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Influenza encephalopathy, a rare manifestation of influenza infection in the adult population which is not widely recognised, can present with confusion and focal neurological symptoms, including aphasia. The aim of this report is to illustrate the unique presentation of influenza encephalopathy and discuss the need for close attention to and monitoring of this rare but highly fatal disease.A 28-year-old woman was admitted with acute-onset confusion and incoherent speech. CT of the head was unremarkable. Cerebrospinal fluid analysis showed elevation of protein, but was otherwise unremarkable. A detailed history revealed recent upper respiratory symptoms which prompted a rapid influenza test which was positive and oseltamivir was started. The patient's confusion and aphasia gradually improved and her speech was back to her baseline by the next day., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Among 182 children with influenza infection in 2016-2017, 18% had neurologic manifestations of influenza (NMI), including seizures and encephalopathy; 85% of these children were infected with the H3N2 strain. Children with NMI had 3.5-times-higher odds of having a neurologic comorbidity than those without NMI and a 10-fold increased odds of hospitalization., (© The Author(s) 2018. Published by Oxford University Press on behalf of The Journal of the Pediatric Infectious Diseases Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Influenza-associated acute encephalopathy (IAE) is more prevalent in children than in adults and often results in neurological sequelae or even death. Diagnosis of IAE is difficult as clinical presentation varies significantly and the influenza virus is rarely detected in cerebrospinal fluid. Moreover, seizures in adults due to influenza infection are rare. Herein, we describe the case of an adult presenting with both acute encephalitis and seizures. A 38-year-old female was admitted to the emergency department with acute respiratory symptoms and fever, followed by quick progression to stupor within 24 h. A rapid antigen test was influenza A-positive, and polymerase chain reaction of nasal secretions confirmed the H3N2 subtype. Brain magnetic resonance imaging showed bilateral water restriction lesions at the thalamus and the cerebellum and an electroencephalogram showed frequent episodic generalized sharp-and-slow waves over the bilateral frontal region. Based on the neuroimaging and laboratory findings, we diagnosed the patient with adult influenza A (H3N2)-related encephalitis complicated by seizure. Treatment with oseltamivir and anticonvulsants led to complete neurologic recovery by day 14. This report describes two unusual neurological manifestations of influenza A, i.e., encephalitis and seizures, in an adult. We emphasize that, in adults presenting with acute viral encephalitis, clinicians should consider influenza infection as part of the differential diagnosis, and that typical neuroimaging in conjunction with laboratory detection of influenza virus and/or intrathecal antibody production suggestive of IAE, may help establish an accurate diagnosis., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: To investigate the clinical manifestations, diagnosis, and treatment of H1N1 influenza A-associated encephalopathy (IAE) in children. Methods: The clinical manifestations, laboratory tests, cranial magnetic resonance imaging (MRI), electroencephalography (EEG) examinations and treatments of seven children with H1N1 IAE hospitalized in Guangzhou Women and Children's Medical Center from December 2018 to January 2019 were retrospectively analyzed. Results: Five of the seven children with H1N1 IAE were female. The age at admission was 4 years and 5 months (range 7 months-9 years). Neurological symptoms occurred simultaneously or early (0-3 days) after the flu-like symptom appeared. The main clinical manifestations of neurological symptoms were seizures (repeated seizures in five cases and status convulsion in two cases, including one case of unexpected fever and repeated seizures in a nine-year old girl) accompanied with altered consciousness (drowsiness in five cases and coma in two cases). Cranial MRI in three cases displayed multifocal lesions, mainly in the bilateral thalamus, brainstem and cerebellar hemisphere. MRI also showed reversible splenial lesion in the corpus callusumin in three cases. EEG tracings were characterized by diffuse slow wave activity in four cases, and status epilepticus was monitored in one case. All the 7 cases were treated with oral oseltamivir. Three cases were treated with pulsed methylprednisolone and intravenous immunoglobulin. One case was treated with intravenous immunoglobulin alone and all the patients received oral oseltamivir. All the patients survived, with three patients had minor neurological sequelae at discharge. Conclusions: The main clinical manifestations of H1N1 IAE are seizures and altered consciousness. Cranial MRI combined with EEG is helpful for early diagnosis. Intravenous immunoglobulin and (or) methylprednisolone should be considered for severe cases.

Acute necrotizing encephalopathy (ANE) is a severe neurologic complication caused by influenza virus that has been infrequently reported in adult population. The diagnosis is made on epidemiological, clinical, and neuroimaging suspicion, but is rarely confirmed by microbiological findings in samples from the central nervous system (CNS), thus making it difficult to define the mechanism of pathogenesis of influenza-associated encephalitis/encephalopathies (IAE). We report a microbiologically documented case of ANE caused by influenza A/H3N2, in a previously healthy adult patient infected during a flu epidemic in Asturias (Spain). Direct viral invasion of the CNS was demonstrated with the isolation of the virus in a brain biopsy.

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.

In the past 3 years, the 2009 pandemic influenza virus H1N1 (pH1N1) has led to many severe or fatal cases. The virus-related factors that cause severe or fatal disease are not clear. The clinical and molecular characteristics of pH1N1 infections with severe or fatal disease were examined to understand the correlation between pH1N1 infection and disease severity. Since 2009, three pH1N1 influenza epidemic outbreaks have occurred in Shenzhen, China. One hundred forty-six severe cases were confirmed in the first wave in 2009. In severe cases, a high proportion (49.3%) of patents displayed high fever (>39.0°C), and 73.2% of patients had pneumonia and tracheobronchitis. Seven fatal cases were recorded: three with viral encephalitis and four with respiratory failure. The results of sequencing and phylogenetic analysis showed that the viruses from fatal or severe cases were scattered throughout the phylogenetic tree. Four substitutions (D222G, D222N, D222E, and Q223R) were observed on the 220-loop of the receptor-binding sites of the HA gene. Both D222G and D222N were associated statistically with severe disease. The 2011 viruses had evolved into two distinct branches. Ten specific point mutations occurred in the 2011 virus. In summary, high fever, lower respiratory tract infections and serious complications were the main features of severe cases. Gene variation seemed not to be the main reason for severe disease. Vaccination is the effective mean to prevent infection and severe disease., (Copyright © 2012 Wiley Periodicals, Inc.)

We present 3 cases of influenza A 2009 H1N1 encephalitis occurring in adults, corroborated by viral genome detection in cerebrospinal fluid (CSF) and evidence of meningeal inflammation on brain histopathology. This paper emphasizes the possibility of viral detection in CSF and stresses the lack of an effective treatment for neurological manifestations of influenza.

Influenza virus is associated with a variety of neurological complications, of which the most commonly encountered are seizures and encephalopathy. Acute encephalitis and postinfectious encephalopathy have been reported infrequently in association with influenza A and B virus infections. We describe two previously healthy adults who presented with encephalopathy with a virologically documented influenza B infection.

Background and Purpose: Influenza viral infection, which results in central nervous system dysfunction, is a major cause of acute encephalopathy (AE). The purpose of this study was to investigate the changes in the concentrations of brain metabolites in children with AE using single-voxel magnetic resonance spectroscopy (MRS) and to provide diagnostic information about the relationship between the symptoms of AE and metabolite concentrations., Materials and Methods: The subjects were 10 children (mean age: 6.2 years; range: 1-13) with AE caused by the novel influenza A virus responsible for the 2009 influenza pandemic. The serial MRS data (TE/TR=30/5000 ms, 3 T) acquired from the basal ganglia (BG) and centrum semiovale (CS) of each patient were categorized into three periods: (1) initial neurological symptom presentation and the start of treatment (n=10), (2) short-term follow-up (n=9) and (3) long-term follow-up (n=3). As controls, the magnetic resonance (MR) spectra of eight age-matched children were also investigated., Results: In both regions, the concentrations of the major metabolites (N-acetylaspartate, creatine, choline, myo-inositol, glutamate/glutamine complex and glutamate) only showed minor fluctuations between the three periods. On the other hand, higher levels of taurine (Tau) were observed in the BG during the second period (P=.005), and increased levels of glucose were observed in the CS during the first (P=.005) and second (P=.036) periods., Conclusions: Serial monitoring of brain metabolite changes was carried out with a clinical MR system. The concentrations of major metabolites only displayed very minor fluctuations in response to mild H1N1-related AE. However, a higher Tau concentration was found to be associated with neurological symptoms. Further studies are required to improve our understanding of the detailed activity of Tau in AE., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Objectives: In April 2009, a novel influenza A (H1N1) pdm virus was identified in Mexico and spread quickly around the world. However, the clinical features of acute encephalopathy associated with 2009 pandemic influenza have not yet been elucidated., Methods: We treated 8 patients (3 boys and 5 girls) aged 4 to 11 years (average age, 8 y 3 months) with influenza virus-associated encephalopathy, who presented at our 2 hospitals between July 2009 and March 2010. We investigated the clinical characteristics, treatments, and outcomes in the patients., Results: In all patients, brain computed tomography showed mild to severe diffuse cerebral edema, and electroencephalography revealed diffuse high-voltage slow waves. They were all treated with oseltamivir and methylprednisolone pulse therapy. Six patients recovered without any sequelae; however, the remaining 2 had residual neurological sequelae. These 2 patients presented with severe disturbance of consciousness, and their central nervous system symptoms appeared within 12 hours after the onset of fever. One patient had periventricular leukomalacia and symptomatic epilepsy by perinatal brain hypoxia, and the other patient had 1 complex febrile and 2 febrile seizures., Conclusions: This study showed that patients with influenza-associated encephalopathy caused by influenza A (H1N1) pdm infection were all older than those with seasonal influenza. Underlying neurological disease or history may be associated with poor prognosis.

The novel pandemic (pdm) influenza A (H1N1) 2009 virus caused an epidemic of critical illness, with some patients developing severe acute respiratory distress syndrome. Pdm H1N1 2009 infection has been reported to cause fatal encephalopathy and myocarditis as well as pneumonia. To investigate the actual characteristics of the encephalopathy associated with pdm H1N1 2009 infection in Japan, questionnaires were distributed and information collected on 207 cases of encephalopathy during one season. The results of the survey showed that encephalopathy was reported predominantly in males. The outcome was recorded in 188 of the 207 cases; 16 of 188 patients (8.5%) died, while 23 (12.2%) had sequelae. Serious cases were distributed across all age groups. Febrile convulsion was noted at a higher rate in medical past-history in cases without sequelae (40 of the 149 cases; 27%) than in serious cases. In contrast, pre-existing epilepsy and mental retardation were observed more frequently in serious cases. Twelve cases exhibited biphasic seizures; one-half of these had sequelae, but none was fatal. Ten cases were accompanied by high cytokine levels, and three of these children died. Among the 149 cases with good outcomes, 29 of 116 cases (25%) showed abnormalities on MRI, and 14 of these demonstrated reversible splenial lesions. Abnormal behaviors, especially delirium and visual hallucinations, were observed more frequently in cases without sequelae. In conclusion, pdm H1N1 2009 infection-associated encephalopathy was a critical disease in children, with rapidly progressive characteristics similar to those of seasonal influenza-associated encephalopathy., (Copyright © 2012 Wiley Periodicals, Inc.)

In adults, influenza A may be accompanied by a variety of neurological findings. Influenza-associated encephalitis (IAE) is rare in adults, and usually follows influenza A after 2 days. In patients with influenza who later develop encephalitis, the diagnosis of IAE is relatively straightforward. We present a rare case of IAE in an adult who presented with viral encephalitis that was later attributed to antecedent influenza A., (Copyright © 2012 Elsevier Inc. All rights reserved.)

A 20-year-old woman infected with the 2009 H1N1 strain of influenza A developed bilateral visual loss. Brain MRI showed restricted diffusion of the parietal and occipital lobes, and her spinal fluid did not contain inflammatory cells. This report describes an unusual case of H1N1 influenza A virus infection primarily affecting the posterior visual pathways.

To clarify the features of acute encephalopathy associated with 2009 pandemic flu. We identified 51 patients with acute encephalopathy with seasonal flu from the data base accumulated by Tokai Pediatric Neurology Society. We also collected 10 patients with acute encephalopathy with 2009 pandemic flu. The clinical course, laboratory data, neuroimaging findings, treatment, and the outcome of these patients were recruited using a structured research form. These data were compared between the two groups. The age was larger in the 2009 pandemic flu group (median, 109.5months) than in the seasonal flu group (median, 44months). There was no significant difference in other demographic data, neurologic symptoms, laboratory and neuroimaging findings, and treatment. Various degrees of neurologic sequelae including death were observed in 32% of the patients in the seasonal flu group, and in 50% in the 2009 pandemic flu groups. The analyses of patients with ages of 6years or older revealed that moderate or more severe sequelae were more frequent in patients with 2009 pandemic flu. Acute encephalopathy with 2009 pandemic flu occurred mainly among children with 6years of age or older, and the outcome was worse in this age group compared with acute encephalopathy with seasonal flu., (Copyright © 2011 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.)

We report an unusual case of pandemic (H1N1) 2009-related encephalitis in an immunocompetent woman. Although rare cases of pandemic (H1N1) 2009 associated with encephalitis have been reported previously, in this patient, direct viral invasion of the central nervous system was shown by simultaneous detection of viral RNA and pleocytosis.

Neurological manifestations and outcomes of children with the 2009 H1N1 virus infection have been reported in three American series and from smaller cohorts and case reports worldwide. Of the 83 children admitted between April 2009 and March 2010 with H1N1 virus infection to a tertiary children's hospital in a European setting, five children aged between 2 and 10 years had neurological symptoms. Four patients had seizures and encephalopathy at presentation. One patient presented with ataxia; one developed neuropsychiatric manifestations, and two developed movement disorders during the disease course. Early neuroimaging showed evidence of acute necrotising encephalopathy (ANE) in one case and non-specific white matter changes in another. Initial neuroimaging was normal for the other three, but interval MRI showed increased signal in bilateral periventricular distribution in one and significant cerebral volume loss in the other. Clinical outcomes varied: two recovered fully while three had residual seizures and/or significant cognitive deficits. Conclusion An analysis of our patients along with all reported cases reveal that seizures and encephalopathy were common neurological presentations associated with pandemic 2009 H1N1 influenza virus infection in children requiring hospital admission. Neuroimaging suggestive of ANE, basal ganglia involvement and volume loss appears to be associated with worse neurological outcome.

We present the case of a 12-year-old boy with acute lymphocytic leukemia who developed pneumonia and multiple brain infarcts compatible with acute necrotic encephalitis. The infectious disease screening tests revealed influenza A H1N1 virus, Staphylococcus aureus in broncho alveolar lavage, E. coli and galactomannan antigen in blood. CNS influenza associated complications are reviewed. This case highlights the importance of magnetic resonance imaging as a diagnostic tool in the assessment of immunocompromised patients with CNS compromise and the value of brain biopsy in the final identification of an infectious disease etiology.

Background: Influenza virus infection of the respiratory tract is associated with a range of neurologic complications. The emergence of 2009 pandemic influenza A (H1N1) virus has been linked to neurological complications, including encephalopathy and encephalitis., Methods: Case report and literature review., Results: We reviewed case management of a 20-year old Hispanic male who developed febrile upper respiratory tract signs and symptoms followed by a confusional state. He had rapid neurologic decline and his clinical course was complicated by refractory seizures and malignant brain edema. He was managed with oseltamavir and peramavir, corticosteroids, intravenous gamma globulin treatment, anticonvulsants, intracranial pressure management with external ventricular drain placement, hyperosmolar therapy, sedation, and mechanical ventilation. Reverse transcriptase polymerase chain reaction analysis of nasal secretions confirmed 2009 H1N1 virus infection; cerebrospinal fluid (CSF) was negative for 2009 H1N1 viral RNA. Follow-up imaging demonstrated improvement in brain edema but restricted diffusion in the basal ganglia. We provide a review of the clinical spectrum of neurologic complications of seasonal influenza and 2009 H1N1, and current approaches towards managing these complications., Conclusions: 2009 H1N1-associated acute encephalitis and encephalopathy appear to be variable in severity, including a subset of patients with a malignant clinical course complicated by high morbidity and mortality. Since the H1N1 influenza virus has not been detected in the CSF or brain tissue in patients with this diagnosis, the emerging view is that the host immune response plays a key role in pathogenesis.

We describe two patients with cerebral manifestations of influenza A (H1N1)v. A 13-year-old boy developed severe cerebral oedema and increased intracranial pressure despite medical treatment and external drainage of cerebrospinal fluid. He was treated with bifrontal decompressive craniectomy with good result. A 25-year-old man with a previous kidney transplant developed encephalopathy and convulsions. Magnetic resonance imaging showed encephalitis. The patient fully recovered. The cases demonstrate that influenza A (H1N1)v can cause seriously and potentially life-threatening neurological complications.

Encephalopathy is an uncommon complication of childhood influenza infection, typically recognized during influenza epidemics. Imaging hallmarks include characteristic thalamic lesions, thalamic necrosis and hemispheric edema. We describe a child with acute influenza A associated necrotizing encephalopathy with MR angiographic evidence of significant cerebral vasculopathy and a hemispheric edema pattern consistent with PRES. This case reinforces that significant cerebral vasculopathy can accompany influenza infection and that influenza is a likely trigger for PRES.

Acute encephalopathy is one of the most serious complications of pediatrics viral infections including influenza. It is characterized clinically by rapidly progressive brain damage following viral infection, and pathologically by brain edema in the absence of direct invasion of the virus and inflammatory cells. Recently, it has been classified into several categories according to the clinical characteristics and pathogenesis. In 2009, an outbreak of AH1N1 (swine) influenza was discovered in North America and quickly spread worldwide. During this pandemic, a number of patients with acute encephalopathy have been reported from all over the world. This article reviews the pathogenesis and classification of acute encephalopathy in general and the epidemiological, clinical and pathological features of pandemic flu-associated encephalopathy in comparison with those of seasonal flu-associated encephalopathy.

The swine-origin influenza A (H1N1) virus was responsible for the pandemic infection in 2009. We report a case of encephalitis diagnosed as the H1N1 virus infection in a young child. The H1N1 virus infection can be causative of the encephalitis, as with other influenza virus infections. For patients presenting with influenza-like illness accompanied by mental status changes or seizures, high suspicion for unusual presentations of influenza A virus infection and careful monitoring, including EEG and intracranial pressure monitoring, are essential for reducing complications.

Seasonal influenza virus infection has been associated with a variety of neurologic complications. We report a case of novel influenza A (H1N1) encephalitis in an infant aged 3 months with an upper respiratory infection, who presented seizures. The infection was confirmed in nasopharyngeal aspirate and cerebrospinal fluid. Treatment with oseltamivir was started. He was discharged without any neurologic sequelae.

We report acute encephalopathy associated with influenza A infection in 3 adults. We detected high cerebrospinal fluid (CSF) and plasma concentrations of CXCL8/IL-8 and CCL2/MCP-1 (CSF/plasma ratios > or =3), and interleukin-6, CXCL10/IP-10, but no evidence of viral neuroinvasion. Patients recovered without sequelae. Hyperactivated cytokine response may play a role in pathogenesis.

The aim of this study was to clarify the difference between influenza and non-influenza cases in clinical symptoms, laboratory and neuroimaging findings, and outcome in children with ANE. We retrospectively studied 22 children with ANE. Eleven of them had virological proof of influenza infection and the other 11 were judged as non-influenza infection. There was no significant difference between influenza and non-influenza cases in sex, antipyretics use and neurological symptoms. Although laboratory data were not different between the two groups, brainstem lesions were relatively more frequent in influenza cases than in non-influenza cases. Outcome was not different between the two groups. The results of our study suggest that the pathogenesis of acute necrotizing encephalopathy will not be dependent on infectious agents.

Avian influenza A (H5N1) viruses in birds in parts of Asia, Africa, and Middle East continue to cause human diseases and to pose the threat of human pandemic flu. Pandemic flu is characterized by respiratory symptoms and is a cause of high fatality rates in the younger population. Previous studies have shown that avian influenza A (H5N1) viruses in humans might also target organs other than lungs. Historical records reveal that in 1918, more than 40 million people died due to influenza pandemic; this pandemic was rapidly followed by an epidemic of encephalitis lethargica in 1919. From the mid-1990's, there have been outbreaks of encephalopathy in Japan which appear to be associated with influenza. In this article, neurological complications associated with influenza have been reviewed by taking a closer look at previous influenza pandemics in the 20th century and seasonal influenza epidemics in Japan; this will enhance preparations against human pandemics. In addition, we have also reviewed a few human cases of avian influenza A (H5N1) infection where the central nervous system (CNS) are involved.

The pathology of human influenza has been studied most intensively during the three pandemics of the last century, the last of which occurred in 1968. It is important to revisit this subject because of the recent emergence of avian H5N1 influenza in humans as well as the threat of a new pandemic. Uncomplicated human influenza virus infection causes transient tracheo-bronchitis, corresponding with predominant virus attachment to tracheal and bronchial epithelial cells. The main complication is extension of viral infection to the alveoli, often with secondary bacterial infection, resulting in severe pneumonia. Complications in extra-respiratory tissues such as encephalopathy, myocarditis, and myopathy occur occasionally. Sensitive molecular and immunological techniques allow us to investigate whether these complications are a direct result of virus infection or an indirect result of severe pneumonia. Human disease from avian influenza virus infections is most severe for subtype H5N1, but also has been reported for H7 and H9 subtypes. In contrast to human influenza viruses, avian H5N1 virus attaches predominantly to alveolar and bronchiolar epithelium, corresponding with diffuse alveolar damage as the primary lesion. Viremia and extra-respiratory complications appear to be more common for infections with avian H5N1 virus than with human influenza viruses. Further understanding and comparison of the pathology of human and avian influenza virus infections only can be achieved by directed and careful pathological analysis of additional influenza cases.

The patient in this study was a 43-year-old woman who had become unconscious after contracting influenza virus type A infection. Brain CT showed severe brain swelling. Brain MRI also showed brain edema with no specific abnormality on T2-weighted images. We diagnosed her as having influenza type A virus-associated encephalopahty and treated her with Oseltamivir, methylprednisolone pulse therapy, and a high dose of intravenous immunoglobulins. In addition, we treated her with hypothermia and a high dose of intravenous ATIII because of the severe brain swelling and possibility of DIC. After the treatments, brain swelling had improved, and she regained consciousness without any sequelae. Adult influenza virus-associated encephalopathy is rare. We were able to successfully treat our patient with primary multidisciplinary treatments without causing sequelae.

Influenza-associated encephalopathy is a clinically diverse syndrome and severe cases are not well documented outside Japan. Clinical, pathological and molecular aspects are described of two fatal cases presenting during 2004 and 2005 winter seasons in The Netherlands. Results showed that severe influenza can resemble hemorrhagic shock and encephalopathy syndrome, and proper testing for influenza virus should be considered in similar cases. The failure to detect viral replication in non-pulmonary organs including the brain would support the pathogenesis of this syndrome is based on proinflammatory cytokine responses.

During a 29-month period, 11 (12%) of 92 hospitalized patients with influenza B virus infection presented neurologic manifestations, which included febrile seizure in 4 cases and encephalopathy/encephalitis in 7 cases. Without appropriate antiviral therapy, recovery was uneventful in all but 1 patient, who had neurologic sequelae of quadriplegia and developmental delay.

CD40 ligand (CD40L) is mainly expressed on activated platelets and CD4+T cells, and it can be cleaved from the cell surface, releasing a soluble CD40L (sCD40L). Most sCD40L is derived from activated platelets. A previous paper revealed that the platelet number of patients with influenza virus-associated encephalopathy (IE) was correlated with the outcome. We determined the utility of sCD40L as a predictor for the prognosis of IE. We measured the serum concentration of sCD40L and the platelet number on the day of hospitalization in 34 patients with IE, 16 with influenza virus-associated febrile seizures (IFS), 19 with influenza virus infection without complications (Flu), and 7 with Epstein-Barr virus (EBV) infection. The serum sCD40L concentrations in IE and IFS were significantly lower than those in controls, Flu, and EBV infections. Serum sCD40L concentrations in the IE group were 0.70+/-0.43 ng/ml for deceased patients, 1.73+/-1.36 ng/ml for those with sequelae, and 3.85+/-2.91 ng/ml for those without sequelae. There was no significant difference in platelet number between IE patients with and without sequelae, while the platelet number of deceased patients with IE was significantly lower than in controls, Flu, and IFS. Serum sCD40L concentration on the day of hospitalization was more correlated with the outcome of IE than platelet number. Our findings suggest that the serum sCD40L concentration during acute IE is important for predicting the prognosis at an early stage.

Purpose: To report an unusual case of retinitis caused by influenza virus., Case: A 30-year-old male claimed partial color blindness after recovery from influenza encephalitis. Visual acuity was 0.3 in the right eye and 0.03 in the left. An ophthalmoscopic fundus examination looked normal, but fluorescein angiography revealed granular hyperfluorescence with multiple dark circular lesions at the posterior pole of both eyes. Serological testing revealed an influenza A virus infection. With corticosteroid pulse therapy (3 days) followed by oral methyl prednisolone for 1 month, visual acuity gradually recovered. Over the following 2-year period, visual acuity has recovered to 1.2 in both eyes, but color sensation still remains impaired., Conclusions: Influenza encephalitis can cause visual loss due to retinitis at the posterior pole., (Copyright (c) 2005 S. Karger AG, Basel.)

In southern Vietnam, a four-year-old boy presented with severe diarrhea, followed by seizures, coma, and death. The cerebrospinal fluid contained 1 white cell per cubic millimeter, normal glucose levels, and increased levels of protein (0.81 g per liter). The diagnosis of avian influenza A (H5N1) was established by isolation of the virus from cerebrospinal fluid, fecal, throat, and serum specimens. The patient's nine-year-old sister had died from a similar syndrome two weeks earlier. In both siblings, the clinical diagnosis was acute encephalitis. Neither patient had respiratory symptoms at presentation. These cases suggest that the spectrum of influenza H5N1 is wider than previously thought., (Copyright 2005 Massachusetts Medical Society.)

We report a 4-year-old boy with hyperprolinaemia type II presenting acute encephalopathy associated with influenza virus type A infection. This case suggests that hyperprolinaemia may cause acute encephalopathy under certain conditions.

We addressed the incidence of influenza-associated acute encephalopathy, which is distinct from Reye syndrome, in children in Japan. Eighty-nine children with a mean age of 3.8 years were reported to have developed this disease during eight influenza seasons (December 1994-April 2002) in Hokkaido, Japan. None of them had received aspirin. Most of the patients rapidly became comatose with or without convulsions with a mean interval of 1.7 days from the onset of fever to the onset of central nervous system symptoms. Thirty-three (37.1%) patients died and 17 (19.1%) patients had neurological sequelae. A total of 53 (59.6%) cases were proved to have an influenza virus infection. Interleukin-6 and tumor necrosis factor-alpha were markedly elevated in serum and cerebrospinal fluid samples from two patients who died after a rapid, fulminant course. A post-mortem examination of one fatal case revealed vasogenic brain edema with generalized vasculopathy, suggesting that the generalized impairment of vascular endothelial cells caused by highly activated cytokines plays a central role in the pathophysiology of this disease. We conclude that influenza-associated acute encephalopathy may be an underestimated syndrome and is another reason to promote vaccination against influenza in infants and younger children.

We report the cases of two patients with influenza-associated encephalitis/encephalopathy (IAEE) who presented with mild CNS manifestations and complete recovery within a few days. Initial MR imaging at days 4 and 5 revealed a lesion in the central portion of the splenium of the corpus callosum with a reduced apparent diffusion coefficient (ADC) value, which completely resolved on follow-up studies at day 10. We postulate two possible mechanisms for decreased ADC; namely, intramyelinic edema and an inflammatory infiltrate.

The use of amantadine has been advocated as treatment for influenza A encephalitis despite limited information regarding cerebrospinal fluid concentrations and the pathogenesis of encephalitis associated with influenza virus infections. We report a 2-year-old child with influenza A encephalitis treated with amantadine who achieved a potentially therapeutic concentration in cerebrospinal fluid. Despite this the child developed significant neurologic impairment.

Introduction: Influenza virus outbreaks occur each year, in France, during autumn and winter. Influenza-associated acute encephalitis were reported during epidemics or pandemics. Sporadic cases are rarely identified probably because influenza virus is not searched among etiology of febrile encephalitis., Exegesis: We report a case of influenza-associated encephalitis complicated by adrenal insufficiency in a young woman. Diagnosis was based on seroconversion of serum influenza virus A antibodies (complement fixation test). Follow up of the patient showed a total recovery., Conclusion: Influenza must be searched for any febrile encephalitis occurring during winter. Reverse transcriptase polymerase chain reaction (RT-PCR) on cerebrospinal fluid should be assessed. It is not actually a routine technique and we do not know yet if it is accurate enough for diagnosis. So, it is important to identify influenza virus and obtain documentary evidence concerning neurological impairment. Nevertheless, a better understanding of pathogenesis and use of vaccination are needed to improve prognosis.