Notes from the Field: Cluster of Acute Flaccid Myelitis in Five Pediatric Patients - Maricopa County, Arizona, 2016

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.

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.

Characteristics of Upper Extremity Recovery in Acute Flaccid Myelitis: A Case Series

BACKGROUND

Clinical characteristics and timing associated with nonsurgical recovery of upper extremity function in acute flaccid myelitis are unknown.

METHODS

A single-institution retrospective case series was analyzed to describe clinical features of acute flaccid myelitis diagnosed between October of 2013 and December of 2016. Patients were consecutively sampled children with a diagnosis of acute flaccid myelitis who were referred to a hand surgeon. Patient factors and initial severity of paralysis were compared with upper extremity muscle strength outcomes using the Medical Research Council scale every 3 months up to 18 months after onset.

RESULTS

Twenty-two patients with acute flaccid myelitis (aged 2 to 16 years) were studied. Proximal upper extremity musculature was more frequently and severely affected, with 56 percent of patients affected bilaterally. Functional recovery of all muscle groups (≥M3) in an individual limb was observed in 43 percent of upper extremities within 3 months. Additional complete limb recovery to greater than or equal to M3 after 3 months was rarely observed. Extraplexal paralysis, including spinal accessory (72 percent), glossopharyngeal/hypoglossal (28 percent), lower extremity (28 percent), facial (22 percent), and phrenic nerves (17 percent), was correlated with greater severity of upper extremity paralysis and decreased spontaneous recovery. There was no correlation between severity of paralysis or recovery and patient characteristics, including age, sex, comorbidities, prodromal symptoms, or time to paralysis.

CONCLUSIONS

Spontaneous functional limb recovery, if present, occurred early, within 3 months of the onset of paralysis. The authors recommend that patients without signs of early recovery warrant consideration for early surgical intervention and referral to a hand surgeon or other specialist in peripheral nerve injury.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, III.

Epidemiological dynamics of enterovirus D68 in the United States and implications for acute flaccid myelitis

Acute flaccid myelitis (AFM) recently emerged in the United States as a rare but serious neurological condition since 2012. Enterovirus D68 (EV-D68) is thought to be a main causative agent, but limited surveillance of EV-D68 in the United States has hampered the ability to assess their causal relationship. Using surveillance data from the BioFire Syndromic Trends epidemiology network in the United States from January 2014 to September 2019, we characterized the epidemiological dynamics of EV-D68 and found latitudinal gradient in the mean timing of EV-D68 cases, which are likely climate driven. We also demonstrated a strong spatiotemporal association of EV-D68 with AFM. Mathematical modeling suggested that the recent dominant biennial cycles of EV-D68 dynamics may not be stable. Nonetheless, we predicted that a major EV-D68 outbreak, and hence an AFM outbreak, would have still been possible in 2020 under normal epidemiological conditions. Nonpharmaceutical intervention efforts due to the ongoing COVID-19 pandemic are likely to have reduced the sizes of EV-D68 and AFM outbreaks in 2020, illustrating the broader epidemiological impact of the pandemic.

Epidemiological dynamics of enterovirus D68 in the US: implications for acute flaccid myelitis

The lack of active surveillance for enterovirus D68 (EV-D68) in the US has hampered the ability to assess the relationship with predominantly biennial epidemics of acute flaccid myelitis (AFM), a rare but serious neurological condition. Using novel surveillance data from the BioFire® Syndromic Trends (Trend) epidemiology network, we characterize the epidemiological dynamics of EV-D68 and demonstrate strong spatiotemporal association with AFM. Although the recent dominant biennial cycles of EV-D68 dynamics may not be stable, we show that a major EV-D68 epidemic, and hence an AFM outbreak, would still be possible in 2020 under normal epidemiological conditions. Significant social distancing due to the ongoing COVID-19 pandemic could reduce the size of an EV-D68 epidemic in 2020, illustrating the potential broader epidemiological impact of the pandemic.

Biennial Upsurge and Molecular Epidemiology of Enterovirus D68 Infection in New York, USA, 2014 to 2018

Enterovirus D68 (EV-D68) infection has been associated with outbreaks of severe respiratory illness and increased cases of nonpolio acute flaccid myelitis. The patterns of EV-D68 circulation and molecular epidemiology are not fully understood. In this study, nasopharyngeal (NP) specimens collected from patients in the Lower Hudson Valley, New York, from 2014 to 2018 were examined for rhinovirus/enterovirus (RhV/EV) by the FilmArray respiratory panel. Selected RhV/EV-positive NP specimens were analyzed using two EV-D68-specific real-time RT-PCR assays, Sanger sequencing and metatranscriptomic next-generation sequencing. A total of 2,398 NP specimens were examined. EV-D68 was detected in 348 patients with NP specimens collected in 2014 (n = 94), 2015 (n = 0), 2016 (n = 160), 2017 (n = 5), and 2018 (n = 89), demonstrating a biennial upsurge of EV-D68 infection in the study area. Ninety-one complete or nearly complete EV-D68 genome sequences were obtained. Genomic analysis of these EV-D68 strains revealed dynamics and evolution of circulating EV-D68 strains since 2014. The dominant EV-D68 strains causing the 2014 outbreak belonged to subclade B1, with a few belonging to subclade B2. New EV-D68 subclade B3 strains emerged in 2016 and continued in circulation in 2018. Clade D strains that are rarely detected in the United States also arose and spread in 2018. The establishment of distinct viral strains and their variable circulation patterns provide essential information for future surveillance, diagnosis, vaccine development, and prediction of EV-D68-associated disease prevalence and potential outbreaks.

A ten-year retrospective evaluation of acute flaccid myelitis at 5 pediatric centers in the United States, 2005-2014

Background

Acute flaccid myelitis (AFM) is a severe illness similar to paralytic poliomyelitis. It is unclear how frequently AFM occurred in U.S. children after poliovirus elimination. In 2014, an AFM cluster was identified in Colorado, prompting passive US surveillance that yielded 120 AFM cases of unconfirmed etiology. Subsequently, increased reports were received in 2016 and 2018. To help inform investigations on causality of the recent AFM outbreaks, our objective was to determine how frequently AFM had occurred before 2014, and if 2014 cases had different characteristics.

Methods

We conducted a retrospective study covering 2005–2014 at 5 pediatric centers in 3 U.S. regions. Possible AFM cases aged ≤18 years were identified by searching discharge ICD-9 codes and spinal cord MRI reports (>37,000). Neuroradiologists assessed MR images, and medical charts were reviewed; possible cases were classified as AFM, not AFM, or indeterminate.

Results

At 5 sites combined, 26 AFM cases were identified from 2005–2013 (average annual number, 3 [2.4 cases/100,000 pediatric hospitalizations]) and 18 from 2014 (12.6 cases/100,000 hospitalizations; Poisson exact p<0.0001). A cluster of 13 cases was identified in September–October 2014 (temporal scan p = 0.0001). No other temporal or seasonal trend was observed. Compared with cases from January 2005–July 2014 (n = 29), cases from August–December 2014 (n = 15) were younger (p = 0.002), more frequently had a preceding respiratory/febrile illness (p = 0.03), had only upper extremities involved (p = 0.008), and had upper extremity monoplegia (p = 0.03). The cases had higher WBC counts in cerebrospinal fluid (p = 0.013).

Conclusion

Our data support emergence of AFM in 2014 in the United States, and those cases demonstrated distinctive features compared with preceding sporadic cases.

Unmet Needs in the Evaluation, Treatment, and Recovery for 167 Children Affected by Acute Flaccid Myelitis Reported by Parents Through Social Media

BACKGROUND

We aimed to characterize the outcomes of 167 children affected by acute flaccid myelitis by leveraging the power of social media.

METHODS

Members of a closed social media (Facebook) group were invited to participate in an anonymous online survey. Descriptive statistics were applied to quantitative responses, and free-text responses were grouped into themes using a grounded theory approach.

RESULTS

Caregivers provided information about 167 affected children; 77% were at least 6 months since onset. Clinical features matched those of larger published case series (e.g., walking impairment in 76.7%, intravenous immunoglobulin treatment in 80.8%; 28.2% tested positive for Enterovirus D68; 17% children had asthma before acute flaccid myelitis onset). Mean duration of initial hospitalization was 49.1 (S.D., 74.0) days, and of initial inpatient rehabilitation was 42.3 (S.D., 67.6) days. Among challenges, parents frequently reported delays in diagnosis, including lack of neurological examination at initial medical evaluation for weakness. Other challenges included familial and professional impact of protracted hospitalizations, uncertainty about cause or prognosis of acute flaccid myelitis, and the dynamic nature of care needs in growing children. The social media group played a critical role not only for social support but also for dissemination of rehabilitation approaches and of networks of expert clinicians.

CONCLUSIONS

Children with acute flaccid myelitis have persistent and dynamic deficits, but many continue to show ongoing functional improvements beyond the initial expected window of recovery. In an emerging disease paralyzing young children, social media can strengthen knowledge networks and focus on rehabilitation.

Pan-viral serology implicates enteroviruses in acute flaccid myelitis

Since 2012, the United States has experienced a biennial spike in pediatric acute flaccid myelitis (AFM).^1–6 Epidemiologic evidence suggests non-polio enteroviruses (EVs) are a potential etiology, yet EV RNA is rarely detected in cerebrospinal fluid (CSF).² We interrogated CSF from children with AFM (n=42) and pediatric other neurologic disease controls (n=58) for intrathecal anti-viral antibodies using a phage display library expressing 481,966 overlapping peptides derived from all known vertebrate and arboviruses (VirScan). We also performed metagenomic next-generation sequencing (mNGS) of AFM CSF RNA (n=20 cases), both unbiased and with targeted enrichment for EVs. Using VirScan, the only viral family significantly enriched by the CSF of AFM cases relative to controls was Picornaviridae, with the most enriched Picornaviridae peptides belonging to the genus Enterovirus (n=29/42 cases versus 4/58 controls). EV VP1 ELISA confirmed this finding (n=22/26 cases versus 7/50 controls). mNGS did not detect additional EV RNA. Despite rare detection of EV RNA, pan-viral serology identified frequently high levels of CSF EV-specific antibodies in AFM compared to controls, providing further evidence for a causal role of non-polio EVs in AFM.

Enterovirus D68 Subclade B3 Circulation in Senegal, 2016: Detection from Influenza-like Illness and Acute Flaccid Paralysis Surveillance

Following the 2014 outbreak, active surveillance of the EV-D68 has been implemented in many countries worldwide. Despite subsequent EV-D68 outbreaks (2014 and 2016) reported in many areas, EV-D68 circulation remains largely unexplored in Africa except in Senegal, where low levels of EV-D68 circulation were first noted during the 2014 outbreak. Here we investigate subsequent epidemiology of EV-D68 in Senegal from June to September 2016 by screening respiratory specimens from ILI and stool from AFP surveillance. EV-D68 was detected in 7.4% (44/596) of patients; 40 with ILI and 4 with AFP. EV-D68 detection was significantly more common in children under 5 years (56.8%, p = 0.016). All EV-D68 strains detected belonged to the newly defined subclade B3. This study provides the first evidence of EV-D68 B3 subclade circulation in Africa from patients with ILI and AFP during a 2016 outbreak in Senegal. Enhanced surveillance of EV-D68 is needed to better understand the epidemiology of EV-D68 in Africa.

Comparative quantitative clinical, neuroimaging, and functional profiles in children with acute flaccid myelitis at acute and convalescent stages of disease

AIM

To quantify characteristics in acute flaccid myelitis (AFM) at acute and convalescent stages.

METHOD

This was a retrospective case series of children with AFM evaluated at a single institution in the USA (2014-2017). Acute inflammatory/ischemic myelopathies were excluded. Neurological assessments and segmental quantitative analysis of signal abnormalities on magnetic resonance imaging (MRI) of the brain and spinal cord were performed.

RESULTS

Sixteen patients (11 males, five females) were evaluated. Median age at onset was 4 years (interquartile range [IQR] 3-6y). All had parainfectious acute-onset limb weakness, lower motor neuron examination, and spinal fluid pleocytosis. On acute spinal cord MRI, longitudinally extensive T2 hyperintensities were identified throughout the spinal cord mostly within grey matter; five out of 12 patients had dorsal brainstem T2 hyperintensities. At a median of 2 months follow-up (IQR 2-3mo), spinal cord MRI improved in seven out of nine patients although focal T2 hyperintensities persisted in cervical and lumbar grey matter. At a median follow-up of 4 months (IQR 2-6mo), Medical Research Council sum score rose from a median of 29 to 32; distal muscle groups improved more than proximal ones; four out of 16 patients were ventilator-dependent; and two out of 16 patients were quadriplegic.

INTERPRETATION

While patients may show marked improvement on neuroimaging from acute to convalescent stages, the majority of children with AFM have limited motor recovery and continued disability. Clinicians should consider the timing of clinical and neuroimaging exams when assessing diagnosis and prognosis.

WHAT THIS PAPER ADDS

During the 2014 to 2017 acute flaccid myelitis outbreak in the USA, clinical recovery was better in distal than proximal muscle groups. Lumbar spinal cord showed more residual abnormalities at convalescence.

Genomic Analyses of Acute Flaccid Myelitis Cases among a Cluster in Arizona Provide Further Evidence of Enterovirus D68 Role

Enteroviruses frequently result in respiratory and gastrointestinal illness; however, multiple subtypes, including poliovirus, can cause severe neurologic disease. Recent biennial increases (i.e., 2014, 2016, and 2018) in cases of non-polio acute flaccid paralysis have led to speculations that other enteroviruses, specifically enterovirus D68 (EV-D68), are emerging to fill the niche that was left from poliovirus eradication. A cluster of 11 suspect cases of pediatric acute flaccid myelitis (AFM) was identified in 2016 in Phoenix, AZ. Multiple genomic analyses identified the presence of EV-D68 in the majority of clinical AFM cases. Beyond limited detection of herpesvirus, no other likely etiologies were found in the cluster. These findings strengthen the likelihood that EV-D68 is a cause of AFM and show that the rapid molecular assays developed for this study are useful for investigations of AFM and EV-D68.

Enteroviruses are a common cause of respiratory and gastrointestinal illness, and multiple subtypes, including poliovirus, can cause neurologic disease. In recent years, enterovirus D68 (EV-D68) has been associated with serious neurologic illnesses, including acute flaccid myelitis (AFM), frequently preceded by respiratory disease. A cluster of 11 suspect cases of pediatric AFM was identified in September 2016 in Phoenix, AZ. To determine if these cases were associated with EV-D68, we performed multiple genomic analyses of nasopharyngeal (NP) swabs and cerebrospinal fluid (CSF) material from the patients, including real-time PCR and amplicon sequencing targeting the EV-D68 VP1 gene and unbiased microbiome and metagenomic sequencing. Four of the 11 patients were classified as confirmed cases of AFM, and an additional case was classified as probable AFM. Real-time PCR and amplicon sequencing detected EV-D68 virus RNA in the three AFM patients from which NP swabs were collected, as well as in a fourth patient diagnosed with acute disseminated encephalomyelitis, a disease that commonly follows bacterial or viral infections, including enterovirus. No other obvious etiological causes for AFM were identified by 16S or RNA and DNA metagenomic sequencing in these cases, strengthening the likelihood that EV-D68 is an etiological factor. Herpes simplex viral DNA was detected in the CSF of the fourth case of AFM and in one additional suspect case from the cluster. Multiple genomic techniques, such as those described here, can be used to diagnose patients with suspected EV-D68 respiratory illness, to aid in AFM diagnosis, and for future EV-D68 surveillance and epidemiology.

Changing how we think about infectious diseases

As we learn more and more about the classes of organisms that infect humans, we are discovering that many organisms, including pathogenic organisms, may have a complex relationship with humans in which infection seldom results in the production disease. In some cases, infection may be just one biological event that occurs during a multievent process that develops sequentially, over time, and involves genetic and environmental factors that may vary among individuals. Consequently, the role of infectious organisms in the development of human disease may not meet all of the criteria normally required to determine when an organism can be called the cause of a disease. This chapter reviews the expanding role of infections in the development of human disease. We discuss prion diseases of humans, a fascinating example of an infectious disease-causing agent that is not a living organism. We also discuss the diseases of unknown etiology for which infectious organisms may play a role. In addition, this chapter reviews some of the misconceptions and recurring errors associated with the classification of infectious diseases that have led to misdiagnoses and have impeded our understanding of the role of organisms in the development of human diseases.

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.

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.