Neurological post-acute sequelae of SARS-CoV-2 infection

Long-term brain fog and cognitive impairment in previously hospitalized COVID-19 patients

OBJECTIVES

Limited research exists on COVID-19 associated brain fog, and on the long-term cognitive and psychiatric sequelae in racially and ethnically diverse patients. We characterize the neuropsychological sequelae of post-acute COVID-19 in a diverse cohort and investigate whether COVID-19 clinical severity remains associated with brain fog and cognitive deficits approximately 2 years post infection.

METHODS

A cross-sectional study of patients with a history of COVID-19 hospitalization (March-September 2020). COVID-19 clinical severity was indexed using the National Early Warning Score 2 and a comprehensive neuropsychological tele-battery was administered 2 years post discharge. Pearson's r correlations assessed association, while independent sample t-tests examined group differences. Significant outcomes were further analyzed using multiple regression and ANCOVAs, adjusting for key covariates.

RESULTS

In 41 adult patients (19 female, 30 Hispanic, 13 Black, mean age of 65 (SD = 15), COVID-19 level of severity was associated with greater number of endorsed brain fog symptoms (Pearson's r = .34, 95% CI [.04, .59]), worse overall cognitive functioning (global cognition: r = -.36, 95% CI [-.61, -.05]) and reduced performance on an attention and working memory task (digit span backwards: r = -.41, 95% CI [-.66, -.09]) at 2-year follow-up. Brain fog symptoms most associated with COVID-19 severity included difficulty focusing (r = .46, 95% CI [.18, .67]), detached (r = .41, 95% CI [.12, .64]) and feeling sleepy (r = .40, 95% CI [.11, .63]). Patients' cognitive performance was generally below average (global cognition z-score: M = -.96, SD = .66), with group differences based on sex and ethnicity evidenced on individual cognitive tests.

DISCUSSION

This study emphasizes the importance of continued research on the long-term effects of COVID-19 infection on neuropsychological outcomes, particularly among underrepresented, health-disparate groups. Greater understanding of these associations could improve detection and treatment of those at increased risk of cognitive decline or impairment.

Post-acute sequelae of SARS-CoV-2 mimic: An important neurological condition

BACKGROUND AND OBJECTIVES

In 2024, the sequalae of the acute phase of coronavirus disease-19 (COVID-19) infection, which include neurological symptoms and are commonly referred to as long COVID or post-acute sequelae of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (PASC), continue to be a substantial health concern; however, similar symptoms are observed in individuals with no previous COVID-19 infection.

METHODS

This was a single-center, retrospective, descriptive case series study. Data were obtained from patients who visited our outpatient clinic specializing in PASC between June 1, 2021, and May 31, 2023. We compared antibody test results between patients with confirmed acute phase infection and those without. We compared differences in demographic and clinical characteristics between patients with positive results during the acute phase of COVID-19 infection and positive anti-SARS-CoV-2 antibody tests (true-PASC), and those with neither (PASC-mimic).

RESULTS

Of 437 patients diagnosed with PASC according to World Health Organization criteria, 222 underwent COVID-19 antibody tests. Of these, 193 patients (86.9%) had a history of confirmed acute phase infection, whereas 29 (13.1%) did not. Of the former, 186 patients (96.4%) were seropositive for anti-nucleotide SARS-CoV-2 antibodies (true-PASC), whereas 19 of the latter tested seronegative for anti-nucleotide SARS-CoV-2 antibodies (PASC-mimic). There were no significant differences in symptom characteristics between true-PASC and PASC-mimic participants.

CONCLUSIONS

It was difficult to identify any clinical features to aid in diagnosing PASC without confirmation of acute COVID-19 infection. The findings indicate the existence of a "PASC-mimic" condition that should be acknowledged and excluded in future PASC-related research studies.

COVID-19 and Long COVID: Disruption of the Neurovascular Unit, Blood-Brain Barrier, and Tight Junctions

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), could affect brain structure and function. SARS-CoV-2 can enter the brain through different routes, including the olfactory, trigeminal, and vagus nerves, and through blood and immunocytes. SARS-CoV-2 may also enter the brain from the peripheral blood through a disrupted blood-brain barrier (BBB). The neurovascular unit in the brain, composed of neurons, astrocytes, endothelial cells, and pericytes, protects brain parenchyma by regulating the entry of substances from the blood. The endothelial cells, pericytes, and astrocytes highly express angiotensin converting enzyme 2 (ACE2), indicating that the BBB can be disturbed by SARS-CoV-2 and lead to derangements of tight junction and adherens junction proteins. This leads to increased BBB permeability, leakage of blood components, and movement of immune cells into the brain parenchyma. SARS-CoV-2 may also cross microvascular endothelial cells through an ACE2 receptor-associated pathway. The exact mechanism of BBB dysregulation in COVID-19/neuro-COVID is not clearly known, nor is the development of long COVID. Various blood biomarkers could indicate disease severity and neurologic complications in COVID-19 and help objectively diagnose those developing long COVID. This review highlights the importance of neurovascular and BBB disruption, as well as some potentially useful biomarkers in COVID-19, and long COVID/neuro-COVID.

A novel combined nomogram for predicting severe acute lower respiratory tract infection in children hospitalized for RSV infection during the post-COVID-19 period

Introduction

Off-season upsurge of respiratory syncytial virus (RSV) infection with changed characteristics and heightened clinical severity during the post-COVID-19 era are raising serious concerns. This study aimed to develop and validate a nomogram for predicting the risk of severe acute lower respiratory tract infection (SALRTI) in children hospitalized for RSV infection during the post-COVID-19 era using machine learning techniques.

Methods

A multicenter retrospective study was performed in nine tertiary hospitals in Yunnan, China, enrolling children hospitalized for RSV infection at seven of the nine participating hospitals during January-December 2023 into the development dataset. Thirty-nine variables covering demographic, clinical, and laboratory characteristics were collected. Primary screening and dimension reduction of data were performed using Least Absolute Shrinkage and Selection Operator (LASSO) regression, followed by identification of independent risk factors for RSV-associated SALRTI using Logistic regression, thus finally establishing a predictive nomogram model. Performance of the nomogram was internally evaluated by receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis (DCA) based on the development dataset. External validation of our model was conducted using same methods based on two independent RSV cohorts comprising pediatric RSV inpatients from another two participating hospitals between January-March 2024.

Results

The development dataset included 1102 patients, 239 (21.7%) of whom developed SALRTI; while the external validation dataset included 249 patients (142 in Lincang subset and 107 in Dali subset), 58 (23.3%) of whom were diagnosed as SALRTI. Nine variables, including age, preterm birth, underlying condition, seizures, neutrophil-lymphocyte ratio (NLR), interleukin-6 (IL-6), lactate dehydrogenase (LDH), D-dimer, and co-infection, were eventually confirmed as the independent risk factors of RSV-associated SALRTI. A predictive nomogram was established via integrating these nine predictors. In both internal and external validations, ROC curves indicated that the nomogram had satisfactory discrimination ability, calibration curves demonstrated good agreement between the nomogram-predicted and observed probabilities of outcome, and DCA showed that the nomogram possessed favorable clinical application potential.

Conclusion

A novel nomogram combining several common clinical and inflammatory indicators was successfully developed to predict RSV-associated SALRTI. Good performance and clinical effectiveness of this model were confirmed by internal and external validations.

A pilot randomized controlled trial of major ozone autohemotherapy for patients with post-acute sequelae of COVID-19

This prospective, randomized, controlled clinical trial assessed the therapeutic effects of major ozone autohemotherapy (O3-MAH) in patients with post-acute sequelae of COVID-19 (PASC). Seventy-three eligible participants were randomly assigned to an O3-MAH plus conventional therapy group (n = 35) or a conventional therapy alone group (n = 38). Symptom score, pulmonary function, 6-minute walk distance (6MWD), and hematological, biochemical, and immunological parameters were evaluated before and after the interventions. Both groups demonstrated improvements in various parameters post-intervention, but efficacy was greater in the O3-MAH group than the conventional treatment group; with intervention effectiveness defined as a ≥ 50 % reduction in symptom score, 25 of 35 patients (71 %) responded to O3-MAH, while 17/38 patients (45 %) responded to conventional treatment alone (P = 0.0325). Significant improvements in symptom scores (P = 0.0478), tidal volume (P = 0.0374), predicted 6MWD (P = 0.0032), and coagulation and inflammatory indicators were noted in the O3-MAH group compared with the conventional treatment group. O3-MAH was more likely to be effective in patients with elevated CRP levels. Furthermore, O3-MAH markedly improved cellular immunity, and this improvement became more pronounced with extended treatment duration. In summary, combining O3-MAH with conventional treatment was more effective than conventional therapy alone in improving symptoms, pulmonary function, inflammation, coagulation, and cellular immunity in patients with PASC. Further research is now warranted to validate these findings and individualize the regimen.

Intrarelationships between suboptimal health status and anxiety symptoms: A network analysis

BACKGROUND

Suboptimal health status is a global public health concern of worldwide academic interest, which is an intermediate health status between health and illness. The purpose of the survey is to investigate the relationship between anxiety statuses and suboptimal health status and to identify the central symptoms and bridge symptoms.

METHODS

This study recruited 26,010 participants aged <60 from a cross-sectional study in China in 2022. General Anxiety Disorder-7 (GAD-7) and suboptimal health status short form (SHSQ-9) were used to quantify the levels of anxiety and suboptimal health symptoms, respectively. The network analysis method by the R program was used to judge the central and bridge symptoms. The Network Comparison Test (NCT) was used to investigate the network differences by gender, place of residence, and age in the population.

RESULTS

In this survey, the prevalence of anxiety symptoms, SHS, and comorbidities was 50.7 %, 54.8 %, and 38.5 %, respectively. "Decreased responsiveness", "Shortness of breath", "Uncontrollable worry" were the nodes with the highest expected influence. "Irritable", "Exhausted" were the two symptom nodes with the highest expected bridge influence in the network. There were significant differences in network structure among different subgroup networks.

LIMITATIONS

Unable to study the causal relationship and dynamic changes among variables. Anxiety and sub-health were self-rated and may be limited by memory bias.

CONCLUSIONS

Interventions targeting central symptoms and bridge nodes may be expected to improve suboptimal health status and anxiety in Chinese residents. Researchers can build symptom networks for different populations to capture symptom relationships.

Microbial infection promotes amyloid pathology in a mouse model of Alzheimer's disease via modulating γ-secretase

Microbial infection as a type of environmental risk factors is considered to be associated with long-term increased risk of dementia, including Alzheimer's disease (AD). AD is characterized by two neuropathologically molecular hallmarks of hyperphosphorylated tau and amyloid-β (Aβ), the latter generated by several biochemically reactive enzymes, including γ-secretase. However, how infectious risk factors contribute to pathological development of the AD core molecules remains to be addressed. In this work, we utilized a modified herpes simplex virus type 1 (mHSV-1) and found that its hippocampal infection locally promotes Aβ pathology in 5 × FAD mice, the commonly used amyloid model. Mechanistically, we identified HSV-1 membrane glycoprotein US7 (Envelope gI) that interacts with and modulates γ-secretase and consequently facilitates Aβ production. Furthermore, we presented evidence that adenovirus-associated virus-mediated locally hippocampal overexpression of the US7 aggravates Aβ pathology in 5 × FAD mice. Collectively, these findings identify a herpesviral factor regulating γ-secretase in the development and progression of AD and represent a causal molecular link between infectious pathogens and neurodegeneration.

Mechanisms by Which SARS-CoV-2 Invades and Damages the Central Nervous System: Apart from the Immune Response and Inflammatory Storm, What Else Do We Know?

Initially reported as pneumonia of unknown origin, COVID-19 is increasingly being recognized for its impact on the nervous system, despite nervous system invasions being extremely rare. As a result, numerous studies have been conducted to elucidate the mechanisms of nervous system damage and propose appropriate coping strategies. This review summarizes the mechanisms by which SARS-CoV-2 invades and damages the central nervous system, with a specific focus on aspects apart from the immune response and inflammatory storm. The latest research findings on these mechanisms are presented, providing new insights for further in-depth research.

Precision Phenotyping for Curating Research Cohorts of Patients with Post-Acute Sequelae of COVID-19 (PASC) as a Diagnosis of Exclusion

Scalable identification of patients with the post-acute sequelae of COVID-19 (PASC) is challenging due to a lack of reproducible precision phenotyping algorithms and the suboptimal accuracy, demographic biases, and underestimation of the PASC diagnosis code (ICD-10 U09.9). In a retrospective case-control study, we developed a precision phenotyping algorithm for identifying research cohorts of PASC patients, defined as a diagnosis of exclusion. We used longitudinal electronic health records (EHR) data from over 295 thousand patients from 14 hospitals and 20 community health centers in Massachusetts. The algorithm employs an attention mechanism to exclude sequelae that prior conditions can explain. We performed independent chart reviews to tune and validate our precision phenotyping algorithm. Our PASC phenotyping algorithm improves precision and prevalence estimation and reduces bias in identifying Long COVID patients compared to the U09.9 diagnosis code. Our algorithm identified a PASC research cohort of over 24 thousand patients (compared to about 6 thousand when using the U09.9 diagnosis code), with a 79.9 percent precision (compared to 77.8 percent from the U09.9 diagnosis code). Our estimated prevalence of PASC was 22.8 percent, which is close to the national estimates for the region. We also provide an in-depth analysis outlining the clinical attributes, encompassing identified lingering effects by organ, comorbidity profiles, and temporal differences in the risk of PASC. The PASC phenotyping method presented in this study boasts superior precision, accurately gauges the prevalence of PASC without underestimating it, and exhibits less bias in pinpointing Long COVID patients. The PASC cohort derived from our algorithm will serve as a springboard for delving into Long COVID's genetic, metabolomic, and clinical intricacies, surmounting the constraints of recent PASC cohort studies, which were hampered by their limited size and available outcome data.

Patients with unmet social needs are at higher risks of developing severe long COVID-19 symptoms and neuropsychiatric sequela

This study investigated long COVID of patients in the Montefiore Health System COVID-19 (CORE) Clinics in the Bronx with an emphasis on identifying health related social needs (HRSNs). We analyzed a cohort of 643 CORE patients (6/26/2020-2/24/2023) and 52,089 non-CORE COVID-19 patients. Outcomes included symptoms, physical, emotional, and cognitive function test scores obtained at least three months post-infection. Socioeconomic variables included median incomes, insurance status, and HRSNs. The CORE cohort was older age (53.38 ± 14.50 vs. 45.91 ± 23.79 years old, p < 0.001), more female (72.47% vs. 56.86%, p < 0.001), had higher prevalence of hypertension (45.88% vs. 23.28%, p < 0.001), diabetes (22.86% vs. 13.83%, p < 0.001), COPD (7.15% vs. 2.28%, p < 0.001), asthma (25.51% vs. 12.66%, p < 0.001), lower incomes (53.81% vs. 43.67%, 1st quintile, p < 0.001), and more unmet social needs (29.81% vs. 18.49%, p < 0.001) compared to non-CORE COVID-19 survivors. CORE patients reported a wide range of severe long-COVID symptoms. CORE patients with unmet HRSNs experienced more severe symptoms, worse ESAS-r scores (tiredness, wellbeing, shortness of breath, and pain), PHQ-9 scores (12.5 (6, 17.75) vs. 7 (2, 12), p < 0.001), and GAD-7 scores (8.5 (3, 15) vs. 4 (0, 9), p < 0.001) compared to CORE patients without. Patients with unmet HRSNs experienced worse long-COVID outcomes compared to those without.

Ebbing Strength, Fading Power: Unveiling the Impact of Persistent Fatigue on Muscle Performance in COVID-19 Survivors

The total number of confirmed cases of COVID-19 caused by SARS-CoV-2 virus infection is over 621 million. Post-COVID-19 syndrome, also known as long COVID or long-haul COVID, refers to a persistent condition where individuals experience symptoms and health issues after the acute phase of COVID-19. The aim of this study was to assess the strength and fatigue of skeletal muscles in people recovered from COVID-19. A total of 94 individuals took part in this cross-sectional study, with 45 participants (referred to as the Post-COVID Cohort, PCC) and 49 healthy age-matched volunteers (Healthy Control Cohort, HCC). This research article uses the direct dynamometry method to provide a detailed analysis of post-COVID survivors' strength and power characteristics. The Biodex System 4 Pro was utilized to evaluate muscle strength characteristics during the fatigue test. The fatigue work in extensors and flexors was significantly higher in the PCC. The PCC also showed significantly less power in both extensors and flexors compared to the HCC. In conclusion, this study provides compelling evidence of the impact of post-COVID-19 fatigue on muscle performance, highlighting the importance of considering these effects in the rehabilitation and care of individuals recovering from the virus. PCC achieved lower muscle strength values than HCC.

Possible Role of Fibrinaloid Microclots in Postural Orthostatic Tachycardia Syndrome (POTS): Focus on Long COVID

Postural orthostatic tachycardia syndrome (POTS) is a common accompaniment of a variety of chronic, inflammatory diseases, including long COVID, as are small, insoluble, 'fibrinaloid' microclots. We here develop the argument, with accompanying evidence, that fibrinaloid microclots, through their ability to block the flow of blood through microcapillaries and thus cause tissue hypoxia, are not simply correlated with but in fact, by preceding it, may be a chief intermediary cause of POTS, in which tachycardia is simply the body's exaggerated 'physiological' response to hypoxia. Similar reasoning accounts for the symptoms bundled under the term 'fatigue'. Amyloids are known to be membrane disruptors, and when their targets are nerve membranes, this can explain neurotoxicity and hence the autonomic nervous system dysfunction that contributes to POTS. Taken together as a system view, we indicate that fibrinaloid microclots can serve to link POTS and fatigue in long COVID in a manner that is at once both mechanistic and explanatory. This has clear implications for the treatment of such diseases.

The impact of COVID-19 on a Southern Chinese cohort with neuromyelitis optica spectrum disorders

BACKGROUND

There are few studies on risk factors for coronavirus disease 2019 (COVID-19) infection in patients with Neuromyelitis Optica Spectrum Disorders (NMOSD). The relationship between NMOSD relapse and COVID-19 needs to be evaluated. The objective of our study is to identify the risk factors of COVID-19 infection and NMOSD relapse among NMOSD patients with COVID-19.

METHOD

A total of 379 NMOSD patients registered in a NMOSD database were included in this case-control study after the end of the COVID-19 quarantine and restriction policies on December 6, 2022 in China. Data were obtained from the database. Additional information was obtained by questionnaires and the Neurology out-patient clinic. The clinical characteristics of NMOSD patients with COVID-19 were described. Risk factors associated with COVID-19 infection and outcome among patients with NMOSD were analyzed. Risk factors associated with relapse in NMOSD patients with COVID-19 were also identified.

RESULTS

239 (63.1%) NMOSD patients were infected with COVID-19. Patients with NMOSD who were infected with COVID-19, in comparison to those without COVID-19, were younger at the time of interview (median [IQR] age: 43.00 [32.00-55.00] vs 49.50 [35.25-56.00] years, P = 0.029), younger at NMOSD onset (median [IQR] age: 38.00 [27.00-51.00] vs 45.00 [32.00-52.75] years, P = 0.013), had abnormal visual evoked potentials before infection (73.4% vs 54.3% P = 0.029), had lower baseline Activities of Daily Living Scale (ADL) scores (median [IQR] ADL: 14.00 [14.00-16.00] vs 14.00 [14.00-19.00], P = 0.014) or lower baseline modified Rankin Scale (mRS) scores (1.12±0.749 vs 1.33±0.991, P = 0.037), and were less frequently treated with more than 10 mg prednisone or 8 mg methylprednisolone (25.0% vs 36.0%,p = 0.026). All 9 NMOSD patients who had symptomatic cerebral syndrome developed moderate/severe COVID-19. A higher percentage of patients with moderate/severe COVID-19 experienced more than one core clinical NMOSD symptoms (61.5% vs 55.1%, p = 0.044), compared to patients with mild COVID-19. Higher risk of NMOSD relapse among NMOSD patients with COVID-19 was associated with higher Expanded Disability Status Scale (EDSS) scores (median[IQR] EDSS: 2.00 [1.00-3.00] vs 1.50 [1.00-2.25], P = 0.037) and drug treatments disruption (21.6% vs 5.0% P<0.001).

CONCLUSIONS

NMOSD patients with younger age, lower baseline ADL or mRS had higher incidence of being diagnosed with COVID-19 during pandemic. Glucocorticoid use may decrease the risk of COVID-19. NMOSD patients with symptomatic cerebral syndrome before the COVID-19 pandemic are associated with worse COVID-19 outcomes. Drug treatment disruption may result in relapse among NMOSD patients with COVID-19.

Is there a role for growth hormone replacement in adults to control acute and post-acute COVID-19?

The SARS-CoV-2 pandemic created a multitude of medical crossroads requiring real time adaptations of best practice covering preventative and interventional aspects of care. Among the many discoveries borne from efforts to address the myriad clinical presentations across multiple organ systems was a common impact on tissues with cells that express the ACE-2 receptor. The vast majority of acute infections began and often ended in the respiratory tract, but more recent evaluations have confirmed significant extrapulmonary manifestations including symptom clusters that extend beyond the acute phase of infection collectively referred to as "post-acute sequelae SARS-CoV-2 infection" (PASC) or more commonly as "long (-haul) COVID". Both acute SARS-CoV-2 infection and PASC are associated with gut microbiome dysbiosis and alterations in the gut-brain and HPA-axis in a subset of the infected. Mounting evidence suggests these extrapulmonary manifestations may ultimately lead to reduced growth hormone (GH) secretion as demonstrated following stimulation tests. Disrupted GH secretion could cause or exacerbate long lasting neuropsychological symptoms as seen in other similar manifesting conditions. Ongoing clinical research has shown promising improvement in PASC patients with fatigue and cognition complaints can be achieved via GH replacement therapy. GH stimulation testing should be considered in PASC workups and future research should delve deeper into the mechanistic effects of GH on acute COVID and PASC.

Clinical characteristics of motor functional neurological disorder manifesting as limb weakness after vaccination against coronavirus disease 2019: A case series

Background

The characteristics of functional limb weakness (FLW) as one of the manifestations of functional neurological disorder after vaccination against coronavirus disease 2019 (COVID-19) remain controversial.

Methods

In this descriptive case series, we aimed to elucidate the characteristics of Japanese patients with FLW who claimed muscle weakness after COVID-19 vaccination among patients who visited our outpatient clinic between 1 June 2021 and 31 December 2022.

Results

Nine patients were diagnosed with FLW (mean age: 30.8 years), including two men and seven women. Seven patients were vaccinated with the BioNTech/Pfizer vaccine and two with the mRNA-1273 Moderna vaccine. All patients demonstrated various positive signs for FLW. Magnetic resonance imaging or computed tomography indicated no abnormality that could explain their symptoms. At the time of the clinic visit, five patients were treated for psychiatric disorders, including depression, insomnia, attention-deficit hyperactivity disorder, and Asperger's syndrome. Muscle weakness spread to the limbs beyond the vaccinated arm in seven patients.

Conclusions

We describe the basic characteristics of FLW in Japanese patients after COVID-19 vaccination. Further recognition of these characteristics could aid the diagnosis of FLW by physicians allowing them to support these patients effectively.

Astrocytes as Drivers and Disruptors of Behavior: New Advances in Basic Mechanisms and Therapeutic Targeting

Astrocytes are emerging as key regulators of cognitive function and behavior. This review highlights some of the latest advances in the understanding of astrocyte roles in different behavioral domains across lifespan and in disease. We address specific molecular and circuit mechanisms by which astrocytes modulate behavior, discuss their functional diversity and versatility, and highlight emerging astrocyte-targeted treatment strategies that might alleviate behavioral and cognitive dysfunction in pathologic conditions. Converging evidence across different model systems and manipulations is revealing that astrocytes regulate behavioral processes in a precise and context-dependent manner. Improved understanding of these astrocytic functions may generate new therapeutic strategies for various conditions with cognitive and behavioral impairments.

SARS-CoV-2 and Brain Health: New Challenges in the Era of the Pandemic

Respiratory viral infections have been found to have a negative impact on neurological functions, potentially leading to significant neurological impairment. The SARS-CoV-2 virus has precipitated a worldwide pandemic, posing a substantial threat to human lives. Growing evidence suggests that SARS-CoV-2 may severely affect the CNS and respiratory system. The current prevalence of clinical neurological issues associated with SARS-CoV-2 has raised significant concerns. However, there needs to be a more comprehensive understanding of the specific pathways by which SARS-CoV-2 enters the nervous system. Based on the available evidence, this review focuses on the clinical neurological manifestations of SARS-CoV-2 and the possible mechanisms by which SARS-CoV-2 invades the brain.

Neurologic Complications of COVID-19

OBJECTIVE

This article describes the spectrum of neurologic complications occurring in acute or postacute infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as well as the neurologic risks and benefits of vaccination against SARS-CoV-2.

LATEST DEVELOPMENTS

Early in the COVID-19 pandemic, reports of neurologic complications of COVID-19 began to surface. A variety of neurologic conditions have since been reported in association with COVID-19. Understanding of the underlying mechanism of COVID-19 neurologic involvement continues to evolve; however, the evidence seems to suggest that aberrant inflammatory responses may play a role. In addition to neurologic symptoms in acute COVID-19, neurologic post-COVID-19 conditions are increasingly recognized. The development of COVID-19 vaccines has been essential in preventing the spread of COVID-19. With increasing numbers of vaccine doses administered, various neurologic adverse events have been reported.

ESSENTIAL POINTS

Neurologists must be aware of the potential acute, postacute, and vaccine-associated neurologic complications associated with COVID-19 and be poised to serve as integral members of multidisciplinary care teams for patients with COVID-19-related conditions.

COVID-19 delirium and encephalopathy: Pathophysiology assumed in the first 3 years of the ongoing pandemic

Background

The coronavirus disease (COVID-19) continues to spread worldwide. It has a high rate of delirium, even in young patients without comorbidities. Infected patients required isolation because of the high infectivity and virulence of COVID-19. The high prevalence of delirium in COVID-19 primarily results from encephalopathy and neuroinflammation caused by acute respiratory distress syndrome (ARDS)-associated cytokine storm. Acute respiratory distress syndrome has been linked to delirium and psychotic symptoms in the subacute phase (4 to 12 weeks), termed post-acute COVID-19 syndrome (PACS), and to brain fog, cognitive dysfunction, and fatigue, termed "long COVID," which persists beyond 12 weeks. However, no review article that mentions "COVID-19 delirium" have never been reported.

Basic Procedures

This narrative review summarizes data on delirium associated with acute severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and related neurological symptoms of persistent post-infection illness (PACS or long COVID) after persistence of cognitive dysfunction. Thus, we describe the pathophysiological hypothesis of COVID-19 delirium and its continuation as long COVID. This review also describes the treatment of delirium complicated by COVID-19 pneumonia.

Main Findings

SARS-CoV-2 infection is associated with encephalopathy and delirium. An association between COVID-19 infection and Alzheimer's disease has been suggested, and studies are being conducted from multiple facets including genetics, cytology, and postmortem study.

Principal Conclusions

This review suggests that COVID-19 has important short and long-term neuropsychiatric effects. Several hypotheses have been proposed that highlight potential neurobiological mechanisms as causal factors, including neuronal-inflammatory pathways by cytokine storm and cellular senescence, and chronic inflammation.

Neurological Dysfunction in Long COVID Should Not Be Labelled as Functional Neurological Disorder

There have been suggestions that Long COVID might be purely functional (meaning psychological) in origin. Labelling patients with neurological dysfunction in Long COVID as having functional neurological disorder (FND) in the absence of proper testing may be symptomatic of that line of thought. This practice is problematic for Long COVID patients, as motor and balance symptoms have been reported to occur in Long COVID frequently. FND is characterized by the presentation of symptoms that seem neurological but lack compatibility of the symptom with a neurological substrate. Although diagnostic classification according to the ICD-11 and DSM-5-TR is dependent predominantly on the exclusion of any other medical condition that could account for the symptoms, current neurological practice of FND classification allows for such comorbidity. As a consequence, Long COVID patients with motor and balance symptoms mislabeled as FND have no longer access to Long COVID care, whereas treatment for FND is seldom provided and is ineffective. Research into underlying mechanisms and diagnostic methods should explore how to determine whether motor and balance symptoms currently diagnosed as FND should be considered one part of Long COVID symptoms, in other words, one component of symptomatology, and in which cases they correctly represent FND. Research into rehabilitation models, treatment and integrated care are needed, which should take into account biological underpinnings as well as possible psychological mechanisms and the patient perspective.

Potential for Early Noninvasive COVID-19 Detection Using Electronic-Nose Technologies and Disease-Specific VOC Metabolic Biomarkers

The established efficacy of electronic volatile organic compound (VOC) detection technologies as diagnostic tools for noninvasive early detection of COVID-19 and related coronaviruses has been demonstrated from multiple studies using a variety of experimental and commercial electronic devices capable of detecting precise mixtures of VOC emissions in human breath. The activities of numerous global research teams, developing novel electronic-nose (e-nose) devices and diagnostic methods, have generated empirical laboratory and clinical trial test results based on the detection of different types of host VOC-biomarker metabolites from specific chemical classes. COVID-19-specific volatile biomarkers are derived from disease-induced changes in host metabolic pathways by SARS-CoV-2 viral pathogenesis. The unique mechanisms proposed from recent researchers to explain how COVID-19 causes damage to multiple organ systems throughout the body are associated with unique symptom combinations, cytokine storms and physiological cascades that disrupt normal biochemical processes through gene dysregulation to generate disease-specific VOC metabolites targeted for e-nose detection. This paper reviewed recent methods and applications of e-nose and related VOC-detection devices for early, noninvasive diagnosis of SARS-CoV-2 infections. In addition, metabolomic (quantitative) COVID-19 disease-specific chemical biomarkers, consisting of host-derived VOCs identified from exhaled breath of patients, were summarized as possible sources of volatile metabolic biomarkers useful for confirming and supporting e-nose diagnoses.