Case-Control Study of Individuals With Small Fiber Neuropathy After COVID-19

Updates on the neurological manifestations of SARS-CoV-2 infection

PURPOSE OF REVIEW

Since its emergence in 2020, the COVID-19 pandemic has created a global surge of survivors experiencing neurologic effects from SARS-CoV-2 infection. This review aims to provide an updated synthesis of the acute and chronic neurological manifestations of COVID-19, and to outline the current therapeutic strategies for these conditions.

RECENT FINDINGS

Epidemiological studies have shown that COVID-19 patients with neurological symptoms during acute infection tend to have poorer hospital and functional outcomes. While the risk of adverse neurologic symptoms including cognitive dysfunction, headache, autonomic dysfunction, and chronic fatigue are thought to be greatest following infection with the original SARS-CoV-2 strain and its alpha variant, they remain prevalent after infection with subsequent less virulent strains as well. Some recent work has also found a link between SARS-CoV-2 and structural brain changes. However, ongoing trials show promising results for pharmacologic and nonpharmacologic treatments targeting the postacute neurological sequelae of COVID-19.

SUMMARY

Lingering neurological manifestations after COVID-19 still pose considerable individual, healthcare system, and socioeconomic repercussions. Both preventive and multimodal treatment approaches are necessary to address these conditions. Further research is required to assess the lasting impacts of SARS-CoV-2 on the nervous system, particularly its potential contribution to the development of neurodegenerative diseases.

Post-COVID-19 Small Fiber Neuropathy as a New Emerging Quality of Life-Threatening Disease: A Systematic Review

Post-acute sequelae of COVID-19 (PASC) syndrome is considered an emergent and diffuse multidisciplinary problem. Compelling evidence suggests that COVID-19 increases symptoms of pre-existent small fiber neuropathy (SFN) and might trigger de novo onset of SFN. In this systematic review, for the first time, we provide a comprehensive overview of the clinical and diagnostic features of PASC-SFN, including the accompanying disorders, disease evolution, and possible treatments, described in the recent literature. Following infection, many patients reported a wide range of symptoms and complications, not self-limiting and independent from previous infection severity. SFN begins more frequently with distal limb burning pain and numbness, which accompany other dysautonomia, cognitive, visual, and osteoarticular disorders involving multiple organ systems. In an initial diagnostic suspicion, some tests might be useful as complementary examinations, such as nerve quantitative sensory testing, electromyography, and optic nerve tomography. Otherwise, definite diagnosis is reached with skin biopsy as the gold standard, along with corneal in vivo microscopy when ocular discomfort is present. Being a long-term condition, multiple and dissimilar symptomatic and disease-modifying drugs were employed for the treatment of this condition with the achievement of partial results, including steroids, pregabalin, gabapentin, duloxetine, vitamins, homotaurine and phosphatidylserine, alpha lipoic acid, immunosuppressants, and intravenous immunoglobulin therapy. PASC-SFN is a complex emerging disease and extremely challenging for physicians. At present, the only feasible management of PASC-SFN is represented by a multidisciplinary tailored approach, with future definitive protocols for diagnosis and treatment deemed essential.

Neurovascular dysregulation in systemic sclerosis: novel insights into pathophysiology, diagnosis, and treatment utilizing invasive cardiopulmonary exercise testing

PURPOSE OF REVIEW

Pathologic abnormalities in skeletal muscle and the systemic vasculature are common in patients with systemic sclerosis (SSc). These abnormalities may lead to impaired systemic peripheral oxygen extraction (EO 2 ), known as neurovascular dysregulation, which may be because of abnormal blood flow distribution in the vasculature, microvascular shunting, and/or skeletal muscle mitochondrial dysfunction. Findings from invasive cardiopulmonary exercising testing (iCPET) provide important insights and enable diagnosis and treatment of this SSc disease manifestation.

RECENT FINDINGS

Recent findings from noninvasive cardiopulmonary exercise testing (niCPET) support the existence of neurovascular dysregulation in patients with SSc. Invasive cardiopulmonary exercise testing (iCPET) has pointed to reduced systemic vascular distensibility as a possible mechanism for neurovascular dysregulation in patients with connective tissue diseases, including SSc.

SUMMARY

Neurovascular dysregulation is likely an underappreciated cause of exercise impairment and dyspnea in patients with SSc in the presence or absence of underlying cardiopulmonary disease. It is posited to be related to microcirculatory and muscle dysfunction. Further studies are needed to clarify the pathophysiology of neurovascular dysregulation in SSc and to identify novel treatment targets and additional therapies.

The Autonomic Nervous System (ANS)-Immune Network in People Living With HIV

Purpose

Pre-clinical studies have demonstrated direct influences of the autonomic nervous system (ANS) on the immune system. However, it remains unknown if connections between the peripheral ANS and immune system exist in humans and contribute to the development of chronic inflammatory disease. This study had three aims: 1.) To examine the relationship between IL-6 and the parasympathetic/vagal component of baroreflex sensitivity (BRS-V) in people with HIV; 2.) To determine if the subtype and severity of HIV-autonomic neuropathy (AN) would predict distinct immunotypes; 3.) To compare the burden of non-AIDS-related co-morbidities between immunotypes.

Methods

79 adult people with well-controlled HIV underwent a standard battery of autonomic function tests summarized as the Composite Autonomic Severity Score and vagal and adrenergic baroreflex sensitivity (BRS-V and BRS-A). Levels of immune biomarkers were measured in all participants using the Target 96 Inflammation Panel on the Olink proteomics platform and immunotypes were identified using unbiased, non-negative matrix factorization. Mass cytometry (CyTOF) was completed on a subset of participants with and without autonomic neuropathy (N = 10).

Results

First, we found reduced BRS-V predicted higher levels of IL-6 (p = 0.002). Second, a pro-inflammatory immunotype defined by elevations in type 1 cytokines (IL-6, IL-17) and increased numbers of CD8 + T-cells was associated with autonomic neuropathy characterized by deficits in sympathetic nervous system activity (aOR = 4.7, p = 0.017). This pro-inflammatory immunotype was older with a greater burden of co-morbidities.

Conclusion

Deficits in the parasympathetic/cardiovagal and the sympathetic nervous system are associated with inflammation and disease burden in people living with HIV. Future longitudinal research is needed to examine causality.

Diagnostic challenges of long COVID in children: a survey of pediatric health care providers' preferences and practices

Introduction

Given the challenges in diagnosing children with long COVID, we sought to explore diagnostic practices and preferences among clinicians.

Methods

A ten-question survey assessed pediatric providers' clinical decision making for identifying and evaluating long COVID in children. Of the 120 survey respondents, 84 (70%) were physicians, 31 (26%) nurse practitioners, and 5 (4%) physician assistants.

Results

The most common categories of symptoms identified as raising suspicion for long COVID in children included cardiopulmonary symptoms, selected by 119 (99%) of pediatric providers, and neurocognitive symptoms, selected by 118 (98%) of providers. However, there was more ambiguity on the primary feature of long COVID, with providers selecting a range of key symptoms. Of all physical exam findings, postural orthostatic tachycardia, was most suggestive of long COVID [identified by 49 (41%) of pediatric providers], whereas one-third of providers reported no specific identifiable exam finding.

Discussion

Pediatric providers report variable decision making in the clinical evaluation of long COVID, with patient demographics and clinical factors impacting whether a diagnosis of long COVID is considered. This variation in diagnosing pediatric long COVID reflects ambiguity in the definition of long COVID in children and the absence of clinical guidelines to support providers in the identification of disease and treatment. This study highlights an area of need for future clinical advances in pediatric long COVID.

The role of antibodies in small fiber neuropathy: a review of currently available evidence

Small fiber neuropathy (SFN) is a peripheral nerve condition affecting thin myelinated Aδ and unmyelinated C-fibers, characterized by severe neuropathic pain and other sensory and autonomic symptoms. A variety of medical disorders can cause SFN; however, more than 50% of cases are idiopathic (iSFN). Some investigations suggest an autoimmune etiology, backed by evidence of the efficacy of IVIG and plasma exchange. Several studies suggest that autoantibodies directed against nervous system antigens may play a role in the development of neuropathic pain. For instance, patients with CASPR2 and LGI1 antibodies often complain of pain, and in vitro and in vivo studies support their pathogenicity. Other antibodies have been associated with SFN, including those against TS-HDS, FGFR3, and Plexin-D1, and new potential targets have been proposed. Finally, a few studies reported the onset of SFN after COVID-19 infection and vaccination, investigating the presence of potential antibody targets. Despite these overall findings, the pathogenic role has been demonstrated only for some autoantibodies, and the association with specific clinical phenotypes or response to immunotherapy remains to be clarified. The purpose of this review is to summarise known autoantibody targets involved in neuropathic pain, putative attractive autoantibody targets in iSFN patients, their potential as biomarkers of response to immunotherapy and their role in the development of iSFN.

Autonomic and Immune Stress Response Networks in Patients Living With HIV

Background and Objectives

Stress response systems are frequently dysregulated in patients with chronic inflammatory disorders. Pre-clinical studies have demonstrated direct influences of the sympathetic and vagal/parasympathetic branches of the autonomic nervous system (ANS) on the immune system. However, these connections have not been examined in humans. We hypothesized that the subtype and severity of autonomic neuropathy (AN) would predict immune phenotypes with distinct clinical and demographic characteristics in people living with HIV.

Methods

This is a cross-sectional study of 79 adult people with a history of well-controlled HIV on stable combination antiretroviral treatment (CART) recruited from a primary care clinic network within the Mount Sinai Health System in New York City. All participants underwent a standardized battery of autonomic function tests summarized as the Composite Autonomic Severity Score (CASS) and vagal and adrenergic baroreflex sensitivity (BRS-V and BRS-A). Immune profiling included: 1) measurement of interleukin-6 (IL-6) as part of the Olink assay Target 96 Inflammation Panel, 2) non-negative matrix factorization (NMF) clustering analyses on Olink immune biomarkers, and 3) mass cytometry (CyTOF) on a subset of participants with and without autonomic neuropathy (N = 10).

Results

Reduced activity of caudal vagal circuitry involved in the cholinergic anti-inflammatory pathway (CAP) predicted higher levels of IL-6 (Spearman's rho = -0.352, p=0.002). The comprehensive assessment of the ANS-immune network showed four immunotypes defined by NMF analyses. A pro-inflammatory immunotype defined by elevations in type 1 cytokines (IL-6, IL-17) and increased numbers of CD8+ T-cells was associated with autonomic neuropathy (AN). This association was driven by deficits in the cardiovascular sympathetic nervous system and remained strongly significant after controlling for the older age and greater burden of co-morbid illness among participants with this immunotype (aOR=4.7, p=0.017).

Discussion

Our results provide novel support for the clinical relevance of the CAP in patients with chronic inflammatory AN. These data also provide insight regarding the role of the sympathetic nervous system and aging in the progression and development of co-morbidities in patients with chronic HIV and support future research aimed at developing therapies focused on modulation of the sympathetic and parasympathetic/vagal nervous system.

Anti-recoverin Antibody-Associated Post-acute COVID Vaccination Syndrome After BNT162b2 in HLA-B27-Positive Spondylarthritis: A Case Report

Retinopathy, small fiber neuropathy (SFN), and encephalopathy associated with recoverin antibodies have not been previously reported as side effects of BNT162b2 vaccination in a patient with HLA-B27-associated spondylarthritis. The patient is a 47-year-old male with a 10-year history of HLA-B27-associated spondylarthritis without recurrence, who developed acute and post-acute COVID vaccination syndrome (ACVS/PACVS) after the first dose of the BNT162b2 vaccine. The PACVS manifested as cerebral disease, eye disease, and SFN. Two years after the onset of the adverse effects, recurrent elevated recoverin antibodies were detected. Despite the administration of various treatments, most symptoms persisted for more than three years, and only a few interventions such as glucocorticoids, hyperbaric oxygen therapy, botulinum toxin, inuspheresis, and HELP (heparin-induced extracorporeal LDL precipitation) apheresis showed a transient beneficial effect. In conclusion, this case offers an example of a collection of symptoms following SARS-CoV-2 vaccination (SC2V) in a patient with a specific autoimmune disorder and positivity for anti-recoverin antibodies. These clinical manifestations may be triggered by an exaggerated immune response known as multisystemic inflammatory syndrome in adults to SC2V. Clinicians should report other similar cases to determine if a pattern exists.

Long COVID Is Not a Functional Neurologic Disorder

Long COVID is a common sequela of SARS-CoV-2 infection. Data from numerous scientific studies indicate that long COVID involves a complex interaction between pathophysiological processes. Long COVID may involve the development of new diagnosable health conditions and exacerbation of pre-existing health conditions. However, despite this rapidly accumulating body of evidence regarding the pathobiology of long COVID, psychogenic and functional interpretations of the illness presentation continue to be endorsed by some healthcare professionals, creating confusion and inappropriate diagnostic and therapeutic pathways for people living with long COVID. The purpose of this perspective is to present a clinical and scientific rationale for why long COVID should not be considered as a functional neurologic disorder. It will begin by discussing the parallel historical development of pathobiological and psychosomatic/sociogenic diagnostic constructs arising from a common root in neurasthenia, which has resulted in the collective understandings of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and functional neurologic disorder (FND), respectively. We will also review the case definition criteria for FND and the distinguishing clinical and neuroimaging findings in FND vs. long COVID. We conclude that considering long COVID as FND is inappropriate based on differentiating pathophysiologic mechanisms and distinguishing clinical findings.

A causal link between autoantibodies and neurological symptoms in long COVID

Acute SARS-CoV-2 infection triggers the generation of diverse and functional autoantibodies (AABs), even after mild cases. Persistently elevated autoantibodies have been found in some individuals with long COVID (LC). Using a >21,000 human protein array, we identified diverse AAB targets in LC patients that correlated with their symptoms. Elevated AABs to proteins in the nervous system were found in LC patients with neurocognitive and neurological symptoms. Purified Immunoglobulin G (IgG) samples from these individuals reacted with human pons tissue and were cross-reactive with mouse sciatic nerves, spinal cord, and meninges. Antibody reactivity to sciatic nerves and meninges correlated with patient-reported headache and disorientation. Passive transfer of IgG from patients to mice led to increased sensitivity and pain, mirroring patient-reported symptoms. Similarly, mice injected with IgG showed loss of balance and coordination, reflecting donor-reported dizziness. Our findings suggest that targeting AABs could benefit some LC patients.