Acute childhood encephalitis and encephalopathy associated with influenza: a prospective 11-year review

Severe Neurological Manifestation Associated With Coronavirus Disease 2019 in Children During the Omicron Variant-Predominant Period

BACKGROUND

The Omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is known to be more infectious and less severe than the other variants. Despite the increasing number of symptomatic patients, severe neurological complications in children with the Omicron variant have been reported rarely, unlike with wild-type or Delta variants. This study aimed to investigate severe neurological complications in children with Omicron variant infection.

METHODS

We conducted a retrospective study of 17 pediatric patients with severe neurological manifestations associated with coronavirus disease 2019 in Korea during the Omicron variant prevalence, from January 1 to April 30, 2022.

RESULTS

Among the 17 patients, 11 had pre-existing neurological disabilities and nine met the criteria for multisystem inflammatory syndrome in children (MIS-C). Four of the five vaccine-eligible patients (12 years and older) were unvaccinated. Severe neurological manifestations included acute necrotizing encephalopathy, acute fulminant cerebral edema, acute disseminated encephalomyelitis, basal ganglia encephalitis, unclassified severe encephalopathy/encephalitis, and refractory status dystonicus. Patients with MIS-C and underlying neurological disabilities had longer median hospital and intensive care unit stays compared with those without these conditions. Five patients survived with new neurological deficits at the one-year follow-up, and three died, all of whom had underlying neurological disabilities.

CONCLUSIONS

This study shows that severe neurological complications in pediatric patients with the Omicron variant of SARS-CoV-2 occur infrequently but may lead to significant morbidity and mortality, especially among those with pre-existing neurological disabilities and unvaccinated individuals. Continued efforts are necessary to prevent and manage such complications in these vulnerable populations.

Viral entry and translation in brain endothelia provoke influenza-associated encephalopathy

Influenza-associated encephalopathy (IAE) is extremely acute in onset, with high lethality and morbidity within a few days, while the direct pathogenesis by influenza virus in this acute phase in the brain is largely unknown. Here we show that influenza virus enters into the cerebral endothelium and thereby induces IAE. Three-weeks-old young mice were inoculated with influenza A virus (IAV). Physical and neurological scores were recorded and temporal-spatial analyses of histopathology and viral studies were performed up to 72 h post inoculation. Histopathological examinations were also performed using IAE human autopsy brains. Viral infection, proliferation and pathogenesis were analyzed in cell lines of endothelium and astrocyte. The effects of anti-influenza viral drugs were tested in the cell lines and animal models. Upon intravenous inoculation of IAV in mice, the mice developed encephalopathy with brain edema and pathological lesions represented by micro bleeding and injured astrocytic process (clasmatodendrosis) within 72 h. Histologically, massive deposits of viral nucleoprotein were observed as early as 24 h post infection in the brain endothelial cells of mouse models and the IAE patients. IAV inoculated endothelial cell lines showed deposition of viral proteins and provoked cell death, while IAV scarcely amplified. Inhibition of viral transcription and translation suppressed the endothelial cell death and the lethality of mouse models. These data suggest that the onset of encephalopathy should be induced by cerebral endothelial infection with IAV. Thus, IAV entry into the endothelium, and transcription and/or translation of viral RNA, but not viral proliferation, should be the key pathogenesis of IAE.

Severe Influenza-Associated Neurological Disease in Australian Children: Seasonal Population-Based Surveillance 2008-2018

BACKGROUND

Influenza-associated neurological disease (IAND) is uncommon but can result in death or neurological morbidity in children. We aimed to describe the incidence, risk factors, and outcome of children with IAND from seasonal influenza in Australia.

METHODS

We analyzed national, population-based, surveillance data for children aged ≤ 14 years with severe influenza and neurological involvement, over 11 Australian influenza seasons, 2008-2018, by the Australian Paediatric Surveillance Unit.

RESULTS

There were 633 laboratory-confirmed cases of severe influenza reported. Of these, 165 (26%) had IAND. The average annual incidence for IAND was 3.39 per million children aged ≤ 14 years. Compared to cases without neurological complications, those with IAND were more likely to have a pre-existing neurological disease (odds ratio [OR] 3.03, P < .001), but most children with IAND did not (n = 135, 82%). Children with IAND were more likely to receive antivirals (OR 1.80, P = .002), require intensive care (OR 1.79, P = .001), require ventilation (OR 1.99; P = .001), and die (OR 2.83, P = .004).

CONCLUSIONS

IAND is a preventable cause of mortality, predominantly in otherwise well children. Incidence estimates validate previous sentinel site estimates from Australia. IAND accounted for a quarter of all severe influenza, is associated with intensive care unit admission, and accounted for half of all influenza deaths.

Mortality and Neurologic Sequelae in Influenza-Associated Encephalopathy: Retrospective Multicenter PICU Cohort in France

OBJECTIVES

To describe and estimate the mortality rate of severe influenza-associated encephalopathy/encephalitis among children admitted to PICUs.

DESIGN

Multicenter retrospective study.

SETTING

Twelve French PICUs.

PATIENTS

All children admitted for influenza-associated encephalopathy/encephalitis between 2010 and 2018 with no severe preexisting chronic neurologic disorders and no coinfection potentially responsible for the disease.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

We collected the clinical presentation; laboratory, electroencephalographic, and MRI findings; and treatments used in the PICU. The primary outcome was mortality. The secondary outcomes included sequelae at discharge and last follow-up. We included 41 patients with a median (interquartile range) age of 4.7 years (2.5-8.2 yr). The main reasons for admission were altered consciousness (59%) and status epilepticus (34%); 48% of patients had meningitis, and one third had acute necrotizing encephalopathy on MRI. Mechanical ventilation was required in 73% of patients and hemodynamic support in 24%. The use of specific treatments was variable; steroids were given to 49% of patients. Seven patients (17%) died in the PICU. Median (interquartile range) PICU stay length was 7 days (2-13 d), and total hospital length of stay was 23 days (7-33 d). On hospital discharge, 49% (n = 20) had neurologic sequelae, with 27% (n = 11) having severe disabilities defined by modified Rankin Score greater than or equal to 4.

CONCLUSIONS

Children requiring PICU admission for influenza-associated encephalopathy/encephalitis have high mortality and morbidity rates. The management remains highly variable due to the lack of guidelines.

Prognostic Factors Among Children With Acute Encephalitis/Encephalopathy Associated With Viral and Other Pathogens

BACKGROUND

Acute encephalitis/encephalopathy (AE) associated with viral and other pathogens leads to neurological sequelae and mortality. Knowing the prognostic factors is therefore important for immediate interventions. We examined early-phase unfavorable prognostic factors among children with AE using a nationwide database.

METHODS

We performed a retrospective cohort study using the Diagnosis Procedure Combination database, which includes approximately half of acute-care inpatients across Japan. We enrolled children aged ≤ 18 years who were hospitalized for AE and discharged from April 2010 to March 2018. The composite unfavorable outcome included the following at discharge: in-hospital death, tracheostomy, enteral tube feeding, and physical rehabilitation. Unfavorable prognostic factors were assessed using a multivariable Poisson regression model including patient characteristics, associated pathogens, and interventions within 2 days of admission adjusting for within-hospital clustering.

RESULTS

This study included 9386 children with AE (median age, 3 years). A total of 241 (2.6%) in-hospital deaths occurred, and 2027 (21.6%) patients had the composite unfavorable outcome. Significant unfavorable prognostic factors were age 12-18 years, congenital anomalies, epilepsy, and Japan Coma Scale score of 100-300 at admission (ie, worse levels of consciousness). In contrast, herpes simplex virus infection and influenza virus infection were associated with favorable outcomes.

CONCLUSIONS

We identified early-phase (within 2 days of admission) unfavorable prognostic factors among children with AE. These findings will help identify patients who may benefit from early aggressive therapeutic interventions.

Contribution of Pro-Inflammatory Molecules Induced by Respiratory Virus Infections to Neurological Disorders

Neurobehavioral alterations and cognitive impairment are common phenomena that represent neuropsychiatric disorders and can be triggered by an exacerbated immune response against pathogens, brain injury, or autoimmune diseases. Pro-inflammatory molecules, such as cytokines and chemokines, are produced in the brain by resident cells, mainly by microglia and astrocytes. Brain infiltrating immune cells constitutes another source of these molecules, contributing to an impaired neurological synapse function, affecting typical neurobehavioral and cognitive performance. Currently, there is increasing evidence supporting the notion that behavioral alterations and cognitive impairment can be associated with respiratory viral infections, such as human respiratory syncytial virus, influenza, and SARS-COV-2, which are responsible for endemic, epidemic, or pandemic outbreak mainly in the winter season. This article will review the brain′s pro-inflammatory response due to infection by three highly contagious respiratory viruses that are the leading cause of acute respiratory illness, morbidity, and mobility in infants, immunocompromised and elderly population. How these respiratory viral pathogens induce increased secretion of pro-inflammatory molecules and their relationship with the alterations at a behavioral and cognitive level will be discussed.

Spatial learning and memory impaired after infection of non-neurotropic influenza virus in BALB/c male mice

During the influenza pandemic or seasonal influenza outbreak, influenza infection can cause acute influenza-associated encephalopathy/encephalitis (IAE), even death. Patients with severe IAE will also have severe neurological sequelae. Neurologic disorders have been demonstrated in the mice treated with peripheral influenza viruses infection, whether neurotropic or non-neurotropic viruses. However, previous studies focused on the acute phase of infection, and rarely paid attention to a longer range of observations. Therefore, the long-term effect of non-neurotropic virus infection on the host is not very clear. In this study, adult mice were infected with influenza virus H1N1/PR8. Then, spontaneous behavior, body weight, expression of cytokines in brain, spatial learning ability and spatial memory ability were observed, until the complete recovery period. The results showed that cytokines in the brain were highly expressed in the convalescent phase (14 day post inoculation, dpi), especially BDNF, IBA1, CX3CL1 and CD200 were still highly expressed in the recovery phase (28 dpi). Otherwise the emotional and spatial memory ability of mice were impacted in the convalescent phase (14 dpi) and the recovery phase (28 dpi). In brief, BALB/c mice infected with non-neurotropic influenza virus H1N1, the weight and motor ability decreased in acute stage. During the recovery period, the body weight and activity ability were completely restored, whereas the emotion disordered, and the ability of spatial learning and memory were impacted in the infected mice. This long-term behavior impact may be the lag injury caused by non-neurotropic influenza infection.

Prognostic Factors for Pediatric Acute Encephalopathy Associated with Severe Brain Edema

BACKGROUND AND OBJECTIVE

Acute encephalopathy is a life-threatening brain dysfunction in children, often associated with a preceding infection and diffuse noninflammatory brain edema. At present, the role of decompressive craniectomy (DC) over the swollen area of the brain is unclear. The risk factors for predicting clinical deterioration also need clarification.

METHODS

A retrospective study of pediatric patients admitted between 2015 and 2019 with acute cerebral encephalopathy was carried out. Patients were classified according to: (1) the preceding pathogens, (2) the syndromic classification, and (3) the extent of brain edema. The syndromic classification is a relatively new classification of acute encephalopathy proposed in 2016 and divides patients into 3 groups: those with systemic inflammatory reactions or "cytokine storms" (group 1), those with status epilepticus but no cytokine storm (group 2), and others (group 3). Glasgow Outcome Scale (GOS) scores of 1-3 were defined as unfavorable, while a GOS score of 4 or 5 was defined as a favorable outcome in this study. DC was performed for select patients with life-threatening signs of brainstem compression.

RESULTS

Nineteen patients (mean age: 23.3 months) were included in the study, 8 (42.1%) of whom had an unfavorable outcome. There was no significant correlation between the types of pathogens and outcome. Unfavorable outcomes were observed in significantly more patients in group 1 (87.5%) than group 2 (14.3%) and group 3 (0%). There was a significant association between diffuse brain edema and unfavorable outcomes (72.7%). Neurosurgical DC was performed in 2 patients to alleviate life-threatening brainstem compression: one with a cytokine storm and diffuse bilateral brain edema, and the other with prolonged status epilepticus causing diffuse right-sided brain edema. The GOS score was 3 and 4, respectively.

CONCLUSION

The risk factors for clinical deterioration in pediatric acute encephalopathy were evaluated based on a variety of classifications, including the new syndromic classification. Laboratory features of cytokine storms and radiological evidence of diffuse brain edema were associated with unfavorable outcomes. The role of surgical decompression is still controversial and should be assessed on a case-by-case basis.

Plasmapheresis for Rescue in Severe Encephalopathy and Multiorgan Failure from Fulminant Influenza (H3N2) Infection

We are presenting a case of 4-years-old previously healthy male with coma, severe acute hepatitis and multiorgan failure in presence of Influenza infection. Literature review highlighted an immune-mediated pathophysiology for such presentations so the child underwent a trial of plasmapheresis which resulted in a rapid clinical improvement and child was discharge in his baseline neurologic status by day 14.

Neurological Manifestations of Influenza A (H1N1): Clinical Features, Intensive Care Needs, and Outcome

OBJECTIVES

To describe neurological manifestations in children with Influenza A (H1N1).

METHODS

This retrospective study was conducted in the Pediatric intensive care unit (PICU) and Pediatric Neurology unit of a tertiary care teaching hospital in North India involving children with PCR confirmed Influenza A (H1N1) with neurological manifestations during 2019 outbreak.

RESULTS

Six children (5 females, 1 male) were enrolled. All presented with neurological symptoms (seizures and altered sensorium) accompanied with fever and respiratory symptoms with duration of illness of 2-7 d. The admission Glasgow Coma Scale ranged from 4 to 12. Only 2 cases showed cerebrospinal fluid pleocytosis. Neuroimaging was suggestive of diffuse cerebral edema, acute necrotizing encephalopathy of childhood, and acute disseminated encephalomyelitis. All were treated with Oseltamivir. Four cases had clinical features of raised intracranial pressure (ICP) and were managed in PICU, 3 of them needed mechanical ventilation, 3 needed vasoactive drugs, 3 received 3% saline infusion, 1 underwent invasive ICP monitoring, and 3 (cases 4, 5 and 6) received intravenous methylprednisolone (30 mg/kg) for 5 d. Total duration of hospital stay was 10-30 d. Case 2 expired due to refractory raised ICP. Among survivors, 3 children had residual neurological deficits and the remaining 2 had achieved premorbid condition.

CONCLUSIONS

Influenza A (H1N1) can present with isolated or predominant neurological manifestations which can contribute to poor outcome. The authors suggest to rule out H1N1 in any child who presents with unexplained neurological manifestations during seasonal outbreaks of H1N1.

Early steroid pulse therapy among children with influenza virus-associated encephalopathy

Background

Influenza virus-associated encephalopathy (IAE) can lead to neurological sequela and mortality among children. Therefore, instant recognition and therapeutic intervention for IAE are crucial. In some clinical subtypes of IAE, steroid pulse therapy might be beneficial, especially when it is administered in the early phase. However, early identification of patients who may benefit from steroid pulse therapy is sometimes difficult. We aimed to assess the effectiveness of early steroid pulse therapy among children with IAE.

Methods

In this retrospective observational study, we used a national database that covers half of the acute care inpatients across Japan to identify inpatients aged ≤ 18 years with a diagnosis of IAE between July 2010 and March 2017. Unfavorable outcome was defined as a composite outcome of sequela including Japan Coma Scale ≥ 10 at discharge, requiring tracheostomy, mechanical ventilation, enteral tube feeding, rehabilitation at discharge, or in-hospital death. Propensity score matching was performed to compare unfavorable outcome and in-hospital mortality between patients with and without steroid pulse therapy within 2 days of admission.

Results

Among 692 patients included in the study, the mean age was 5.8 years, and 55.8% were male. The overall in-hospital mortality was 1.3%, and the proportion of the unfavorable outcome was 15.0%. We observed no significant difference in the unfavorable outcome between matched patients (168 patients in each group) with and without early steroid pulse therapy (13.7% vs 8.3%; P = 0.16) or in-hospital mortality (0.6% vs 1.2%; P = 1.0).

Conclusions

We did not observe the effectiveness of early steroid pulse therapy on patient outcomes among children with IAE in our study population including all clinical subtypes of IAE. Further studies considering severity of illness are warranted to determine whether steroid pulse therapy is beneficial, especially for specific clinical subtypes of IAE.

Neurological complications associated with influenza in season 2017/18 in Austria- a retrospective single center study

BACKGROUND

Neurological complications associated with influenza (NCI) are rare events in adults with seasonal influenza. Information about the characteristics of neurological complications and the burden of disease has been limited to case reports, mainly during the pandemic 2009. Influenza-associated encephalopathy/encephalitis (IAE) is one of the most severe and frequently reported NCI, mostly caused by influenza A. Isolated case reports exist about NCI caused by influenza B.

OBJECTIVES

The aim of this single center retrospective study is the better understanding of the frequency and the characteristics of NCI in adults in season 2017-2018, depending on the influenza subtype A or B.

STUDY DESIGN

We reviewed 874 adult patients with laboratory confirmed influenza admitted to the Christian Doppler University Hospital Salzburg, Austria from December 2017 until March 2018 looking for NCI.

RESULTS

37 (4 %) of the 874 patients with confirmed influenza had NCI. 4 (11 %) had influenza A and 33 (89 %) had influenza B. IAE was the most frequent complication diagnosed in 24 (65 %) patients, of whom all but one had influenza B and 3 (13 %) had neurological residuals. Moreover 6 (16 %) had isolated epileptic seizures, 2 (5 %) had acute inflammatory demyelinating polyneuropathy (AIDP), and 5 (14 %) were classified as having infection-associated stroke.

CONCLUSIONS

We report an incidence of 4 % for NCI and a high frequency of IAE caused by subtype B. Therefore, we recommend considering both influenza A and B as an etiologic factor of encephalopathy and other neurological disease in adults.

Acute encephalopathy associated with influenza infection: Case report and review of the literature

Influenza has been associated with neurological complications. We describe the case of a toddler who presented with symptoms and signs of acute encephalopathy and hydrocephalus. Neuroimaging demonstrated cerebral edema and multifocal diffusion restriction in the thalamus and splenium of the corpus callosum. Influenza A was detected from the nasopharyngeal aspirate. The final diagnosis was acute influenza-associated encephalopathy. Despite treatment with a neuraminidase inhibitor and intravenous immune globulin, the toddler developed neurological sequelae. This case highlights a rare but severe complication of influenza in young children and the importance of influenza vaccination.

Nationwide survey of influenza-associated acute encephalopathy in Japanese adults

BACKGROUND

Knowledge of adult patients with influenza-associated acute encephalopathy (IAE) is limited. We conducted a detailed survey to investigate the prevalence, clinical features, associated outcomes, and prognostic factors in adult IAE patients.

METHOD

A nationwide questionnaire on IAE patients was sent to the departments of Internal Medicine, Neurology, Neurosurgery, and Emergency and Critical Care at all hospitals with ≥200 beds in Japan.

RESULTS

118 patients were diagnosed with IAE during the 2013/14 to 2015/16 influenza seasons, and the estimated annual incidence of IAE in Japanese adults was 0.98/1000,000 population. 44 patients were subsequently enrolled in the detailed study. 93% of patients exhibited disturbance of consciousness. Convulsions and delirious behavior were present in 26% and 40% of patients, respectively. 65% of patients received pulse corticosteroid therapy with methylprednisolone and 21% of patients received intravenous gamma-globulin therapy. 63% of patients achieved a good recovery, but 7% died. Multiple logistic regression analysis revealed that plasma glucose level demonstrated a statistically significant association with poor outcome.

CONCLUSION

This nationwide survey provided data for the annual incidence and clinical features of IAE in Japanese adults. Hyperglycemia was indicated as an independent predictor of poor prognosis in IAE patients and reflected systemic hypercytokinemia in IAE pathogenesis.

Adenovirus-Associated Central Nervous System Disease in Children

OBJECTIVE

To characterize the spectrum and salient clinical features of adenovirus-associated neurologic disease in immunocompetent children.

STUDY DESIGN

Previously healthy children (aged 1 month-18 years) with central nervous system (CNS) disease associated with adenovirus infection were identified via the Encephalitis Registry (1996-2016) and Microbiology Database (2000-2016) at The Hospital for Sick Children, Toronto, and by systematic review of the literature. The data were pooled and analyzed to identify the spectrum of illness, clinical outcome, and risk factors for death or neurologic impairment.

RESULTS

Neurologic complications associated with adenovirus infection in our institution included febrile seizures, encephalitis, acute disseminated encephalomyelitis, and aseptic meningitis. A total of 48 immunocompetent children with adenovirus-associated CNS disease were included in the pooled analysis-38 from the literature and 10 from our institution. In 85% of cases, the virus was detected in the respiratory or gastrointestinal tract, but not the cerebrospinal fluid. Eighteen of the 48 (38%) patients either died or suffered permanent neurologic sequelae. Predictors of adverse outcome included younger age, coagulopathy, the absence of meningismus, serotype 2 virus, and the presence of seizures. After multivariable adjustment, only seizures remained a significant risk factor.

CONCLUSION

Adenovirus is a rare cause of CNS disease in immunocompetent children. Disease spectrum is variable, ranging from mild aspetic meningitis and fully reversible encephalopathy to severe, potentially fatal, acute necrotizing encephalopathy.

Incidence of hospitalisation for severe complications of influenza virus infection in Japanese patients between 2012 and 2016: a cross-sectional study using routinely collected administrative data

OBJECTIVE

To calculate the incidence of hospitalisation due to acute respiratory failure, pneumonia, acute respiratory distress syndrome (ARDS), febrile seizures and encephalitis/encephalopathy among influenza-positive patients in Japan, where point-of-care tests are routinely used to diagnose influenza.

DESIGN

A cross-sectional study using routinely collected data.

SETTING

Japanese clinics and hospitals between 2012 and 2016.

PARTICIPANTS

Japanese patients aged 0-74 years diagnosed with influenza by a rapid test in employment-related health insurance records.

PRIMARY OUTCOME MEASURES

Incidence of hospitalisation per 100 000 influenza-positive episodes.

RESULTS

We included over 16 million influenza-positive episodes, 1.0% of whom were hospitalised. Of these, 3361 were acute respiratory failure, 27 253 pneumonia, 18 ARDS, 2603 febrile seizure and 159 encephalitis/encephalopathy. The percentage of hospitalisations by age was 2.96% of patients aged 0-1 years, 0.77% aged 2-5, 0.51% aged 6-12, 0.78% aged 13-18, 1.36% aged 19-44, 1.19% aged 45-64, and 2.21% aged 65-74. The incidence of hospitalisations from these five complications combined was highest in influenza-positive patients aged 0-1 years (943 per 100 000) compared with 307 in those aged 2-5 years and 271 in those aged 65-74 years. For pneumonia, the incidence was highest for influenza-positive patients aged 0-5 years and 65 years or more. There were statistically significant decreasing trends over the years in the incidence of all-cause hospitalisations, pneumonia and febrile seizures.

CONCLUSIONS

Japanese administrative data revealed that 1.0% of influenza-positive patients aged under 75 years were hospitalised. Male patients had a higher incidence of pulmonary complications and febrile seizures. Children aged 0-5 years and adults aged 65-74 years were at high risk of being admitted to hospital for pneumonia.

Pandemic 2009 influenza A (H1N1)-associated deaths among children in China: A retrospective analysis

Importance

A cluster of influenza-associated deaths occurred among children during pandemic 2009 influenza A (H1N1) in China, but the risk factors and causes for death have not been clarified.

Objective

We describe the clinical findings regarding 2009 influenza A (H1N1)-associated pediatric deaths in China, including the risk factors for death.

Methods

The definition of 2009 influenza A (H1N1)-associated pediatric death is death in a child who is younger than 14 years and has laboratory-confirmed influenza. We collected data of total 810 hospitalized patients with 2009 influenza A (H1N1) infection from September 2009 to February 2010 in 17 hospitals across China. The clinical characteristics, laboratory abnormalities, and treatment course were retrospectively studied.

Results

Of the 810 patients hospitalized with 2009 influenza A (H1N1) infection, 19 (2.3%) died. Ten patients died from severe pneumonia and acute respiratory distress syndrome; eight died from encephalopathy/encephalitis; one died from secondary fungal meningitis. Patients who died were more likely than patients who survived to have neutrophilia, lymphopenia, elevated C-reactive protein, and elevations of lactate dehydrogenase, creatine kinase, creatine kinase-MB, aspartate aminotransferase and alanine aminotransferase. There were no significant differences in the median age, median time from onset of illness to admission, underlying chronic disease, and initiation of antiviral therapy within 48 hours of illness onset, between patients who died and those who survived.

Interpretation

The risk factors for pediatric death associated with 2009 influenza A (H1N1) infection are different from those of seasonal influenza. The most common causes of death are viral pneumonia, acute respiratory distress syndrome, and encephalopathy/encephalitis.

Influenza-Associated Acute Necrotizing Encephalopathy in Siblings

Encephalopathy is an important complication associated with influenza, most frequently observed in young children, with a wide range of severity. The most severe category of influenza-associated encephalopathy (IAE) is acute necrotizing encephalopathy (ANE), characterized by high frequency of neurologic sequelae and fatal outcomes. We report two young siblings who developed fever and seizures with altered mental status. Influenza A(H1N1)pdm09 virus infection was identified in upper respiratory tract specimens from both patients, and neuroimaging revealed bilateral inflammatory lesions, consistent with acute necrotizing encephalopathy. Neither child had received influenza vaccination. Both children progressed to critical illness and required invasive mechanical ventilation. In addition to critical care management, both patients received high-dose corticosteroids, mannitol, anticonvulsants, and antiviral treatment of influenza. The older child recovered fully and was discharged 2 weeks after illness onset, but the younger sibling developed severe brainstem edema and cerebellar tonsillar herniation, and died on illness day 11. Both children tested positive for Ran Binding Protein 2 (RANBP2) gene mutations. RANBP2 is a genetic polymorphism associated with recurrent episodes of necrotizing encephalitis with respiratory viral infections. Annual influenza vaccination is especially important for ANE survivors, with or without RANBP2 mutations, their household contacts, and caregivers. During influenza season, close monitoring of any child with a history of neurological complications associated with respiratory illness is indicated, with prompt initiation of antiviral treatment with onset of acute respiratory illness, and influenza testing performed by molecular assay.

Characteristics and Outcomes of Influenza-Associated Encephalopathy Cases Among Children and Adults in Japan, 2010-2015

Background

Influenza-associated encephalopathy (IAE) can result in severe neurologic disease with high mortality. Most IAE cases are reported among children worldwide. Understanding of IAE among adults is limited.

Methods

Data were collected on IAE cases reported through the National Epidemiological Surveillance of Infectious Diseases database in Japan from 2010 through 2015. IAE cases were stratified by age category and analyzed using descriptive statistics to assess differences in characteristics and outcomes.

Results

Among 385 IAE cases, median age at diagnosis was 7 years (range, 0-90), and 283 (74%) were aged <18 years. Mean seasonal incidence of IAE cases among children and adults (aged ≥18 years) was 2.83 and 0.19 cases per 1000000 population, respectively. IAE incidence did not vary by predominant influenza A virus subtype. IAE frequency was highest in school-aged (5-12 years) children (38%), followed by children aged 2-4 years (21%) and adults aged 18-49 years (11%). The proportion of cases with seizures was more common in children. There were more cases with cerebrospinal fluid pleocytosis among adults than in children (P < .01), especially among those aged 18-49 (17%) and 50-64 (19%) years. Case fatality proportion was highest in those aged 40-64 (17%) and ≥65 (20%) years.

Conclusions

We found differences in the clinical features of IAE between adults and children in Japan. Although IAE incidence was higher in children, mortality was higher in adults. Efforts are needed to prevent and improve survival of patients with IAE, especially in adults.

Clinical prediction rule for neurological sequelae due to acute encephalopathy: a medical community-based validation study in Harima, Japan

OBJECTIVES

This study aimed to verify the screening performance of our clinical prediction rule for neurological sequelae due to acute encephalopathy (NSAE-CPR), which previously identified the following three variables as predictive of poor outcomes: (1) refractory status epilepticus; (2) consciousness disturbance and/or hemiplegia at 6 hours from onset and (3) aspartate aminotransferase >90 IU/L within 6 hours of onset.

DESIGN

Medical community-based multicentre retrospective cohort study.

SETTING

Six regional hospitals in Harima and one tertiary centre in Kobe, Japan, from 2008 to 2012.

PARTICIPANTS

We enrolled a total of 1612 patients aged <16 years who met the diagnostic criteria for an initial diagnosis of complex febrile seizure. Patients with a history of neurological disease and those included in the derivation cohort were excluded.

PRIMARY OUTCOME MEASURES

Univariate and multivariate analyses were performed to determine the association between each of the three predictor variables and poor AE outcome (Pediatric Cerebral Performance Category score ≥2). Receiver operating characteristic curve (ROC) analysis was also performed to assess the screening performance of the NSAE-CPR.

RESULTS

The ROC analysis identified at least one of the three predictive variables as an optimal cut-off point, with an area under the curve of 0.915 (95% CI 0.825 to 1.000). The sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios and Matthews correlation coefficient were 0.867, 0.954, 0.149, 0.999, 18.704, 0.140 and 0.349, respectively.

CONCLUSIONS

Our findings indicate that the NSAE-CPR can be used for the screening and identification of patients with poor outcomes due to acute encephalopathy within 6 hours of onset.

Influenza-associated Encephalitis/Encephalopathy Identified by the Australian Childhood Encephalitis Study 2013-2015

BACKGROUND

Influenza-associated encephalitis/encephalopathy (IAE) is an important cause of acute encephalitis syndrome in children. IAE includes a series of clinicoradiologic syndromes or acute encephalopathy syndromes that have been infrequently reported outside East Asia. We aimed to describe cases of IAE identified by the Australian Childhood Encephalitis study.

METHODS

Children ≤ 14 years of age with suspected encephalitis were prospectively identified in 5 hospitals in Australia. Demographic, clinical, laboratory, imaging, and outcome at discharge data were reviewed by an expert panel and cases were categorized by using predetermined case definitions. We extracted cases associated with laboratory identification of influenza virus for this analysis; among these cases, specific IAE syndromes were identified where clinical and radiologic features were consistent with descriptions in the published literature.

RESULTS

We identified 13 cases of IAE during 3 southern hemisphere influenza seasons at 5 tertiary children's hospitals in Australia; 8 children with specific acute encephalopathy syndromes including: acute necrotizing encephalopathy, acute encephalopathy with biphasic seizures and late diffusion restriction, mild encephalopathy with reversible splenial lesion, and hemiconvulsion-hemiplegia syndrome. Use of influenza-specific antiviral therapy and prior influenza vaccination were infrequent. In contrast, death or significant neurologic morbidity occurred in 7 of the 13 children (54%).

CONCLUSIONS

The conditions comprising IAE are heterogeneous with varied clinical features, magnetic resonance imaging changes, and outcomes. Overall, outcome of IAE is poor emphasizing the need for optimized prevention, early recognition, and empiric management.

Abnormal parietal encephalomalacia associated with schizophrenia: A case report

RATIONALE

It is widely believed that structural abnormalities of the brain contribute to the pathophysiology of schizophrenia. The parietal lobe is a central hub of multisensory integration, and abnormities in this region might account for the clinical features of schizophrenia. However, few cases of parietal encephalomalacia associated with schizophrenia have been described.

PATIENT CONCERNS AND DIAGNOSES

In this paper, we present a case of a 25-year-old schizophrenia patient with abnormal parietal encephalomalacia. The patient had poor nutrition and frequently had upper respiratory infections during childhood and adolescence. She showed severe schizophrenic symptoms such as visual hallucinations for 2 years. After examining all her possible medical conditions, we found that the patient had a lesion consistent with the diagnosis of encephalomalacia in her right parietal lobe and slight brain atrophy.

INTERVENTIONS

The patient was prescribed olanzapine (10 mg per day).

OUTCOMES

Her symptoms significantly improved after antipsychotic treatment and were still well controlled 1 year later.

LESSONS

This case suggested that parietal encephalomalacia, which might be caused by inflammatory and infectious conditions in early life and be aggravated by undernutrition, might be implicated in the etiology of schizophrenia.

Review of the aetiology, diagnostics and outcomes of childhood encephalitis from 1970 to 2009

AIM

Encephalitis is a rare, serious condition, and antiviral therapies, increased knowledge of inflammatory pathways and improved diagnostics have increased the therapeutic possibilities. We describe 40 years of childhood encephalitis in Sweden, covering the diagnostics, aetiology and outcomes.

METHODS

We reviewed the clinical data that were available for all children discharged from the Karolinska University Hospital in Stockholm following treatment for encephalitis from 1970 to 2009. The hospital treated all children in the region with the condition during the study period.

RESULTS

There were 408 episodes of encephalitis from 1970 to 2009 and the incidence was similar over the whole period, ranging from 6.4 to 8.7 per 100 000 child years. Although mortality markedly decreased from 10% in the first decade to zero in the last decade, and aetiologies shifted, no clear long-term improvements in outcome were seen. The need for intensive care was unchanged (18-20%) for each of the study intervals, possibly indicating that the severity of cases remained unaltered.

CONCLUSION

Understanding the pathophysiological mechanisms of encephalitis is vitally important for developing more efficient treatment regimens. As well as reporting the results of this 40-year study, this study considers possible explanations, addresses current therapeutic options and explores directions for central nervous system infection research.

Paediatric Virology: A rapidly increasing educational challenge

The '2nd Workshop on Paediatric Virology', which took place on Saturday the 8th of October 2016 in Athens, Greece, provided an overview on recent views and advances on Paediatric Virology. Emphasis was given to HIV-1 management in Greece, a country under continuous financial crisis, hepatitis B vaccination in Africa, treatment options for hepatitis C virus in childhood, Zika virus in pregnancy and infancy, the burden of influenza on childhood, hand-foot-mouth disease and myocarditis associated with Coxsackie viruses. Other general topics covered included a critical evaluation of Paediatric Accident and Emergency viral infections, multimodality imaging of viral infections in children, surgical approaches of otolaryngologists to complex viral infections, new advances in the diagnosis and treatment of viral conjunctivitis and novel molecular diagnostic methods for HPV in childhood. A brief historical overview of the anti-vaccination movement was also provided, as well as presentations on the educational challenge of Paediatric Virology as a new subspecialty of Paediatrics. This review highlights selected lectures and discussions of the workshop.

Neurological Complications of Respiratory Disease

The respiratory and central nervous systems are intimately connected. Ventilatory control is strictly regulated by central mechanisms in a complex process that involves central and peripheral chemoreceptors, baroreceptors, the cardiovascular system, and specific areas of the brain responsible for autonomic control. Disorders of the lung and respiratory system can interfere with these mechanisms and temporarily or permanently disrupt this complex network resulting in mild to severe neurological sequelae. This article explores the wide variety of neurological problems resulting from respiratory dysfunction, with emphasis on its pathophysiology, clinical features, prognosis, and long-term outcome.

Influenza

Influenza is one of the commonest infections in human populations, and causing substantial morbidity and mortality globally. The influenza virus is divided into different types and subtypes, three of which are currently circulating widely in humans: influenza A(H3N2) and influenza B. The virus undergoes constant evolution, leading to annual seasonal winter epidemics in temperate countries and necessitating annual updates to the vaccine. Rarely, completely new influenza viruses can emerge in human populations, giving rise to influenza pandemics. Children aged <5 years (especially those <2 years) and those with underlying illness such as cardiac, respiratory and severe neurologic disease have an increased risk of severe outcomes associated with influenza. Pregnant women have an increased risk of severe influenza. Complications may involve the respiratory tract (e.g. otitis media or pneumonia) or, less commonly, other organ systems (e.g. encephalitis or myocarditis). Specific antiviral treatment should be offered as soon as possible for hospitalized children with presumed or confirmed influenza and for influenza of any severity for children at high risk of severe complications of influenza without waiting for laboratory confirmation. Antiviral treatment is usually not warranted for uncomplicated influenza as this is usually self-limiting. Annual influenza vaccination should be offered to all individuals at increased risk for complications of influenza. Vaccine cannot be given to children aged <6 months but maternal influenza immunization during pregnancy is recommended and can confer protection to the young infant.

Indications for the performance of neuroimaging in children

Pediatric neurology relies on ultrasound, computed tomography (CT), and magnetic resonance (MR) imaging. CT prevails in acute neurologic presentations, including traumatic brain injury (TBI), nontraumatic coma, stroke, and status epilepticus, because of easy availability, with images of diagnostic quality, e.g., to exclude hemorrhage, usually completed quickly enough to avoid sedation. Concerns over the risks of ionizing radiation mean re-imaging and higher-dose procedures, e.g., arteriography and venography, require justification. T1/T2-weighted imaging (T1/T2-WI) MR with additional sequences (arteriography, venography, T2*, spectroscopy, diffusion tensor, perfusion, diffusion- (DWI) and susceptibility-weighted imaging (SWI)) often clarifies the diagnosis, which may alter management in acute settings, as well as chronic conditions, e.g., epilepsy. Clinical acumen remains essential to avoid imaging, e.g., in genetic epilepsies or migrainous headaches responding to treatment, or to target sequences to specific diagnosis, e.g., T1/T2-WI for shunt dysfunction (with SWI for TBI); DWI, arteriography including neck vessels, and venography for acute hemiplegia or coma; coronal temporal cuts for partial epilepsy; or muscle imaging for motor delay. The risk of general anesthesia is low; "head-only" scanners may allow rapid MRI without sedation. Timely and accurate reporting, with discrepancy discussion between expert neuroradiologists, is important for management of the child and the family's expectations.

Neurology of the H1N1 pandemic in Singapore: a nationwide case series of children and adults

Neurologic complications have long been associated with influenza. A novel strain of influenza A (H1N1) first described in humans to have outbreak potential in 2009 in Mexico went on to become the first influenza pandemic of this century. We evaluated the neurologic complications of the novel influenza A (H1N1) 2009 in children and adults admitted to all public hospitals in Singapore during the influenza A (H1N1) 2009 pandemic between May 2009 and March 2010. All patients were positive for novel H1N1 infection and presented with neurologic symptoms prior to oseltamivir treatment. Ninety-eight patients (median age 6.6 years, range 0.4-62.6) were identified; 90 % were younger than 18 years; 32 % suffered from preexisting neurological, respiratory, or cardiac disease; and 66 % presented with seizures. Of those presenting with seizures, new onset seizures were the most common manifestation (n = 40, 61.5 %), followed by breakthrough seizures (n = 18, 27.7 %) and status epilepticus (n = 7, 10.8 %). Influenza-associated encephalopathy occurred in 20 %. The majority of children (n = 88) presented with seizures (n = 63, 71.6 %), encephalopathy (n = 19, 21.6 %), and syncope (n = 4, 4.5 %). Among adults, a wider range of neurological conditions were seen, with half of them presenting with an exacerbation of their underlying neurological disease. The neurological symptoms developed at a median of 2 days after the onset of systemic symptoms. The median length of hospital stay was 3 days, and 79 % were monitored in general wards. Neurologic complications associated with the novel influenza A (H1N1) 2009 strain were generally mild and had a good outcome. They occurred more frequently in patients with underlying neurological disorders. Seizures and encephalopathy were the most common manifestations, similar to other influenza virus strains.

Acute pediatric encephalitis neuroimaging: single-institution series as part of the California encephalitis project

PURPOSE

Diagnosing pediatric encephalitis is challenging because of varied clinical presentation, nonspecific neuroimaging features, and rare confirmation of causality. We reviewed acute neuroimaging of children with clinically suspected encephalitis to identify findings that may correlate with etiology and length of stay.

METHODS

Imaging of 141 children with clinically suspected encephalitis as part of The California Encephalitis Project from 2005 to 2012 at a single institution was reviewed to compare the extent of neuroimaging abnormalities to patient age, gender, length of stay, and unknown, possible, or confirmed pathogen. Scan review was blinded and categorized by extent and distribution of abnormal findings.

RESULTS

Abnormal findings were evident on 23% (22/94) of computed tomography and 50% (67/134) of magnetic resonance imaging studies in the acute setting. Twenty children with normal admission computed tomography had abnormal findings on magnetic resonance imaging performed within 2 days. Length of stay was significantly longer among children with abnormal acute magnetic resonance imaging (P < 0.001) and correlated with increased complexity (Spearman rho = 0.4, P < 0.001) categorized as: no imaging abnormality, meningeal enhancement and/or focal nonenhancing lesion, multifocal lesions, confluent lesions, and lesions plus diffusion restriction, hemorrhage, or hydrocephalus. There was no correlation between neuroimaging findings and an identifiable pathogen (P = 0.8).

CONCLUSION

Abnormal magnetic resonance imaging findings are more common than abnormal computed tomography findings in pediatric encephalitis. Increasing complexity of magnetic resonance imaging findings correlated with disease severity as evidenced by longer length of stay, but were not specific for an identifiable pathogen using a standardized diagnostic encephalitis panel.

A child with acute encephalopathy associated with quadruple viral infection

Pediatric acute encephalopathy (AE) was sometimes attributed to virus infection. However, viral infection does not always result in AE. The risk factors for developing infantile AE upon virus infection remain to be determined. Here, we report an infant with AE co-infected with human herpesvirus-6 (HHV-6) and three picornaviruses, including coxsackievirus A6 (CVA6), Enterovirus D68 (EV-D68), and human parechovirus (HPeV). EV-D68 was vertically transmitted to the infant from his mother. CVA6 and HPeV were likely transmitted to the infant at the nursery school. HHV-6 might be re-activated in the patient. It remained undetermined, which pathogen played the central role in the AE pathogenesis. However, active, simultaneous infection of four viruses should have evoked the cytokine storm, leading to the pathogenesis of AE.

CONCLUSION

an infant case with active quadruple infection of potentially AE-causing viruses was seldom reported partly because systematic nucleic acid-based laboratory tests on picornaviruses were not common. We propose that simultaneous viral infection may serve as a risk factor for the development of AE.

Infectious and autoantibody-associated encephalitis: clinical features and long-term outcome

BACKGROUND AND OBJECTIVES

Pediatric encephalitis has a wide range of etiologies, clinical presentations, and outcomes. This study seeks to classify and characterize infectious, immune-mediated/autoantibody-associated and unknown forms of encephalitis, including relative frequencies, clinical and radiologic phenotypes, and long-term outcome.

METHODS

By using consensus definitions and a retrospective single-center cohort of 164 Australian children, we performed clinical and radiologic phenotyping blinded to etiology and outcomes, and we tested archived acute sera for autoantibodies to N-methyl-D-aspartate receptor, voltage-gated potassium channel complex, and other neuronal antigens. Through telephone interviews, we defined outcomes by using the Liverpool Outcome Score (for encephalitis).

RESULTS

An infectious encephalitis occurred in 30%, infection-associated encephalopathy in 8%, immune-mediated/autoantibody-associated encephalitis in 34%, and unknown encephalitis in 28%. In descending order of frequency, the larger subgroups were acute disseminated encephalomyelitis (21%), enterovirus (12%), Mycoplasma pneumoniae (7%), N-methyl-D-aspartate receptor antibody (6%), herpes simplex virus (5%), and voltage-gated potassium channel complex antibody (4%). Movement disorders, psychiatric symptoms, agitation, speech dysfunction, cerebrospinal fluid oligoclonal bands, MRI limbic encephalitis, and clinical relapse were more common in patients with autoantibodies. An abnormal outcome occurred in 49% of patients after a median follow-up of 5.8 years. Herpes simplex virus and unknown forms had the worst outcomes. According to our multivariate analysis, an abnormal outcome was more common in patients with status epilepticus, magnetic resonance diffusion restriction, and ICU admission.

CONCLUSIONS

We have defined clinical and radiologic phenotypes of infectious and immune-mediated/autoantibody-associated encephalitis. In this resource-rich cohort, immune-mediated/autoantibody-associated etiologies are common, and the recognition and treatment of these entities should be a clinical priority.

Acute encephalitis in children: Progress and priorities from an Australasian perspective

Encephalitis is a complex neurological syndrome caused by inflammation of the brain that occurs with highest incidence in children. It is challenging to diagnose and manage due to the variety of aetiologies and non-specific clinical presentations. We discuss the recent progress in clinical case definitions; review recent, large, prospective epidemiological studies; and describe aetiologies. We emphasise infectious causes relevant to children in Australasia but also consider emerging immune-mediated syndromes responsive to immune therapies. We identify priorities for future research in children, given the potential for climate change and international travel to influence the emergence of infectious agents in our region.

Geme JW. A 33-month-old with fever and altered mental status

A 33-month-old girl presented with 3 days of fever and 1 day of multiple paroxysmal episodes of screaming with apparent unresponsiveness, flexed lower extremities, clenched hands, and upward eye deviation. These events lasted seconds to a minute at a time and occurred only during sleep. She slept peacefully between episodes and was easily awakened. She had a history of mild speech delay and mild intermittent asthma but was otherwise healthy. She was tired-appearing and fussy on examination with dry mucous membranes, but her examination was otherwise normal. A complete blood count with differential and serum levels of sodium, potassium, chloride, and calcium were normal, but her bicarbonate level was 12 mmol/L. Her fingerstick glucose level was 69 mg/dL. Urine dipstick was notable for large ketones, and a urine drug screen was normal. Cerebrospinal fluid examination yielded 2 white blood cells and 1040 red blood cells/mm(3) with normal chemistries. A computed tomography (CT) scan of her head was unremarkable, and an abdominal ultrasound demonstrated no evidence of intussusception. Over the course of her hospitalization, these paroxysmal episodes persisted, and she subsequently developed mutism, right-sided weakness, and difficulty swallowing liquids. Here we present her case, diagnostic evaluation, and ultimate diagnosis.

Neurologic manifestations and complications of pandemic influenza A H1N1 in Malaysian children: what have we learnt from the ordeal?

INTRODUCTION

In 2009, pandemic influenza A H1N1 emerged in Mexico and subsequently spread worldwide. In Malaysia, there were more than a thousand of confirmed cases among children. The general clinical characteristics of these children have been well-published. However, the description of neurologic complications is scarce.

OBJECTIVE

This study aims to describe the characteristics of neurologic manifestations and complications in a national paediatric cohort with pandemic influenza A H1N1.

METHODS

During the pandemic, children (12 years or less) admitted for novel influenza A H1N1 in 68 Malaysian public hospitals, were prospectively enrolled into national database. The clinical, laboratory and neuro-imaging data for children with neurologic manifestations, hospitalized from 15th June 2009 till 30th November 2009, was reviewed.

RESULTS

Of 1244 children with influenza A H1N1 during the study period, 103 (8.3%) presented with influenza-related neurological manifestations. The mean age of our study cohort was 4.2 years (SD: 3.3 years). Sixty percent of them were males. Sixty-nine (66.9%) were diagnosed as febrile seizures, 16 (15.5%) as breakthrough seizures with underlying epilepsy, 14 (13.6%) as influenza-associated encephalopathy or encephalitis (IAE) and 4 (3.9%) as acute necrotizing encephalopathy of childhood (ANEC). All 4 available CSF specimens were negative for influenza viral PCR. Among 14 children with brain-imaging done, 9 were abnormal (2: cerebral oedema, 4: ANEC and 3: other findings). There were four deaths and three cases with permanent neurological sequelae.

CONCLUSION

About one-tenth of children with pandemic influenza A H1N1 presented with neurologic complications. The most common diagnosis was febrile seizures. One-fifth of those children with neurologic presentation had IAE or ANEC, which carried higher mortality and morbidity. This large national study provides us useful data to better manage children with neurologic complications in the future pandemic influenza outbreaks.

Clinical presentation of severe viral encephalitis with known causative agents in children: a retrospective study on 16 patients hospitalized in a pediatric intensive care unit (2008-2011)

A retrospective analysis was conducted in a French pediatric hospital in Lyon. Subjects were 16 patients diagnosed with acute viral encephalitis with identified causative agents who were admitted to the pediatric intensive care unit from 2008 to 2011. The median length of stay was 6 days. The outcome was favorable for 77% of the patients. Analysis of biological and clinical findings based on causative agents did not reveal clinical patterns or neurological findings specific to the causal viruses. Nevertheless, uncommon clinical pictures and severe neurological complications were highlighted, in particular for children with influenza-related encephalitis and herpes simplex encephalitis. This case series exemplifies the difficulties, even pitfalls, in establishing a diagnosis of encephalitis, especially in neonates. It points out significant differences in the clinical presentation of encephalitis in children compared with clinical pictures described in previously published large-scale studies on encephalitis mainly conducted in adults.

Neonatal influenza infection causes pathological changes in the mouse brain

Influenza A virus infections have been proposed to be associated with a broad spectrum of central nervous system complications that range from acute encephalitis/encephalopathy to neuropsychiatric disorders in humans. In order to study early influenza virus exposure in the brain, we created an influenza-infection model in neonatal mice to investigate infection route and resulting pathological changes in the brain. Real-time polymerase chain reaction and immunohistochemical analyses showed that influenza virus infection induced by an intraperitoneal injection was first detected as early as 1 day post infection (dpi), and the peak infection was observed at 5 dpi. The viral antigen was detected in a wide range of brain regions, including: the cerebral cortex, hippocampus, cerebellum, and brainstem. Apoptotic cell death and gliosis were detected in the areas of viral infection. Significant increases in proinflammatory cytokine expression were also observed at 5 dpi. Viral RNAs were detected in the cerebrospinal fluid of infected adult mice as early as 1 dpi. In addition, many infected cells were observed near the ventricles, indicating that the virus may enter the brain parenchyma through the ventricles. These results demonstrate that influenza virus may effectively infect broad regions of the brain through the hematogenous route, potentially through the cerebrospinal fluid along the ventricles, and subsequently induce neuropathological changes in the neonatal mouse brain.

Delayed primary HHV-7 infection and neurologic disease

BACKGROUND

Primary human herpesvirus 7 (HHV-7) infection occurs almost universally during the first 5 years of life and is rarely accompanied by central nervous system (CNS) symptoms such as febrile seizures. The present retrospective study investigated the role of primary HHV-7 infection in CNS disease in children, including adolescents.

METHODS

The study included all children who had neurologic disease aged younger than 18 years seen at the Hospital for Sick Children, Toronto, Canada, between April 1, 1998 and December 31, 2011, whose cerebrospinal fluid (CSF) was found by polymerase chain reaction to contain HHV-7 DNA. Where sera were available, HHV-7 IgG antibody titers and avidity were measured to differentiate primary from past infection.

RESULTS

HHV-7 DNA was detected in the CSF of 57 (1.9%) of the 2972 children tested. In 3 adolescents primary HHV-7 infection (low avidity IgG) was confirmed as the cause of neurologic disease, 2 who had encephalitis and 1 who had Guillain-Barré syndrome. Eighteen children had possible HHV-7 disease (no alternative cause identified and indeterminate antibody result or serum not available), 7 encephalitis, 8 meningitis, and 3 demyelinating disorders. HHV-7 disease was excluded in 36 children on the basis of past infection (high IgG avidity) and/or an alternative cause.

CONCLUSIONS

Primary HHV-7 infection delayed into adolescence can cause serious neurologic disease. HHV-7 DNA in CSF alone is insufficient to prove an etiologic association. Combining CSF polymerase chain reaction with serology is essential to prove primary infection when investigating HHV-7 CNS disease.

Neurologic aspects of influenza viruses

Although influenza A and B viruses are primarily known as respiratory viruses and mainly infected only the upper respiratory tract in humans, patients with influenza often develop signs and symptoms that are not due to the respiratory system. Frequently individuals with influenza develop headaches, meningismus, and even seizures in addition to their typical respiratory symptoms. In the past decades, influenza viruses have also been associated with serious non-respiratory signs. The famous 1918 strain of influenza was associated with von Economo's encephalitis lethargica and postencephalitic parkinsonism. In the 1960s influenza virus infections in children were associated with Reye's syndrome characterized often by fatty non-inflammatory hepatic disease and an encephalopathy with marked non-inflammatory cerebral edema. Intermittently children with influenza develop focal myalgia and myositis. Guillain–Barré syndrome was epidemiologically associated with the 1978 killed influenza vaccine but not subsequent vaccines. Although occasional children with influenza have developed encephalopathy, from 2000 through 2004 there was an increase in the number of serious cases of acute necrotizing encephalopathy accompanying infection with the influenza A 2009 strain. The current H5N1 strain of bird influenza occasionally infects humans with a high mortality rate and some appear to have central nervous signs. This chapter explores what is known about these influenza neurologic associations.

Neurological and muscular manifestations associated with influenza B infection in children

BACKGROUND

Influenza viruses have been associated with various neurological and muscular symptoms. The aim of this study was to evaluate the pediatric neurological and muscular manifestations of influenza B during a 5-month epidemic at a single center.

METHODS

We retrospectively reviewed the medical records of 355 pediatric patients with laboratory-confirmed influenza B infection.

RESULTS

Neurological and muscular symptoms were exhibited by 28 patients (7.9%). The mean age was 48.7 ± 25.2 months. The mean time between respiratory symptoms and neurological symptoms was 2.2 ± 1.5 days. The most common symptom was seizure (19/28, 67.9%), followed by myositis (5/28, 17.9%), increased intracerebral pressure (1/28, 3.6%), delirium (1/28, 3.6%), and severe headache (1/28, 3.6%). There was one severe case of meningitis with myocarditis (1/28, 3.6%). All seizures were febrile: 15 simple febrile seizures (78.9%), three complex febrile seizures (15.8%), and one febrile status epilepticus (5.3%). The mean age of nine patients with their first seizures was 37.9 ± 22.2 months, which was older than the typical age of onset for febrile seizure. All the patients, except one, were treated with oseltamivir. There were no deaths or chronic debilitating sequelae.

CONCLUSIONS

The neurological and muscular complications of influenza B infection in children are relatively mild, and febrile seizure is the most common. However, clinicians should be alert to the possibility of rare severe complications during influenza B outbreaks.

Therapeutic indicators of acute encephalopathy in patients with complex febrile seizures

BACKGROUND

The aim of this study was to identify predictors of neurologic damage in children with febrile seizures or altered consciousness within 6 h of seizure onset.

METHODS

The present study included 86 children (age range, 4-159 months old), who fulfilled the diagnostic criteria for complex febrile seizures on admission between October 2002 and November 2008. Using the Pediatric Cerebral Performance Category Scale (PCPC), the children were classified into two groups: poor outcome (PCPC = 2-6) and good outcome (PCPC = 1). Clinical profiles and laboratory findings were compared between the groups.

RESULTS

Of the 86 children, 17 fell into the poor outcome and 69 into the good outcome group. Using univariate analysis, three early risk factors for poor outcome were identified: (i) consciousness disturbance or hemiplegia at 6 h from onset; (ii) refractory status epilepticus; and (iii) elevation of aspartate aminotransferase to >90 IU/L within 6 h of onset. Using these criteria, children in the poor outcome group were identified with a 94% sensitivity and 67% specificity rate (odds ratio, 36.6; 95% confidence interval: 4.87-1560). During the study period, the inpatients who met the criteria for acute encephalopathy also fell into the poor outcome group.

CONCLUSIONS

The development of neurologic damage in children with complex febrile seizures can be predicted within 6 h of onset, using the identified risk factors. The authors propose an assumption of severe febrile seizures (SFS) in children who fulfill these risk factors. Using SFS as an inclusion criterion, an interventional study for acute encephalopathy can be designed.

The burden of influenza B: a structured literature review

We reviewed the epidemiology, clinical characteristics, disease severity, and economic burden of influenza B as reported in the peer-reviewed published literature. We used MEDLINE to perform a systematic literature review of peer-reviewed, English-language literature published between 1995 and 2010. Widely variable frequency data were reported. Clinical presentation of influenza B was similar to that of influenza A, although we observed conflicting reports. Influenza B-specific data on hospitalization rates, length of stay, and economic outcomes were limited but demonstrated that the burden of influenza B can be significant. The medical literature demonstrates that influenza B can pose a significant burden to the global population. The comprehensiveness and quality of reporting on influenza B, however, could be substantially improved. Few articles described complications. Additional data regarding the incidence, clinical burden, and economic impact of influenza B would augment our understanding of the disease and assist in vaccine development.

Acute viral infections of the central nervous system in immunocompetent adults: diagnosis and management

Patients with viral infections of the central nervous system (CNS) may present with a variety of neurological symptoms, most commonly dominated by either encephalitis or meningitis. The aetiological panorama varies in different parts of the world as well as over time. Thus, virological first-line diagnostics must be adapted to the current epidemiological situation and to the individual patient history, including recent travels. This review focuses on the diagnostics and treatment of viral CNS infections in the immunocompetent host from a Northern European perspective. Effective vaccines are available for viruses such as poliovirus and tick-borne encephalitis virus (TBEV) and for the childhood diseases morbilli (measles), rubella (German measles), parotitis (mumps) and varicella (chickenpox). However, cases do appear due to suboptimal immunization rates. In viral CNS infections, epidemiological surveillance is essential for establishing preventive strategies and for detecting emerging viruses. Knowledge of the possibilities and limitations of diagnostic methods for specific viral CNS infections is vital. A positive cerebral spinal fluid (CSF) polymerase chain reaction (PCR) finding is usually reliable for aetiological diagnosis. The demonstration of intrathecal antibody synthesis is useful for confirming the aetiology in a later stage of disease, hitherto sufficiently evaluated in herpes simplex encephalitis (HSE) and tick-borne encephalitis (TBE). Despite improved virological and differential diagnostic methods, aetiology remains unknown in about half of the cases with suspected viral encephalitis. Antiviral treatment is available chiefly for infections caused by herpesviruses, and acyclovir (aciclovir) is the drug of choice for empirical therapy in suspected viral encephalitis. However, randomized, controlled antiviral trials have only been conducted for HSE, while such studies are lacking in other viral CNS infections. Viral cytolysis and immune-mediated mechanisms may contribute to varying extents to neurological damage. Although the brain damage is believed to depend, to a varying degree, on the intrathecal host immune response, the use of corticosteroids in viral CNS infections is scarcely studied, as is specific treatment for neuroinflammation. Improved antiviral and immunomodulating treatment is desirable. Since neurological sequelae are still abundant, follow-up after severe viral CNS disease must include a neuropsychological assessment and an individually adapted rehabilitation plan.

Influenza-associated neurological complications

While mostly diagnosed in the pediatric population, neurological complications of pandemic influenza A infection may affect young and previously healthy adults, and may follow a fulminant, severe, and occasionally fatal course. We reviewed severe neurological complications secondary to influenza infection reported in the literature, in attempt to outline recurrent syndromes that may assist the clinician in making a timely diagnosis. Vigilance and awareness of these clinical entities are key in the neurologist and intensivist's role in surveillance and early recognition of pandemic influenza, and in ensuring improved survival for affected patients.

National surveillance of influenza-associated encephalopathy in Japan over six years, before and during the 2009-2010 influenza pandemic

Influenza-associated encephalopathy (IAE) is a serious complication of influenza and is reported most frequently in Japan. This paper presents an assessment of the epidemiological characteristics of influenza A (H1N1) 2009-associated encephalopathy in comparison to seasonal IAE, based on Japanese national surveillance data of influenza-like illness (ILI) and IAE during flu seasons from 2004–2005 through 2009–2010. In each season before the pandemic, 34–55 IAE cases (mean 47.8; 95% confidence interval: 36.1–59.4) were reported, and these cases increased drastically to 331 during the 2009 pandemic (6.9-fold the previous seasons). Of the 331 IAE cases, 322 cases were reported as influenza A (H1N1) 2009-associated encephalopathy. The peaks of IAE were consistent with the peaks of the influenza epidemics and pandemics. A total of 570 cases of IAE (seasonal A, 170; seasonal B, 50; influenza A (H1N1) 2009, 322; unknown, 28) were reported over six seasons. The case fatality rate (CFR) ranged from 4.8 to 18.2% before the pandemic seasons and 3.6% in the 2009 pandemic season. The CFR of pandemic-IAE was 3.7%, which is lower than that of influenza A−/B-associated encephalopathy (12.9%, p<0.001; 14.0%, p = 0.002; respectively). The median age of IAE was 7 years during the pandemic, which is higher than that of influenza A−/B-associated encephalopathy (4, p<0.001; 4.5, p = 0.006; respectively). However, the number of pandemic-IAE cases per estimated ILI outpatients peaked in the 0–4-year age group and data both before and during the pandemic season showed a U-shape pattern. This suggests that the high incidence of influenza infection in the 0–4 year age group may lead to a high incidence of IAE in the same age group in a future influenza season. Further studies should include epidemiologic case definitions and clinical details of IAE to gain a more accurate understanding of the epidemiologic status of IAE.

Acute Infantile Encephalopathy Predominantly Affecting The Frontal Lobes (AIEF)

Acute Infantile Encephalopathy Predominantly Affecting the Frontal Lobes (AIEF) is a relatively recent described entity. This article includes case reports of two patients who had bifrontal involvement during acute febrile encephalopathy. Case 1 describes a 1-y-old boy who presented with hyperpyrexia and dialeptic seizures. Imaging revealed significant bilateral frontal lobe involvement while serology proved presence of Influenza B infection. Over a period of one wk, he recovered with significant cognitive decline and perseveratory behavior. Another 6-y-old boy presented with language and behavioral problems suggestive of frontal dysfunction after recovering from prolonged impairment of consciousness following a convulsive status epilepticus. Bilateral superior frontal lesions with gyral swelling was evident on neuroimaging. These cases are among the very few cases of AIEF described in recent literature and the article also reviews this unique subtype of acute encephalopathy.

Encephalitis with thalamic and basal ganglia abnormalities: etiologies, neuroimaging, and potential role of respiratory viruses

BACKGROUND

Encephalitis is a severe neurological syndrome with devastating consequences. Despite extensive testing, the etiology often remains unknown. Involvement of the thalamus or basal ganglia (T/BG) occurs in a subset of patients with encephalitis and may be an important etiological clue. In order to improve diagnosis of T/BG patients, we reviewed this subgroup within the California Encephalitis Project (CEP).

METHODS

Data from T/BG cases enrolled in CEP were retrospectively reviewed. Cases were stratified by age and grouped by etiological classification: infectious, postinfectious, and noninfectious. Neuroimaging reports were examined and compared between etiologies.

RESULTS

T/BG neuroimaging abnormalities were reported in 6% of 3236 CEP cases. An etiology was found in 76%: 37% infectious, 16% postinfectious, and 23% noninfectious. The most frequently identified infectious agents were respiratory viruses, accounting for 31%, predominantly in children. Other infections more common in the T/BG group included Creutzfeldt-Jakob disease, arbovirus, and Mycobacterium tuberculosis. Infectious and postinfectious cases had higher median cerebrospinal fluid white blood cell count than noninfectious etiologies. Notably, T/BG neuroimaging characteristics were associated with distinct etiologies. In particular, symmetric hemorrhagic abnormalities involving the thalamus were most frequently found within the respiratory virus group.

CONCLUSIONS

T/BG involvement in patients with suspected encephalitis was associated with specific etiologies. In addition to agents with established predilection for the T/BG such as M. tuberculosis and arboviruses, a surprisingly high number of cases were associated with respiratory viruses, especially in children. Neuroimaging abnormalities in such patients can aid clinicians in narrowing the etiological scope and in guiding testing.