Acute flaccid myelitis: A clinical review of US cases 2012-2015

Acute Flaccid Myelitis Associated With Enterovirus D68: A Review

Acute flaccid myelitis is a disease that affects the anterior horn cells of the spinal cord, leading to rapid onset of flaccid paralysis. Recent biennial epidemics, beginning in the summer of 2014, have been associated with enterovirus D68, although the underlying pathophysiology is unknown. Patients present with asymmetric flaccid weakness of the extremities, with cranial neuropathy and without encephalopathy, and often have residual disability. Here we review the current literature on this disabling disease and discuss treatment modalities and ongoing research.

Infectious myelitis

Infectious pathogens can directly affect the spinal cord or trigger autoimmune reactions, which may result in permanent damage to cord structures. The most common aetiology comes from virus but depend on age, location of the patient and co-morbidities. Acute Flaccid paralysis and acute transverse myelitis are considered as emergencies. Differential diagnosis is mainly relapses of autoimmune diseases, which can mimic infectious myelopathies.

Incidence, Risk Factors and Outcomes Among Children With Acute Flaccid Myelitis: A Population-based Cohort Study in a California Health Network Between 2011 and 2016

BACKGROUND

Acute flaccid myelitis (AFM) is defined as an acute onset of limb weakness with longitudinal spinal gray matter lesions. Reporting bias and misdiagnosis confound epidemiologic studies of AFM. We mitigated these confounders by using a large data set to assess AFM incidence, risk factors and outcomes in a fixed population.

METHODS

A retrospective cohort study was conducted within Kaiser Permanente Northern California population among children 1-18 years. Cases met radiographic and clinical criteria for AFM and were confirmed by two clinicians. Clinical and demographic data were assessed.

RESULTS

A total of 28 patients met study criteria for AFM between January 1, 2011 and December 31, 2016, an overall rate of 1.46 per 100,000 person-years. Incidence increased from 0.30 to 1.43 cases/per 100,000 person-years between 2011 and 2016, respectively. Median age was 9 years. Risk factors included male sex, Asian ancestry and history of asthma, atopic dermatitis or head injury. Risk factors associated with poliomyelitis were absent. Prodromal illness was common; enterovirus was the most common pathogen detected (n = 5). Among the 27 patients with 12-month follow-up, most demonstrated some improvement, 11 (41.0%) had full recovery, but several had significant deficits with one death reported after the study period.

CONCLUSIONS

We employed a closed-population study to generate AFM incidence, risk and outcome data. Our findings support previous reports of male sex and atopy as risk factors. Interval increase in incidence, predisposing Asian ancestry and history of head injury were unique findings to this study. Overall prognosis was better than prior reports, but recovery was incomplete in several patients.

Acute Flaccid Myelitis

Acute flaccid myelitis is a poliolike illness affecting mainly children, which seems to occur every 2 years in the late summer and early fall. The 2018 outbreak was alarming to parents and healthcare providers because the etiology is still under investigation and long-term outcomes are unclear. Becoming familiar with what is known about the epidemiology and clinical characteristics of acute flaccid myelitis enables neuroscience nurses to disseminate accurate information and recognize and report suspicious symptoms.

Functional Improvement of Upper and Lower Extremity After Decompression and Neurolysis and Nerve Transfer in a Pediatric Patient with Acute Flaccid Myelitis

Patient: Female, 5

Final Diagnosis: Enterovirus infection

Symptoms: Weakness in all 4 limbs

Medication: —

Clinical Procedure: Nerve decompression • neurolysis and nerve transfer

Specialty: Neurosurgery

Serial MRI findings of acute flaccid myelitis during an outbreak of enterovirus D68 infection in Japan

OBJECIVE

To clarify the neuroimaging findings of children with acute flaccid myelitis during an outbreak of EV-D68 infection.

METHODS

We performed a detailed review of the spinal and cranial MRI results of 54 children with acute flaccid myelitis. We focused on the range of longitudinal lesions, the localization and appearance of lesions within a horizontal section, Gadolinium-enhancement, and changes over time.

RESULTS

All children had longitudinal spinal lesions involving central gray matter. Twenty-six children had lesions spanning the entire spine. Six of them had weakness in all limbs, whereas seven had weakness of only one limb. Thirty-eight children had lesions in both gray and white matter and limb weakness tended to be more severe in these children. During the acute period, spinal lesions showed bilateral ill-defined widespread T2 hyperintensity. During the subacute period, lesions were well defined and confined to the anterior horn. The distribution of limb weakness was correlated with the appearance of lesions during the subacute period. Gadolinium enhancement was performed in 37 children, and enhancement was seen in the cauda equina in 29 children. Enhancement was infrequent within 2 days after onset but was seen in almost all children thereafter. Twenty-two children had brainstem lesions continuous with spinal lesions.

CONCLUSION

Extensive longitudinal spinal lesions were characteristic in children with acute flaccid myelitis. Lesions were usually bilateral and widespread during the acute period, whereas localization to the anterior horn could become obvious. Although enhancement of the cauda equina was often observed, its appearance was sometimes delayed.

Acute Flaccid Myelitis: A Clinical Overview for 2019

Acute flaccid myelitis (AFM) is characterized by flaccid paralysis of one or more limbs, often following a viral illness, with magnetic resonance imaging findings consistent with inflammation of the spinal cord gray matter. It is unclear whether all patients with AFM will have full recovery of neurologic function. Since 2014, there have been several clusters of AFM in the United States, with a 3-fold increase in reported AFM cases recorded in 2018 compared with the previous year. Epidemiological evidence supports a temporal association between respiratory enteroviral illness, particularly with enteroviruses D68 and A71, and clustering of AFM cases. However, causality has yet to be established. Treatment of AFM is primarily supportive. Adjunctive therapies such as intravenous immunoglobulin, corticosteroids, plasmapheresis, and fluoxetine have not been found to improve long-term outcomes. Further research is urgently needed to characterize and optimize management of this emerging, yet poorly understood, condition.

Clinical Subpopulations in a Sample of North American Children Diagnosed With Acute Flaccid Myelitis, 2012-2016

IMPORTANCE

Acute flaccid myelitis (AFM) is an emerging poliolike illness of children whose clinical spectrum and associated pathogens are only partially described. The case definition is intentionally encompassing for epidemiologic surveillance to capture all potential AFM cases. Defining a restrictive, homogenous subpopulation may aid our understanding of this emerging disease.

OBJECTIVE

To evaluate the extent to which the US Centers for Disease Control and Prevention (CDC) case definition of AFM incorporates possible alternative diagnoses and to assess the plausibility of a case definition that enriches the biological homogeneity of AFM for inclusion in research studies.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective case analysis of children younger than 18 years diagnosed as having AFM between 2012 and 2016 using the CDC case definition. Group 1 included patients recruited from the United States and Canada based on the CDC case definition of AFM. Group 2 included patients referred to the Johns Hopkins Transverse Myelitis Center for evaluation of suspected AFM. Patients' records and imaging data were critically reviewed by 3 neurologists to identify those cases with definable alternative diagnoses, and the remaining patients were categorized as having restrictively defined AFM (rAFM). Clinical characteristics were compared between patients with rAFM (cases) and those with alternative diagnoses, and a case description distinguishing these AFM groups was identified. Interrater reliability of this description was confirmed for a subset of cases by a fourth neurologist. Data were analyzed between May 2017 and November 2018.

MAIN OUTCOMES AND MEASURES

Proportion of patients with possible alternative diagnosis.

RESULTS

Of the 45 patients who met the CDC AFM case definition and were included, the mean age was 6.1 years; 27 were boys (60%); and 37 were white (82%), 3 were Asian (7%), 1 was Hispanic (2%), and 4 were mixed race/ethnicity (9%). Of the included patients, 34 were classified as having rAFM, and 11 had alternate diagnoses (including transverse myelitis, other demyelinating syndromes, spinal cord stroke, Guillain-Barre syndrome, Chiari I myelopathy, and meningitis). Factors differing between groups were primarily asymmetry of weakness, lower motor neuron signs, preceding viral syndrome, symptoms evolving over hours to days, absence of sensory deficits, and magnetic resonance imaging findings. A case description was able to reliably define the rAFM group.

CONCLUSIONS AND RELEVANCE

We present an approach for defining a homogeneous research population that may more accurately reflect the pathogenesis of the prototypical poliomyelitis-like subgroup of AFM. The definition of rAFM forms a blueprint for inclusion criteria in future research efforts, but more work is required for refinement and external validation.

An increase in reports of acute flaccid paralysis (AFP) in the United Kingdom, 1 January 2018-21 January 2019: early findings

During 2018, the United Kingdom experienced an increase in reports of cases of acute flaccid paralysis (AFP). As at 21 January 2019, 40 cases had been identified with a peak in October 2018. The increase was temporally associated with an upsurge in enterovirus (EV) D68 activity. Enterovirus was detected in 15 cases, mainly from respiratory tract samples; nine were typed as EV-D68. A national task force has been established and investigations are ongoing.

Acute flaccid myelitis and enterovirus D68: lessons from the past and present

Acute flaccid myelitis is characterized by the combination of acute flaccid paralysis and a spinal cord lesion largely restricted to the gray matter on magnetic resonance imaging. The term acute flaccid myelitis was introduced in 2014 after the upsurge of pediatric cases in the USA with enterovirus D68 infection. Since then, an increasing number of cases have been reported worldwide. Whereas the terminology is new, the clinical syndrome has been recognized in the past in association with several other neurotropic viruses such as poliovirus.Conclusion: This review presents the current knowledge on acute flaccid myelitis with respect to the clinical presentation and its differential diagnosis with Guillain-Barré syndrome and acute transverse myelitis. We also discuss the association with enterovirus D68 and the presumed pathophysiological mechanism of this infection causing anterior horn cell damage. Sharing clinical knowledge and insights from basic research is needed to make progress in diagnosis, treatment, and prevention of this new polio-like disease. What is Known: • Acute flaccid myelitis (AFM) is a polio-like condition characterized by rapid progressive asymmetric weakness, together with specific findings on MRI • AFM has been related to different viral agents, but recent outbreaks are predominantly associated with enterovirus D68. What is New: • Improving knowledge on AFM must increase early recognition and adequate diagnostic procedures by clinicians. • The increasing incidence of AFM urges cooperation between pediatricians, neurologists, and microbiologists for the development of treatment and preventive options.

Twenty-nine Cases of Enterovirus-D68-associated Acute Flaccid Myelitis in Europe 2016: A Case Series and Epidemiologic Overview

BACKGROUND

Enterovirus-D68 (EV-D68) is a respiratory virus within the genus Enterovirus and the family of Picornaviridae. Genetically, it is closely related to rhinovirus that replicates in the respiratory tract and causes respiratory disease. Since 2014, EV-D68 has been associated with the neurologic syndrome of acute flaccid myelitis (AFM).

METHODS

In October 2016, questionnaires were sent out to a European network including 66 virologists and clinicians, to develop an inventory of EV-D68-associated AFM cases in Europe. Clinical and virologic information of case patients was requested. In addition, epidemiologic information on EV testing was collected for the period between March and October 2016.

RESULTS

Twenty-nine cases of EV-D68-associated AFM were identified, from 12 different European countries. Five originated from France, 5 from Scotland and 3 each from Sweden, Norway and Spain. Twenty-six were children (median age 3.8 years), 3 were adults. EV-D68 was detected in respiratory materials (n = 27), feces (n = 8) and/or cerebrospinal fluid (n = 2). Common clinical features were asymmetric flaccid limb weakness, cranial nerve deficits and bulbar symptoms. On magnetic resonance imaging, typical findings were hyperintensity of the central cord and/or brainstem; low motor amplitudes with normal conduction velocities were seen on electromyography. Full clinical recovery was rare (n = 3), and 2 patients died. The epidemiologic data from 16 European laboratories showed that of all EV-D68-positive samples, 99% was detected in a respiratory specimen.

CONCLUSIONS

For 2016, 29 EV-D68-related AFM cases were identified in mostly Western Europe. This is likely an underestimation, because case identification is dependent on awareness among clinicians, adequate viral diagnostics on respiratory samples and the capability of laboratories to type EVs.

A neonatal mouse model of Enterovirus D68 infection induces both interstitial pneumonia and acute flaccid myelitis

Enterovirus D68 (EV-D68) is a causative agent of recent outbreaks of severe respiratory illness, pneumonia and acute flaccid myelitis (AFM) worldwide. The study of the pathogenesis, vaccines and anti-viral drugs for EV-D68 infection has been reported. Given the previously described mouse model of EV-D68, we sought to establish a neonatal mice model inducing both pneumonia and AFM. The neonatal BALB/c mice were inoculated intraperitoneally with the EV-D68 strain (named15296-virus) which was produced by the reverse genetics method. The infected mice displayed limb paralysis, tachypnea and even death, which were similar to the clinical symptoms of human infections. Moreover, the results of histopathologic examination and immunohistochemical staining showed acidophilic necrosis in the muscle, the spinal cord and alveolar wall thickening in the lung, indicating that EV-D68 exhibited strong tropism to the muscles, spinal cord and lung. Furthermore, the results of real-time PCR also suggested that the viral loads in the blood, spinal cord, muscles and lung were higher than those in other tissues at different time points post-infection. Additionally, the neonatal mouse model was used for evaluating the EV-D68 infection. The results of the anti-serum passive and maternal antibody protection indicated that the neonatal mice could be protected against the EV-D68 challenge, and displayed that both the serum of 15296-virus and prototype-virus (Fermon) were performing a certain cross-protective activity against the 15296-virus challenge. In summary, the above results proved that our neonatal mouse model possessed not only the interstitial pneumonia and AFM simultaneously but also a potentiality to evaluate the protective effects of EV-D68 vaccines and anti-viral drugs in the future.

Enterovirus D68 - The New Polio?

Enterovirus D68 (EV-D68) has emerged over the recent years, with large outbreaks worldwide. Increased occurrence has coincided with improved clinical awareness and surveillance of non-polio enteroviruses. Studies showing its neurotropic nature and the change in pathogenicity have established EV-D68 as a probable cause of Acute Flaccid Myelitis (AFM). The EV-D68 storyline shows many similarities with poliovirus a century ago, stimulating discussion whether EV-D68 could be ascertaining itself as the "new polio." Increasing awareness amongst clinicians, incorporating proper diagnostics and integrating EV-D68 into accessible surveillance systems in a way that promotes data sharing, will be essential to reveal the burden of disease. This will be a necessary step in preventing EV-D68 from becoming a threat to public health.

Safety, tolerability, and efficacy of fluoxetine as an antiviral for acute flaccid myelitis

OBJECTIVE

To determine the safety, tolerability, and efficacy of fluoxetine for proven or presumptive enterovirus (EV) D68-associated acute flaccid myelitis (AFM).

METHODS

A multicenter cohort study of US patients with AFM in 2015-2016 compared serious adverse events (SAEs), adverse effects, and outcomes between fluoxetine-treated patients and untreated controls. Fluoxetine was administered at the discretion of treating providers with data gathered retrospectively. The primary outcome was change in summative limb strength score (SLSS; sum of Medical Research Council strength in all 4 limbs, ranging from 20 [normal strength] to 0 [complete quadriparesis]) between initial examination and latest follow-up, with increased SLSS reflecting improvement and decreased SLSS reflecting worsened strength.

RESULTS

Fifty-six patients with AFM from 12 centers met study criteria. Among 30 patients exposed to fluoxetine, no SAEs were reported and adverse effect rates were similar to unexposed patients (47% vs 65%, p = 0.16). The 28 patients treated with >1 dose of fluoxetine were more likely to have EV-D68 identified (57.1% vs 14.3%, p < 0.001). Their SLSS was similar at initial examination (mean SLSS 12.9 vs 14.3, p = 0.31) but lower at nadir (mean SLSS 9.25 vs 12.82, p = 0.02) and latest follow-up (mean SLSS 12.5 vs 16.4, p = 0.005) compared with the 28 patients receiving 1 (n = 2) or no (n = 26) doses. In propensity-adjusted analysis, SLSS from initial examination to latest follow-up decreased by 0.2 (95% confidence interval [CI] -1.8 to +1.4) in fluoxetine-treated patients and increased by 2.5 (95% CI +0.7 to +4.4) in untreated patients (p = 0.015).

CONCLUSION

Fluoxetine was well-tolerated. Fluoxetine was preferentially given to patients with AFM with EV-D68 identified and more severe paralysis at nadir, who ultimately had poorer long-term outcomes.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that for patients with EV-D68-associated AFM, fluoxetine is well-tolerated and not associated with improved neurologic outcomes.

Nerve Transfers for Enterovirus D68-Associated Acute Flaccid Myelitis: A Case Series

BACKGROUND

Acute flaccid myelitis is associated with enterovirus D68 -induced inflammation and destruction of cervical anterior horn cells. To date, no medical intervention has altered the disease course.

METHODS

We report two pediatric patients who were treated with nerve transfer in three limbs with sustained upper extremity neuropathy. Postoperative outcomes included muscle strength, graded on the British Medical Research Council (BMRC) scale, range of motion, and electromyography.

RESULTS

Two years postoperatively, Patient 1 had improved elbow flexion to BMRC grade 4+, 125° of flexion, and discrete to decreased motor unit recruitment in targeted muscles. Twenty-one months postoperatively, Patient 2 demonstrated right brachialis flexion to BMRC grade 4+/5 and deltoid firing with simultaneous pectoralis major recruitment, and limited but active flexor digitorum profundus flexion.

CONCLUSIONS

Both patients continue to demonstrate functional recovery two years postoperatively. These outcomes suggest a promising reconstructive technique for this emerging and devastating viral endemic.

Contemporary Circulating Enterovirus D68 Strains Have Acquired the Capacity for Viral Entry and Replication in Human Neuronal Cells

Since the EV-D68 outbreak during the summer of 2014, evidence of a causal link to a type of limb paralysis (AFM) has been mounting. In this article, we describe a neuronal cell culture model (SH-SY5Y cells) in which a subset of contemporary 2014 outbreak strains of EV-D68 show infectivity in neuronal cells, or neurotropism. We confirmed the difference in neurotropism in vitro using primary human neuron cell cultures and in vivo with a mouse paralysis model. Using the SH-SY5Y cell model, we determined that a barrier to viral entry is at least partly responsible for neurotropism. SH-SY5Y cells may be useful in determining if specific EV-D68 genetic determinants are associated with neuropathogenesis, and replication in this cell line could be used as rapid screening tool for identification of neurotropic EV-D68 strains. This may assist with better understanding of pathogenesis and epidemiology and with the development of potential therapies.

Enterovirus D68 (EV-D68) has historically been associated with respiratory illnesses. However, in the summers of 2014 and 2016, EV-D68 outbreaks coincided with a spike in polio-like acute flaccid myelitis/paralysis (AFM/AFP) cases. This raised concerns that EV-D68 could be the causative agent of AFM during these recent outbreaks. To assess the potential neurotropism of EV-D68, we utilized the neuroblastoma-derived neuronal cell line SH-SY5Y as a cell culture model to determine if differential infection is observed for different EV-D68 strains. In contrast to HeLa and A549 cells, which support viral infection of all EV-D68 strains tested, SH-SY5Y cells only supported infection by a subset of contemporary EV-D68 strains, including isolates from the 2014 outbreak. Viral replication and infectivity in SH-SY5Y were assessed using multiple assays: virus production, cytopathic effects, cellular ATP release, and VP1 capsid protein production. Similar differential neurotropism was also observed in differentiated SH-SY5Y cells, primary human neuron cultures, and a mouse paralysis model. Using the SH-SY5Y cell culture model, we determined that barriers to viral binding and entry were at least partly responsible for the differential infectivity phenotype. Transfection of genomic RNA into SH-SY5Y generated virions for all EV-D68 isolates, but only a single round of replication was observed from strains that could not directly infect SH-SY5Y. In addition to supporting virus replication and other functional studies, this cell culture model may help identify the signatures of virulence to confirm epidemiological associations between EV-D68 strains and AFM and allow for the rapid identification and characterization of emerging neurotropic strains.

Enterovirus D68 and acute flaccid myelitis-evaluating the evidence for causality

Increased circulation of enterovirus D68 in 2014 and 2016 temporally and geographically coincided with increases in cases of acute flaccid myelitis, an uncommon condition of paralysis due to lesions in the anterior horn of the spinal cord. The identification of enterovirus D68 in respiratory specimens from cases of acute flaccid myelitis worldwide further supports an association, yet the absence of direct virus isolation from affected tissues, infrequent detection in cerebrospinal fluid, and the absence, until recently, of an animal model has left the causal nature of the relationship unproven. In this Personal View we evaluate epidemiological and biological evidence linking enterovirus D68 and acute flaccid myelitis. We applied the Bradford Hill criteria to investigate the evidence for a causal relationship and highlight the importance of comprehensive surveillance and research to further characterise the role of enterovirus D68 in acute flaccid myelitis and pursue effective therapies and prevention strategies.

Acute Flaccid Paralysis and Enteroviral Infections

PURPOSE OF REVIEW

The focus of this review is on enterovirus (EV)-associated acute flaccid paralysis (AFP) due to spinal cord anterior horn cell disease. Emphasis is placed on the epidemiology, pathogenesis, diagnosis, treatment, and outcome of AFP caused by polioviruses, vaccine-derived polioviruses, EV-D68, and EV-A71.

RECENT FINDINGS

Since the launch of The Global Polio Eradication Initiative in 1988, the worldwide incidence of polio has been reduced by 99.9%, with small numbers of poliomyelitis cases being reported only in Afghanistan, Pakistan, and Nigeria. With the planned phaseout of oral polio vaccine, vaccine-associated poliomyelitis is also expected to be eliminated. In their place, other EVs, chiefly EV-D68 and EV-A71, have emerged as the principal causes of AFP. There is evidence that the emergence of EV-D68 as a cause of severe respiratory disease and AFP was due to recent genetic virus evolution. Antiviral medications targeting EV-D68, EV-A71, and other EVs will likely be available in the near future. An effective EV-A71 vaccine has been developed, and preliminary investigations suggest an EV-D68 vaccine could be on the horizon. The eradication of poliomyelitis and vaccine-associated poliomyelitis is near, after which other EVs, presently EV-D68 and EV-A71, will be the principle viral causes of AFP. Moving forward, it is essential that EV outbreaks, in particular those associated with neurologic complications, be investigated carefully and the causal strains identified, so that treatment and prevention efforts can be rapidly developed and implemented.

Enteroviral Infection: The Forgotten Link to Amyotrophic Lateral Sclerosis?

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease that primarily attacks motor neurons in the brain and spinal cord, leading to progressive paralysis and ultimately death. Currently there is no effective therapy. The majority of ALS cases are sporadic, with no known family history; unfortunately the etiology remains largely unknown. Contribution of Enteroviruses (EVs), a family of positive-stranded RNA viruses including poliovirus, coxsackievirus, echovirus, enterovirus-A71 and enterovirus-D68, to the development of ALS has been suspected as they can target motor neurons, and patients with prior poliomyelitis show a higher risk of motor neuron disease. Multiple efforts have been made to detect enteroviral genome in ALS patient tissues over the past two decades; however the clinical data are controversial and a causal relationship has not yet been established. Recent evidence from in vitro and animal studies suggests that enterovirus-induced pathology remarkably resembles the cellular and molecular phenotype of ALS, indicating a possible link between enteroviral infection and ALS pathogenesis. In this review, we summarize the nature of enteroviral infection, including route of infection, cells targeted, and viral persistence within the central nervous system (CNS). We review the molecular mechanisms underlying viral infection and highlight the similarity between viral pathogenesis and the molecular and pathological features of ALS, and finally, discuss the potential role of enteroviral infection in frontotemporal dementia (FTD), a disease that shares common clinical, genetic, and pathological features with ALS, and the significance of anti-viral therapy as an option for the treatment of ALS.

Encephalitis in US Children

Encephalitis is an uncommon but severe disease characterized by neurologic dysfunction with central nervous system inflammation. Children with encephalitis should receive supportive care and empiric therapies for common and treatable causes while prioritizing diagnostic evaluation for common, treatable, and high-risk conditions. Even with an extensive diagnostic workup, an infectious cause is identified in less than half of cases, suggesting a role for postinfectious or noninfectious processes.

Clinical Features of Acute Flaccid Myelitis Temporally Associated With an Enterovirus D68 Outbreak: Results of a Nationwide Survey of Acute Flaccid Paralysis in Japan, August-December 2015

Background

Acute flaccid myelitis (AFM) is an acute flaccid paralysis syndrome with spinal motor neuron involvement of unknown etiology. We investigated the characteristics and prognostic factors of AFM clusters coincident with an enterovirus D68 (EV-D68) outbreak in Japan during autumn 2015.

Methods

An AFM case series study was conducted following a nationwide survey from August to December 2015. Radiographic and neurophysiologic data were subjected to centralized review, and virology studies were conducted for available specimens.

Results

Fifty-nine AFM cases (58 definite, 1 probable) were identified, including 55 children and 4 adults (median age, 4.4 years). The AFM epidemic curve showed strong temporal correlation with EV-D68 detection from pathogen surveillance, but not with other pathogens. EV-D68 was detected in 9 patients: 5 in nasopharyngeal, 2 in stool, 1 in cerebrospinal fluid (adult case), and 1 in tracheal aspiration, nasopharyngeal, and serum samples (a pediatric case with preceding steroid usage). Cases exhibited heterogeneous paralysis patterns from 1- to 4-limb involvement, but all definite cases had longitudinal spinal gray matter lesions on magnetic resonance imaging (median, 20 spinal segments). Cerebrospinal fluid pleocytosis was observed in 50 of 59 cases (85%), and 8 of 29 (28%) were positive for antiganglioside antibodies, as frequently observed in Guillain-Barré syndrome. Fifty-two patients showed variable residual weakness at follow-up. Good prognostic factors included a pretreatment manual muscle strength test unit score >3, normal F-wave persistence, and EV-D68-negative status.

Conclusions

EV-D68 may be one of the causative agents for AFM, while host susceptibility factors such as immune response could contribute to AFM development.

A Mouse Model of Enterovirus D68 Infection for Assessment of the Efficacy of Inactivated Vaccine

In recent years, enterovirus D68 (EVD68) has been reported increasingly to be associated with severe respiratory tract infections and acute flaccid myelitis (AFM) in children all over the world. Yet, no effective vaccines or antiviral drugs are currently available for EVD68. Although several experimental animal models have been developed, immunogenicity and protective efficacy of inactivated EVD68 vaccines has not been fully evaluated. To promote the development of vaccines, we established an Institute of Cancer Research (ICR) suckling mouse model of EVD68 infection in this study. The results showed that ICR neonatal mice up to about nine days of age were susceptible to infection with EVD68 clinical strain US/MO/14-18947 by intraperitoneal injection. The infected mice exhibited progressive limb paralysis prior to death and the mortality of mice was age- and virus dose-dependent. Tissue viral load analysis showed that limb muscle and spinal cord were the major sites of viral replication. Moreover, histopathologic examination revealed the severe necrosis of the limb and juxtaspinal muscles, suggesting that US/MO/14-18947 has a strong tropism toward muscle tissues. Additionally, β-propiolactone-inactivated EVD68 vaccine showed high purity and quality and induced robust EVD68-specific neutralizing antibody responses in adult mice. Importantly, results from both antisera transfer and maternal immunization experiments clearly showed that inactivated EVD68 vaccine was able to protect against lethal viral infection in the mouse model. In short, these results demonstrate the successful establishment of the mouse model of EVD68 infection for evaluating candidate vaccines against EVD68 and also provide important information for the development of inactivated virus-based EVD68 vaccines.

Surgical treatment of enterovirus D68 brainstem encephalitis-induced dysphagia

Cluster of acute flaccid paralysis and cranial nerve dysfunction was associated with a 2014 outbreak of enterovirus D68 (EV-D68) respiratory illness in US. We describe a 33 year-old male patient of refractory dysphagia due to EV-D68-induced brainstem encephalitis successfully treated by surgery. Following acute upper respiratory tract infection, he developed dysphagia and bilateral facial paralysis. A coughing reflex was readily produced when the laryngopharyngeal fiberscope touched the epiglottis, however, water infusion induced only very weak and slow swallowing reflex, suggesting that only motor component was impaired but sensory function was preserved during swallowing. Despite eight months-conservative rehabilitations, Food Intake Level Scale (FILS) remained level 4. Therefore, corrective surgeries including cricopharyngeal myotomy, laryngeal suspension, and pharyngeal flap were performed. Thirty-six days after surgery, FILS rapidly and dramatically improved to level 8. This is the first report describing a successful surgical intervention for EV-D68-induced refractory dysphagia. Surgical treatment was suitable for EV-D68-induced dysphagia, perhaps because sensory function was preserved and only motor disturbance was present during the pharyngeal stage of swallowing.

Acute Transverse Myelitis Caused by Echovirus 11 in a Pediatric Patient: Case Report and Review of the Current Literature

A 12-year-old boy presented with acute flaccid weakness of the right upper extremity and was found to have acute flaccid myelitis with transverse myelitis involving the cervical cord (C1-T1). An interdisciplinary team-based approach was undertaken, including input from a generalist, an infectious diseases physician, and a pediatric neurologist. Consultation was sought from the Minnesota Department of Health to investigate for a potential etiology and source of the responsible infection. Evaluation for an infectious etiology demonstrated infection with human echovirus 11. The patient recovered with some disability. Echovirus 11 is among the more common etiologies of acute flaccid myelitis and should be considered in the differential diagnosis of this increasingly recognized pediatric infection.

Causation of Acute Flaccid Paralysis by Myelitis and Myositis in Enterovirus-D68 Infected Mice Deficient in Interferon αβ/γ Receptor Deficient Mice

Enterovirus D68 (EV-D68) caused a large outbreak in the summer and fall of 2014 in the United States. It causes serious respiratory disease, but causation of associated paralysis is controversial, because the virus is not routinely identified in cerebrospinal fluid. To establish clinical correlates with human disease, we evaluated EV-D68 infection in non-lethal paralysis mouse models. Ten-day-old mice lacking interferon responses were injected intraperitoneally with the virus. Paralysis developed in hindlimbs. After six weeks of paralysis, the motor neurons were depleted due to viral infection. Hindlimb muscles were also infected and degenerating. Even at the earliest stage of paralysis, muscles were still infected and were degenerating, in addition to presence of virus in the spinal cord. To model natural respiratory infection, five-day-old mice were infected intranasally with EV-D68. Two of the four infected mice developed forelimb paralysis. The affected limbs had muscle disease, but no spinal cord infection was detected. The unique contributions of this study are that EV-D68 causes paralysis in mice, and that causation by muscle disease, with or without spinal cord disease, may help to resolve the controversy that the virus can cause paralysis, even if it cannot be identified in cerebrospinal fluid.

Evaluating Treatment Efficacy in a Mouse Model of Enterovirus D68-Associated Paralytic Myelitis

Background

Enterovirus D68 (EV-D68)-associated acute flaccid myelitis (AFM) is a devastating neurological disease for which there are no treatments of proven efficacy. The unpredictable temporal and geographic distribution of cases and the rarity of the disease make it unlikely that data from randomized controlled trials will be available to guide therapeutic decisions. We evaluated the following 3 widely used empirical therapies for the ability to reduce the severity of paralysis in a mouse model of EV-D68 infection: (1) human intravenous immunoglobulin (hIVIG), (2) fluoxetine, and (3) dexamethasone.

Methods

Neonatal mice were injected intramuscularly with a human 2014 EV-D68 isolate that reliably induces paralysis in mice due to infection and loss of spinal cord motor neurons. Mice receiving treatments were evaluated for motor impairment, mortality, and spinal cord viral load.

Results

hIVIG, which contained neutralizing antibodies to EV-D68, reduced paralysis in infected mice and decreased spinal cord viral loads. Fluoxetine had no effect on motor impairment or viral loads. Dexamethasone treatment worsened motor impairment, increased mortality, and increased viral loads.

Conclusion

Results in this model of EV-D68-associated AFM provide a rational basis for selecting empirical therapy in humans and establish this model as a useful system for evaluating other potential therapies.

Acute Flaccid Myelitis: Etiologic Challenges, Diagnostic and Management Considerations

PURPOSE OF REVIEW

Purpose of review Acute flaccid myelitis is a polio-like illness defined by the acute onset of flaccid paralysis in the setting spinal MRI demonstrating a longitudinal lesion in the gray matter of the cord. This paper aims to review the current state of knowledge and key clinical points for the diagnosis and management of acute flaccid myelitis.

RECENT FINDINGS

Recent findings There were clusters of AFM noted in California and Colorado in 2014, with additional cases across the USA that year, and another spike in cases in 2016. Patients have been managed with classic treatments for transverse myelitis, but in general without benefit, although some colleagues have noted anecdotal improvement in individual patients. Our current practice at the Children's Hospital of Philadelphia is to initiate therapy with intravenous immunoglobulin (IVIG) upon recognition of acute flaccid myelitis in hopes of boosting humoral immunity, and to provide an emphasis on rehabilitation services, including physical and occupational therapy. There is some data that suggests a connection to the virus enterovirus D68 (EV D68), but there has been no definitive link. Publications regarding longer-term outcomes in these patients are early in development and, thus far, only provide data for 6 to 12 months from onset. Summary AFM is a serious illness with long-term consequences, and we have much to learn. Key areas in need of further investigation involve etiology, host susceptibilities, treatment options, and long-term outcome. Individual clinicians can assist in these efforts by the prompt reporting of cases of AFM to the US Centers for Disease Control and Prevention.

Seroepidemiological and phylogenetic characterization of neurotropic enteroviruses in Ireland, 2005-2014

Enteroviruses (EVs) are associated with a broad spectrum of clinical presentation, including aseptic meningitis (AM), encephalitis, hand, foot and mouth disease, acute flaccid paralysis, and acute flaccid myelitis. Epidemics occur sporadically and are associated with increased cases of AM in children. The present study describes the seroepidemiological analysis of circulating EVs in Ireland from 2005 to 2014 and phylogenetic characterization of echovirus 30 (E-30), enterovirus A71 (EV-A71), and enterovirus D68 (EV-D68). EV VP1 genotyping was applied to viral isolates and clinical samples, including cerebrospinal fluid (CSF), and those isolates that remained untypeable by neutralising anti-sera. An increase in AM cases from 2010 to 2014 was associated with an E-30 genogroup variant VII and sequences clustered phylogenetically with those detected in AM outbreaks in France and Italy. EV-D68 viral RNA was not detected in CSF samples and no neurological involvement was reported. Three EV-A71 positive CSF samples were identified in patients presenting with AM. A phylogenetic analysis of respiratory-associated EV-D68 and EV-A71 cases in circulation was performed to determine baseline epidemiological data. EV-D68 segregated with clades B and B(1) and EV-A71 clustered as subgenogroup C2. The EV VP1 genotyping method was more sensitive than neutralising anti-sera methods by virus culture and importantly demonstrated concordance between EV genotypes in faecal and CSF samples which should facilitate EV screening by less invasive sampling approaches in AM presentations.

Inherited Paediatric Motor Neuron Disorders: Beyond Spinal Muscular Atrophy

Paediatric motor neuron diseases encompass a group of neurodegenerative diseases characterised by the onset of muscle weakness and atrophy before the age of 18 years, attributable to motor neuron loss across various neuronal networks in the brain and spinal cord. While the genetic underpinnings are diverse, advances in next generation sequencing have transformed diagnostic paradigms. This has reinforced the clinical phenotyping and molecular genetic expertise required to navigate the complexities of such diagnoses. In turn, improved genetic technology and subsequent gene identification have enabled further insights into the mechanisms of motor neuron degeneration and how these diseases form part of a neurodegenerative disorder spectrum. Common pathophysiologies include abnormalities in axonal architecture and function, RNA processing, and protein quality control. This review incorporates an overview of the clinical manifestations, genetics, and pathophysiology of inherited paediatric motor neuron disorders beyond classic SMN1-related spinal muscular atrophy and describes recent advances in next generation sequencing and its clinical application. Specific disease-modifying treatment is becoming a clinical reality in some disorders of the motor neuron highlighting the importance of a timely and specific diagnosis.

First Report of a Fatal Case Associated with EV-D68 Infection in Hong Kong and Emergence of an Interclade Recombinant in China Revealed by Genome Analysis

A fatal case associated with enterovirus D68 (EV-D68) infection affecting a 10-year-old boy was reported in Hong Kong in 2014. To examine if a new strain has emerged in Hong Kong, we sequenced the partial genome of the EV-D68 strain identified from the fatal case and the complete VP1, and partial 5′UTR and 2C sequences of nine additional EV-D68 strains isolated from patients in Hong Kong. Sequence analysis indicated that a cluster of strains including the previously recognized A2 strains should belong to a separate clade, clade D, which is further divided into subclades D1 and D2. Among the 10 EV-D68 strains, 7 (including the fatal case) belonged to the previously described, newly emerged subclade B3, 2 belonged to subclade B1, and 1 belonged to subclade D1. Three EV-D68 strains, each from subclades B1, B3, and D1, were selected for complete genome sequencing and recombination analysis. While no evidence of recombination was noted among local strains, interclade recombination was identified in subclade D2 strains detected in mainland China in 2008 with VP2 acquired from clade A. This study supports the reclassification of subclade A2 into clade D1, and demonstrates interclade recombination between clades A and D2 in EV-D68 strains from China.

A mouse model of paralytic myelitis caused by enterovirus D68

In 2014, the United States experienced an epidemic of acute flaccid myelitis (AFM) cases in children coincident with a nationwide outbreak of enterovirus D68 (EV-D68) respiratory disease. Up to half of the 2014 AFM patients had EV-D68 RNA detected by RT-PCR in their respiratory secretions, although EV-D68 was only detected in cerebrospinal fluid (CSF) from one 2014 AFM patient. Given previously described molecular and epidemiologic associations between EV-D68 and AFM, we sought to develop an animal model by screening seven EV-D68 strains for the ability to induce neurological disease in neonatal mice. We found that four EV-D68 strains from the 2014 outbreak (out of five tested) produced a paralytic disease in mice resembling human AFM. The remaining 2014 strain, as well as 1962 prototype EV-D68 strains Fermon and Rhyne, did not produce, or rarely produced, paralysis in mice. In-depth examination of the paralysis caused by a representative 2014 strain, MO/14-18947, revealed infectious virus, virion particles, and viral genome in the spinal cords of paralyzed mice. Paralysis was elicited in mice following intramuscular, intracerebral, intraperitoneal, and intranasal infection, in descending frequency, and was associated with infection and loss of motor neurons in the anterior horns of spinal cord segments corresponding to paralyzed limbs. Virus isolated from spinal cords of infected mice transmitted disease when injected into naïve mice, fulfilling Koch’s postulates in this model. Finally, we found that EV-D68 immune sera, but not normal mouse sera, protected mice from development of paralysis and death when administered prior to viral challenge. These studies establish an experimental model to study EV-D68-induced myelitis and to better understand disease pathogenesis and develop potential therapies.

Reports of polio-like paralysis, referred to as acute flaccid myelitis (AFM), have recently emerged in association with infections caused by enterovirus D68 (EV-D68). In the second half of 2014, 120 cases of AFM, mostly in young children, were reported during a nationwide outbreak of EV-D68 respiratory disease. The number of AFM cases has risen again in 2016. Although epidemiological evidence between EV-D68 infection and AFM is accumulating, a causal link has not been definitely established. Here we demonstrate that strains of EV-D68 recovered during the 2014 epidemic can cause a paralytic illness in mice that resembles human AFM. Evidence that EV-D68 causes paralysis in this mouse model include: (1) loss of spinal cord motor neurons innervating paralyzed limbs, (2) detection of virus in the spinal cord and, specifically, motor neurons, (3) transmission of neurological disease when injecting virus isolated from spinal cords of paralyzed mice into naïve mice, thus fulfilling Koch’s postulates, and (4) the ability to prevent AFM by pre-administering serum containing EV-D68 antibodies from previously infected mice. This experimental mouse model can be used to better understand the pathogenesis of EV-D68-induced CNS disease and to facilitate the development of potential therapies.

Upsurge of Enterovirus D68, the Netherlands, 2016

In June and July 2016, we identified 8 adults and 17 children with respiratory enterovirus D68 infections. Thirteen children required intensive care unit admission because of respiratory insufficiency, and 1 had concomitant acute flaccid myelitis. Phylogenetic analysis showed that all of 20 sequences obtained belong to the recently described clade B3.