- Email: [email protected]
Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
Official Journal of the European Paediatric Neurology Society
Original article
Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016 Victor Ruggieri a,*, Maria Ivana Paz a, Marı´a Gabriela Peretti a, Carlos Rugilo b, Rosa Bologna c, Cecilia Freire d, Silvana Vergel a, Andrea Savransky a a
Department of Neurology, Hospital de Pediatrı´a Prof. Dr. “J.P. Garrahan”, Buenos Aires, Argentina Department of Neuroradiology, Hospital de Pediatrı´a Prof. Dr. “J.P. Garrahan”, Buenos Aires, Argentina c Department of Infectious Diseases, Hospital de Pediatrı´a Prof. Dr. “J.P. Garrahan”, Buenos Aires, Argentina d n, Buenos Aires, Argentina Department of Neuroviruses Hospital Nacional de Microbiologı´a Dr. Malbra b
article info
abstract
Article history:
Objective: To report a outbreak of 11 cases of acute asymmetric flaccid myelopathy due to
Received 12 January 2017
spinal motor neuron injury.
Received in revised form
Material and methods: Eleven children, six male, with a mean age of 3 years presented with
21 June 2017
acute flaccid myelitis. We analyzed clinical features, etiology, neuroradiological images,
Accepted 13 July 2017
treatment, and outcome. Results: Nine children had bilateral and asymmetric flaccid myelitis of the upper limbs, 1
Keywords:
had upper limb monoplegia, and 1 presented with hemiparesis. The cranial nerves were
Acute flaccid myelitis
involved in 6 patients and 4 required mechanical ventilation. In all cases acute flaccid
Poliomyelitis
myelitis co-occurred with upper airway infection and/or fever. Spinal cord magnetic
Enterovirus-D68
resonance imaging was abnormal in all, showing 2 different patterns: A linear pattern
Acute myelopathy
involving the anterior horns and another that was more heterogeneous showing spinal cord expansion. The lesions were non-enhancing in all. In 5/11 patients involvement of the medulla oblongata and pons was also observed. None of the patients presented with supratentorial lesions. In 4/11 children, the human enterovirus subtype D68 (HEV-D68) was identified in the airway and in 1/11 in the cerebrospinal fluid as well. In the remaining patients different enterovirus species A, B, and C variants were detected, as well as rhinovirus in 1 and influenza in another. Ten children received treatment with intravenous immunoglobulin and steroids and 4 of these children also underwent plasma exchange. Treatment did not lead to clinical improvement. Conclusions: In a patient with acute flaccid myelitis, HEV-D68 infection should be ruled out. Cases in which the virus was not detected were considered as “false negatives” as samples
* Corresponding author. E-mail address: [email protected] (V. Ruggieri). http://dx.doi.org/10.1016/j.ejpn.2017.07.008 1090-3798/© 2017 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
2
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
were collected late in course of the disease. The lack of response to anti-inflammatory and immunomodulatory treatment suggests a direct viral mechanism. This study is to our knowledge the first on an HEV-D68-infection-related cluster in Latin America. © 2017 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
A child with acute flaccid myelopathy is always an emergency. Early diagnosis and treatment initiation may make the difference between the degree of sequelae or possible ad integrum recovery.1,2 Although the etiology can be infectious, immune-mediated, or structural, injury to the spinal cord gray matter caused by direct viral infection is currently considered to be uncommon, due to the almost worldwide control of poliomyelitis. Different enteroviruses, including HEV-A71, HEV-A70, HEV-C105, Coxsackie A7, other Coxsackie A, and echoviruses, may trigger acute flaccid myelitis.3,4 In 2014, an HEV-D68-associated outbreak of acute flaccid myelitis was reported in Colorado (USA). The clinical course and outcome of these cases were similar to that of poliomyelitis leading to international surveillance of these cases. Currently, control and management protocols have been developed by the Centers for Disease Control (CDC).5,6 The aim of this study was to report an outbreak of 11 cases with asymmetric acute flaccid myelitis due to spinal motor neuron involvement analyzing clinical features, laboratory tests, imaging studies, etiology, management, and short-term outcome.
2.
Material and methods
We conducted a retrospective study of eleven children who presented with asymmetric acute flaccid myelitis at a third level national pediatric hospital between April and May 2016. All patients met the clinical definition of acute flaccid myelitis and no age limits were considered in the inclusion criteria. Acute flaccid myelitis cases were defined as patients with acute flaccid weakness and radiological (MRI) or neurophysiological evidence of acute spinal motor neuron injury. Patients syndrome, stroke, transwho met criteria for Guillain-Barre verse myelitis, myasthenia gravis, or botulism were excluded. Cerebrospinal fluid, serum samples, nasopharyngeal swab specimens, and stool specimens were submitted to the na n) for infectious tional reference laboratory (Hospital Malbra agent testing.
3.
Laboratory tests
In this group of patients the following complementary studies were performed: Cerebral Spinal Fluid (CSF) was tested for enteroviruses, arboviruses (Saint Louis, West Nile, Zika, and dengue), herpes virus type 1, 2, and 6, cytomegalovirus, Epstein Barr virus, adenoviruses, varicella zoster, and influenza viruses
using polymerase chain reaction (PCR), additional to cultures for common pathogens and mycobacteria. Detection of oligoclonal band (OCB) was performed using isoelectric focusing. A nasopharyngeal swab (NPS) was performed followed by PCR for the detection of enteroviruses, respiratory syncytial virus, parainfluenza, influenza, and adenoviruses and by indirect immunofluorescence assays for influenza (H1N1 and H3N2), adenoviruses, and Mycoplasma. Stools were tested for enteroviruses (wild-type, Sabin-like, and vaccine-derived polioviruses) and botulinum toxin using PCR. When enterovirus was detected in CSF, nasopharyngeal swab, or stools by reverse transcription (RT)-nested-PCR, genotyping with amplified VP1 RT-snPCR was performed. Serum was investigated for enteroviruses, arboviruses (Zika and dengue), cytomegalovirus, Epstein Barr virus, adenoviruses, varicella zoster, Mycoplasma using serology techniques. Saint Louis, West Nile viruses, herpes virus type 1, 2, and 6 were tested with PCR. Finally, detection of oligoclonal bands (OCB) was performed using isoelectric focusing. When an enterovirus species was detected, viral subtype analysis was performed using sequencing techniques. Needle electromyography (EMG) and nerve conduction studies were performed with an 8-channel Akonic device according to the guidelines of the International Federation of Clinical Neurophysiology.
4.
Results
Eleven children, six of whom were boys, were seen at our institution with symptoms of acute flaccid myelitis in April and May 2016. The children had a mean age of 3 years and 2 months, ranging from 3 months to 6 years. All the children came from different neighborhoods of Buenos Aires. All patients had been vaccinated against polio and no travel was documented in any of them. The ethnic background of all patients was Spanish and Italian living for several generations in Argentina. None had shared contacts.
5.
Clinical features (Table 1)
All children were previously healthy without a significant family history. The onset of the neurological signs and symptoms coincided with an upper respiratory infection and/ or fever. None of the patients presented with sensory findings, bowel and bladder dysfunction, or encephalopathy.
Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
Table 1 e Clinical features, ancillary studies and treatment. Total cases (N ¼ 11) Prodromal symptoms Previous or concomitant disease Fever >38 C Neurological manifestations Proximal weakness Asymmetric involvement of the upper limbs Lower limb monoplegia Hemiparesis Hypo- or areflexia Associated symptoms Neck weakness Neck pain Pain in the limbs Cranial nerve involvement Peripheral VII cranial nerve Lower cranial nerves Peripheral VII and lower cranial nerves Diaphragmatic paralysis Need for mechanical ventilation Invasive Non-Invasive Diagnostic studies Cerebrospinal fluid Pleocytosis (>5 cells) Hyperproteinemia (>45 mg/dl) Brain magnetic resonance imaging Supratentorial lesions Brain stem lesions Spinal cord magnetic resonance imaging Diffuse lesions with gray and white matter involvement with cervical predominance Expansion Gray matter involvement without contrast enhancement Treatment during hospital stay Intravenous methylprednisolone Intravenous immunoglobulin Plasma exchange None
11 11 11 9 1 1 11 7 3 4 6 3 5 2 5 4 2 2
7 2
7 5 4
10 10 4 1
Table 2 e Viruses identified. Cases 1 2 3 4 5 6 7 8 9 10 11
Neurological manifestations at disease onset were asymmetrical weakness in the upper limbs (9/11), monoplegia in an upper limb (1/11), and hemiparesis (1/11). All patients presented with predominantly proximal weakness and hypoor areflexia. The associated symptoms were neck weakness (7/11), and pain in the neck (3/11) and in the limbs (4/11). Lower cranial nerve dysfunction was observed in five patients, associated with bilateral involvement of the peripheral VII nerve in two and unilateral involvement of the VII cranial nerve in one. In all these five children involvement of the lower cranial nerves was associated with diaphragmatic paralysis. Four patients needed admission to the intensive care unit in the first 24e48 h after disease onset; two required mechanical ventilation and two non-invasive ventilation. Six months after onset, all patients continue suffering from severe symptoms, with persistent limb paralysis, predominantly in the upper limbs. One of them has quadriparesis and remains on mechanical ventilation. In some patients a slight improvement was observed: 1/2 was weaned from mechanical ventilation, in 4/5 cranial nerve palsy resolved, in 6/7 neck weakness resolved, and neck and limb pain resolved in all.
6.
0 5
NPS
CSF
SS
Serum
HEV-B HEV-D68 HEV-D68 N/P Influenza () HRV-C N/P HEV-D68 HEV-D68 ()
() () () () () () () () () HEV-D68 ()
HEV-B N/P () HEV-A () HEV-C () HEV-C HEV-C HEV-B N/P
() () () () () () () () () () ()
HEV: Human Enterovirus, HRV: human rhinovirus, NPS: nasopharyngeal swab, CSF: cerebrospinal fluid, SS: stool samples, (): Negative, N/P: no performed.
3
Results of ancillary studies
CSF: In all patients lumbar puncture was performed. Seven patients presented with pleocytosis (white blood cell count > 5/mL) with predominance of lymphocytes and elevated protein levels in two. Screening for OCB (performed in five patients) was negative. Common-pathogen and mycobacterial cultures were negative in all patients. HEV-D68 was detected in only one patient; PCR for viruses in CSF was negative in the remaining patients. Nasopharyngeal swab: Nasopharyngeal samples were collected in nine patients, within the first five days of disease onset in four of them. Five were positive for enteroviruses of which four were enterovirus HEV-D68. In the latter four patients the sample was collected within the first five days after symptom onset. Of the remaining patients one was positive for influenza and another for rhinovirus. Results were negative in two samples. Stools: Stool samples, collected in nine children, were positive for enterovirus type A, B, and C in six. Serum: No pathogens were isolated from serum samples, collected in five cases, and screening for oligoclonal bands was also negative. The results of the laboratory tests are shown in Table 2 (appendix). MRI: All patients underwent complete brain and spinal cord MRI with and without gadolinium contrast within 72 h after symptom onset. Brain MRIs were normal at the supratentorial level. Lesions in the pons were observed in five patients, associated with involvement of the medulla oblongata in four. The lesions were hyperintense in T2-weighted and FLAIR images, predominantly dorsal, without contrast enhancement or mass effect (Fig. 1). All patients had lesions in the spinal cord. In seven the lesions were hyperintense in T2-weighted and FLAIR images, predominantly central, diffuse in the gray and white matter
Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
4
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
Fig. 1 e Brain MRI. Axial images in T2-weighted (a) and FLAIR (b) sequences. Brain MRI sagittal images in T2-weighted (c) sequences. A hyperintense signal is observed in the dorsal pons and medulla oblongata. Spinal cord MRI T2-weighted (c) Lesion that involve gray and white matter, with longitudinal extension from C2 to C8 (pattern II).
Fig. 2 e Spinal cord MRI. Sagittal and axial T2-weighted (a and b) images show mild expansion of the spinal cord and central spinal cord lesion that involve gray and white matter, with longitudinal extension from C2 to C8 (pattern II).
Fig. 3 e Spinal cord MRI. Axial and sagittal T2-weighted (aeb). Axial images reveal asymmetrical involvement of the anterior horns (“owl's eye sign”). A linear hyperintense signal is observed the anterior gray matter from C3 to C7 (pattern I). Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
extending three or more vertebral segments in length, without contrast enhancement, predominantly affecting the cervical cord. In five of these children expansion of the spinal cord was observed (Fig. 2). The remaining four patients had nonenhancing hyperintense images in T2 and STIR in the gray matter of the anterior spinal cord (Fig. 3). A second spinal cord MRI was performed at a mean of 20 days in four patients; In three of them the pattern had changed. The spinal cord expansion had resolved and the diffuse central involvement had changed to a longitudinal image in the anterior gray matter. No changes were observed in the remaining patient. Electrophysiological testing was performed in the first week after symptom onset. EMG: was performed in seven patients. The studies showed sensory and motor nerve conduction within normal limits. The EMG tracing performed with needle electrodes showed electrical silence at rest. At maximum levels of voluntary effort, a poor intermediate tracing with increasedamplitude motor unit potentials was observed, some of which were fragmented and others polyphasic. Treatment: As the acute myelopathy was considered to be inflammatory or immune-mediated at onset, 10/11 children were treated with pulse steroids (methylprednisolone) at 30 mg/kg/day to a maximum of 1 g/day combined with IVIG 2 g/kg and plasma exchange in 4/11 cases, with a range of 2e8 exchanges each; a watchful waiting policy was adopted in only one.
7.
Discussion
Myelopathies associated with spinal motor neuron injury have become rare due to the almost worldwide eradication of poliomyelitis. In the analysis of our patients, a clear clinically homogenous pattern characterized by asymmetrical flaccid myelitis preceded by or concomitant with upper airway infection and fever was recognized. Pain occurring in the neck or limbs was a common finding (7/11) coinciding with findings by other authors.3 The upper limbs were most commonly involved. In all cases symptom progression was within 24e48 h, mainly affecting proximal muscles with hypo- or areflexia. In two patients disease progression was severe, leading to respiratory difficulties requiring mechanical ventilation. Clinically, our patients were diagnosed with acute myelopathy with predominant motor involvement. No sensory symptoms were observed in any of the patients. Therefore, myelopathy associated with spinal motor neuron injury of infectious (poliomyelitis or non-polio enterovirus) or vascular etiology was suspected.4,7 Following the diagnostic protocol for patients with findings suspicious for acute myelopathy, a full brain and spinal cord MRI with and without contrast was requested and once a structural cause was ruled out, a lumbar puncture was performed for the detection of infectious agents.2,8 In seven children an EMG with conduction velocity was performed when flaccid myelitis was diagnosed. In all cases, the results showed preservation of motor and sensory peripheral nerve
5
trunks associated with a clearly neuropathogenic EMG tracing consistent with spinal cord injury. Unlike findings in previous studies, in all the patients in our series the supratentorial MRI was normal. Lesions were found at brain stem in five.3 The imaging findings in the spinal cord revealed two different patterns: Pattern I: Showing lesions exclusively in the anterior spinal cord gray matter. This is the typical image described in patients with an enterovirus infection.1 However, only four patients (36%) presented with this pattern at symptom onset. The gray matter lesions were asymmetrical in the majority of the cases, with increased involvement of the clinically more affected side. Pattern II: Showing central spinal cord lesions with diffuse involvement of the gray and white matter extending longitudinally (seven patients). Even though the patients had diffuse myelitis along the entire spinal cord, cervical cord manifestations were predominant. Unlike findings of previous studies, contrast enhancement of the cranial nerves was not observed in any of our patients, not even in those who had compatible clinical manifestations.3,9 In four of our patients a follow up MRI was performed at a mean of 20 days. The images revealed that three had evolved from pattern II to pattern I, resulting in a predominance of the latter pattern in our series. As three patients developed pattern I in the course of the disease, while four presented with that pattern at onset, it may be speculated that, in time, all patients might evolve to that particular radiological pattern. It is important to highlight that on neuroimaging anterior gray matter involvement is not only found in infectious myelopathies. Similar images may be observed in post-infectious or vascular disorders. Nevertheless, the clinical manifestations in our patients were not compatible with these conditions.1,10 Moreover, in the context of a cluster of patients with clinically similar features, a viral infection, including HEVD68, should be considered. Seven of 11 patients presented with pleocytosis in the CSF and OCB screening was negative in five patients studied. In only one patient HEV-D68 was isolated in the CSF. This patient had a worse outcome with severe motor sequelae and need for mechanical ventilation. In previous studies detection of HEVD68 in CSF yielded either negative or very few positive results.3,11 Up to 2005, only two isolated cases with acute myelopathy associated with HEV-D68 detected in CSF were reported and outcome was fatal in both.12 In five patients early nasopharyngeal swabs for the detection of enterovirus were done. Four were positive for D68. Therefore, when enterovirus-D68-associated flaccid myelitis is suspected, nasopharyngeal swab is the method of choice to search for the viral agent. Evaluating the first four patients, once bacterial infections had been ruled out, an immune-mediated disease was considered and they were treated with IVIG, IV steroids, and plasma exchange without response. The lack of response to
Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
6
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
treatment together with the identification of enteroviruses in nasopharyngeal swab specimens or CSF and the absence of OCB led us to reconsider the possibility of an immunemediated mechanism in the spinal cord. Therefore, based on the CDC guidelines on acute flaccid myelitis, we decided to withhold treatment in the last patient.5 Different enteroviruses, including enterovirus D68, have been associated with gray-matter (polio-like) acute myelopathy.11e14 In our series, enterovirus D68 was isolated in four patients. Although enteroviruses A71 and C105 have been associated with flaccid myelitis in other outbreaks, they were not identified in our samples.13,15 Even though the pathophysiology is largely unknown, several authors have postulated a mechanism via hematogenous spread (transient viremia) or through the retrograde axonal transport system, which may explain the low detection rate of enteroviruses in CSF.13 Recently, Hixon et al. reproduced HEV-D68 viral infection in a mouse model hypothesizing that dissemination occurs via the neural pathway. The viral antigen was detected almost exclusively in cells consistent with motor neurons, suggesting that direct viral injury, rather than a post-infectious immunemediated process is the most likely mechanism of neuronal cell loss and subsequent paralysis.16 Although the age of presentation (3.6 years) of our patients is similar to that reported by other authors, cases with flaccid paralysis associated with enterovirus D68 have been described in different age groups.12,17 Finally, based on the homogenous clinical and neuroradiological findings, we may consider the cases in which HEVD68 was not identified to be probable false negatives as the samples were collected more than 10 days after symptom onset in agreement with recent reports by other authors who observed an association between delay in sampling and reduced pathogen isolation (including HEV-D68).6 Considering these findings, pediatric neurologists should be aware that in patients with flaccid myelopathy associated with these neuroradiological images HEV-D68 infection is a possible etiology and nasopharyngeal swabs should be taken within the first five days after onset. In our series, patients slightly improved but severe lesions remained. Longer follow-up studies would be necessary to assess sequelae. Nevertheless, based on previous reports, we believe no significant changes will be observed in the long term.3
8.
Conclusions
In a child with acute flaccid myelitis, adequately immunized and in whom wild-type or vaccine-related poliomyelitis has been ruled out, HEV-D68 should be considered as a possible causative agent. Subtype D68 (isolated in four of our patients) seems to have an affinity for the gray matter of the spinal cord and, although the pathophysiological mechanism remains unclear, the lack of response to antiinflammatory and immunomodulatory therapy and the absence of OCB in CSF are suggestive of direct infection of the spinal cord.
The neuroradiological findings may lead to the diagnosis when the lesions are clearly confined to the spinal cord gray matter although more unspecific findings, such as diffuse lesions with spinal cord expansion, should also be considered. It is noteworthy that in our series no specific radiological pattern of HEV-D68 infection was found. Short-term outcome is associated with severe poliomyelitis-like neurological deficits. Nevertheless, more time will be necessary to define long-term sequelae. Finally, in child with asymmetric flaccid myelitis awareness of the possibility of an enterovirus, especially D68, infection is essential to start the usual early infection control measures for respiratory viruses to avoid disease spread, as currently no specific vaccines or antiviral medication exist. To our knowledge, this outbreak of HEV-D68-related acute flaccid myelitis is the first in Argentina and Latin America.
Conflicts of interest The authors have no conflicts of interest to declare.
references
1. Jacob A, Weinshenker BG. An approach to the diagnosis of acute transverse myelitis. Semin Neurol 2008;28:105e20. ticas en nin ~ os y 2. Arroyo HA. Mielopatı´as agudas no trauma adolescentes. Rev Neurol 2013;57(1):S129e38. 3. Van Haren K, Ayscue P, Waubant E, et al. Acute flaccid myelitis of unknown etiology in California, 2012-2015. JAMA 2015;314(24):2663e71. 4. Cho TA, Vaitkevicius H. Infectious myelopathies. Contin lifelong Learn Neurol 2012;18(6):1351e73. 5. Center for Disease Control and Prevention (CDC). Acute flaccid myelitis: interim considerations for clinical management. November 7, 2014. 6. Aliabadi N, Messacar K, Pastula D, Robinson C, Leshem E, Sejvar J, Nix W, Oberste M, Feikin D, Dominguez S. Enterovirus D68 infection in children with acute flaccid myelitis, Colorado, USA, 2014. Emerg Infect Dis 2016 Aug;22(8):1387e94. 7. West T, Hess C, Cree B. Acute transverse myelitis: demyelinating, inflammatory, and infectious myelopathy. Semin Neurol 2012;32:97e113. 8. Schmalstieg W, Weinshenker B. Approach to acute or subacute myelopathy. Neurology 2010;75(1):S2e8. 9. Maloney JA, Mirsky DM, Dominguez SR, Scheriner T, Stence NV. MRI findings in children with acute flaccid paralysis and cranial nerve dysfunction occurring during the 2014 enterovirus D68 outbreak. AJNR Am J Neuroradiol 2015 Feb. 36:245e50. 10. Sheerin F, Collison K, Quaghebeur G. Magnetic resonance imaging of acute intramedullary myelopathy: radiological differential diagnosis for the on-call radiologist. Clin Radiol 2009;64:84e94. 11. Greninger A, Naccache S, Massacar K, et al. A novel outbreak enterovirus D68 strain associated with acute flaccid myelitis cases in the USA (2012e14): a retrospective cohort study. Lancet Infect Dis 2015 March 31;15:671e82. 12. Holm-Hansen CC, Midgley SE, Fischer TK. Global emergence of enterovirus D68: a systematic review. Lancet Infect Dis 2016 May;16(5):e64e75.
Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
13. Huang HI, Shih SR. Neurotropic enterovirus infections in the central nervous system. Viruses 2015;7:6051e66. 14. Crone M, Tellier R, Xing-Chang Wei Y. Polio-like illness associated with outbreak of upper respiratory tract infection in children. J Child Neurol 2016 June 1;31(4):409e14. 15. Horner L, Poulter M, Brenton JN, Turner R. Acute flaccid paralysis associated with novel enterovirus C105. Emerg Infect Dis 2015;21(10).
7
16. Hixon Alison M, Yu Guixia, Smith Leser J, Yagi Shigeo, Clarke Penny, Chiu Charles Y, Tyler Kenneth L. A mouse model of paralytic myelitis caused by enterovirus D68. PLos Pathog 2017 Feb 23;13(2). 17. Yea C, Bitnun A, Robinson J, et al. Longitudinal outcomes in the 2014 acute flaccid paralysis cluster in Canada. J Child Neurol 2017 Mar;32(3):301e7.
Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
Official Journal of the European Paediatric Neurology Society
Original article
Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016 Victor Ruggieri a,*, Maria Ivana Paz a, Marı´a Gabriela Peretti a, Carlos Rugilo b, Rosa Bologna c, Cecilia Freire d, Silvana Vergel a, Andrea Savransky a a
Department of Neurology, Hospital de Pediatrı´a Prof. Dr. “J.P. Garrahan”, Buenos Aires, Argentina Department of Neuroradiology, Hospital de Pediatrı´a Prof. Dr. “J.P. Garrahan”, Buenos Aires, Argentina c Department of Infectious Diseases, Hospital de Pediatrı´a Prof. Dr. “J.P. Garrahan”, Buenos Aires, Argentina d n, Buenos Aires, Argentina Department of Neuroviruses Hospital Nacional de Microbiologı´a Dr. Malbra b
article info
abstract
Article history:
Objective: To report a outbreak of 11 cases of acute asymmetric flaccid myelopathy due to
Received 12 January 2017
spinal motor neuron injury.
Received in revised form
Material and methods: Eleven children, six male, with a mean age of 3 years presented with
21 June 2017
acute flaccid myelitis. We analyzed clinical features, etiology, neuroradiological images,
Accepted 13 July 2017
treatment, and outcome. Results: Nine children had bilateral and asymmetric flaccid myelitis of the upper limbs, 1
Keywords:
had upper limb monoplegia, and 1 presented with hemiparesis. The cranial nerves were
Acute flaccid myelitis
involved in 6 patients and 4 required mechanical ventilation. In all cases acute flaccid
Poliomyelitis
myelitis co-occurred with upper airway infection and/or fever. Spinal cord magnetic
Enterovirus-D68
resonance imaging was abnormal in all, showing 2 different patterns: A linear pattern
Acute myelopathy
involving the anterior horns and another that was more heterogeneous showing spinal cord expansion. The lesions were non-enhancing in all. In 5/11 patients involvement of the medulla oblongata and pons was also observed. None of the patients presented with supratentorial lesions. In 4/11 children, the human enterovirus subtype D68 (HEV-D68) was identified in the airway and in 1/11 in the cerebrospinal fluid as well. In the remaining patients different enterovirus species A, B, and C variants were detected, as well as rhinovirus in 1 and influenza in another. Ten children received treatment with intravenous immunoglobulin and steroids and 4 of these children also underwent plasma exchange. Treatment did not lead to clinical improvement. Conclusions: In a patient with acute flaccid myelitis, HEV-D68 infection should be ruled out. Cases in which the virus was not detected were considered as “false negatives” as samples
* Corresponding author. E-mail address: [email protected] (V. Ruggieri). http://dx.doi.org/10.1016/j.ejpn.2017.07.008 1090-3798/© 2017 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
2
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
were collected late in course of the disease. The lack of response to anti-inflammatory and immunomodulatory treatment suggests a direct viral mechanism. This study is to our knowledge the first on an HEV-D68-infection-related cluster in Latin America. © 2017 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.
1.
Introduction
A child with acute flaccid myelopathy is always an emergency. Early diagnosis and treatment initiation may make the difference between the degree of sequelae or possible ad integrum recovery.1,2 Although the etiology can be infectious, immune-mediated, or structural, injury to the spinal cord gray matter caused by direct viral infection is currently considered to be uncommon, due to the almost worldwide control of poliomyelitis. Different enteroviruses, including HEV-A71, HEV-A70, HEV-C105, Coxsackie A7, other Coxsackie A, and echoviruses, may trigger acute flaccid myelitis.3,4 In 2014, an HEV-D68-associated outbreak of acute flaccid myelitis was reported in Colorado (USA). The clinical course and outcome of these cases were similar to that of poliomyelitis leading to international surveillance of these cases. Currently, control and management protocols have been developed by the Centers for Disease Control (CDC).5,6 The aim of this study was to report an outbreak of 11 cases with asymmetric acute flaccid myelitis due to spinal motor neuron involvement analyzing clinical features, laboratory tests, imaging studies, etiology, management, and short-term outcome.
2.
Material and methods
We conducted a retrospective study of eleven children who presented with asymmetric acute flaccid myelitis at a third level national pediatric hospital between April and May 2016. All patients met the clinical definition of acute flaccid myelitis and no age limits were considered in the inclusion criteria. Acute flaccid myelitis cases were defined as patients with acute flaccid weakness and radiological (MRI) or neurophysiological evidence of acute spinal motor neuron injury. Patients syndrome, stroke, transwho met criteria for Guillain-Barre verse myelitis, myasthenia gravis, or botulism were excluded. Cerebrospinal fluid, serum samples, nasopharyngeal swab specimens, and stool specimens were submitted to the na n) for infectious tional reference laboratory (Hospital Malbra agent testing.
3.
Laboratory tests
In this group of patients the following complementary studies were performed: Cerebral Spinal Fluid (CSF) was tested for enteroviruses, arboviruses (Saint Louis, West Nile, Zika, and dengue), herpes virus type 1, 2, and 6, cytomegalovirus, Epstein Barr virus, adenoviruses, varicella zoster, and influenza viruses
using polymerase chain reaction (PCR), additional to cultures for common pathogens and mycobacteria. Detection of oligoclonal band (OCB) was performed using isoelectric focusing. A nasopharyngeal swab (NPS) was performed followed by PCR for the detection of enteroviruses, respiratory syncytial virus, parainfluenza, influenza, and adenoviruses and by indirect immunofluorescence assays for influenza (H1N1 and H3N2), adenoviruses, and Mycoplasma. Stools were tested for enteroviruses (wild-type, Sabin-like, and vaccine-derived polioviruses) and botulinum toxin using PCR. When enterovirus was detected in CSF, nasopharyngeal swab, or stools by reverse transcription (RT)-nested-PCR, genotyping with amplified VP1 RT-snPCR was performed. Serum was investigated for enteroviruses, arboviruses (Zika and dengue), cytomegalovirus, Epstein Barr virus, adenoviruses, varicella zoster, Mycoplasma using serology techniques. Saint Louis, West Nile viruses, herpes virus type 1, 2, and 6 were tested with PCR. Finally, detection of oligoclonal bands (OCB) was performed using isoelectric focusing. When an enterovirus species was detected, viral subtype analysis was performed using sequencing techniques. Needle electromyography (EMG) and nerve conduction studies were performed with an 8-channel Akonic device according to the guidelines of the International Federation of Clinical Neurophysiology.
4.
Results
Eleven children, six of whom were boys, were seen at our institution with symptoms of acute flaccid myelitis in April and May 2016. The children had a mean age of 3 years and 2 months, ranging from 3 months to 6 years. All the children came from different neighborhoods of Buenos Aires. All patients had been vaccinated against polio and no travel was documented in any of them. The ethnic background of all patients was Spanish and Italian living for several generations in Argentina. None had shared contacts.
5.
Clinical features (Table 1)
All children were previously healthy without a significant family history. The onset of the neurological signs and symptoms coincided with an upper respiratory infection and/ or fever. None of the patients presented with sensory findings, bowel and bladder dysfunction, or encephalopathy.
Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
Table 1 e Clinical features, ancillary studies and treatment. Total cases (N ¼ 11) Prodromal symptoms Previous or concomitant disease Fever >38 C Neurological manifestations Proximal weakness Asymmetric involvement of the upper limbs Lower limb monoplegia Hemiparesis Hypo- or areflexia Associated symptoms Neck weakness Neck pain Pain in the limbs Cranial nerve involvement Peripheral VII cranial nerve Lower cranial nerves Peripheral VII and lower cranial nerves Diaphragmatic paralysis Need for mechanical ventilation Invasive Non-Invasive Diagnostic studies Cerebrospinal fluid Pleocytosis (>5 cells) Hyperproteinemia (>45 mg/dl) Brain magnetic resonance imaging Supratentorial lesions Brain stem lesions Spinal cord magnetic resonance imaging Diffuse lesions with gray and white matter involvement with cervical predominance Expansion Gray matter involvement without contrast enhancement Treatment during hospital stay Intravenous methylprednisolone Intravenous immunoglobulin Plasma exchange None
11 11 11 9 1 1 11 7 3 4 6 3 5 2 5 4 2 2
7 2
7 5 4
10 10 4 1
Table 2 e Viruses identified. Cases 1 2 3 4 5 6 7 8 9 10 11
Neurological manifestations at disease onset were asymmetrical weakness in the upper limbs (9/11), monoplegia in an upper limb (1/11), and hemiparesis (1/11). All patients presented with predominantly proximal weakness and hypoor areflexia. The associated symptoms were neck weakness (7/11), and pain in the neck (3/11) and in the limbs (4/11). Lower cranial nerve dysfunction was observed in five patients, associated with bilateral involvement of the peripheral VII nerve in two and unilateral involvement of the VII cranial nerve in one. In all these five children involvement of the lower cranial nerves was associated with diaphragmatic paralysis. Four patients needed admission to the intensive care unit in the first 24e48 h after disease onset; two required mechanical ventilation and two non-invasive ventilation. Six months after onset, all patients continue suffering from severe symptoms, with persistent limb paralysis, predominantly in the upper limbs. One of them has quadriparesis and remains on mechanical ventilation. In some patients a slight improvement was observed: 1/2 was weaned from mechanical ventilation, in 4/5 cranial nerve palsy resolved, in 6/7 neck weakness resolved, and neck and limb pain resolved in all.
6.
0 5
NPS
CSF
SS
Serum
HEV-B HEV-D68 HEV-D68 N/P Influenza () HRV-C N/P HEV-D68 HEV-D68 ()
() () () () () () () () () HEV-D68 ()
HEV-B N/P () HEV-A () HEV-C () HEV-C HEV-C HEV-B N/P
() () () () () () () () () () ()
HEV: Human Enterovirus, HRV: human rhinovirus, NPS: nasopharyngeal swab, CSF: cerebrospinal fluid, SS: stool samples, (): Negative, N/P: no performed.
3
Results of ancillary studies
CSF: In all patients lumbar puncture was performed. Seven patients presented with pleocytosis (white blood cell count > 5/mL) with predominance of lymphocytes and elevated protein levels in two. Screening for OCB (performed in five patients) was negative. Common-pathogen and mycobacterial cultures were negative in all patients. HEV-D68 was detected in only one patient; PCR for viruses in CSF was negative in the remaining patients. Nasopharyngeal swab: Nasopharyngeal samples were collected in nine patients, within the first five days of disease onset in four of them. Five were positive for enteroviruses of which four were enterovirus HEV-D68. In the latter four patients the sample was collected within the first five days after symptom onset. Of the remaining patients one was positive for influenza and another for rhinovirus. Results were negative in two samples. Stools: Stool samples, collected in nine children, were positive for enterovirus type A, B, and C in six. Serum: No pathogens were isolated from serum samples, collected in five cases, and screening for oligoclonal bands was also negative. The results of the laboratory tests are shown in Table 2 (appendix). MRI: All patients underwent complete brain and spinal cord MRI with and without gadolinium contrast within 72 h after symptom onset. Brain MRIs were normal at the supratentorial level. Lesions in the pons were observed in five patients, associated with involvement of the medulla oblongata in four. The lesions were hyperintense in T2-weighted and FLAIR images, predominantly dorsal, without contrast enhancement or mass effect (Fig. 1). All patients had lesions in the spinal cord. In seven the lesions were hyperintense in T2-weighted and FLAIR images, predominantly central, diffuse in the gray and white matter
Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
4
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
Fig. 1 e Brain MRI. Axial images in T2-weighted (a) and FLAIR (b) sequences. Brain MRI sagittal images in T2-weighted (c) sequences. A hyperintense signal is observed in the dorsal pons and medulla oblongata. Spinal cord MRI T2-weighted (c) Lesion that involve gray and white matter, with longitudinal extension from C2 to C8 (pattern II).
Fig. 2 e Spinal cord MRI. Sagittal and axial T2-weighted (a and b) images show mild expansion of the spinal cord and central spinal cord lesion that involve gray and white matter, with longitudinal extension from C2 to C8 (pattern II).
Fig. 3 e Spinal cord MRI. Axial and sagittal T2-weighted (aeb). Axial images reveal asymmetrical involvement of the anterior horns (“owl's eye sign”). A linear hyperintense signal is observed the anterior gray matter from C3 to C7 (pattern I). Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
extending three or more vertebral segments in length, without contrast enhancement, predominantly affecting the cervical cord. In five of these children expansion of the spinal cord was observed (Fig. 2). The remaining four patients had nonenhancing hyperintense images in T2 and STIR in the gray matter of the anterior spinal cord (Fig. 3). A second spinal cord MRI was performed at a mean of 20 days in four patients; In three of them the pattern had changed. The spinal cord expansion had resolved and the diffuse central involvement had changed to a longitudinal image in the anterior gray matter. No changes were observed in the remaining patient. Electrophysiological testing was performed in the first week after symptom onset. EMG: was performed in seven patients. The studies showed sensory and motor nerve conduction within normal limits. The EMG tracing performed with needle electrodes showed electrical silence at rest. At maximum levels of voluntary effort, a poor intermediate tracing with increasedamplitude motor unit potentials was observed, some of which were fragmented and others polyphasic. Treatment: As the acute myelopathy was considered to be inflammatory or immune-mediated at onset, 10/11 children were treated with pulse steroids (methylprednisolone) at 30 mg/kg/day to a maximum of 1 g/day combined with IVIG 2 g/kg and plasma exchange in 4/11 cases, with a range of 2e8 exchanges each; a watchful waiting policy was adopted in only one.
7.
Discussion
Myelopathies associated with spinal motor neuron injury have become rare due to the almost worldwide eradication of poliomyelitis. In the analysis of our patients, a clear clinically homogenous pattern characterized by asymmetrical flaccid myelitis preceded by or concomitant with upper airway infection and fever was recognized. Pain occurring in the neck or limbs was a common finding (7/11) coinciding with findings by other authors.3 The upper limbs were most commonly involved. In all cases symptom progression was within 24e48 h, mainly affecting proximal muscles with hypo- or areflexia. In two patients disease progression was severe, leading to respiratory difficulties requiring mechanical ventilation. Clinically, our patients were diagnosed with acute myelopathy with predominant motor involvement. No sensory symptoms were observed in any of the patients. Therefore, myelopathy associated with spinal motor neuron injury of infectious (poliomyelitis or non-polio enterovirus) or vascular etiology was suspected.4,7 Following the diagnostic protocol for patients with findings suspicious for acute myelopathy, a full brain and spinal cord MRI with and without contrast was requested and once a structural cause was ruled out, a lumbar puncture was performed for the detection of infectious agents.2,8 In seven children an EMG with conduction velocity was performed when flaccid myelitis was diagnosed. In all cases, the results showed preservation of motor and sensory peripheral nerve
5
trunks associated with a clearly neuropathogenic EMG tracing consistent with spinal cord injury. Unlike findings in previous studies, in all the patients in our series the supratentorial MRI was normal. Lesions were found at brain stem in five.3 The imaging findings in the spinal cord revealed two different patterns: Pattern I: Showing lesions exclusively in the anterior spinal cord gray matter. This is the typical image described in patients with an enterovirus infection.1 However, only four patients (36%) presented with this pattern at symptom onset. The gray matter lesions were asymmetrical in the majority of the cases, with increased involvement of the clinically more affected side. Pattern II: Showing central spinal cord lesions with diffuse involvement of the gray and white matter extending longitudinally (seven patients). Even though the patients had diffuse myelitis along the entire spinal cord, cervical cord manifestations were predominant. Unlike findings of previous studies, contrast enhancement of the cranial nerves was not observed in any of our patients, not even in those who had compatible clinical manifestations.3,9 In four of our patients a follow up MRI was performed at a mean of 20 days. The images revealed that three had evolved from pattern II to pattern I, resulting in a predominance of the latter pattern in our series. As three patients developed pattern I in the course of the disease, while four presented with that pattern at onset, it may be speculated that, in time, all patients might evolve to that particular radiological pattern. It is important to highlight that on neuroimaging anterior gray matter involvement is not only found in infectious myelopathies. Similar images may be observed in post-infectious or vascular disorders. Nevertheless, the clinical manifestations in our patients were not compatible with these conditions.1,10 Moreover, in the context of a cluster of patients with clinically similar features, a viral infection, including HEVD68, should be considered. Seven of 11 patients presented with pleocytosis in the CSF and OCB screening was negative in five patients studied. In only one patient HEV-D68 was isolated in the CSF. This patient had a worse outcome with severe motor sequelae and need for mechanical ventilation. In previous studies detection of HEVD68 in CSF yielded either negative or very few positive results.3,11 Up to 2005, only two isolated cases with acute myelopathy associated with HEV-D68 detected in CSF were reported and outcome was fatal in both.12 In five patients early nasopharyngeal swabs for the detection of enterovirus were done. Four were positive for D68. Therefore, when enterovirus-D68-associated flaccid myelitis is suspected, nasopharyngeal swab is the method of choice to search for the viral agent. Evaluating the first four patients, once bacterial infections had been ruled out, an immune-mediated disease was considered and they were treated with IVIG, IV steroids, and plasma exchange without response. The lack of response to
Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
6
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
treatment together with the identification of enteroviruses in nasopharyngeal swab specimens or CSF and the absence of OCB led us to reconsider the possibility of an immunemediated mechanism in the spinal cord. Therefore, based on the CDC guidelines on acute flaccid myelitis, we decided to withhold treatment in the last patient.5 Different enteroviruses, including enterovirus D68, have been associated with gray-matter (polio-like) acute myelopathy.11e14 In our series, enterovirus D68 was isolated in four patients. Although enteroviruses A71 and C105 have been associated with flaccid myelitis in other outbreaks, they were not identified in our samples.13,15 Even though the pathophysiology is largely unknown, several authors have postulated a mechanism via hematogenous spread (transient viremia) or through the retrograde axonal transport system, which may explain the low detection rate of enteroviruses in CSF.13 Recently, Hixon et al. reproduced HEV-D68 viral infection in a mouse model hypothesizing that dissemination occurs via the neural pathway. The viral antigen was detected almost exclusively in cells consistent with motor neurons, suggesting that direct viral injury, rather than a post-infectious immunemediated process is the most likely mechanism of neuronal cell loss and subsequent paralysis.16 Although the age of presentation (3.6 years) of our patients is similar to that reported by other authors, cases with flaccid paralysis associated with enterovirus D68 have been described in different age groups.12,17 Finally, based on the homogenous clinical and neuroradiological findings, we may consider the cases in which HEVD68 was not identified to be probable false negatives as the samples were collected more than 10 days after symptom onset in agreement with recent reports by other authors who observed an association between delay in sampling and reduced pathogen isolation (including HEV-D68).6 Considering these findings, pediatric neurologists should be aware that in patients with flaccid myelopathy associated with these neuroradiological images HEV-D68 infection is a possible etiology and nasopharyngeal swabs should be taken within the first five days after onset. In our series, patients slightly improved but severe lesions remained. Longer follow-up studies would be necessary to assess sequelae. Nevertheless, based on previous reports, we believe no significant changes will be observed in the long term.3
8.
Conclusions
In a child with acute flaccid myelitis, adequately immunized and in whom wild-type or vaccine-related poliomyelitis has been ruled out, HEV-D68 should be considered as a possible causative agent. Subtype D68 (isolated in four of our patients) seems to have an affinity for the gray matter of the spinal cord and, although the pathophysiological mechanism remains unclear, the lack of response to antiinflammatory and immunomodulatory therapy and the absence of OCB in CSF are suggestive of direct infection of the spinal cord.
The neuroradiological findings may lead to the diagnosis when the lesions are clearly confined to the spinal cord gray matter although more unspecific findings, such as diffuse lesions with spinal cord expansion, should also be considered. It is noteworthy that in our series no specific radiological pattern of HEV-D68 infection was found. Short-term outcome is associated with severe poliomyelitis-like neurological deficits. Nevertheless, more time will be necessary to define long-term sequelae. Finally, in child with asymmetric flaccid myelitis awareness of the possibility of an enterovirus, especially D68, infection is essential to start the usual early infection control measures for respiratory viruses to avoid disease spread, as currently no specific vaccines or antiviral medication exist. To our knowledge, this outbreak of HEV-D68-related acute flaccid myelitis is the first in Argentina and Latin America.
Conflicts of interest The authors have no conflicts of interest to declare.
references
1. Jacob A, Weinshenker BG. An approach to the diagnosis of acute transverse myelitis. Semin Neurol 2008;28:105e20. ticas en nin ~ os y 2. Arroyo HA. Mielopatı´as agudas no trauma adolescentes. Rev Neurol 2013;57(1):S129e38. 3. Van Haren K, Ayscue P, Waubant E, et al. Acute flaccid myelitis of unknown etiology in California, 2012-2015. JAMA 2015;314(24):2663e71. 4. Cho TA, Vaitkevicius H. Infectious myelopathies. Contin lifelong Learn Neurol 2012;18(6):1351e73. 5. Center for Disease Control and Prevention (CDC). Acute flaccid myelitis: interim considerations for clinical management. November 7, 2014. 6. Aliabadi N, Messacar K, Pastula D, Robinson C, Leshem E, Sejvar J, Nix W, Oberste M, Feikin D, Dominguez S. Enterovirus D68 infection in children with acute flaccid myelitis, Colorado, USA, 2014. Emerg Infect Dis 2016 Aug;22(8):1387e94. 7. West T, Hess C, Cree B. Acute transverse myelitis: demyelinating, inflammatory, and infectious myelopathy. Semin Neurol 2012;32:97e113. 8. Schmalstieg W, Weinshenker B. Approach to acute or subacute myelopathy. Neurology 2010;75(1):S2e8. 9. Maloney JA, Mirsky DM, Dominguez SR, Scheriner T, Stence NV. MRI findings in children with acute flaccid paralysis and cranial nerve dysfunction occurring during the 2014 enterovirus D68 outbreak. AJNR Am J Neuroradiol 2015 Feb. 36:245e50. 10. Sheerin F, Collison K, Quaghebeur G. Magnetic resonance imaging of acute intramedullary myelopathy: radiological differential diagnosis for the on-call radiologist. Clin Radiol 2009;64:84e94. 11. Greninger A, Naccache S, Massacar K, et al. A novel outbreak enterovirus D68 strain associated with acute flaccid myelitis cases in the USA (2012e14): a retrospective cohort study. Lancet Infect Dis 2015 March 31;15:671e82. 12. Holm-Hansen CC, Midgley SE, Fischer TK. Global emergence of enterovirus D68: a systematic review. Lancet Infect Dis 2016 May;16(5):e64e75.
Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008
e u r o p e a n j o u r n a l o f p a e d i a t r i c n e u r o l o g y x x x ( 2 0 1 7 ) 1 e7
13. Huang HI, Shih SR. Neurotropic enterovirus infections in the central nervous system. Viruses 2015;7:6051e66. 14. Crone M, Tellier R, Xing-Chang Wei Y. Polio-like illness associated with outbreak of upper respiratory tract infection in children. J Child Neurol 2016 June 1;31(4):409e14. 15. Horner L, Poulter M, Brenton JN, Turner R. Acute flaccid paralysis associated with novel enterovirus C105. Emerg Infect Dis 2015;21(10).
7
16. Hixon Alison M, Yu Guixia, Smith Leser J, Yagi Shigeo, Clarke Penny, Chiu Charles Y, Tyler Kenneth L. A mouse model of paralytic myelitis caused by enterovirus D68. PLos Pathog 2017 Feb 23;13(2). 17. Yea C, Bitnun A, Robinson J, et al. Longitudinal outcomes in the 2014 acute flaccid paralysis cluster in Canada. J Child Neurol 2017 Mar;32(3):301e7.
Please cite this article in press as: Ruggieri V, et al., Enterovirus D68 infection in a cluster of children with acute flaccid myelitis, Buenos Aires, Argentina, 2016, European Journal of Paediatric Neurology (2017), http://dx.doi.org/10.1016/j.ejpn.2017.07.008