West nile poliomyelitis in a 7-year-old child

Acute Myelopathy in Childhood

Acute myelopathy presenting in childhood can be clinically classified based on the location of injury (with resulting spinal syndrome) or the cause (broadly traumatic or non-traumatic). Types of nontraumatic myelopathy include ischaemic, infectious, inflammatory, nutritional, and metabolic causes, some of which may be part of a systemic illness such as systemic lupus erythematosus or a demyelinating disease such as multiple sclerosis. Nonaccidental injury is an important consideration in cases of traumatic myelopathy, which may often be associated with other injuries. Assessment should include neuroimaging of the brain and spinal cord, with further investigations targeted based on the most likely differential diagnoses; for example, a child with suspected demyelinating disease may require specialist cerebrospinal fluid and serological testing. Management also will differ based on the cause of the myelopathy, with several of these treatments more efficacious with earlier initiation, necessitating prompt recognition, diagnosis, and treatment of children presenting with symptoms of a myelopathy. Important components of holistic care may include physiotherapy and occupational therapy, with multidisciplinary team involvement as required (for example psychological support or specialist bowel and bladder teams).

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.

Pediatric West Nile Virus-Associated Neuroinvasive Disease: A Review of the Literature

Over the past two decades, West Nile virus has become the most common arbovirus in North America, leading to several outbreaks and infecting thousands of people. Mosquitos help transmit the virus in the majority of cases, but transmission occurs via blood transfusions, organ transplantation, and possibly pregnancy and breastfeeding. While most infected patients experience mild to no symptoms, thousands of West Nile virus-associated neuroinvasive cases have been reported in the United States, with over 700 cases occurring in children from 2003 to 2016. Neuroinvasive disease presents as meningitis, encephalitis, or acute flaccid paralysis, and carries a high likelihood of poor outcome, including severe neurological disability or death. To date, no pharmacologic treatment has proven effective. Therapeutic clinical trials have not been successfully completed due to the sporadic nature of viral outbreaks and resultant poor study enrollment. Although older age and chronic disease are risk factors for neuroinvasive West Nile virus disease in adults, the specific factors that influence the risk in pediatric populations have not been fully elucidated. This review summarizes the most recent literature regarding West Nile virus-associated neuroinvasive disease, especially as it pertains to the pediatric population. Moreover, the review describes the epidemiology, clinical, laboratory, and radiographic findings, and outlines the various therapies that have been trialed and potential future research directions.

Recognition and Management of Acute Flaccid Myelitis in Children

BACKGROUND

In 2014-2015, several regions of the United States experienced an outbreak of acute flaccid myelitis in pediatric patients. A common, unique feature was disease localization to the gray matter of the spinal cord.

METHODS

We report 11 children, ages 13 months to 14 years (median 9 years), in the Intermountain West who presented with extremity weakness (n = 10) or cranial neuropathy (n = 1) of varying severity without an apparent etiology.

RESULTS

All children experienced acute paralysis, and 10 had symptoms or signs that localized to the spinal cord. Maximum paralysis occurred within 4 days of onset in all patients. All had spinal gray matter lesions consistent with acute myelitis detected by magnetic resonance imaging; no single infectious cause was identified. Despite therapy with intravenous immunoglobulin, corticosteroids, or plasma exchange, nine of 10 (90%) children had motor deficits at follow-up.

CONCLUSIONS

Recognition of this disorder enables clinicians to obtain appropriate imaging and laboratory testing, initiate treatment, and provide families with accurate prognostic information. In contrast to other causes of acute flaccid paralysis in childhood, most children with acute flaccid myelitis have residual neurological deficits.

The Interferon-Stimulated Gene Ifi27l2a Restricts West Nile Virus Infection and Pathogenesis in a Cell-Type- and Region-Specific Manner

The mammalian host responds to viral infections by inducing expression of hundreds of interferon-stimulated genes (ISGs). While the functional significance of many ISGs has yet to be determined, their cell type and temporal nature of expression suggest unique activities against specific pathogens. Using a combination of ectopic expression and gene silencing approaches in cell culture, we previously identified Ifi27l2a as a candidate antiviral ISG within neuronal subsets of the central nervous system (CNS) that restricts infection by West Nile virus (WNV), an encephalitic flavivirus of global concern. To investigate the physiological relevance of Ifi27l2a in the context of viral infection, we generated Ifi27l2a(-/-) mice. Although adult mice lacking Ifi27l2a were more vulnerable to lethal WNV infection, the viral burden was greater only within the CNS, particularly in the brain stem, cerebellum, and spinal cord. Within neurons of the cerebellum and brain stem, in the context of WNV infection, a deficiency of Ifi27l2a was associated with less cell death, which likely contributed to sustained viral replication and higher titers in these regions. Infection studies in a primary cell culture revealed that Ifi27l2a(-/-) cerebellar granule cell neurons and macrophages but not cerebral cortical neurons, embryonic fibroblasts, or dendritic cells sustained higher levels of WNV infection than wild-type cells and that this difference was greater under conditions of beta interferon (IFN-β) pretreatment. Collectively, these findings suggest that Ifi27l2a has an antiviral phenotype in subsets of cells and that at least some ISGs have specific inhibitory functions in restricted tissues.

IMPORTANCE

The interferon-stimulated Ifi27l2a gene is expressed differentially within the central nervous system upon interferon stimulation or viral infection. Prior studies in cell culture suggested an antiviral role for Ifi27l2a during infection by West Nile virus (WNV). To characterize its antiviral activity in vivo, we generated mice with a targeted gene deletion of Ifi27l2a. Based on extensive virological analyses, we determined that Ifi27l2a protects mice from WNV-induced mortality by contributing to the control of infection of the hindbrain and spinal cord, possibly by regulating cell death of neurons. This antiviral activity was validated in granule cell neurons derived from the cerebellum and in macrophages but was not observed in other cell types. Collectively, these data suggest that Ifi27l2a contributes to innate immune restriction of WNV in a cell-type- and tissue-specific manner.

Spinal Nerve Root Enhancement on MRI Scans in Children: A Review

Spinal nerve root enhancement in pediatric patients is generally nonspecific, and clinical and laboratory correlation is essential. Nerve root enhancement indicates lack of integrity of the blood-nerve barrier. In this review, we will present a range of pediatric conditions that can present with spinal nerve root enhancement including inflammatory, infectious, hereditary, and neoplastic causes. Familiarity with the various pathologic entities associated with spinal nerve root enhancement is important for a concise differential diagnosis in the appropriate clinical setting. This will avoid unnecessary additional investigations.

West Nile virus infection in children

West Nile virus (WNV) is an emerging flavivirus responsible for an increasing number of outbreaks of neuroinvasive disease in North America, Europe, and neighboring countries. Almost all WNV infections in humans are transmitted through the bite of infected mosquitoes. Transmission during pregnancy and through breastfeeding has been reported, but the risk seems to be very low. West Nile disease in children is less common (1-5% of all WNV cases) and associated with milder symptoms and better outcome than in elderly individuals, even though severe neuroinvasive disease and death have been reported also among children. However, the incidence of WNV infection and disease in children is probably underestimated and the disease spectrum is not fully understood because of lack of reporting and underdiagnosis in children. Infection is diagnosed by detection of WNV-specific antibodies in serum and WNV RNA in plasma and urine. Since no effective WNV-specific drugs are available, therapy is mainly supportive.

MRI findings in children with acute flaccid paralysis and cranial nerve dysfunction occurring during the 2014 enterovirus D68 outbreak

BACKGROUND AND PURPOSE

Enterovirus D68 was responsible for widespread outbreaks of respiratory illness throughout the United States in August and September 2014. During this time, several patients presented to our institution with acute flaccid paralysis and cranial nerve dysfunction. The purpose of this report is to describe the unique imaging findings of this neurologic syndrome occurring during an enterovirus D68 outbreak.

MATERIALS AND METHODS

Patients meeting a specific case definition of acute flaccid paralysis and/or cranial nerve dysfunction and presenting to our institution during the study period were included. All patients underwent routine MR imaging of the brain and/or spinal cord, including multiplanar T1, T2, and contrast-enhanced T1-weighted imaging.

RESULTS

Eleven patients met the inclusion criteria and underwent MR imaging of the brain and/or spinal cord. Nine patients presented with brain stem lesions, most commonly involving the pontine tegmentum, with bilateral facial nerve enhancement in 1 patient. Ten patients had longitudinally extensive spinal cord lesions; those imaged acutely demonstrated involvement of the entire central gray matter, and those imaged subacutely showed lesions restricted to the anterior horn cells. Ventral cauda equina nerve roots enhanced in 4 patients, and ventral cervical nerve roots enhanced in 3, both only in the subacute setting.

CONCLUSIONS

Patients presenting with acute flaccid paralysis and/or cranial nerve dysfunction during the recent enterovirus D68 outbreak demonstrate unique imaging findings characterized by brain stem and gray matter spinal cord lesions, similar to the neuroimaging findings described in previous outbreaks of viral myelitis such as enterovirus 71 and poliomyelitis.

Unusual case of West Nile Virus flaccid paralysis in a 10-year-old child

West Nile virus infection is asymptomatic in most cases. West Nile virus neuroinvasive disease includes encephalitis, meningitis, and/or acute flaccid paralysis. In children, acute flaccid paralysis as the solo presentation of West Nile virus disease is rare. It develops abruptly and progresses rapidly early in the disease course. We report on a 10-year-old child who presented with a slowly progressive left leg flaccid paralysis over 4 weeks. He tested positive for West Nile virus in both blood and cerebrospinal fluid. Spinal MRI showed enhancement of the ventral nerve roots. This was also supported by electrophysiological studies. One week after the plateauing of his left leg paralysis, he was readmitted to the hospital with left hand weakness. Complete recovery of his recurrent weakness was observed after prompt 5-day course of intravenous immunoglobulin G therapy. However, no improvement was noticed in the left foot drop. To our knowledge, this is the first case report of West Nile virus disease in children presented with a slowly progressive flaccid paralysis, and a recurrent weakness recovered after intravenous immunoglobulin G administration.

Inflammatory, vascular, and infectious myelopathies in children

Acute nontraumatic myelopathies of childhood include inflammatory, infectious, and vascular etiologies. Inflammatory immune-mediated disorders of the spinal cord can be categorized as idiopathic isolated transverse myelitis, neuromyelitis optica, and multiple sclerosis. In recent years, human T-cell lymphotropic virus type 1, West Nile virus, enterovirus-71, and Lyme disease have been increasingly recognized as infectious etiologies of myelopathy, and poliomyelitis remains an important etiology in world regions where vaccination programs have not been universally available. Vascular etiologies include vasculopathies (systemic lupus erythematosus, small vessel primary angiitis of the central nervous system), arteriovenous malformations, and spinal cord infarction (fibrocartilaginous embolism, diffuse hypoxic ischemia-mediated infarction). Vascular myelopathies are less common than inflammatory and infectious myelopathies, but are more likely to lead to devastating clinical deficits. Current therapeutic strategies include acute anti-inflammatory treatment and rehabilitation. Stem cell transplantation, nerve graft implantation, and stimulation of endogenous repair mechanisms represent promising strategies for spinal cord repair.