Acute Flaccid Myelitis in the United States: 2015-2017

Acute Flaccid Myelitis With Human Rhinovirus A19 Detection: Case Report and Literature Review

Human rhinovirus (HRV) has been sporadically detected in patients with acute flaccid myelitis (AFM). We report a case of AFM in a 2-year-old boy with severe neurologic sequelae, whose nasopharyngeal and stool samples tested positive for HRV-A19. Clinical information related to AFM with HRV is limited. Further study of the association of AFM with HRV is warranted.

Neuromuscular problems of the critically Ill neonate and child

Acute neuromuscular disorders occasionally occur in the Pediatric Neurologic Intensive Care Unit. Many of these are primary disorders of the motor unit that may present acutely or exacerbate during an intercurrent illness. Additionally, acute neuromuscular disorders may develop during an acute systemic illness requiring intensive care management that predispose the child to another set of acute motor unit disorders. This chapter discusses acute neuromuscular crises in the infant, toddler, and adolescent, as well as neuromuscular disorders resulting from critical illness.

Enterovirus-D68 - A Reemerging Non-Polio Enterovirus that Causes Severe Respiratory and Neurological Disease in Children

The past decade has seen the global reemergence and rapid spread of enterovirus D68 (EV-D68), a respiratory pathogen that causes severe respiratory illness and paralysis in children. EV-D68 was first isolated in 1962 from children with pneumonia. Sporadic cases and small outbreaks have been reported since then with a major respiratory disease outbreak in 2014 associated with an increased number of children diagnosed with polio-like paralysis. From 2014-2018, major outbreaks have been reported every other year in a biennial pattern with > 90% of the cases occurring in children under the age of 16. With the outbreak of SARS-CoV-2 and the subsequent COVID-19 pandemic, there was a significant decrease in the prevalence EV-D68 cases along with other respiratory diseases. However, since the relaxation of pandemic social distancing protocols and masking mandates the number of EV-D68 cases have begun to rise again - culminating in another outbreak in 2022. Here we review the virology, pathogenesis, and the immune response to EV-D68, and discuss the epidemiology of EV-D68 infections and the divergence of contemporary strains from historical strains. Finally, we highlight some of the key challenges in the field that remain to be addressed.

Duration of Enterovirus D68 RNA Shedding in the Upper Respiratory Tract and Transmission among Household Contacts, Colorado, USA

Enterovirus D68 (EV-D68) causes cyclical outbreaks of respiratory disease and acute flaccid myelitis. EV-D68 is primarily transmitted through the respiratory route, but the duration of shedding in the respiratory tract is unknown. We prospectively enrolled 9 hospitalized children with EV-D68 respiratory infection and 16 household contacts to determine EV-D68 RNA shedding dynamics in the upper respiratory tract through serial midturbinate specimen collections and daily symptom diaries. Five (31.3%) household contacts, including 3 adults, were EV-D68-positive. The median duration of EV-D68 RNA shedding in the upper respiratory tract was 12 (range 7-15) days from symptom onset. The most common symptoms were nasal congestion (100%), cough (92.9%), difficulty breathing (78.6%), and wheezing (57.1%). The median illness duration was 20 (range 11-24) days. Understanding the duration of RNA shedding can inform the expected rate and timing of EV-D68 detection in associated acute flaccid myelitis cases and help guide public health measures.

Emerging trends and insights in acute flaccid myelitis: a comprehensive review of neurologic manifestations

Acute Flaccid Myelitis (AFM) is a neurological condition in the anterior portion of the spinal cord and can be characterised as paraplegia (paralysis of the lower limbs), and cranial nerve dysfunction. These lesions are caused by the infection due to Enterovirus 68 (EV-D68); a member of the Enterovirus (EV) family belongs to the Enterovirus species within the Picornavirus family and a Polio-like virus. In many cases, the facial, axial, bulbar, respiratory, and extraocular muscles were affected, hence reducing the overall quality of the patient's life. Moreover, severe pathological conditions demand hospitalisation and can cause mortality in a few cases. The data from previous case studies and literature suggest that the prevalence is high in paediatric patients, but careful clinical assessment and management can decrease the risk of mortality and paraplegia. Moreover, the clinical and laboratory diagnosis can be performed by Magnetic resonance imaging (MRI) of the spinal cord followed by Reverse transcription polymerase chain reaction (rRT-PCR) and VP1 seminested PCR assay of the cerebrospinal fluid (CSF), stool, and serum samples can reveal the disease condition to an extent. The primary measure to control the outbreak is social distancing as advised by public health administrations, but more effective ways are yet to discover. Nonetheless, vaccines in the form of the whole virus, live attenuated, sub-viral particles, and DNA vaccines can be an excellent choice to treat these conditions. The review discusses a variety of topics, such as epidemiology, pathophysiology, diagnosis/clinical features, hospitalisation/mortality, management/treatment, and potential future developments.

Challenges in the Clinical Recognition of Acute Flaccid Myelitis and its Implications

OBJECTIVES

To explore the challenges in diagnosing acute flaccid myelitis (AFM) and evaluate clinical features and treatment paradigms associated with under recognition.

STUDY DESIGN

This was a retrospective multicenter study of pediatric patients (≤18 years) who were diagnosed with AFM from 2014 to 2018 using the Centers for Disease Control and Prevention's case definition.

RESULTS

In 72% of the cases (126 of 175), AFM was not considered in the initial differential diagnosis (n = 108; 61.7%) and/or the patient was not referred for acute care (n = 90; 51.4%) at the initial clinical encounter, and this did not improve over time. Although many features of the presentation were similar in those initially diagnosed with AFM and those who were not; preceding illness, constipation, and reflexes differed significantly between the 2 groups. Patients with a non-AFM initial diagnosis more often required ventilatory support (26.2% vs 12.2%; OR, 0.4; 95% CI, 0.2-1.0; P = .05). These patients received immunomodulatory treatment later (3 days vs 2 days after neurologic symptom onset; 95% CI, -2 to 0; P = .05), particularly intravenous immunoglobulin (5 days vs 2 days; 95% CI, -4 to -2; P < .001).

CONCLUSIONS

Delayed recognition of AFM is concerning because of the risk for respiratory decompensation and need for intensive care monitoring. A non-AFM initial diagnosis was associated with delayed treatment that could have a clinical impact, particularly as new treatment options emerge.

Acute Flaccid Myelitis: Review of Clinical Features, Diagnosis, and Management with Nerve Transfers

BACKGROUND

Acute flaccid myelitis (AFM) is a devastating neurologic condition in children, manifesting as acute limb weakness and/or paralysis. Despite increased awareness of AFM following initiation of U.S. surveillance in 2014, no treatment consensus exists. The purpose of this systematic review was to summarize the most current knowledge regarding AFM epidemiology, cause, clinical features, diagnosis, and supportive and operative management, including nerve transfer.

METHODS

The authors systematically reviewed the literature based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using multiple databases to search the keywords ("acute flaccid myelitis"), ('acute flaccid myelitis'/exp OR 'acute flaccid myelitis'), and (Acute AND flaccid AND myelitis). Included articles reported on (1) AFM diagnosis and (2) patient-specific data regarding epidemiology, cause, clinical features, diagnostic features, or management of AFM.

RESULTS

Ninety-nine articles were included in this review. The precise cause and pathophysiologic mechanism of AFM remain undetermined, but AFM is strongly associated with nonpolio enterovirus infections. Clinical presentation typically comprises preceding viral prodrome, pleocytosis, spinal cord lesions on T2-weighted magnetic resonance imaging, and acute onset of flaccid weakness/paralysis with hyporeflexia in at least one extremity. Supportive care includes medical therapy and rehabilitation. Early studies of nerve transfer for AFM have shown favorable outcomes for patients with persistent weakness.

CONCLUSIONS

Supportive care and physical therapy are the foundation of a multidisciplinary approach to managing AFM. For patients with persistent limb weakness, nerve transfer has shown promise for improving function in distal muscle groups. Surgeons must consider potential spontaneous recovery, patient selection, donor nerve availability, recipient nerve appropriateness, and procedure timing.

Six- and 12-month functional outcomes among patients with confirmed acute flaccid myelitis (AFM) with onset in 2018, United States

PURPOSE

Acute flaccid myelitis (AFM), an uncommon but serious neurologic condition, primarily affects children, and can progress quickly to paralysis and respiratory failure. Data on long-term outcomes of patients with AFM are limited. This study reports on functional status through 12 months for AFM patients who became ill in 2018 in the United States.

METHODS

Health departments collected information on outcomes at 6 and 12 months after onset of AFM using a standardized form that asked patients or their parents/guardians about functional status. Analyses were restricted to confirmed cases.

RESULTS

Of the 238 confirmed AFM cases reported to CDC in 2018, 90 (38%) had assessments at 6 months, 82 (34%) at 12 months, and 49 (21%) at both 6 and 12 months. Among the 49 patients with data at both time points, the proportion of patients reporting significant or severe impairment at 6 months ranged from 2% to 59% depending on the outcome. Although proportions decreased by 12 months and ranged from 2% to 51%, most patients had some impairment at 12 months. No deaths were reported.

CONCLUSION

Six- and 12-month outcomes in patients with onset of AFM in 2018 span a wide range of functionality, particularly of upper and lower extremities. Importantly, improvement appears to occur over time in some patients.

Pseudotyped Viruses for Enterovirus

Using a non-pathogenic pseudotyped virus as a surrogate for a wide-type virus in scientific research complies with the recent requirements for biosafety. Enterovirus (EV) contains many species of viruses, which are a type of nonenveloped virus. The preparation of its corresponding pseudotyped virus often needs customized construction compared to some enveloped viruses. This article describes the procedures and challenges in the construction of pseudotyped virus for enterovirus (pseudotyped enterovirus, EVpv) and also introduces the application of EVpv in basic virological research, serological monitoring, and the detection of neutralizing antibody (NtAb).

Acute flaccid myelitis a review of the literature

Acute flaccid myelitis (AFM) is a rare neurological disorder that first rose to national attention in 2014. This neurological disorder has a biennial presentation with every other even year being a peak year. Most patients present in childhood 5 days after a prodromal infection. Patients usually present with muscle weakness and hypo or areflexia in the summer or fall months. Clinical outcomes are variable however most patients do not improve. Currently there are no definitive prognostic factors or etiologies found. However, it is thought that enterovirus-D68 (EV-D68) could be a potential component in the pathobiology of AFM. Treatment options are limited with variable options and no consensus. Supportive therapy has been shown to be the most effective thus far. With our review of the literature, we highlight the recent growing evidence of a possible relationship between EV-D68 and AFM. Additionally, we identify the knowledge gaps in AFM with treatment and prognostic factors.

Magnetic Resonance Imaging for Spine Emergencies

This article is devoted to the MR imaging evaluation of spine emergencies, defined as spinal pathologic conditions that pose an immediate risk of significant morbidity or mortality to the patient if not diagnosed and treated in a timely manner. MR imaging plays a central role in the timely diagnosis of spine emergencies. A summary of MR imaging indications and MR imaging protocols tailored for a variety of spinal emergencies will be presented followed by a review of key imaging findings for the most-encountered emergent spine pathologic conditions. Pathologic conditions will be broadly grouped into traumatic and atraumatic pathologic conditions. For traumatic injuries, a practical and algorithmic diagnostic approach based on the AO Spine injury classification system will be presented focused on subaxial spine trauma. Atraumatic spinal emergencies will be dichotomized into compressive and noncompressive subtypes. The location of external compressive disease with respect to the thecal sac is fundamental to establishing a differential diagnosis for compressive emergencies, whereas specific patterns of spinal cord involvement on MR imaging will guide the discussion of inflammatory and noninflammatory causes of noncompressive myelopathy.

Does acute flaccid myelitis cause respiratory failure in children?

INTRODUCTION

Acute flaccid myelitis (AFM) is a rare disease that affects spinal cord gray matter, results in acute flaccid weakness of one or more limbs and predominantly involves the cervical spinal cord, which places patients at higher risk for respiratory failure. Our study aims to describe respiratory failure in pediatric AFM patients with emphasis on the need for assisted ventilation and respiratory nerve involvement from an acute and long-term perspective.

MATERIALS AND METHODS

We reviewed the medical records of patients diagnosed with AFM seen in a multidisciplinary clinic for persistent limb weakness between 2016 and 2020.

RESULTS

We studied 54 patients, 35% were female. The median age of patients at illness onset was 5 years (range 7 months-19 years). The median age of patients at the time of study was 8.5 years (range 2-20 years). Eleven patients (20%) required assisted ventilation for acute respiratory failure. Of those that experienced acute respiratory failure, 81% developed chronic respiratory failure. Fifty-six percent of patients with chronic respiratory failure were able to wean off assisted ventilation by 1 year. All patients that experienced unilateral diaphragm impairment with AFM onset experienced acute and chronic respiratory failure.

DISCUSSION

Many patients with AFM may experience respiratory compromise and develop chronic respiratory failure. However, most of these patients can be weaned off ventilatory support by 1 year from illness onset. Most children with unilateral diaphragm impairment can sustain adequate ventilation without the need for long-term ventilatory support.

A Review of the Diagnosis and Management of Acute Flaccid Myelitis in the Emergency Department

ABSTRACT

Since 2014, biennial rises in acute flaccid myelitis (AFM) have brought attention to this rare but debilitating condition. Children with AFM typically present with acute onset, flaccid weakness accompanied by longitudinally extensive gray matter injury demonstrated on magnetic resonance imaging. A clearer understanding of the epidemiology and suspected pathogenesis of AFM may result in increased recognition. The purpose of this review article is to guide emergency physicians in recognizing key clinical features, initiating diagnostic evaluation and providing appropriate interventions for children with suspected AFM.

Global prevalence and case fatality rate of Enterovirus D68 infections, a systematic review and meta-analysis

A substantial amount of epidemiological data has been reported on Enterovirus D68 (EV-D68) infections after the 2014 outbreak. Our goal was to map the case fatality rate (CFR) and prevalence of current and past EV-D68 infections. We conducted a systematic review (PROSPERO, CRD42021229255) with published articles on EV-68 infections in PubMed, Embase, Web of Science and Global Index Medicus up to January 2021. We determined prevalences using a model random effect. Of the 4,329 articles retrieved from the databases, 89 studies that met the inclusion criteria were from 39 different countries with apparently healthy individuals and patients with acute respiratory infections, acute flaccid myelitis and asthma-related diseases. The CFR estimate revealed occasional deaths (7/1353) related to EV-D68 infections in patients with severe acute respiratory infections. Analyses showed that the combined prevalence of current and past EV-D68 infections was 4% (95% CI = 3.1-5.0) and 66.3% (95% CI = 40.0-88.2), respectively. The highest prevalences were in hospital outbreaks, developed countries, children under 5, after 2014, and in patients with acute flaccid myelitis and asthma-related diseases. The present study shows sporadic deaths linked to severe respiratory EV-D68 infections. The study also highlights a low prevalence of current EV-D68 infections as opposed to the existence of EV-D68 antibodies in almost all participants of the included studies. These findings therefore highlight the need to implement and/or strengthen continuous surveillance of EV-D68 infections in hospitals and in the community for the anticipation of the response to future epidemics.

Using the Acute Flaccid Paralysis Surveillance System to Identify Cases of Acute Flaccid Myelitis, Australia, 2000‒2018

Since 2012, the United States has reported a distinct syndrome of acute flaccid paralysis (AFP) with anterior myelitis, predominantly in children. This polio-like syndrome was termed acute flaccid myelitis (AFM). Australia routinely conducts AFP surveillance to exclude poliomyelitis. We reviewed 915 AFP cases in Australia for children <15 years of age during 2000‒2018 and reclassified a subset to AFM by using the US Council of State and Territorial Epidemiologists case definition. We confirmed 37 AFM cases by using magnetic resonance imaging findings and 4 probable AFM cases on the basis of cerebrospinal fluid pleocytosis. Nonpolio enteroviruses were detected in 33% of AFM cases from which stool samples were tested. Average annual AFM incidence was 0.07 cases/100,000 person-years in children <15 years of age. AFM occurred sporadically in Australia before 2010 but regularly since then, indicating sustained, albeit rare, clinical manifestation in children. The AFP surveillance system in Australia is well-positioned to identify future AFM cases.

Description of Bone Health Changes in a Cohort of Children With Acute Flaccid Myelitis (AFM)

OBJECTIVES

To qualitatively describe bone health changes in children with acute flaccid myelitis (AFM) and assess relationships with muscle mass and strength and functional performance.

METHODS

Retrospective analysis of a cohort of 79 children with AFM seen consecutively in one specialized academic center between January 1, 2007, and December 31, 2019.

RESULTS

Of the 79 participants who were aged 4 months to 21 years old, 41 (52%) had bone density measured by dual energy absorptiometry (DXA) and 32 of them (78%) were diagnosed with low bone mass (LBM). We recorded 25 fractures that occurred after onset of neurologic deficit in 14 of the children in the cohort (18%). Lean muscle mass correlated with bone mass and functional performance as assessed by Physical Abilities and Mobility Scale (PAMS) but not with muscle strength as assessed by manual muscle testing (MMT). Bone density in the lower limbs was associated with ambulatory status.

CONCLUSION

Children with AFM have a high likelihood of muscle and bone loss and frequently sustain pathologic fractures. Bone health in children with AFM should be carefully monitored, and efforts should be made to preserve bone mass and maximize muscle mass.

Surgical Innovations to Restore Function in Pediatric Peripheral Nerve Conditions

Peripheral nerve injuries in children can result in devastating lifelong deficits. Because of the time-sensitive nature of muscle viability and the limited speed of nerve regeneration, early recognition and treatment of nerve injuries are essential to restore function. Innovative surgical techniques have been developed to combat the regenerative length and speed; these include nerve transfers. Nerve transfers involve transferring a healthy, expendable donor nerve to an injured nerve to restore movement and sensation. Nerve transfers are frequently used to treat children affected by conditions, including UE trauma, brachial plexus birth injury, and acute flaccid myelitis. Pediatricians play an important role in the outcomes of children with these conditions through early diagnosis and timely referrals. With this review, we aim to provide awareness of state-of-the-art surgical treatment options that significantly improve the function of children with traumatic nerve injuries, brachial plexus birth injury, and acute flaccid myelitis.

Development of Novel PCR Assays for Improved Detection of Enterovirus D68

Enterovirus D68 (EV-D68) causes a range of clinical manifestations, including asthma-like illness, severe respiratory disease, and acute flaccid myelitis. EV-D68 has caused worldwide outbreaks since 2014 and is now recognized as a reemerging infection in many countries. EV-D68-specific PCR assays are widely used for the diagnosis of EV-D68 infection; however, assay sensitivity is a concern because of genetic changes in recently circulated EV-D68. To address this, we summarized EV-D68 sequences from previously reported world outbreaks from 2014 through 2020 on GenBank, and found several mutations at the primer and probe binding sites of the existing EV-D68-specific PCR assays. Subsequently, we designed two novel assays corresponding to the recently reported EV-D68 sequences: an EV-D68-specific real-time and seminested PCR. In an analysis of 22 EV-D68 confirmed cases during a recent EV-D68 outbreak in Japan, the new real-time PCR had higher sensitivity than the existing assay (100% versus 45%, P < 0.01) and a lower median C_T value (27.8 versus 32.8, P = 0.005). Sensitivity was higher for the new nonnested PCR (91%) than for the existing seminested PCR assay (50%, P < 0.01). The specificity of the new real-time PCR was 100% using samples from non-EV-D68-infected cases (n = 135). In conclusion, our novel assays had higher sensitivity than the existing assay and might lead to more accurate diagnosis of recently circulating EV-D68. To prepare for future EV-D68 outbreaks, EV-D68-specific assays must be continuously monitored and updated.

Lower Extremity Nerve Transfers in Acute Flaccid Myelitis Patients: A Case Series

Acute flaccid myelitis (AFM) is characterized by flaccid paralysis following prodromal symptoms. Complete recovery is rare, and patients typically have residual extremity weakness. This study aimed to describe the technique and outcomes of lower extremity nerve transfers for children with AFM.

Unraveling the Mysteries of Acute Flaccid Myelitis: Scientific Opportunities and Priorities for Future Research

Since 2014, cases of acute flaccid myelitis (AFM) have been reported in the United States in increasing numbers biennially, occurring in the late summer and early fall. Although there is unlikely to be a single causative agent of this syndrome, non-polio enteroviruses, including enterovirus D-68 (EV-D68), have had epidemiological and laboratory associations with AFM. Much remains to be known about AFM and AFM-associated enteroviruses, including disease pathogenesis and the best strategies for development of therapeutics or preventive modalities including vaccines. To catalyze research that addresses these scientific and clinical gaps, the National Institute of Allergy and Infectious Diseases convened a workshop entitled "AFM Preparedness: Addressing EV-D68 and Other AFM-Associated Enteroviruses" on 19-20 February 2020.

Acute Myelopathy: Vascular and Infectious Diseases

Vascular and infectious causes are rare but important causes of spinal cord injury. High suspicion for these processes is necessary, as symptoms may progress over hours to days, resulting in delayed presentation and diagnosis and worse outcomes. History and clinical examination findings can assist with localization of the affected vascular territory and spinal level, which will assist with focusing spinal imaging. Open and/or endovascular surgical management depends on the associated vascular abnormality. Infectious myelopathy treatment consists of targeted antimicrobial therapy when possible, infectious source control, and again, close monitoring for systemic complications.

Quantification and Trends of Rotavirus and Enterovirus in Untreated Sewage Using Reverse Transcription Droplet Digital PCR

The quantification and trends in concentrations for naturally occurring rotaviruses (RV) and enteroviruses (EV) in untreated sewage in various wastewater systems have not often been compared. There is now greater interest in monitoring the infections in the community including live vaccine efficacy by evaluating untreated sewage. The goals of this study were to 1) survey the concentrations of naturally occurring RV and EV in untreated sewage using a reverse transcription-droplet digital polymerase chain reaction (RT-ddPCR) and 2) investigate the use of a new adsorption elution (bag-mediated filtration system (BMFS) using ViroCap filters) against more traditional polyethylene glycol (PEG) precipitation for virus concentration. Sewage samples were collected from lagoons in Kenya and Michigan (MI), the United States (USA) and from wastewater treatment plants (WWTPs) in the USA. RVs were detected at geometric mean concentrations in various locations, California (CA) 1.31 × 10⁵ genome copies/L (gc/L), Kenya (KE) 2.71 × 10⁴ gc/L and Virginia (VA) 1.48 × 10⁵ gc/L, and EVs geometric means were 3.72 × 10⁶ gc/L (CA), 1.18 × 10⁴ gc/L (Kenya), and 6.18 × 10³ gc/L (VA). The mean RV concentrations using BMFS-ViroCap in split samples compared to PEG precipitation methods demonstrated that the levels were only 9% (#s BMFS/PEG) in the Michigan lagoons which was significantly different (p < 0.01). This suggests that RV concentrations in Kenya are around 1.69 × 10⁶ gc/L. Overall, there was no difference in concentrations for the other sampling locations across the methods of virus recovery (i.e., PEG precipitation and HA filters) using one-way ANOVA (F = 1.7, p = 0.2739) or Tukey-Kramer pairwise comparisons (p > 0.05). This study provides useful data on RV and EV concentrations in untreated sewage in Kenya and the USA. It also highlights on the usefulness of the RT-ddPCR for absolute quantification of RV and EV in sewage samples. The BMFS using ViroCap filters while less efficient compared to the more traditional PEG precipitation method was able to recover RVs and EVs in untreated sewage and may be useful in poor resource settings while underestimating viruses by 1 to 1.5 logs.

Acute flaccid myelitis: long-term outcomes recorded in the CAPTURE study compared with paediatric transverse myelitis

Background

Since 2014, the USA has documented three outbreaks of acute flaccid myelitis (AFM). Unique features and treatment responses of this myelitis variant have not been prospectively studied. This study prospectively measured outcomes in paediatric myelitis patients relative to treatments.

Methods

This was a prospective, multicentre, non-randomised, observational cohort study. The study duration was 5 years and the length of follow-up was 1 year. This study collected data from children and families in North America. Patients were enrolled at academic centres with expertise in myelitis or online via a web portal. Paediatric patients diagnosed with myelitis were eligible for enrolment in the study within 6 months of onset of symptoms. Patients were characterised as transverse myelitis (TM) or the AFM variant based on clinical and radiographic findings.

Results

The cohort of 90 patients included patients with AFM and TM. Of the 51 patients with AFM there was evidence of two clinically relevant patterns. This included a grey matter restricted form of AFM and a cohort with concomitant white matter that could explain lower extremity motor deficits in patients with lesions restricted to the cervical spine. The improvement in deficits with the use of corticosteroids was similar to what was observed in the TM cohort (p=0.97).

Conclusions

Clinicians should consider on a case by case basis the approach to therapy for AFM patients. Prospective controlled studies of long-term outcomes would be useful in this growing patient population.

Acute flaccid myelitis: cause, diagnosis, and management

Acute flaccid myelitis (AFM) is a disabling, polio-like illness mainly affecting children. Outbreaks of AFM have occurred across multiple global regions since 2012, and the disease appears to be caused by non-polio enterovirus infection, posing a major public health challenge. The clinical presentation of flaccid and often profound muscle weakness (which can invoke respiratory failure and other critical complications) can mimic several other acute neurological illnesses. There is no single sensitive and specific test for AFM, and the diagnosis relies on identification of several important clinical, neuroimaging, and cerebrospinal fluid characteristics. Following the acute phase of AFM, patients typically have substantial residual disability and unique long-term rehabilitation needs. In this Review we describe the epidemiology, clinical features, course, and outcomes of AFM to help to guide diagnosis, management, and rehabilitation. Future research directions include further studies evaluating host and pathogen factors, including investigations into genetic, viral, and immunological features of affected patients, host-virus interactions, and investigations of targeted therapeutic approaches to improve the long-term outcomes in this population.

Characteristics of Patients with Acute Flaccid Myelitis, United States, 2015-2018

Differences between years with and without increased activity suggest differences in viral etiologies.

Observed peaks of acute flaccid myelitis (AFM) cases have occurred biennially since 2014 in the United States. We aimed to determine if AFM etiology differed between peak and nonpeak years, considering that clinical features of AFM differ by virus etiology. We compared clinical and laboratory characteristics of AFM cases that occurred during peak (2016 and 2018, n = 366) and nonpeak (2015 and 2017, n = 50) years. AFM patients in peak years were younger (5.2 years) than those in nonpeak years (8.3 years). A higher percentage of patients in peak years than nonpeak years had pleocytosis (86% vs. 60%), upper extremity involvement (33% vs. 16%), and an illness preceding limb weakness (90% vs. 62%) and were positive for enterovirus or rhinovirus RNA (38% vs. 16%). Enterovirus D68 infection was associated with AFM only in peak years. Our findings suggest AFM etiology differs between peak and nonpeak years.

Acute flaccid myelitis outbreak through 2016-2018: A multicenter experience from Turkey

AIM

We aim to describe the demographic characteristics, etiology, neurophysiology, imaging findings, treatment, prognosis, and prognostic factors of acute flaccid myelitis.

METHODS

The clinical data, laboratory test and, magnetic resonance imaging (MRI) results of pediatric patients diagnosed with acute flaccid myelitis according to the Centers for Disease Control criteria between August 1, 2016, and December 31, 2018, from 13 centers in Turkey were reviewed.

RESULTS

Of the 34 cases identified, 31 were confirmed (91.2%). Eighteen patients (55.9%) were boys. The median patient age was 4 years (interquartile range 2.5-6.9 years). Most of the patients were admitted in 2018 (n = 27). A preceding history of a febrile illness was reported in all patients, with a median of 4 days (interquartile range 3-7 days) before symptom onset. Thirty-one patients had T2 hyperintensity on spinal MRI, and 18 patients had cerebrospinal fluid pleocytosis. The most common infectious agents were entero/rhinoviruses (n = 5) in respiratory specimens. All patients except one received immunotherapy either alone or in combination. Among 27 patients with follow-up data 24 had persistent weakness. Involvement of four limbs together with an abnormal brain MRI at onset were associated with a poor prognosis.

CONCLUSION

The number of patients with acute flaccid myelitis increased since 2012, spiking with every 2-year interval, largely in the pediatric population. The median age decreases with every outbreak. Clinicians should be aware of the clinical picture for early collection of specimens and early start of rehabilitation programs. Further studies are needed to better characterize the etiology, pathogenesis, risk factors, and treatment of this rare condition.

Nerve transfers for acute flaccid myelitis: a case series

BACKGROUND

Acute flaccid myelitis (AFM) syndrome consists of loss of lower motor neurons following a viral infection, with preserved sensory function. It usually affects the upper limbs asymmetrically, with proximal more than distal muscle involvement.

METHODS

Five cases were surgically treated with nerve transfers: spinal accessory to suprascapular nerve transfer (4 patients), branch of radial nerve to axillary nerve transfer (Somsak's procedure) (2 patients), and transfer of a fascicle of the ulnar nerve to the motor branch to the biceps (Oberlin's procedure) (1 patient).

RESULTS

Motor improvement was seen in three cases. Widespread motor involvement was associated with poor outcome.

CONCLUSION

This small series of cases reinforces that nerve transfers are a reliable option for treatment of selected children with AFM.

Enterovirus D68 molecular and cellular biology and pathogenesis

In recent years, enterovirus D68 (EV-D68) has advanced from a rarely detected respiratory virus to a widespread pathogen responsible for increasing rates of severe respiratory illness and acute flaccid myelitis (AFM) in children worldwide. In this review, we discuss the accumulating data on the molecular features of EV-D68 and place these into the context of enterovirus biology in general. We highlight similarities and differences with other enteroviruses and genetic divergence from own historical prototype strains of EV-D68. These include changes in capsid antigens, host cell receptor usage, and viral RNA metabolism collectively leading to increased virulence. Furthermore, we discuss the impact of EV-D68 infection on the biology of its host cells, and how these changes are hypothesized to contribute to motor neuron toxicity in AFM. We highlight areas in need of further research, including the identification of its primary receptor and an understanding of the pathogenic cascade leading to motor neuron injury in AFM. Finally, we discuss the epidemiology of the EV-D68 and potential therapeutic approaches.

Acute Flaccid Myelitis: A Single Pediatric Center Experience From 2014 to 2019

BACKGROUND

Acute flaccid myelitis has emerged as the leading cause of acute flaccid paralysis in children. Acute flaccid myelitis leads to significant physical disability; hence, objective outcome measures to study disease severity and progression are desirable. In addition, nerve transfer to improve motor function in affected children needs further study.

METHODS

Retrospective study of acute flaccid myelitis subjects managed at Children's Healthcare of Atlanta from August 2014 to December 2019. Clinical, electromyography and nerve conduction study, neuropsychological functional independence (WeeFIM), and nerve transfer data were reviewed.

RESULTS

Fifteen children (11 boys and 4 girls) mean age 5.1±3.2 years (range 14 months to 12 years) were included. All subjects (n = 15) presented with severe asymmetric motor weakness and absent tendon reflexes. Motor nerve conduction study of the affected limbs in 93% (n = 14) showed absent or markedly reduced amplitude. Ten patients received comprehensive inpatient rehabilitation and neuropsychological evaluation. Admission and discharge WeeFIM scores showed deficits most consistent and pronounced in the domains of self-care and mobility. Multiple nerve transfer surgery was performed on 13 limbs (9 upper and 4 lower extremities) in 6 children. Postsurgery (mean duration of 10.4 ± 5.7 months) follow-up demonstrated improvement on active movement scale (AMS) in 4 subjects.

CONCLUSION

Acute flaccid myelitis affects school-age children with asymmetric motor weakness, absent tendon reflexes, and reduced or absent motor amplitude on nerve conduction study. Comprehensive rehabilitation and nerve transfer led to improvement in motor function on neuropsychology WeeFIM and AMS scores.

Acute flaccid myelitis in Canada, 2018 to 2019

Starting in 2014, biennial clusters of acute flaccid myelitis (AFM), frequently described as "polio-like" illness, have been reported across the United States and elsewhere, often linked to enteroviruses. To assess AFM trends in Canada, we reviewed the Canadian Acute Flaccid Paralysis Surveillance System (CAFPSS) for cases reported during the 2018 and 2019 calendar years that meet the Centers for Disease Control and Prevention case definitions for AFM. A total of 10 cases (8 in 2018 and 2 in 2019) met the confirmed AFM case definition and 30 (26 in 2018 and 4 in 2019) met the probable AFM case definition. Sixty percent of confirmed and probable cases were younger than five years old, and all cases had symptom onset between the months of July and October. Enteroviruses were detected in 50% of confirmed cases. At the time of writing this report, 2020 AFM data were not yet available; it is unknown if a spike in AFM cases will be seen in 2020.

Cryo-EM structures reveal two distinct conformational states in a picornavirus cell entry intermediate

The virions of enteroviruses such as poliovirus undergo a global conformational change after binding to the cellular receptor, characterized by a 4% expansion, and by the opening of holes at the two and quasi-three-fold symmetry axes of the capsid. The resultant particle is called a 135S particle or A-particle and is thought to be on the pathway to a productive infection. Previously published studies have concluded that the membrane-interactive peptides, namely VP4 and the N-terminus of VP1, are irreversibly externalized in the 135S particle. However, using established protocols to produce the 135S particle, and single particle cryo-electron microscopy methods, we have identified at least two unique states that we call the early and late 135S particle. Surprisingly, only in the "late" 135S particles have detectable levels of the VP1 N-terminus been trapped outside the capsid. Moreover, we observe a distinct density inside the capsid that can be accounted for by VP4 that remains associated with the genome. Taken together our results conclusively demonstrate that the 135S particle is not a unique conformation, but rather a family of conformations that could exist simultaneously.

Update on acute flaccid myelitis: recognition, reporting, aetiology and outcomes

Acute flaccid myelitis, defined by acute flaccid limb weakness in the setting of grey matter lesions of the spinal cord, became increasingly recognised in 2014 following outbreaks in Colorado and California, temporally associated with an outbreak of enterovirus D68 respiratory disease. Since then, there have been biennial increases in late summer/early fall. A viral infectious aetiology, most likely enteroviral, is strongly suspected, but a definitive connection has yet to be established. Patients typically present with asymmetric weakness, maximal proximally, in the setting of a febrile illness. MRI demonstrates T2/FLAIR abnormalities in the central grey matter of the spinal cord, and cerebrospinal fluid typically shows a lymphocytic pleocytosis with variable elevation in protein. The weakness may be progressive over several days and involve respiratory muscles, making early recognition and close monitoring essential. Other complications in the acute period may include autonomic instability and bowel/bladder involvement. There is no clear recommended treatment at this time, although intravenous immunoglobulin, steroids and plasma exchange have been used. Intensive therapies and rehab services have shown benefit in maximising function, and surgical interventions may be considered in cases without optimal response to therapies. Close attention should also be paid to psychosocial factors. Prognosis is generally guarded, and additional factors that predict final outcome, including host factors and treatment effects, have yet to be elucidated. Multicentre collaborative efforts will be required to provide answers about this rare but serious disorder.

Enterovirus D68-Associated Acute Flaccid Myelitis, United States, 2020

Acute flaccid myelitis (AFM) is a serious neurologic condition that causes limb weakness or paralysis in previously healthy children. Since clusters of cases were first reported in 2014, nationwide surveillance has demonstrated sharp increases in AFM cases in the United States every 2 years, most occurring during late summer and early fall. Given this current biennial pattern, another peak AFM season is expected during fall 2020 in the United States. Scientific understanding of the etiology and the factors driving the biennial increases in AFM has advanced rapidly in the past few years, although areas of uncertainty remain. The Centers for Disease Control and Prevention and AFM partners are focused on answering key questions about AFM epidemiology and mechanisms of disease. This article summarizes the current understanding of AFM etiology and outlines priorities for surveillance and research as we prepare for a likely surge in cases in 2020.

Vital Signs: Clinical Characteristics of Patients with Confirmed Acute Flaccid Myelitis, United States, 2018

Background

Acute flaccid myelitis (AFM) is a serious neurologic syndrome that affects mostly children and is characterized by the acute onset of limb weakness or paralysis. Since U.S. surveillance for AFM began in 2014, reported cases have peaked biennially. This report describes the clinical characteristics of AFM patients during 2018, the most recent peak year.

Methods

Medical records from persons meeting AFM clinical criterion (acute onset of flaccid limb weakness) were submitted to CDC. Patients with confirmed AFM met the clinical criterion and had magnetic resonance imaging indicating spinal cord lesions largely restricted to gray matter and spanning one or more vertebral segments. Symptoms, physical findings, test and imaging results, and hospitalization data were abstracted and described.

Results

Among 238 patients with confirmed AFM during 2018, median age was 5.3 years. Among the 238 patients, 205 (86%) had onset during August–November. Most (92%) had prodromal fever, respiratory illness, or both beginning a median of 6 days before weakness onset. In addition to weakness, common symptoms at clinical evaluation were gait difficulty (52%), neck or back pain (47%), fever (35%), and limb pain (34%). Among 211 who were outpatients when weakness began, most (76%) sought medical care within 1 day, and 64% first sought treatment at an emergency department. Overall, 98% of patients were hospitalized, 54% were admitted to an intensive care unit, and 23% required endotracheal intubation and mechanical ventilation.

Conclusion

Clinicians should suspect AFM in children with acute flaccid limb weakness, especially during August–November and when accompanied by neck or back pain and a recent history of febrile respiratory illness. Increasing awareness in frontline settings such as emergency departments should aid rapid recognition and hospitalization for AFM.

Enterovirus infection and acute flaccid myelitis

Recent outbreaks of limb paralysis similar to poliomyelitis, termed acute flaccid myelitis (AFM), have prompted intense investigation into potential etiology. Peaks of AFM were seen in the United States in 2012, 2014, 2016 and 2018, coincident with peaks in enterovirus transmission, particularly EV-D68. Similar peaks of AFM and EV-D68 circulation were reported in other parts of the world. The causal relationship between EV-D68 is still not widely accepted as it is for poliovirus and EV-A71, the latter of which is endemic in the US. Recent in vitro and mouse model data as well as enhanced-sensitivity diagnostic assays have provided further evidence linking the causal relationship between EV-D68 and AFM. In addition, an outbreak of EV-A71-associated AFM was recently described, highlighting the possibility of an additional emerging non-polio enterovirus of public health concern. As AFM is a devastating disease with poor prognosis in many children, particularly those with EV-D68, recent studies call for increased surveillance, pursuit of novel therapeutics and strategies to prevent transmission before the next outbreak.