage and other pathological conditions caused by SARS-CoV-2, such as an aberrant interferon response, cytokine storm, lymphopenia, and hypercoagulation, to provide treatment ideas. This review may offer new insights into preventing or treating brain damage in COVID-19.

Current clinical findings of acute neurological syndromes after SARS-CoV-2 infection

Neuro-COVID, a condition marked by persistent symptoms post-COVID-19 infection, notably affects various organs, with a particular focus on the central nervous system (CNS). Despite scant evidence of SARS-CoV-2 invasion in the CNS, the increasing incidence of Neuro-COVID cases indicates the onset of acute neurological symptoms early in infection. The Omicron variant, distinguished by heightened neurotropism, penetrates the CNS via the olfactory bulb. This direct invasion induces inflammation and neuronal damage, emphasizing the need for vigilance regarding potential neurological complications. Our multicenter study represents a groundbreaking revelation, documenting the definite presence of SARS-CoV-2 in the cerebrospinal fluid (CSF) of a significant proportion of Neuro-COVID patients. Furthermore, notable differences emerged between RNA-CSF-positive and negative patients, encompassing aspects such as blood-brain barrier integrity, extent of neuronal damage, and the activation status of inflammation. Despite inherent limitations, this research provides pivotal insights into the intricate interplay between SARS-CoV-2 and the CNS, underscoring the necessity for ongoing research to fully comprehend the virus's enduring effects on the CNS. The findings underscore the urgency of continuous investigation Neuro-COVID to unravel the complexities of this relationship, and pivotal in addressing the long-term consequences of COVID-19 on neurological health.

Systemic inflammation relates to neuroaxonal damage associated with long-term cognitive dysfunction in COVID-19 patients

BACKGROUND AND OBJECTIVES

Cognitive deficits are increasingly recognized as a long-term sequela of severe COVID-19. The underlying processes and molecular signatures associated with these long-term neurological sequalae of COVID-19 remain largely unclear, but may be related to systemic inflammation-induced effects on the brain. We studied the systemic inflammation-brain interplay and its relation to development of long-term cognitive impairment in patients who survived severe COVID-19. Trajectories of systemic inflammation and neuroaxonal damage blood biomarkers during ICU admission were analyzed and related to long-term cognitive outcomes.

METHODS

Prospective longitudinal cohort study of patients with severe COVID-19 surviving ICU admission. During admission, blood was sampled consecutively to assess levels of inflammatory cytokines and neurofilament light chain (NfL) using an ultrasensitive multiplex Luminex assay and single molecule array technique (Simoa). Cognitive functioning was evaluated using a comprehensive neuropsychological assessment six months after ICU-discharge.

RESULTS

Ninety-six patients (median [IQR] age 61 [55-69] years) were enrolled from March 2020 to June 2021 and divided into two cohorts: those who received no COVID-19-related immunotherapy (n = 28) and those treated with either dexamethasone or dexamethasone and tocilizumab (n = 68). Plasma NfL concentrations increased in 95 % of patients during their ICU stay, from median [IQR] 23 [18-38] pg/mL at admission to 250 [160-271] pg/mL after 28 days, p < 0.001. Besides age, glomerular filtration rate, immunomodulatory treatment, and C-reactive protein, more specific markers of systemic inflammation at day 14 (i.e., interleukin (IL)-8, tumour necrosis factor, and IL-1 receptor antagonist) were significant predictors of blood NfL levels at day 14 of ICU admission (R2 = 44 %, p < 0.001), illustrating the association between sustained systemic inflammation and neuroaxonal damage. Twenty-six patients (27 %) exhibited cognitive impairment six months after discharge from the ICU. NfL concentrations showed a more pronounced increase in patients that developed cognitive impairment (p = 0.03). Higher NfL predicted poorer outcome in information processing speed (Trail Making Test A, r = -0.26, p = 0.01; Letter Digit Substitution Test, r = -0.24, p = 0.02).

DISCUSSION

Prolonged systemic inflammation in critically ill COVID-19 patients is related to neuroaxonal damage and subsequent long-term cognitive impairment. Moreover, our findings suggest that plasma NfL concentrations during ICU stay may possess prognostic value in predicting future long-term cognitive impairment in patients that survived severe COVID-19.

Toxoplasma gondii infection and brain inflammation: A two-sample mendelian randomization analysis

Background

Toxoplasma gondii is an opportunistic parasitic protozoan that can cause highly fatal toxoplasmic encephalitis when the host immune system is compromised. However, the transition from chronic to acute infection remains poorly understood. In this study, we conducted a 180-day observation of tissue damage and inflammation in the brains of mice infected with T. gondii. Subsequently, we investigated the inflammatory factors that T. gondii infection may alter using two-sample Mendelian randomization (MR) analysis.

Methods

We first established a mouse model of T. gondii infection. Subsequently, the mice were euthanized, the brain tissue collected, and immunohistochemistry and hematoxylin and eosin staining performed to observe tissue damage and inflammatory conditions at various time points. Our study also included a published large-scale genome-wide association study meta-analysis that encompassed the circulating concentrations of 41 cytokines. This dataset included 8293 individuals from three independent population cohorts in Finland. Genetic association data for T. gondii were sourced from the Integrative Epidemiology Unit and European Bioinformatics Institute datasets, which included 5010 and 559 individuals of European ancestry, respectively. To assess the causal relationship between T. gondii infection and inflammatory biomarkers, we applied a two-sample MR.

Results

Inflammation and damage resulting from T. gondii infection varied among the distinct regions of the mouse brain. Based on the MR analysis results, three inflammatory biomarkers were chemically assigned to Chemokines and Others, including IP10 (interferon gamma inducible protein-10), MCP1 (monocyte chemoattractant protein-1), and TRAIL (TNF-related apoptosis-inducing ligand).

Conclusion

Our study commenced with the assessment of tissue damage and progression of inflammation in distinct regions of the mouse brain after T. gondii infection. Subsequently, using MR analysis, we detected potential alterations in inflammatory factors associated with this infection. These findings offer valuable insights into the mechanisms underlying toxoplasmic encephalitis and suggest directions for the prevention and treatment of T. gondii infections.

Regulation and functions of the NLRP3 inflammasome in RNA virus infection

Virus infection is one of the greatest threats to human life and health. In response to viral infection, the host's innate immune system triggers an antiviral immune response mostly mediated by inflammatory processes. Among the many pathways involved, the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome has received wide attention in the context of viral infection. The NLRP3 inflammasome is an intracellular sensor composed of three components, including the innate immune receptor NLRP3, adaptor apoptosis-associated speck-like protein containing CARD (ASC), and the cysteine protease caspase-1. After being assembled, the NLRP3 inflammasome can trigger caspase-1 to induce gasdermin D (GSDMD)-dependent pyroptosis, promoting the maturation and secretion of proinflammatory cytokines such as interleukin-1 (IL-1β) and interleukin-18 (IL-18). Recent studies have revealed that a variety of viruses activate or inhibit the NLRP3 inflammasome via viral particles, proteins, and nucleic acids. In this review, we present a variety of regulatory mechanisms and functions of the NLRP3 inflammasome upon RNA viral infection and demonstrate multiple therapeutic strategies that target the NLRP3 inflammasome for anti-inflammatory effects in viral infection.

Systematic review and evidence gap mapping of biomarkers associated with neurological manifestations in patients with COVID-19

OBJECTIVE

This study aimed to synthesize the existing evidence on biomarkers related to coronavirus disease 2019 (COVID-19) patients who presented neurological events.

METHODS

A systematic review of observational studies (any design) following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and the Cochrane Collaboration recommendations was performed (PROSPERO: CRD42021266995). Searches were conducted in PubMed and Scopus (updated April 2023). The methodological quality of nonrandomized studies was assessed using the Newcastle‒Ottawa Scale (NOS). An evidence gap map was built considering the reported biomarkers and NOS results.

RESULTS

Nine specific markers of glial activation and neuronal injury were mapped from 35 studies published between 2020 and 2023. A total of 2,237 adult patients were evaluated in the included studies, especially during the acute phase of COVID-19. Neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) biomarkers were the most frequently assessed (n = 27 studies, 77%, and n = 14 studies, 40%, respectively). Although these biomarkers were found to be correlated with disease severity and worse outcomes in the acute phase in several studies (p < 0.05), they were not necessarily associated with neurological events. Overall, 12 studies (34%) were judged as having low methodological quality, 9 (26%) had moderate quality, and 9 (26%) had high quality.

CONCLUSIONS

Different neurological biomarkers in neurosymptomatic COVID-19 patients were identified in observational studies. Although the evidence is still scarce and conflicting for some biomarkers, well-designed longitudinal studies should further explore the pathophysiological role of NfL, GFAP, and tau protein and their potential use for COVID-19 diagnosis and management.

Para-infectious brain injury in COVID-19 persists at follow-up despite attenuated cytokine and autoantibody responses

To understand neurological complications of COVID-19 better both acutely and for recovery, we measured markers of brain injury, inflammatory mediators, and autoantibodies in 203 hospitalised participants; 111 with acute sera (1-11 days post-admission) and 92 convalescent sera (56 with COVID-19-associated neurological diagnoses). Here we show that compared to 60 uninfected controls, tTau, GFAP, NfL, and UCH-L1 are increased with COVID-19 infection at acute timepoints and NfL and GFAP are significantly higher in participants with neurological complications. Inflammatory mediators (IL-6, IL-12p40, HGF, M-CSF, CCL2, and IL-1RA) are associated with both altered consciousness and markers of brain injury. Autoantibodies are more common in COVID-19 than controls and some (including against MYL7, UCH-L1, and GRIN3B) are more frequent with altered consciousness. Additionally, convalescent participants with neurological complications show elevated GFAP and NfL, unrelated to attenuated systemic inflammatory mediators and to autoantibody responses. Overall, neurological complications of COVID-19 are associated with evidence of neuroglial injury in both acute and late disease and these correlate with dysregulated innate and adaptive immune responses acutely.

Delayed onset Bickerstaff brainstem encephalitis overlapping Miller-Fisher Syndrome during SARS-CoV-2 infection

Bickerstaff brainstem encephalitis (BBE) is a neuroimmunologic disease characterized by the acute onset of external ophthalmoplegia, ataxia, and consciousness disturbance, mostly subsequent to an infection. BBE is considered to be a variant of Miller-Fisher syndrome (MFS), which also exhibits external ophthalmoplegia and ataxia but not presenting consciousness alterations. Therefore, these two medical conditions are included in the clinical spectrum of the "Fisher-Bickerstaff syndrome" ( Shahrizaila and Yuki in J Neurol Neurosurg Psychiatry 84(5):576-583) [1]. With regard to the etiopathogenesis, increasing evidence worldwide suggests that SARS-CoV-2 infection-enhanced immune response is involved in a wide range of neurological complications such as Guillain-Barré syndrome (GBS), MFS, acute necrotizing encephalitis (ANE), myelitis, acute disseminated encephalomyelitis (ADEM), and, although very rarely, BBE either (Hosseini et al. in Rev Neurosci 32:671-691) [2]. We report a case of a patient affected by delayed onset BBE overlapping MFS during a mild SARS-CoV-2 infection. To the best of our knowledge, similar cases have never been reported.

The long-term health outcomes, pathophysiological mechanisms and multidisciplinary management of long COVID

There have been hundreds of millions of cases of coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). With the growing population of recovered patients, it is crucial to understand the long-term consequences of the disease and management strategies. Although COVID-19 was initially considered an acute respiratory illness, recent evidence suggests that manifestations including but not limited to those of the cardiovascular, respiratory, neuropsychiatric, gastrointestinal, reproductive, and musculoskeletal systems may persist long after the acute phase. These persistent manifestations, also referred to as long COVID, could impact all patients with COVID-19 across the full spectrum of illness severity. Herein, we comprehensively review the current literature on long COVID, highlighting its epidemiological understanding, the impact of vaccinations, organ-specific sequelae, pathophysiological mechanisms, and multidisciplinary management strategies. In addition, the impact of psychological and psychosomatic factors is also underscored. Despite these crucial findings on long COVID, the current diagnostic and therapeutic strategies based on previous experience and pilot studies remain inadequate, and well-designed clinical trials should be prioritized to validate existing hypotheses. Thus, we propose the primary challenges concerning biological knowledge gaps and efficient remedies as well as discuss the corresponding recommendations.

Cerebrospinal fluid cytokines in COVID-19: a review and meta-analysis

INTRODUCTION

Neurological involvement can occur in patients with SARS-CoV-2 infections, resulting in coronavirus disease 2019 (COVID-19). Cytokine alterations are associated with neurological symptoms in COVID-19. We performed a review of cytokines in the cerebrospinal fluid (CSF) of patients with COVID-19.

METHODS

Two reviewers independently searched PubMed for all relevant articles published prior to November 11, 2022. Active SARS-CoV-2 infection and CSF cytokine analyses were required for inclusion.

RESULTS

Three-hundred forty-six patients with COVID-19 and 356 controls from 28 studies were included. SARS-CoV-2 PCR was positive in the CSF of 0.9% (3/337) of patients with COVID-19. Thirty-seven different cytokines were elevated in the CSF of patients with COVID-19 when compared to controls and the standards set forth by individual assays used in each study. Of the 37 cytokines, IL-6 and IL-8 were most commonly elevated. CSF IL-6 is elevated in 60%, and CSF IL-8 is elevated in 51% of patients with COVID-19.

CONCLUSION

Levels of several inflammatory cytokines are elevated in the CSF of patients with COVID-19, and SARS-CoV-2 PCR is often not isolated in the CSF of patients with COVID-19. Many patients with COVID-19 have neurological symptoms and given the cytokine elevations in the absence of detectable viral RNA in cerebrospinal fluid; further study of the CSF cytokine profiles and pathogenesis of neurological symptoms in COVID-19 is needed.

Blood Biomarkers as Prognostic Indicators for Neurological Injury in COVID-19 Patients: A Systematic Review and Meta-Analysis

Coronavirus disease 2019 (COVID-19) has been linked to various neurological complications. This meta-analysis assessed the relationship between glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) levels in the blood and neurological injury in COVID-19 patients. A comprehensive search of various databases was conducted until 18 August 2023, to find studies reporting GFAP and NfL blood levels in COVID-19 patients with neurological complications. GFAP and NfL levels were estimated between COVID-19 patients and healthy controls, and meta-analyses were performed using RevMan 5.4 software for analysis. In the 21 collected studies, it was found that COVID-19 patients had significantly higher levels of pooled GFAP (SMD = 0.52; 95% CI: 0.31, 0.73; p ≤ 0.001) and NfL (SMD = 0.60; 95% CI: 0.37, 0.82; p ≤ 0.001) when compared to the healthy controls. The pooled GFAP (SMD = 0.86; 95% CI: 0.26, 1.45; p ≤ 0.01) and NfL (SMD = 0.87; 95% CI: 0.48, 1.26; p ≤ 0.001) were significantly higher in non-survivors. These findings indicate a significant association between COVID-19 severity and elevated levels of GFAP and NfL, suggesting that GFAP and NfL could serve as potential diagnostic and prognostic markers for the early detection and monitoring of COVID-19-related neurological injuries.

SARS-CoV-2 and autoantibodies in the cerebrospinal fluid of COVID-19 patients: prospective multicentre cohort study

Disease mechanisms underlying neurological and neuropsychiatric symptoms after coronavirus disease 2019 (COVID-19), termed neuro-COVID, are poorly understood. Investigations of the cerebrospinal fluid (CSF) for the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA and antibodies, as well as autoantibodies against neuronal surface antigens, could improve our understanding in that regard. We prospectively collected CSF and blood from patients investigated by lumbar puncture for neurological or neuropsychiatric symptoms during or after COVID-19. Primary outcomes were the presence of (i) SARS-CoV-2 RNA in CSF via polymerase chain reaction (PCR), (ii) SARS-CoV-2 immunoglobulin G (IgG) anti-S receptor-binding-domain antibodies via the Euroimmun and Wantai assays and (iii) IgG autoantibodies against neuronal surface antigens using commercial cell- and tissue-based assays (Euroimmun). Secondary outcomes were (i) routine CSF investigations and (ii) correlation between SARS-CoV-2 antibody levels in CSF with serum levels, blood-brain barrier permeability and peripheral inflammation. We obtained CSF from 38 COVID-19 patients (mean age 56.5 ± 19.2 years, 53% women) who developed neurological and neuropsychiatric symptoms. CSF pleocytosis (>5 cells) was observed in 9/38 patients (23.7%), elevated CSF protein (>0.50 g/L) in 13/38 (34.2%) and elevated CSF/serum albumin ratio in 12/35 (34.3%). PCR for SARS-CoV-2 RNA in CSF was negative in all. SARS-CoV-2 CSF antibodies were detected in 15/34 (44.1%; Euroimmun assay) and 7/31 (22.6%; Wantai assay) individuals, but there were no signs of intrathecal SARS-CoV-2 IgG production. SARS-CoV-2 CSF antibodies were positively correlated with serum levels (R = 0.93, P < 0.001), blood-brain barrier permeability (R = 0.47, P = 0.006), peripheral inflammation (R = 0.51, P = 0.002) and admission to the intensive care unit [odds ratio (OR) 17.65; 95% confidence interval (CI) 1.18-264.96; P = 0.04; n = 15]. Cell-based assays detected weakly positive NMDAR, LGI1 and CASPR2 antibodies in serum of 4/34 (11.8%) patients but not in CSF. The tissue-based assay showed anti-neuronal fluorescence in CSF from one individual, staining for Purkinje cells. In summary, whereas we did not detect active SARS-CoV-2 infection in the CSF, SARS-CoV-2 antibodies were prevalent. The absence of intrathecal antibody production points towards blood-brain barrier impairment as the origin of CSF SARS-CoV-2 antibodies. In contrast, CSF autoantibodies against neuronal surface antigens were rare. There was no evidence for a clinical correlate of these antibodies. We conclude that, rather than specific autoimmune neuronal injury, non-specific effects of critical illness including an impaired blood-brain barrier are more likely to contribute to neuro-COVID.

Epidemiology, clinical presentation, pathophysiology, and management of long COVID: an update

The increasing number of coronavirus disease 2019 (COVID-19) infections have highlighted the long-term consequences of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection called long COVID. Although the concept and definition of long COVID are described differently across countries and institutions, there is general agreement that it affects multiple systems, including the immune, respiratory, cardiovascular, gastrointestinal, neuropsychological, musculoskeletal, and other systems. This review aims to provide a synthesis of published epidemiology, symptoms, and risk factors of long COVID. We also summarize potential pathophysiological mechanisms and biomarkers for precise prevention, early diagnosis, and accurate treatment of long COVID. Furthermore, we suggest evidence-based guidelines for the comprehensive evaluation and management of long COVID, involving treatment, health systems, health finance, public attitudes, and international cooperation, which is proposed to improve the treatment strategies, preventive measures, and public health policy making of long COVID.

No evidence for neuronal damage or astrocytic activation in cerebrospinal fluid of Neuro-COVID-19 patients with long-term persistent headache

Headache is one of the most common neurological manifestations of COVID-19, but it is unclear whether chronic headache as a symptom of Post-COVID-19 is associated with ongoing CNS damage. We compared cerebrospinal fluid (CSF) levels of markers of CNS damage and inflammation in Post-COVID-19 patients with persistent headache to hospitalized acute COVID-19 patients with neurological symptoms and to non-COVID-19 disease-controls. CSF levels of neurofilament light chain, Ubiquitin carboxyl-terminal hydrolase L1 and Tau were similar in patients with persistent headache in post-COVID-19 compared to acute COVID-19 patients and all control groups. Levels of glial fibrillary astrocytic protein were lower in patients with persistent headache in post-COVID-19 compared to some control groups of patients with neurological disease. Therefore, our pilot study of CSF markers indicates that persistent post-COVID-19 headache is not a sign of underlying neuronal damage or glial activation.

Case report: Presentations and cytokine profiles of inflammatory non-pulmonary COVID-19 and related diseases in children

The coronavirus disease 2019 (COVID-19) pandemic has evolved to dynamic waves of different SARS-CoV-2 variants. Initially, children diagnosed with COVID-19 presented pulmonary involvement characterized by mild diseases. In the later waves of the COVID-19 pandemic, life-threatening non-pulmonary inflammatory diseases such as (1) aseptic meningoencephalitis (ME), (2) acute necrotizing encephalopathies (ANE), and (3) multisystem inflammatory syndrome in children (MIS-C) have been reported, affecting the pediatric population. To alert timely identification and prevention of the life-threatening non-pulmonary COVID-19, we present the cases of ME, ANE, and MIS-C in terms of clinical manifestation, cytokine profile, and follow-up consequences. Based on the immunopathogenesis and risk factors associated with non-pulmonary COVID-19, we delineate strategies for an early diagnosis and treatment to reduce morbidity and mortality in children.

Pathophysiology, diagnosis, and management of neuroinflammation in covid-19

Although neurological complications of SARS-CoV-2 infection are relatively rare, their potential long term morbidity and mortality have a significant impact, given the large numbers of infected patients. Covid-19 is now in the differential diagnosis of a number of common neurological syndromes including encephalopathy, encephalitis, acute demyelinating encephalomyelitis, stroke, and Guillain-Barré syndrome. Physicians should be aware of the pathophysiology underlying these presentations to diagnose and treat patients rapidly and appropriately. Although good evidence has been found for neurovirulence, the neuroinvasive and neurotropic potential of SARS-CoV-2 is limited. The pathophysiology of most complications is immune mediated and vascular, or both. A significant proportion of patients have developed long covid, which can include neuropsychiatric presentations. The mechanisms of long covid remain unclear. The longer term consequences of infection with covid-19 on the brain, particularly in terms of neurodegeneration, will only become apparent with time and long term follow-up.

Pearls & Oy-sters: Hemorrhagic Myelitis Following SARS-CoV-2 Infection

Hemorrhage in the setting of myelitis is rarely seen in clinical practice. We report a series of 3 women aged 26, 43, and 44 years, who presented with acute hemorrhagic myelitis within 4 weeks of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Two required intensive care, and 1 had severe disease with multiorgan failure. Serial MRI of the spine demonstrated T2-weighted hyperintensity with T1-weighted postcontrast enhancement in the medulla and cervical spine (patient 1) and thoracic spine (patients 2 and 3). Hemorrhage was identified on precontrast T1-weighted, susceptibility-weighted, and gradient echo sequences. Distinct from typical inflammatory or demyelinating myelitis, clinical recovery was poor in all cases, with residual quadriplegia or paraplegia, despite immunosuppression. These cases highlight that although hemorrhagic myelitis is rare, it can occur as a post/parainfectious complication of SARS-CoV-2 infection.

Frequency and Referral Patterns of Neural Antibody Studies During the COVID-19 Pandemic: Experience From an Autoimmune Neurology Center

OBJECTIVE

To determine whether the frequency of paraneoplastic or autoimmune encephalitis antibodies examined in a referral center changed during the COVID-19 pandemic.

METHODS

The number of patients who tested positive for neuronal or glial (neural) antibodies during pre-COVID-19 (2017-2019) and COVID-19 (2020-2021) periods was compared. The techniques used for antibody testing did not change during these periods and included a comprehensive evaluation of cell-surface and intracellular neural antibodies. The chi-square test, Spearman correlation, and Python programming language v3 were used for statistical analysis.

RESULTS

Serum or CSF from 15,390 patients with suspected autoimmune or paraneoplastic encephalitis was examined. The overall positivity rate for antibodies against neural-surface antigens was similar in the prepandemic and pandemic periods (neuronal 3.2% vs 3.5%; glial 6.1 vs 5.2) with a mild single-disease increase in the pandemic period (anti-NMDAR encephalitis). By contrast, the positivity rate for antibodies against intracellular antigens was significantly increased during the pandemic period (2.8% vs 3.9%, p = 0.01), particularly Hu and GFAP.

DISCUSSION

Our findings do not support that the COVID-19 pandemic led to a substantial increase of known or novel encephalitis mediated by antibodies against neural-surface antigens. The increase in Hu and GFAP antibodies likely reflects the progressive increased recognition of the corresponding disorders.

Clinical characteristics of unvaccinated or incompletely vaccinated children with neurological manifestations due to SARS-CoV-2 Omicron infection

Omicron generally causes milder disease than previous strains of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), especially in fully vaccinated individuals. However, incompletely vaccinated children may develop Omicron-related complications such as those affecting the central nervous system. To characterize the spectrum of clinical manifestations of neuro-COVID and to identify potential biomarkers associated with clinical outcomes, we recruited 15 children hospitalized for Omicron-related neurological manifestations in three hospitals in Hong Kong (9 boys and 6 girls aged 1-13 years). All were unvaccinated or incompletely vaccinated. Fourteen (93.3%) were admitted for convulsion, including benign febrile seizure (n = 7), complex febrile seizure (n = 2), seizure with fever (n = 3), and recurrent breakthrough seizure (n = 2), and the remaining nonconvulsive patient developed encephalopathic state with impaired consciousness. None of the seven children with benign febrile seizure and six of eight children with other neurological manifestations had residual deficits at 9-month follow-up. SARS-CoV-2 RNA was undetectable in the cerebrospinal fluid (CSF) specimens of seven patients who underwent lumbar puncture. Spike-and-wave/sharp waves affecting the frontal lobes were detected in four of seven (57.1%) patients who underwent electroencephalogram. Children with Omicron-related neurological manifestations had significantly higher blood levels of IL-6 (p < 0.001) and CHI3L1 (p = 0.022) than healthy controls, and higher CSF levels of IL-6 (p = 0.002) than children with non-COVID-19-related febrile illnesses. Higher CSF-to-blood ratios of IL-8 and CHI3L1 were associated with longer length of stay, whereas higher ratios of IL-6 and IL-8 were associated with higher blood tau level. The role of CSF:blood ratio of IL-6, IL-8, and CHI3L1 as prognostic markers for neuro-COVID should be further evaluated.

Long-term effects of SARS-CoV-2 infection on human brain and memory

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have caused several waves of outbreaks. From the ancestral strain to Omicron variant, SARS-CoV-2 has evolved with the high transmissibility and increased immune escape against vaccines. Because of the multiple basic amino acids in the S1-S2 junction of spike protein, the widespread distribution of angiotensin-converting enzyme 2 (ACE2) receptor in human body and the high transmissibility, SARS-CoV-2 can infect multiple organs and has led to over 0.7 billion infectious cases. Studies showed that SARS-CoV-2 infection can cause more than 10% patients with the Long-COVID syndrome, including pathological changes in brains. This review mainly provides the molecular foundations for understanding the mechanism of SARS-CoV-2 invading human brain and the molecular basis of SARS-CoV-2 infection interfering with human brain and memory, which are associated with the immune dysfunction, syncytia-induced cell death, the persistence of SARS-CoV-2 infection, microclots and biopsychosocial aspects. We also discuss the strategies for reducing the Long-COVID syndrome. Further studies and analysis of shared researches will allow for further clarity regarding the long-term health consequences.

[COVID-19: Neurological manifestations and complications during the acute phase of the disease]

The neurological manifestations and complications of the acute phase of COVID-19 are numerous. They mainly concern the central nervous system in the frequent forms of encephalopathy, encephalitis and neurovascular pathologies. Peripheral neurological manifestations mainly include acute polyneuropathies such as Guillain-Barré syndrome and intensive care neuromyopathies. Most of these manifestations were described during the first wave of the pandemic. The epidemiological, clinical, paraclinical, pathophysiological and therapeutic aspects are addressed in this general review of the literature published from 2020 to early 2023.

Immunohematologic Biomarkers in COVID-19: Insights into Pathogenesis, Prognosis, and Prevention

Coronavirus disease 2019 (COVID-19) has had profound effects on the health of individuals and on healthcare systems worldwide. While healthcare workers on the frontlines have fought to quell multiple waves of infection, the efforts of the larger research community have changed the arch of this pandemic as well. This review will focus on biomarker discovery and other efforts to identify features that predict outcomes, and in so doing, identify possible effector and passenger mechanisms of adverse outcomes. Identifying measurable soluble factors, cell-types, and clinical parameters that predict a patient's disease course will have a legacy for the study of immunologic responses, especially stimuli, which induce an overactive, yet ineffectual immune system. As prognostic biomarkers were identified, some have served to represent pathways of therapeutic interest in clinical trials. The pandemic conditions have created urgency for accelerated target identification and validation. Collectively, these COVID-19 studies of biomarkers, disease outcomes, and therapeutic efficacy have revealed that immunologic systems and responses to stimuli are more heterogeneous than previously assumed. Understanding the genetic and acquired features that mediate divergent immunologic outcomes in response to this global exposure is ongoing and will ultimately improve our preparedness for future pandemics, as well as impact preventive approaches to other immunologic diseases.

Laboratory Findings and Biomarkers in Long COVID: What Do We Know So Far? Insights into Epidemiology, Pathogenesis, Therapeutic Perspectives and Challenges

Long COVID (LC) encompasses a constellation of long-term symptoms experienced by at least 10% of people after the initial SARS-CoV-2 infection, and so far it has affected about 65 million people. The etiology of LC remains unclear; however, many pathophysiological pathways may be involved, including viral persistence; a chronic, low-grade inflammatory response; immune dysregulation and a defective immune response; the reactivation of latent viruses; autoimmunity; persistent endothelial dysfunction and coagulopathy; gut dysbiosis; hormonal and metabolic dysregulation; mitochondrial dysfunction; and autonomic nervous system dysfunction. There are no specific tests for the diagnosis of LC, and clinical features including laboratory findings and biomarkers may not specifically relate to LC. Therefore, it is of paramount importance to develop and validate biomarkers that can be employed for the prediction, diagnosis and prognosis of LC and its therapeutic response, although this effort may be hampered by challenges pertaining to the non-specific nature of the majority of clinical manifestations in the LC spectrum, small sample sizes of relevant studies and other methodological issues. Promising candidate biomarkers that are found in some patients are markers of systemic inflammation, including acute phase proteins, cytokines and chemokines; biomarkers reflecting SARS-CoV-2 persistence, the reactivation of herpesviruses and immune dysregulation; biomarkers of endotheliopathy, coagulation and fibrinolysis; microbiota alterations; diverse proteins and metabolites; hormonal and metabolic biomarkers; and cerebrospinal fluid biomarkers. At present, there are only two reviews summarizing relevant biomarkers; however, they do not cover the entire umbrella of current biomarkers, their link to etiopathogenetic mechanisms or the diagnostic work-up in a comprehensive manner. Herein, we aim to appraise and synopsize the available evidence on the typical laboratory manifestations and candidate biomarkers of LC, their classification based on pathogenetic mechanisms and the main LC symptomatology in the frame of the epidemiological and clinical aspects of the syndrome and furthermore assess limitations and challenges as well as potential implications in candidate therapeutic interventions.

SARS-CoV-2 S1 protein causes brain inflammation by reducing intracerebral acetylcholine production

Neurological complications that occur in SARS-CoV-2 infection, such as olfactory dysfunction, brain inflammation, malaise, and depressive symptoms, are thought to contribute to long COVID. However, in autopsies of patients who have died from COVID-19, there is normally no direct evidence that central nervous system damage is due to proliferation of SARS-CoV-2. For this reason, many aspects of the pathogenesis mechanisms of such symptoms remain unknown. Expressing SARS-CoV-2 S1 protein in the nasal cavity of mice was associated with increased apoptosis of the olfactory system and decreased intracerebral acetylcholine production. The decrease in acetylcholine production was associated with brain inflammation, malaise, depressive clinical signs, and decreased expression of the cytokine degrading factor ZFP36. Administering the cholinesterase inhibitor donepezil to the mice improved brain inflammation, malaise and depressive clinical signs. These findings could contribute to the elucidation of the pathogenesis mechanisms of neurological complications associated with COVID-19 and long COVID.

Neurological Diseases Define the Cytokine Profile in CFS during SARS-CoV-2 Infection in Highly Ill Patients

Neuroinflammation is critical in developing and progressing neurological diseases. The underlying pro-inflammatory cytokine expression combined with additional mechanisms in the neuropathology, such as oxidative stress, brain-blood barrier damage, and endothelial dysfunction, could contribute to the susceptibility to developing severe COVID-19. The physiopathology of SARS-CoV-2 and other human coronaviruses (H-CoVs) has not been completely understood; however, they have all been linked to a disproportionated response of the immune system, particularly an exacerbated cytokine production and the dysregulation of total cell counts. In this article, based on the compilation of studies reported by our working group regarding COVID-19 and neurological diseases, we propose that the inflammation observed in the central nervous system, through a CSF analysis, could be conditioned by neurological disease(s) and enhanced by COVID-19. Therefore, it is necessary to determine the cytokine profile in different neurological disorders to propose adequate treatments and avoid severe forms of the disease in these patients.

Prognostic performance of blood neurofilament light chain protein in hospitalized COVID-19 patients without major central nervous system manifestations: an individual participant data meta-analysis

BACKGROUND AND AIMS

To investigate the prognostic value of blood neurofilament light chain protein (NfL) levels in the acute phase of coronavirus disease 2019 (COVID-19).

METHODS

We conducted an individual participant data (IPD) meta-analysis after screening on MEDLINE and Scopus to May 23rd 2022. We included studies with hospitalized adult COVID-19 patients without major COVID-19-associated central nervous system (CNS) manifestations and with a measurement of blood NfL in the acute phase as well as data regarding at least one clinical outcome including intensive care unit (ICU) admission, need of mechanical ventilation (MV) and death. We derived the age-adjusted measures NfL Z scores and conducted mixed-effects modelling to test associations between NfL Z scores and other variables, encompassing clinical outcomes. Summary receiver operating characteristic curves (SROCs) were used to calculate the area under the curve (AUC) for blood NfL.

RESULTS

We identified 382 records, of which 7 studies were included with a total of 669 hospitalized COVID-19 cases (mean age 66.2 ± 15.0 years, 68.1% males). Median NfL Z score at admission was elevated compared to the age-corrected reference population (2.37, IQR: 1.13-3.06, referring to 99th percentile in healthy controls). NfL Z scores were significantly associated with disease duration and severity. Higher NfL Z scores were associated with a higher likelihood of ICU admission, need of MV, and death. SROCs revealed AUCs of 0.74, 0.80 and 0.71 for mortality, need of MV and ICU admission, respectively.

CONCLUSIONS

Blood NfL levels were elevated in the acute phase of COVID-19 patients without major CNS manifestations and associated with clinical severity and poor outcome. The marker might ameliorate the performance of prognostic multivariable algorithms in COVID-19.

Cerebrospinal Fluid Protein Markers Indicate Neuro-Damage in SARS-CoV-2-Infected Nonhuman Primates

Neurologic manifestations are among the most frequently reported complications of COVID-19. However, given the paucity of tissue samples and the highly infectious nature of the etiologic agent of COVID-19, we have limited information to understand the neuropathogenesis of COVID-19. Therefore, to better understand the impact of COVID-19 on the brain, we used mass-spectrometry-based proteomics with a data-independent acquisition mode to investigate cerebrospinal fluid (CSF) proteins collected from two different nonhuman primates, Rhesus Macaque and African Green Monkeys, for the neurologic effects of the infection. These monkeys exhibited minimal to mild pulmonary pathology but moderate to severe central nervous system (CNS) pathology. Our results indicated that CSF proteome changes after infection resolution corresponded with bronchial virus abundance during early infection and revealed substantial differences between the infected nonhuman primates and their age-matched uninfected controls, suggesting these differences could reflect altered secretion of CNS factors in response to SARS-CoV-2-induced neuropathology. We also observed the infected animals exhibited highly scattered data distributions compared to their corresponding controls indicating the heterogeneity of the CSF proteome change and the host response to the viral infection. Dysregulated CSF proteins were preferentially enriched in functional pathways associated with progressive neurodegenerative disorders, hemostasis, and innate immune responses that could influence neuroinflammatory responses following COVID-19. Mapping these dysregulated proteins to the Human Brain Protein Atlas found that they tended to be enriched in brain regions that exhibit more frequent injury following COVID-19. It, therefore, appears reasonable to speculate that such CSF protein changes could serve as signatures for neurologic injury, identify important regulatory pathways in this process, and potentially reveal therapeutic targets to prevent or attenuate the development of neurologic injuries following COVID-19.

Dopamine Transmission Imbalance in Neuroinflammation: Perspectives on Long-Term COVID-19

Dopamine (DA) is a key neurotransmitter in the basal ganglia, implicated in the control of movement and motivation. Alteration of DA levels is central in Parkinson’s disease (PD), a common neurodegenerative disorder characterized by motor and non-motor manifestations and deposition of alpha-synuclein (α-syn) aggregates. Previous studies have hypothesized a link between PD and viral infections. Indeed, different cases of parkinsonism have been reported following COVID-19. However, whether SARS-CoV-2 may trigger a neurodegenerative process is still a matter of debate. Interestingly, evidence of brain inflammation has been described in postmortem samples of patients infected by SARS-CoV-2, which suggests immune-mediated mechanisms triggering the neurological sequelae. In this review, we discuss the role of proinflammatory molecules such as cytokines, chemokines, and oxygen reactive species in modulating DA homeostasis. Moreover, we review the existing literature on the possible mechanistic interplay between SARS-CoV-2-mediated neuroinflammation and nigrostriatal DAergic impairment, and the cross-talk with aberrant α-syn metabolism.

An eye to the future: Acute and long-term neuro-ophthalmological and neurological complications of COVID-19

COVID-19 has had a significant impact on the global population and has produced compelling evidence of non-pulmonary organ dysfunction, including the nervous system. It is vital that specialists in ophthalmology and neurology are informed of the potential complications of COVID-19 and gain a deeper understanding of how COVID-19 can cause diseases of the nervous system. In this review we detail four possible mechanisms by which COVID-19 infection may result in neurological or neuro-ophthalmological complications: (1) Toxic and metabolic effects of severe pulmonary COVID-19 disease on the neural axis including hypoxia and the systemic hyper-inflammatory state, (2) endothelial dysfunction, (3) dysimmune responses directed again the neuroaxis, and (4) direct neuro-invasion and injury by the virus itself. We explore the pathological evidence for each of these and how they may link to neuro-ophthalmological disorders. Finally, we explore the evidence for long-term neurological and neuro-ophthalmological complications of COVID-19, with a focus on neurodegeneration.

Cerebrospinal fluid biomarkers in SARS-CoV-2 patients with acute neurological syndromes

BACKGROUND AND PURPOSE

Mechanisms underlying acute brain injury in SARS-CoV-2 patients remain poorly understood. A better characterization of such mechanisms remains essential to preventing long-term neurological sequelae. Our present aim was to study a panel of biomarkers of neuroinflammation and neurodegeneration in the cerebrospinal fluid (CSF) of NeuroCOVID patients.

METHODS

We retrospectively collected clinical and CSF biomarkers data from 24 NeuroCOVID adults seen at the University Hospital of Guadeloupe between March and June 2021.

RESULTS

Among 24 NeuroCOVID patients, 71% had encephalopathy and 29% meningoencephalitis. A number of these patients also experienced de novo movement disorder (33%) or stroke (21%). The CSF analysis revealed intrathecal immunoglobulin synthesis in 54% of NeuroCOVID patients (two with a type 2 pattern and 11 with a type 3) and elevated neopterin levels in 75% of them (median 9.1nM, IQR 5.6-22.1). CSF neurofilament light chain (NfL) was also increased compared to a control group of non-COVID-19 patients with psychiatric illnesses (2905ng/L, IQR 1428-7124 versus 1222ng/L, IQR 1049-1566). Total-tau was elevated in the CSF of 24% of patients, whereas protein 14-3-3, generally undetectable, reached intermediate levels in two patients. Finally, CSF Aß1-42 was reduced in 52.4% of patients (median 536ng/L, IQR 432-904) with no change in the Aß1-42/Aß1-40 ratio (0.082, IQR 0.060-0.096).

CONCLUSIONS

We showed an elevation of CSF biomarkers of neuroinflammation in NeuroCOVID patients and a rise of CSF NfL, evocative of neuronal damage. However, longitudinal studies are needed to determine whether NeuroCOVID could evolve into a chronic neurodegenerative condition.

Alzheimer's disease and COVID-19: Interactions, intrinsic linkages, and the role of immunoinflammatory responses in this process

Alzheimer's disease (AD) and COVID-19 share many common risk factors, such as advanced age, complications, APOE genotype, etc. Epidemiological studies have also confirmed the internal relationship between the two diseases. For example, studies have found that AD patients are more likely to suffer from COVID-19, and after infection with COVID-19, AD also has a much higher risk of death than other chronic diseases, and what's more interesting is that the risk of developing AD in the future is significantly higher after infection with COVID-19. Therefore, this review gives a detailed introduction to the internal relationship between Alzheimer's disease and COVID-19 from the perspectives of epidemiology, susceptibility and mortality. At the same time, we focused on the important role of inflammation and immune responses in promoting the onset and death of AD from COVID-19.

Transient Changes in the Plasma of Astrocytic and Neuronal Injury Biomarkers in COVID-19 Patients without Neurological Syndromes

The levels of several glial and neuronal plasma biomarkers have been found to increase during the acute phase in COVID-19 patients with neurological symptoms. However, replications in patients with minor or non-neurological symptoms are needed to understand their potential as indicators of CNS injury or vulnerability. Plasma levels of glial fibrillary acidic protein (GFAP), neurofilament light chain protein (NfL), and total Tau (T-tau) were determined by Single molecule array (Simoa) immunoassays in 45 samples from COVID-19 patients in the acute phase of infection [moderate (n = 35), or severe (n = 10)] with minor or non-neurological symptoms; in 26 samples from fully recovered patients after ~2 months of clinical follow-up [moderate (n = 23), or severe (n = 3)]; and in 14 non-infected controls. Plasma levels of the SARS-CoV-2 receptor, angiotensin-converting enzyme 2 (ACE2), were also determined by Western blot. Patients with COVID-19 without substantial neurological symptoms had significantly higher plasma concentrations of GFAP, a marker of astrocytic activation/injury, and of NfL and T-tau, markers of axonal damage and neuronal degeneration, compared with controls. All these biomarkers were correlated in COVID-19 patients at the acute phase. Plasma GFAP, NfL and T-tau levels were all normalized after recovery. Recovery was also observed in the return to normal values of the quotient between the ACE2 fragment and circulating full-length species, following the change noticed in the acute phase of infection. None of these biomarkers displayed differences in plasma samples at the acute phase or recovery when the COVID-19 subjects were sub-grouped according to occurrence of minor symptoms at re-evaluation 3 months after the acute episode (so called post-COVID or "long COVID"), such as asthenia, myalgia/arthralgia, anosmia/ageusia, vision impairment, headache or memory loss. Our study demonstrated altered plasma GFAP, NfL and T-tau levels in COVID-19 patients without substantial neurological manifestation at the acute phase of the disease, providing a suitable indication of CNS vulnerability; but these biomarkers fail to predict the occurrence of delayed minor neurological symptoms.

Links between COVID-19 and Parkinson's disease/Alzheimer's disease: reciprocal impacts, medical care strategies and underlying mechanisms

The impact of coronavirus disease 2019 (COVID-19) pandemic on patients with neurodegenerative diseases and the specific neurological manifestations of COVID-19 have aroused great interest. However, there are still many issues of concern to be clarified. Therefore, we review the current literature on the complex relationship between COVID-19 and neurodegenerative diseases with an emphasis on Parkinson's disease (PD) and Alzheimer's disease (AD). We summarize the impact of COVID-19 infection on symptom severity, disease progression, and mortality rate of PD and AD, and discuss whether COVID-19 infection could trigger PD and AD. In addition, the susceptibility to and the prognosis of COVID-19 in PD patients and AD patients are also included. In order to achieve better management of PD and AD patients, modifications of care strategies, specific drug therapies, and vaccines during the pandemic are also listed. At last, mechanisms underlying the link of COVID-19 with PD and AD are reviewed.

Review of Neurofilaments as Biomarkers in Sepsis-Associated Encephalopathy

Sepsis is a common and fatal disease, especially in critically ill patients. Sepsis-associated encephalopathy (SAE) is a diffuse brain dysfunction with acute altered consciousness, permanent cognitive impairment, and even coma, accompanied by sepsis, without direct central nervous system infection. When managing SAE, early identification and quantification of axonal damage facilitate faster and more accurate diagnosis and prognosis. Although no specific markers for SAE have been identified, several biomarkers have been proposed. Neurofilament light chain (NFL) is a highly expressed cytoskeletal component of neurofilament (NF) proteins that can be found in blood and cerebrospinal fluid (CSF) after exposure to axonal injury. NFs can be used as diagnostic and prognostic biomarkers for sepsis-related brain injury. Phosphorylation of NFs contributes to the maturation and stabilization of cytoskeletal structures, especially axons, and facilitates axonal transport, including mitochondrial transport and energy transport. The stability of NF proteins can be assessed by monitoring the expression of NF genes. Furthermore, phosphorylation levels of NFs can be monitored to determine mitochondrial axonal transport associated with cellular energy metabolism at distal axons to assess progression during SAE treatment. This paper provides new insights into the biological characteristics, detection techniques, and scientific achievements of NFs, and discusses the underlying mechanisms and future research directions of NFs in SAE.

Monkeypox-Associated Central Nervous System Disease: A Case Series and Review

OBJECTIVE

Monkeypox virus (MPXV) disease has been declared a public health emergency by the World Health Organization, creating an urgent need for neurologists to be able to recognize, diagnosis, and treat MPXV-associated neurologic disease.

METHODS

Three cases of MPXV-associated central nervous system (CNS) disease occurring during the 2022 outbreak, and their associated imaging findings are presented, with 2 cases previously published in a limited capacity in a public health bulletin.

RESULTS

Three previously healthy immunocompetent gay men in their 30s developed a febrile illness followed by progressive neurologic symptoms with presence of a vesiculopustular rash. MPXV nucleic acid was detected by polymerase chain reaction (PCR) from skin lesions of 2 patients, with the third patient having indeterminate testing but an epidemiologic link to a confirmed MPXV disease case. Cerebrospinal fluid demonstrated a lymphocytic pleocytosis, elevated protein, and negative MPXV-specific PCR. In 2 patients, magnetic resonance imaging of the brain and spine demonstrated partially enhancing, longitudinally extensive central spinal cord lesions with multifocal subcortical, basal ganglia, thalamic, cerebellar, and/or brainstem lesions. The third patient had thalamic and basal ganglia lesions. All patients received 14 days of tecovirimat, and 2 patients also received multiple forms of immunotherapy, including intravenous immunoglobulin, pulsed high-dose steroids, plasmapheresis, and/or rituximab. Good neurologic recovery was observed in all cases.

INTERPRETATION

MPXV can be associated with CNS disease. It is unclear whether this is from a parainfectious immune-mediated injury or direct CNS viral invasion. ANN NEUROL 2023.