Peripheral nervous system manifestations of infectious diseases

Hand conditions as sequelae of infection with COVID-19: a literature review

Patients have attended our clinics with various hand pathologies after contracting COVID-19 or receiving vaccination. We postulate the virus stimulates a systemic inflammatory response that triggers these pathologies and conducted a search of the literature for associated conditions. Twenty publications were included for this review. Three studies identified skeletal muscle inflammation, and several identified reactive arthritis post-infection. Rheumatoid arthritis post-infection was also recognized, along with crystalline arthropathy. Carpal tunnel syndrome was seen in two cases. There is a current paucity in published scientific material regarding COVID-19 sequalae in the hand. This review aims to stimulate discussion in how a virus can induce pathological processes causing common hand pathologies.

Beyond the acute phase: a comprehensive literature review of long-term sequelae resulting from infectious diseases

Infectious diseases have consistently served as pivotal influences on numerous civilizations, inducing morbidity, mortality, and consequently redirecting the course of history. Their impact extends far beyond the acute phase, characterized by the majority of symptom presentations, to a multitude of adverse events and sequelae that follow viral, parasitic, fungal, or bacterial infections. In this context, myriad sequelae related to various infectious diseases have been identified, spanning short to long-term durations. Although these sequelae are known to affect thousands of individuals individually, a comprehensive evaluation of all potential long-term effects of infectious diseases has yet to be undertaken. We present a comprehensive literature review delineating the primary sequelae attributable to major infectious diseases, categorized by systems, symptoms, and duration. This compilation serves as a crucial resource, illuminating the long-term ramifications of infectious diseases for healthcare professionals worldwide. Moreover, this review highlights the substantial burden that these sequelae impose on global health and economies, a facet often overshadowed by the predominant focus on the acute phase. Patients are frequently discharged following the resolution of the acute phase, with minimal long-term follow-up to comprehend and address potential sequelae. This emphasizes the pressing need for sustained vigilance, thorough patient monitoring, strategic health management, and rigorous research to understand and mitigate the lasting economic and health impacts of infectious diseases more fully.

Borna disease virus 1 infection in alpacas: Comparison of pathological lesions and viral distribution to other dead-end hosts

Borna disease is a progressive meningoencephalitis caused by spillover of the Borna disease virus 1 (BoDV-1) to horses and sheep and has gained attention due to its zoonotic potential. New World camelids are also highly susceptible to the disease; however, a comprehensive description of the pathological lesions and viral distribution is lacking for these hosts. Here, the authors describe the distribution and severity of inflammatory lesions in alpacas (n = 6) naturally affected by this disease in comparison to horses (n = 8) as known spillover hosts. In addition, the tissue and cellular distribution of the BoDV-1 was determined via immunohistochemistry and immunofluorescence. A predominant lymphocytic meningoencephalitis was diagnosed in all animals with differences regarding the severity of lesions. Alpacas and horses with a shorter disease duration showed more prominent lesions in the cerebrum and at the transition of the nervous to the glandular part of the pituitary gland, as compared to animals with longer disease progression. In both species, viral antigen was almost exclusively restricted to cells of the central and peripheral nervous systems, with the notable exception of virus-infected glandular cells of the Pars intermedia of the pituitary gland. Alpacas likely represent dead-end hosts similar to horses and other spillover hosts of BoDV-1.

Antimicrobial Properties of Capsaicin: Available Data and Future Research Perspectives

Capsaicin is a phytochemical derived from plants of the genus Capsicum and subject of intensive phytochemical research due to its numerous physiological and therapeutical effects, including its important antimicrobial properties. Depending on the concentration and the strain of the bacterium, capsaicin can exert either bacteriostatic or even bactericidal effects against a wide range of both Gram-positive and Gram-negative bacteria, while in certain cases it can reduce their pathogenicity by a variety of mechanisms such as mitigating the release of toxins or inhibiting biofilm formation. Likewise, capsaicin has been shown to be effective against fungal pathogens, particularly Candida spp., where it once again interferes with biofilm formation. The parasites Toxoplasma gondi and Trypanosoma cruzi have been found to be susceptible to the action of this compound too while there are also viruses whose invasiveness is significantly dampened by it. Among the most encouraging findings are the prospects for future development, especially using new formulations and drug delivery mechanisms. Finally, the influence of capsaicin in somatostatin and substance P secretion and action, offers an interesting array of possibilities given that these physiologically secreted compounds modulate inflammation and immune response to a significant extent.

People's experiences living with peripheral neuropathy: a qualitative study

Introduction

Peripheral neuropathy is a neurological disorder characterised by pain, numbness, or tingling due to nerve damage. Peripheral neuropathy is one of the main health issues in Kuwait and is a rising concern which affects a large proportion of the population, therefore the lived experience needs to be explored to identify areas for improvement in care. This qualitative study explored the experiences of people living with peripheral neuropathy in Kuwait.

Methods

Semi-structured interviews were conducted with 25 participants recruited from the Neurology Outpatient Clinic of the Ibn Sina Hospital in Kuwait. The interview questions explored their experiences and understanding of pain along with the impact on their daily life. The interviews were audio recorded, transcribed and translated into English then coded using NVivo 12. Thematic analysis was conducted to identify patterns and themes in the data.

Results

Three major themes were identified including treatment beliefs (perceived effectiveness of treatment and seeking alternative treatments), the barriers to pain management (medication side effects, relationships with healthcare professionals and lack of information and access to healthcare), and the impact on quality of life (impact on work and social, physical, and psychological consequences). Self-efficacy was a key construct and over-arching theme that was discussed in all aspects, which finds reflection in the protection motivation theory.

Discussion

This paper presents the experiences of people living with peripheral neuropathy and highlights there is scope for improvement of current treatments in Kuwait. Self-management strategies are recommended alongside prescribed medication and healthcare professionals are encouraged to use a patient-centered approach. More importantly, information and support on the condition to promote coping strategies and self-efficacy should be adopted to improve quality of life. These findings can be implemented locally and globally to improve the quality of care provided to people living with peripheral neuropathy.

Post-infectious Painful Sensory Neuronopathy Following Giardia Infection Responsive to Intravenous Immunoglobulin Treatment

Sensory neuronopathy is a rare pure sensory disorder with characteristic clinical features of early-onset ataxia and a multifocal distribution of non-length-dependent sensory deficits. Diabetes is the most common cause of length-dependent peripheral neuropathy. However, in acute to subacute presentations, conditions such as autoimmune diseases, paraneoplastic syndrome, exposure to toxins, and viral infection could be common etiologies. This report presents a patient with sensory neuronopathy following a Giardia infection. Gait disturbance, neuropathic pain, ataxia, and pseudoathetosis improved by varying degrees following the monthly maintenance of intravenous immunoglobulin (IVIG). An immune-mediated or direct pathogenic attack can explain the underlying pathogenesis behind this patient's peripheral nerve dysfunction.

Risks of Severe COVID-19 Outcomes Among Patients With Diabetic Polyneuropathy in the United States

CONTEXT

Diabetic neuropathy (DN) affects more than 50% of diabetic patients who are also likely to have compromised immune system and respiratory function, both of which can make them susceptible to the SARS-CoV-2 virus.

OBJECTIVE

To assess the risk of severe COVID-19 illness among adults with DN, compared with those with no DN and those with no diabetes.

SETTING

The analysis utilized electronic health records from 55 US health care organizations in the TriNetX research database.

DESIGN

A retrospective cohort study.

PARTICIPANTS

The analysis included 882 650 adults diagnosed with COVID-19 in January 2020 to June 2021, including 16 641 with DN, 81 329 with diabetes with no neuropathy, and 784 680 with no diabetes.

OUTCOME MEASURES

The presence of health care utilization (admissions to emergency department, hospital, intensive care unit), 30-day mortality, clinical presentation (cough, fever, hypoxemia, dyspnea, or acute respiratory distress syndrome), and diagnostic test results after being infected affected by COVID-19.

RESULTS

The DN cohort was 1.19 to 2.47 times more likely than the non-DN cohorts to utilize care resources, receive critical care, and have higher 30-day mortality rates. Patients with DN also showed increased risk (1.13-2.18 times) of severe symptoms, such as hypoxemia, dyspnea, and acute respiratory distress syndrome.

CONCLUSIONS

Patients with DN had a significantly greater risk of developing severe COVID-19-related complications than those with no DN. It is critical for the public health community to continue preventive measures, such as social distancing, wearing masks, and vaccination, to reduce infection rates, particularly in higher risk groups, such as those with DN.

Comparison of Herpes Simplex Virus Reactivation Frequency in Acute Idiopathic Cranial Mononeuropathy and Normal Population by Serological Assay

Background: Herpes simplex virus (HSV) is a neurotropic DNA virus with a high prevalence. Following primary infection, HSV remains dormant in the neural ganglia. Secondary infection can emerge after the reactivation of latent infection, presenting as neurological manifestations. Previous studies have demonstrated the relationship between HSV reactivation and selective involvement of cranial nerves. Depending on the affected nerve, cranial mononeuropathies can present with symptoms, including diplopia, blurred vision, vertigo, unilateral facial palsy, speech impairment, swallowing difficulties, and hoarseness. Objectives: This study used a serological assay to compare HSV reactivation frequency between patients with recent idiopathic cranial mononeuropathies and normal individuals. Methods: Plasma samples from 35 idiopathic cranial mononeuropathy cases (57.2% women, mean age 58.37 years) and 35 age and sex-matched healthy controls were analyzed for anti-HSV immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies by enzyme-linked immunosorbent assay (ELISA). Results: Anti-HSV IgG antibody was positive in 91.4% of patients and 88.6% of controls. The mean serum anti-HSV IgG antibody level was significantly higher in patients (146.78 ± 60 RU/mL) than in the controls (130.61 ± 52.99 RU/mL) (P-value = 0.037). Anti-HSV IgM antibody was positive in 37.1% of patients and 14.3% of controls (P = 0.042). Conclusions: The frequency of HSV reactivation was significantly higher in patients with acute idiopathic cranial mononeuropathy than in the healthy controls, indicating the possible role of HSV as an etiology of cranial mononeuropathy.

Neuropathic Pain Associated with COVID-19: a Systematic Review of Case Reports

PURPOSE OF REVIEW

Researchers suggests that patients with COVID-19 develop neuropathic pain within weeks or months following infection and that patients with neuropathic pain and COVID-19 sometimes present with deterioration of neurologic complications and pain exacerbation. The objective of this systematic review is to discuss the case-reports having neuropathic pain during and after COVID-19 infection.

RECENT FINDINGS

Case reports that has described about patients getting neuropathy or neuropathic pain around the disease either immediately or late post COVID were included. The data was extracted and qualitatively synthesised. Literature was searched and 939 articles were found. 12 articles were screened as per the eligibility criteria and finally, 6 case reports on neuropathic pain in Covid-19 were selected from the database and manual search and finalised for analysis. 2 cases of herpes zoster and post herpetic neuralgia, 2 cases of intense burning pain, 1 case of trigeminal neuralgia and 1 of brachial plexopathy included for the review. Covid 19 viral neurogenic invasion is something very newly discovered topic of discussion in the field of research. With the passage of time, more cases will emerge and more data will be available for research. The review is registered in Prospero with no. CRD42021257060.

Possible complex regional pain syndrome following SARS-CoV-2 infection: Case report

SARS-CoV-2 infection has various manifestations including neurological and musculoskeletal system involvement. COVID-19 infection causes peripheral nerve lesions including small fibre neuropathy. Complex regional pain syndrome is a debilitating neurological condition manifested by predominantly pain associated with other sensory, motor, autonomic and tropic involvement. Identification and early treatment of CRPS has better prognosis. Here, we report a 21-year-old woman presented with pain, hyperalgesia, and swelling of left upper and lower limb following SARS-CoV-2 infection managed as possible complex regional pain syndrome.

Chronic pain and infection: mechanisms, causes, conditions, treatments, and controversies

Throughout human history, infection has been the leading cause of morbidity and mortality, with pain being one of the cardinal warning signs. However, in a substantial percentage of cases, pain can persist after resolution of acute illness, manifesting as neuropathic, nociplastic (eg, fibromyalgia, irritable bowel syndrome), or nociceptive pain. Mechanisms by which acute infectious pain becomes chronic are variable and can include immunological phenomena (eg, bystander activation, molecular mimicry), direct microbe invasion, central sensitization from physical or psychological triggers, and complications from treatment. Microbes resulting in a high incidence of chronic pain include bacteria such as the Borrelia species and Mycobacterium leprae, as well as viruses such as HIV, SARS-CoV-2 and herpeses. Emerging evidence also supports an infectious cause in a subset of patients with discogenic low back pain and inflammatory bowel disease. Although antimicrobial treatment might have a role in treating chronic pain states that involve active infectious inflammatory processes, their use in chronic pain conditions resulting from autoimmune mechanisms, central sensitization and irrevocable tissue (eg, arthropathy, vasculitis) or nerve injury, are likely to cause more harm than benefit. This review focuses on the relation between infection and chronic pain, with an emphasis on common viral and bacterial causes.

Autonomic dysfunction in patients with COVID‑19

Purpose

Autonomic dysfunction in patients with viral infections has been described before. In this study, we aimed to evaluate autonomic functions in patients with the coronavirus infectious disease 2019 (COVİD-19).

Methods

In this cross-sectional study, we compared 112 patients who had recovered from COVID-19 and 106 healthy controls. Symptoms of autonomic dysfunction were assessed with the SCOPA-AUT scale.

Results

Pupillomotor, urinary and sudomotor subscores of SCOPA-AUT scale were significantly higher in the COVID-19 patient group (p = 0.03, p = 0,006, p = 0.0001, respectively). There were no significant difference in terms of gastrointestinal, cardiovascular, sexual subscores and total SCOPA-AUT scores between the patient and control groups. The presence of fatigue symptom in the acute phase of COVID-19 increased the total SCOPA-AUT score by 2.2 points (p = 0.04) whereas the presence of smell loss (OR = 5.82, p = 0.01) and dyspnea (OR = 5.8, p = 0.03) were significant risk factors for pupillomotor dysfunction. The urinary, cardiovascular, sexual subscores and the total score of SCOPA-AUT scale were positively correlated with the age of the patient group.

Conclusion

Our study suggests that many patients might have prolonged symptoms of autonomic dysfunction after the acute phase of COVID-19 that might worsen the clinical recovery.

The Interplay Between Neuroinfections, the Immune System and Neurological Disorders: A Focus on Africa

Neurological disorders related to neuroinfections are highly prevalent in Sub-Saharan Africa (SSA), constituting a major cause of disability and economic burden for patients and society. These include epilepsy, dementia, motor neuron diseases, headache disorders, sleep disorders, and peripheral neuropathy. The highest prevalence of human immunodeficiency virus (HIV) is in SSA. Consequently, there is a high prevalence of neurological disorders associated with HIV infection such as HIV-associated neurocognitive disorders, motor disorders, chronic headaches, and peripheral neuropathy in the region. The pathogenesis of these neurological disorders involves the direct role of the virus, some antiretroviral treatments, and the dysregulated immune system. Furthermore, the high prevalence of epilepsy in SSA (mainly due to perinatal causes) is exacerbated by infections such as toxoplasmosis, neurocysticercosis, onchocerciasis, malaria, bacterial meningitis, tuberculosis, and the immune reactions they elicit. Sleep disorders are another common problem in the region and have been associated with infectious diseases such as human African trypanosomiasis and HIV and involve the activation of the immune system. While most headache disorders are due to benign primary headaches, some secondary headaches are caused by infections (meningitis, encephalitis, brain abscess). HIV and neurosyphilis, both common in SSA, can trigger long-standing immune activation in the central nervous system (CNS) potentially resulting in dementia. Despite the progress achieved in preventing diseases from the poliovirus and retroviruses, these microbes may cause motor neuron diseases in SSA. The immune mechanisms involved in these neurological disorders include increased cytokine levels, immune cells infiltration into the CNS, and autoantibodies. This review focuses on the major neurological disorders relevant to Africa and neuroinfections highly prevalent in SSA, describes the interplay between neuroinfections, immune system, neuroinflammation, and neurological disorders, and how understanding this can be exploited for the development of novel diagnostics and therapeutics for improved patient care.

A k-mer based approach for classifying viruses without taxonomy identifies viral associations in human autism and plant microbiomes

Viruses are an underrepresented taxa in the study and identification of microbiome constituents; however, they play an essential role in health, microbiome regulation, and transfer of genetic material. Only a few thousand viruses have been isolated, sequenced, and assigned a taxonomy, which limits the ability to identify and quantify viruses in the microbiome. Additionally, the vast diversity of viruses represents a challenge for classification, not only in constructing a viral taxonomy, but also in identifying similarities between a virus' genotype and its phenotype. However, the diversity of viral sequences can be leveraged to classify their sequences in metagenomic and metatranscriptomic samples, even if they do not have a taxonomy. To identify and quantify viruses in transcriptomic and genomic samples, we developed a dynamic programming algorithm for creating a classification tree out of 715,672 metagenome viruses. To create the classification tree, we clustered proportional similarity scores generated from the k-mer profiles of each of the metagenome viruses to create a database of metagenomic viruses. The resulting Kraken2 database of the metagenomic viruses can be found here: https://www.osti.gov/biblio/1615774 and is compatible with Kraken2. We then integrated the viral classification database with databases created with genomes from NCBI for use with ParaKraken (a parallelized version of Kraken provided in Supplemental Zip 1), a metagenomic/transcriptomic classifier. To illustrate the breadth of our utility for classifying metagenome viruses, we analyzed data from a plant metagenome study identifying genotypic and compartment specific differences between two Populus genotypes in three different compartments. We also identified a significant increase in abundance of eight viral sequences in post mortem brains in a human metatranscriptome study comparing Autism Spectrum Disorder patients and controls. We also show the potential accuracy for classifying viruses by utilizing both the JGI and NCBI viral databases to identify the uniqueness of viral sequences. Finally, we validate the accuracy of viral classification with NCBI databases containing viruses with taxonomy to identify pathogenic viruses in known COVID-19 and cassava brown streak virus infection samples. Our method represents the compulsory first step in better understanding the role of viruses in the microbiome by allowing for a more complete identification of sequences without taxonomy. Better classification of viruses will improve identifying associations between viruses and their hosts as well as viruses and other microbiome members. Despite the lack of taxonomy, this database of metagenomic viruses can be used with any tool that utilizes a taxonomy, such as Kraken, for accurate classification of viruses.

MRI Evaluation of Various Elbow, Forearm, and Wrist Neuropathies: A Pictorial Review

Upper extremity entrapment neuropathies are common and can cause pain, sensory loss, and muscle weakness leading to functional disability. We conducted a retrospective review from January 2007 until March 2020 of the magnetic resonance imaging (MRI) features of intrinsic and extrinsic causes of wrist, forearm, and elbow neuropathies of 637 patients who received a diagnosis of neuropathy by means of clinical and electrodiagnostic testing. We discuss cases with varying intrinsic and extrinsic nerve pathologies, including postoperative examples, affecting the median, radial, and ulnar nerve.Our collection of cases demonstrates a diversity of intrinsic and extrinsic causative factors. Intrinsic pathologies include neuritis as well as tumors arising from the nerve. Extrinsic causes resulting in nerve entrapment include masses, acute and chronic posttraumatic cases, anatomical variants, inflammatory and crystal deposition, calcium pyrophosphate deposition disease, and dialysis-related amyloidosis. Finally, we review postsurgical cases, such as carpal tunnel release and ulnar nerve transposition.Although upper extremity neuropathies tend to have a typical clinical presentation, imaging, particularly MRI, plays a vital role in evaluating the etiology and severity of each neuropathy and ultimately helps guide clinical management.

Infections of the Peripheral Nervous System

PURPOSE OF REVIEW

This article describes infections that affect the peripheral nervous system, including their clinical features, differential diagnoses, and treatments.

RECENT FINDINGS

Rates of pyomyositis have increased recently in the United States, possibly because of an increase in risk factors such as IV drug use, obesity, and diabetes. Other peripheral nervous system infections, such as diphtheria, have become more common in older patients secondary to a lack of revaccination or waning immunity. Although recommended treatment regimens for most infections remain unchanged over recent years, debate over the ideal dosing and route of administration continues for some infections such as tetanus and leprosy (Hansen disease).

SUMMARY

Infections of the peripheral nervous system are varied in terms of the type of infection, localization, and potential treatment. Nerve conduction studies and EMG can help determine localization, which is key to determining an initial differential diagnosis. It is important to recognize infections quickly to minimize diagnostic delays that could lead to patient morbidity and mortality.

Neuropathic pain post-COVID-19: a case report

A 61-year-old man with no significant medical history developed fever, headache and mild shortness of breath. He tested positive for SARS-CoV-2 and self-isolated at home, not requiring hospital admission. One week after testing positive, he developed acute severe burning pain affecting his whole body, subsequently localised distally in the limbs. There was no ataxia or autonomic failure. Neurological examination was unremarkable. Electrophysiological tests were unremarkable. Skin biopsy, lumbar puncture, enhanced MRI of the brachial plexus and MRI of the neuroaxis were normal. His pain was inadequately controlled with pregabalin but improved while on a weaning regimen of steroids. This case highlights the variety of possible symptoms associated with SARS-CoV-2 infection.

Guillain-Barré syndrome and COVID-19: an observational multicentre study from two Italian hotspot regions

OBJECTIVE

Single cases and small series of Guillain-Barré syndrome (GBS) have been reported during the SARS-CoV-2 outbreak worldwide. We evaluated incidence and clinical features of GBS in a cohort of patients from two regions of northern Italy with the highest number of patients with COVID-19.

METHODS

GBS cases diagnosed in 12 referral hospitals from Lombardy and Veneto in March and April 2020 were retrospectively collected. As a control population, GBS diagnosed in March and April 2019 in the same hospitals were considered.

RESULTS

Incidence of GBS in March and April 2020 was 0.202/100 000/month (estimated rate 2.43/100 000/year) vs 0.077/100 000/month (estimated rate 0.93/100 000/year) in the same months of 2019 with a 2.6-fold increase. Estimated incidence of GBS in COVID-19-positive patients was 47.9/100 000 and in the COVID-19-positive hospitalised patients was 236/100 000. COVID-19-positive patients with GBS, when compared with COVID-19-negative subjects, showed lower MRC sum score (26.3±18.3 vs 41.4±14.8, p=0.006), higher frequency of demyelinating subtype (76.6% vs 35.3%, p=0.011), more frequent low blood pressure (50% vs 11.8%, p=0.017) and higher rate of admission to intensive care unit (66.6% vs 17.6%, p=0.002).

CONCLUSIONS

This study shows an increased incidence of GBS during the COVID-19 outbreak in northern Italy, supporting a pathogenic link. COVID-19-associated GBS is predominantly demyelinating and seems to be more severe than non-COVID-19 GBS, although it is likely that in some patients the systemic impairment due to COVID-19 might have contributed to the severity of the whole clinical picture.

Identification of tetracycline combinations as EphB1 tyrosine kinase inhibitors for treatment of neuropathic pain

Previous studies have demonstrated that the synaptic EphB1 receptor tyrosine kinase is a major mediator of neuropathic pain, suggesting that targeting the activity of this receptor might be a viable therapeutic option. Therefore, we set out to determine if any FDA-approved drugs can act as inhibitors of the EphB1 intracellular catalytic domain. An in silico screen was first used to identify a number of tetracycline antibiotics which demonstrated potential docking to the ATP-binding catalytic domain of EphB1. Kinase assays showed that demeclocycline, chlortetracycline, and minocycline inhibit EphB1 kinase activity at low micromolar concentrations. In addition, we cocrystallized chlortetracycline and EphB1 receptor, which confirmed its binding to the ATP-binding domain. Finally, in vivo administration of the three-tetracycline combination inhibited the phosphorylation of EphB1 in the brain, spinal cord, and dorsal root ganglion (DRG) and effectively blocked neuropathic pain in mice. These results indicate that demeclocycline, chlortetracycline, and minocycline can be repurposed for treatment of neuropathic pain and potentially for other indications that would benefit from inhibition of EphB1 receptor kinase activity.

What Every Neuropathologist Needs to Know: Peripheral Nerve Biopsy

Peripheral neuropathy is a common disorder with many possible etiologies including metabolic diseases, inflammatory conditions, infections, malignancy, inherited diseases, drugs, and toxins. In most instances, diagnosis and treatment plan can be established based on clinical presentation, family history, laboratory results, genetic testing, and electrophysiological studies. But in some situations, a peripheral nerve biopsy remains a valuable tool. This is especially true in patients with rapidly progressive disease, with atypical presentation or for whom other approaches fail to yield a definitive diagnosis. The pathologic examination starts with basic decisions about specimen triage. A few basic questions help to provide an initial framework for the assessment of a nerve biopsy-is the specimen adequate; are there inflammatory changes; are there vascular changes; is there amyloid; are there changes to axonal density and the Schwann cell-myelin-axon unit. In the appropriate context and with such an approach peripheral nerve biopsies can still represent a clinically helpful test.

Guillain-Barré syndrome associated with SARS-CoV-2 infection: A systematic review and individual participant data meta-analysis

Several published reports have described a possible association between Guillain-Barré syndrome (GBS) and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. This systematic review aimed to summarize and meta-analyze the salient features and prognosis of SARS-CoV-2-associated GBS. We searched the PubMed (Medline), Web of Science and Cochrane databases for articles published between 01 January 2020 and 05 August 2020 using SARS-CoV-2 and GBS-related keywords. Data on sociodemographic characteristics, antecedent symptoms, clinical, serological and electrophysiological features, and hospital outcomes were recorded. We included 45 articles from 16 countries reporting 61 patients with SARS-CoV-2-associated GBS. Most (97.7%) articles were from high- and upper-middle-income countries. Forty-two (68.9%) of the patients were male; median (interquartile range) age was 57 (49-70) years. Reverse transcriptase polymerase chain reaction for SARS-CoV-2 was positive in 90.2% of patients. One report of SARS-CoV-2-associated familial GBS was found which affected a father and daughter of a family. Albuminocytological dissociation in cerebrospinal fluid was found in 80.8% of patients. The majority of patients (75.5%) had a demyelinating subtype of GBS. Intravenous immunoglobulin and plasmapheresis were given to 92.7% and 7.3% of patients, respectively. Around two-thirds (65.3%) of patients had a good outcome (GBS-disability score ≤ 2) on discharge from hospital. Two patients died in hospital. SARS-CoV-2-associated GBS mostly resembles the classical presentations of GBS that respond to standard treatments. Extensive surveillance is required in low- and lower-middle-income countries to identify and report similar cases/series. Further large-scale case-control studies are warranted to strengthen the current evidence. PROSPERO Registration Number CRD42020201673.

Guillain-Barré syndrome in SARS-CoV-2 infection: an instant systematic review of the first six months of pandemic

A systematic review from 1 January to 30 June 2020 revealed 42 patients with Guillain-Barré syndrome (GBS) associated with SARS-CoV-2 infection. Single cases and small series were reported from 13 countries, the majority from Europe (79.4%) and especially from Italy (30.9%). SARS-CoV-2 infection was demonstrated by nasopharyngeal swab (85.7%) and serology (14.3%). Median time between COVID-19 and GBS onset in 36 patients was 11.5 days (IQR: 7.7-16). The most common clinical features were: limb weakness (76.2%), hypoareflexia (80.9 %), sensory disturbances (66.7 %) and facial palsy (38.1%). Dysautonomia occurred in 19%, respiratory failure in 33.3% and 40.5% of patients were admitted in intensive care unit. Most patients (71.4%) had the classical clinical presentation but virtually all GBS variants and subtypes were reported. Cerebrospinal fluid (CSF) albumin-cytological dissociation was found in 28/36 (77.8%) and PCR for SARS-CoV-2 was negative in 25/25 patients. Electrodiagnosis was demyelinating in 80.5% and levels 1 and 2 of Brighton criteria of diagnostic certainty, when applicable, were fulfilled in 94.5% patients. Antiganglioside antibodies were positive in only 1/22 patients. Treatments were intravenous immunoglobulin and/or plasma exchange (92.8%) with, at short-time follow-up, definite improvement or recovery in 62.1% of patients. One patient died. In conclusion, the most frequent phenotype of GBS in SARS-CoV-2 infection is the classical sensorimotor demyelinating GBS responding to the usual treatments. The time interval between infectious and neuropathic symptoms, absence of CSF pleocytosis and negative PCR support a postinfectious mechanism. The abundance of reports suggests a pathogenic link between SARS-CoV-2 infection and GBS but a case-control study is greatly needed.

Neurological Aspects of SARS-CoV-2 Infection: Mechanisms and Manifestations

The human infection of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a public health emergency of international concern that has caused more than 16.8 million new cases and 662,000 deaths as of July 30, 2020. Although coronavirus disease 2019 (COVID-19), which is associated with this virus, mainly affects the lungs, recent evidence from clinical and pathological studies indicates that this pathogen has a broad infective ability to spread to extrapulmonary tissues, causing multiorgan failure in severely ill patients. In this regard, there is increasing preoccupation with the neuroinvasive potential of SARS-CoV-2 due to the observation of neurological manifestations in COVID-19 patients. This concern is also supported by the neurotropism previously documented in other human coronaviruses, including the 2002-2003 SARS-CoV-1 outbreak. Hence, in the current review article, we aimed to summarize the spectrum of neurological findings associated with COVID-19, which include signs of peripheral neuropathy, myopathy, olfactory dysfunction, meningoencephalitis, Guillain-Barré syndrome, and neuropsychiatric disorders. Furthermore, we analyze the mechanisms underlying such neurological sequela and discuss possible therapeutics for patients with neurological findings associated with COVID-19. Finally, we describe the host- and pathogen-specific factors that determine the tissue tropism of SARS-CoV-2 and possible routes employed by the virus to invade the nervous system from a pathophysiological and molecular perspective. In this manner, the current manuscript contributes to increasing the current understanding of the neurological aspects of COVID-19 and the impact of the current pandemic on the neurology field.

Type I Interferons Act Directly on Nociceptors to Produce Pain Sensitization: Implications for Viral Infection-Induced Pain

One of the first signs of viral infection is body-wide aches and pain. Although this type of pain usually subsides, at the extreme, viral infections can induce painful neuropathies that can last for decades. Neither of these types of pain sensitization is well understood. A key part of the response to viral infection is production of interferons (IFNs), which then activate their specific receptors (IFNRs) resulting in downstream activation of cellular signaling and a variety of physiological responses. We sought to understand how type I IFNs (IFN-α and IFN-β) might act directly on nociceptors in the dorsal root ganglion (DRG) to cause pain sensitization. We demonstrate that type I IFNRs are expressed in small/medium DRG neurons and that their activation produces neuronal hyper-excitability and mechanical pain in mice. Type I IFNs stimulate JAK/STAT signaling in DRG neurons but this does not apparently result in PKR-eIF2α activation that normally induces an anti-viral response by limiting mRNA translation. Rather, type I IFNs stimulate MNK-mediated eIF4E phosphorylation in DRG neurons to promote pain hypersensitivity. Endogenous release of type I IFNs with the double-stranded RNA mimetic poly(I:C) likewise produces pain hypersensitivity that is blunted in mice lacking MNK-eIF4E signaling. Our findings reveal mechanisms through which type I IFNs cause nociceptor sensitization with implications for understanding how viral infections promote pain and can lead to neuropathies.SIGNIFICANCE STATEMENT It is increasingly understood that pathogens interact with nociceptors to alert organisms to infection as well as to mount early host defenses. Although specific mechanisms have been discovered for diverse bacterial and fungal pathogens, mechanisms engaged by viruses have remained elusive. Here we show that type I interferons, one of the first mediators produced by viral infection, act directly on nociceptors to produce pain sensitization. Type I interferons act via a specific signaling pathway (MNK-eIF4E signaling), which is known to produce nociceptor sensitization in inflammatory and neuropathic pain conditions. Our work reveals a mechanism through which viral infections cause heightened pain sensitivity.

Cytotoxic Immunity in Peripheral Nerve Injury and Pain

Cytotoxicity and consequent cell death pathways are a critical component of the immune response to infection, disease or injury. While numerous examples of inflammation causing neuronal sensitization and pain have been described, there is a growing appreciation of the role of cytotoxic immunity in response to painful nerve injury. In this review we highlight the functions of cytotoxic immune effector cells, focusing in particular on natural killer (NK) cells, and describe the consequent action of these cells in the injured nerve as well as other chronic pain conditions and peripheral neuropathies. We describe how targeted delivery of cytotoxic factors via the immune synapse operates alongside Wallerian degeneration to allow local axon degeneration in the absence of cell death and is well-placed to support the restoration of homeostasis within the nerve. We also summarize the evidence for the expression of endogenous ligands and receptors on injured nerve targets and infiltrating immune cells that facilitate direct neuro-immune interactions, as well as modulation of the surrounding immune milieu. A number of chronic pain and peripheral neuropathies appear comorbid with a loss of function of cellular cytotoxicity suggesting such mechanisms may actually help to resolve neuropathic pain. Thus while the immune response to peripheral nerve injury is a major driver of maladaptive pain, it is simultaneously capable of directing resolution of injury in part through the pathways of cellular cytotoxicity. Our growing knowledge in tuning immune function away from inflammation toward recovery from nerve injury therefore holds promise for interventions aimed at preventing the transition from acute to chronic pain.

Leprosy: A rare case of infectious peripheral neuropathy in the United States

Peripheral neuropathy can be the initial presentation of leprosy. Diagnosis can be challenging unless skin manifestations are recognized. Skin biopsy and Fite staining are the keys to the diagnosis. It is important to treat coexisting Lepra reactions, peripheral neuropathy and side effects of the therapeutic agents. This is a complex clinical course of a patient with lepromatous leprosy.

A Comparative Review of Chemotherapy-Induced Peripheral Neuropathy in In Vivo and In Vitro Models

Chemotherapy-induced peripheral neuropathy (CIPN) is an adverse effect caused by several classes of widely used anticancer therapeutics. Chemotherapy-induced peripheral neuropathy frequently leads to dose reduction or discontinuation of chemotherapy regimens, and CIPN symptoms can persist long after completion of chemotherapy and severely diminish the quality of life of patients. Differences in the clinical presentation of CIPN by widely diverse classifications of anticancer agents have spawned multiple mechanistic hypotheses that seek to explain the pathogenesis of CIPN. Despite its clinical relevance, common occurrence, and extensive investigation, the pathophysiology of CIPN remains unclear. Furthermore, there is no unequivocal gold standard for the prevention and treatment of CIPN. Herein, we review in vivo and in vitro models of CIPN with a focus on histopathological changes and morphological features aimed at understanding the pathophysiology of CIPN and identify gaps requiring deeper exploration. An elucidation of the underlying mechanisms of CIPN is imperative to identify potential targets and approaches for prevention and treatment.

The neuropathology of fatal encephalomyelitis in human Borna virus infection

After many years of controversy, there is now recent and solid evidence that classical Borna disease virus 1 (BoDV-1) can infect humans. On the basis of six brain autopsies, we provide the first systematic overview on BoDV-1 tissue distribution and the lesion pattern in fatal BoDV-1-induced encephalitis. All brains revealed a non-purulent, lymphocytic sclerosing panencephalomyelitis with detection of BoDV-1-typical eosinophilic, spherical intranuclear Joest–Degen inclusion bodies. While the composition of histopathological changes was constant, the inflammatory distribution pattern varied interindividually, affecting predominantly the basal nuclei in two patients, hippocampus in one patient, whereas two patients showed a more diffuse distribution. By immunohistochemistry and RNA in situ hybridization, BoDV-1 was detected in all examined brain tissue samples. Furthermore, infection of the peripheral nervous system was observed. This study aims at raising awareness to human bornavirus encephalitis as differential diagnosis in lymphocytic sclerosing panencephalomyelitis. A higher attention to human BoDV-1 infection by health professionals may likely increase the detection of more cases and foster a clearer picture of the disease.

Infectious diseases causing autonomic dysfunction

OBJECTIVES

To review infectious diseases that may cause autonomic dysfunction.

METHODS

Review of published papers indexed in medline/embase.

RESULTS

Autonomic dysfunction has been reported in retrovirus (human immunodeficiency virus (HIV), human T-lymphotropic virus), herpes viruses, flavivirus, enterovirus 71 and lyssavirus infections. Autonomic dysfunction is relatively common in HIV-infected patients and heart rate variability is reduced even in early stages of infection. Orthostatic hypotension, urinary dysfunction and hypohidrosis have been described in tropical spastic paraparesis patients. Varicella zoster reactivation from autonomic ganglia may be involved in visceral disease and chronic intestinal pseudo-obstruction. Autonomic and peripheral nervous system dysfunction may happen in acute tick-borne encephalitis virus infections. Hydrophobia, hypersalivation, dyspnea, photophobia, and piloerection are frequently observed in human rabies. Autonomic dysfunction and vagal denervation is common in Chagas disease. Neuronal depopulation occurs mainly in chagasic heart disease and myenteric plexus, and megacolon, megaesophagus and cardiomyopathy are common complications in the chronic stage of Chagas disease. Parasympathetic autonomic dysfunction precedes left ventricle systolic dysfunction in Chagas disease. A high prevalence of subclinical autonomic neuropathy in leprosy patients has been reported, and autonomic nerve dysfunction may be an early manifestation of the disease. Autonomic dysfunction features in leprosy include anhidrosis, impaired sweating function, localised alopecia ,and reduced heart rate variability. Urinary retention and intestinal pseudo-obstruction have been described in Lyme disease. Diphtheritic polyneuropathy, tetanus and botulism are examples of bacterial infections releasing toxins that affect the autonomic nervous system.

CONCLUSIONS

Autonomic dysfunction may be responsible for additional morbidity in some infectious diseases.

The role of primary infection of Schwann cells in the aetiology of infective inflammatory neuropathies

Numerous different pathogens are responsible for infective peripheral neuropathies and this is generally the result of the indirect effects of pathogen infection, namely anti pathogen antibodies cross reacting with epitopes on peripheral nerve, auto reactive T cells attacking myelin, circulating immune complexes and complement fixation. Primary infection of Schwann cells (SC) associated with peripheral nerve inflammation is rare requiring pathogens to cross the Blood Peripheral Nerve Barrier (BPNB) evade anti-pathogen innate immune pathways and invade the SC. Spirochetes Borrelia bourgdorferi and Trepomema pallidum are highly invasive, express surface lipo proteins, but despite this SC are rarely infected. However, Trypanosoma cruzi (Chaga's disease) and Mycobacterium leprae. Leprosy are two important causes of peripheral nerve infection and both demonstrate primary infection of SC. This is due to two novel strategies; T. cruzi express a trans-silalidase that mimics host neurotrophic factors and infects SC via tyrosine kinase receptors. M. leprae demonstrates multi receptor SC tropism and subsequent infection promotes nuclear reprogramming and dedifferentiation of host SC into progenitor stem like cells (pSLC) that are vulnerable to M. leprae infection. These two novel pathogen evasion strategies, involving stem cells and receptor mimicry, provide potential therapeutic targets relevant to the prevention of peripheral nerve inflammation by inhibiting primary SC infection.