Acute necrotizing encephalopathy during novel influenza A (H1N1) virus infection

Clinical characteristics and risk factors for bilateral lateral geniculate body pathology: a systematic review of the literature

BACKGROUND

Case presentation of acute onset bilateral painless vision loss caused by bilateral infarction of the lateral geniculate bodies (LGB) and a systematic review of the literature.

METHODS

A descriptive case report is presented on a 17-year-old female diagnosed with acute pancreatitis who developed acute onset bilateral painless vision loss. A systematic literature review of cases with bilateral LGB lesions was conducted across three electronic databases (PubMed/PubMed Central/MEDLINE, Scopus, and ScienceDirect). The review was conducted in concordance with PRISMA guidelines and prospectively registered on PROSPERO (CRD42022362491).

RESULTS

The reported 17-year-old female was found to have MRI findings consistent with bilateral hemorrhagic infarction of the LGB and Purtscher-like retinopathy. A systematic literature review of bilateral LGB infarction yielded 23 records for analysis. 19/23 (82.6%) of reported cases occurred in women. Bilateral vision loss was noted in all cases. The average reported age was 27 years old with a range from 2-50. Gastrointestinal pathology (e.g., pancreatitis, gastroenteritis) was present in 8/23 (34.7%) of cases. 8/23 (34.7%) cases had neuroimaging or pathological evidence of hemorrhagic transformation of the infarct. Most cases experienced partial recovery of visual loss; only one case (4.7%) had complete visual recovery. 9/23 (39.1%) cases were reported from the United States and 4/23 (17.3%) from India.

CONCLUSIONS

Bilateral LGB lesion is a rare cause of vision loss, typically caused by systemic diseases and with female preponderance. Purported pathophysiology relates to increased vulnerability of the LGB to ischemic and metabolic stress.

Pathogenesis and Management of Acute Necrotizing Encephalopathy

INTRODUCTION

During the COVID-19 pandemic, many cases of acute necrotizing encephalopathy (ANE) secondary to COVID-19 have been reported. ANE is characterized by a rapid onset, a fulminant course, and low morbidity and fatality rates. Therefore, clinicians need to be vigilant for such disorders, especially during the influenza virus and COVID-19 epidemics.

AREAS COVERED

The authors summarize the most recent studies on the clinical spectrum and treatment essentials of ANE to provide references for prompt diagnosis and improved treatment of this rare but fatal disease.

EXPERT OPINION

ANE is a type of necrotizing lesion of the brain parenchyma. There are two major types of reported cases. One is isolated and sporadic ANE, which is primarily caused by viral infections, particularly influenza and HHV-6 virus. The other type is familial recurrent ANE, which is caused by RANBP2 gene mutations. ANE patients have rapid progression and a very poor prognosis, with acute brain dysfunction occurring within days of viral infection and requiring admission to the intensive care unit. Clinicians still need to investigate and find solutions for the problems of early detection and treatment of ANE.

One-year-old boy with refractory Listeria monocytogenes meningitis due to persistent hypercytokinemia

We had a case of Listeria monocytogenes (LM) meningitis complicated with hypercytokinemia and hemophagocytic lymphohistiocytosis in a healthy 22-month-old boy. He was admitted to our hospital with a fever, vomiting, mild consciousness disturbances, and extraocular muscle paralysis. Magnetic resonance imaging (MRI) revealed bilateral deep white matter lesions. After receiving ampicillin, meropenem, and gentamicin, his cerebrospinal fluid (CSF) culture results turned negative on the third day of hospitalization. However, the fever intermittently persisted, and it took approximately 40 days to completely resolve. During this period, various inflammatory cytokine levels, particularly neopterin, in the blood and CSF remained elevated. Therefore, long-term administration of corticosteroids in addition to antibiotics was required. The use of dexamethasone appeared to be effective for neurological disorders such as consciousness disturbance and extraocular muscle paralysis associated with abnormal brain MRI findings. LM meningitis may present with encephalopathy and persistent fever due to hypercytokinemia. In such cases, corticosteroid therapy should be considered.

A sudden death due to acute necrotizing encephalopathy associated with influenza A virus infection: An autopsy case report

Influenza occasionally causes central nervous system disorders. Acute necrotizing encephalopathy (ANE) is one of the most severe influenza-associated complications, predominantly affecting infants and young children under 5 years of age. We present this case as it involves a very rare complication of influenza infection that is known to have a high rate of mortality. A 5-year-old girl presented with a high fever and convulsions. Her condition deteriorated rapidly, and she died within 24 h. Autopsy revealed extensive brain edema, multifocal perivascular hemorrhage, and necrosis of neurons without inflammatory cell infiltration in the pons and bilateral thalamus. Tests for influenza virus A and antibodies to it were positive. The girl's death was attributed to ANE associated with influenza A infection based on the clinical presentation, the postmortem neuropathology, and identification of the virus. The goal of this report is to draw attention to the potentially serious complications of influenza A infection. We hope that the lethal outcome of this disease will be fully recognized by medical personnel.

An Unusual Case of Acute Hemorrhagic Necrotizing Encephalomyelitis in a COVID-19 Patient

Acute disseminated encephalomyelitis, also known as ADEM, is a rare autoimmune demyelinating disease of the central nervous system that has been correlated with viral infections and vaccinations and has a range of presentations, where it can present as a mild neurological dysfunction or more severe manifestations ending in chronic neurological sequelae or even death; therefore, it is considered to be a diagnostic challenge. We present a case of ADEM diagnosed in a previously healthy male patient with a recent infection of SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2). Early diagnosis and management with intravenous immunoglobulins held the key to a good outcome.

Parameters Indicating Development of Influenza-Associated Acute Necrotizing Encephalopathy: Experiences from a Single Center

Background

Influenza-associated acute necrotizing encephalopathy (IANE) can be lethal and disabling and have a sudden onset and deteriorate rapidly but lacks early diagnostic indicators. We aimed to examine the early clinical diagnostic indicators in children with IANE.

Material/Methods

Acute influenza patients were grouped according to their clinical manifestations: flu alone (FA), flu with febrile seizure (FS), influenza-associated encephalopathy (IAE), and IANE. The clinical features, biomarkers, neuroelectrophysiological results, and neuroimaging examination results were compared.

Results

A total of 31 patients were included (FA (n=4), FS (n=8), IAE (n=14), and IANE (n=5)). The IANE group, whose mean age was 3.7 years, was more likely to show rapid-onset seizure, acute disturbance of consciousness (ADOC), Babinski’s sign, and death/sequela. More patients in the IANE group required tracheal intubation mechanical ventilation and received intravenous immunoglobulins (IVIG) and glucocorticoids. The alanine aminotransferase (ALT), aspartate transaminase (AST), and lactate dehydrogenase (LDH) levels in the IANE group were significantly higher than in the FS and IAE groups. The aquaporin-4 (AQP-4) antibody and malondialdehyde (MDA) levels in the serum and cerebrospinal fluid (CSF) were notably higher in IANE patients in the acute stage compared with FS and IAE patients. All patients in the IANE group had positive neuroimaging findings.

Conclusions

Early clinical warning factors for IANE include rapid-onset seizures in patients under 4 years of age, ADOC, and pathological signs. Increased AQP-4 antibodies and MDA levels in CSF might contribute to early diagnosis. Early magnetic resonance venography (MRV) and susceptibility-weighted imaging (SWI) sequences, or thrombelastography to identify deep vein thrombosis, might indicate clinical deterioration.

Genetic Acute Necrotizing Encephalopathy Associated with RANBP2: Clinical and Therapeutic Implications in Pediatrics

Genetic (also known as familial) acute necrotizing encephalopathy (ANE1) is a rare disease presenting with encephalopathy often following preceding viral febrile illness in patients with a genetic predisposition resulting from a missense mutation in the gene encoding RAN Binding Protein 2 (RANBP2). The acute episode is characterized by deterioration in consciousness, often with focal neurologic deficits and seizures. Additionally, symmetric multifocal brain lesions are seen in the bilateral thalami as well as other characteristic regions, involving both gray and white matter. Prognosis is variable, with a high mortality rate and most surviving patients having persistent neurologic deficits. Early treatment with high dose steroids is associated with a more favorable outcome, however the diagnosis is often overlooked resulting in delayed treatment. The RANBP2 mutation associated with ANE1 causes an incompletely penetrant predisposition to encephalopathy in the setting of febrile illness through a mechanism that remains elusive. There are several non-mutually exclusive hypotheses suggesting possible etiologies for this phenotype based on the many functions of RANBP2 within the cell. These include dysfunctions in nucleocytoplasmic trafficking and intracellular metabolic regulation, as well as cytokine storm, and abnormal distribution of mitochondria. This narrative review explores these key concepts of the RANBP2 mutation and its clinical and therapeutic implications in pediatric populations.

Neurologic Manifestations of Severe Respiratory Viral Contagions

Endemic and pandemic viral respiratory infections have recently emerged as a critical topic of investigation given the recent severe acute respiratory syndrome coronavirus-2 outbreak. Data from such outbreaks indicate that severe systemic comorbidities including acute neurologic illness are associated with illness and lead to significant outcome differences. Herein, we will discuss the neurologic manifestations of severe viral respiratory infections including coronavirus, influenza, respiratory syncytial virus, metapneumovirus, and enterovirus.

Data Sources

PubMed and EMBASE were searched by two independent investigators up to March 2020.

Study Selection

Data selection included preclinical and clinical studies detailing neurologic manifestations of viral respiratory infections.

Data Extraction and Synthesis

Two independent investigators reviewed and extracted the data.

Conclusions

Neurologic manifestations including seizures, status epilepticus, encephalitis, critical illness neuromyopathy, acute disseminated encephalomyelitis, acute necrotizing encephalitis, Guillan-Barré syndrome, transverse myelitis, and acute flaccid myelitis have all been associated with severe viral respiratory infections. Having an understanding of the direct neurotropism of such viruses is imperative to understanding pathogenesis, clinical presentation, and potential treatment paradigms aimed at improving morbidity and mortality.

Acute Encephalitis Syndrome with an Unusual Diagnosis

Four-year old boy was admitted with acute onset of fever with seizures and altered sensorium. His mother had history of contact with influenza A H1N1 virus (H1N1) infection. Blood counts, electrolytes, blood sugar and ammonia were normal. Liver enzymes were mildly elevated. CSF study showed elevated protein, normal sugar and no pleocytosis. Cerebrospinal fluid (CSF) viral panel was negative. Magnetic resonance imaging brain was suggestive of acute necrotizing encephalopathy. His throat swab and sputum polymerase chain reaction was positive for H1N1. He was managed with ventilation, intravenous steroids and other supportive measures. At discharge his sensorium improved but had neurological sequelae. We are presenting this case as this is a very rare complication of H1N1 infection with high rate of mortality. Early supportive measures and steroids/intravenous immunoglobulin may save the patient.

Acute Necrotizing Encephalopathy in Children: a Long Way to Go

BACKGROUND

Acute necrotizing encephalopathy (ANE) is a rare, but potentially life threatening neurological condition in children. This study aimed to investigate its clinical spectrum, diagnostic and therapeutic dilemma, and prognosis.

METHODS

Twelve children with ANE were included in the study. The diagnosis was made by clinical and radiological characteristics from January 1999 to December 2017 and their clinical data were retrospectively analyzed.

RESULTS

A total of 12 children aged 6 to 93 months at onset (5 male: 7 female) were evaluated. The etiology was found in 4 of them (influenza A, H1N1; coxsackie A 16; herpes simplex virus; and RANBP2 gene/mycoplasma). The most common initial presentations were seizures (67%) and altered mental status (58%). The majority of the subjects showed elevation of aspartate aminotransferase/alanine aminotransferase with normal ammonia and increased cerebrospinal fluid protein without pleocytosis. Magnetic resonance imaging revealed increased T2 signal density in bilateral thalami in all patients, but the majority of the subjects (67%) also had lesions in other areas including tegmentum and white matter. Despite the aggressive immunomodulatory treatments, the long-term outcome was variable. One child and two sisters with genetic predisposition passed away.

CONCLUSION

ANE is a distinctive type of acute encephalopathy with diverse clinical spectrum. Even though the diagnostic criteria are available, they might not be watertight. In addition, treatment options are still limited. Further studies for better outcome are needed.

Neurologic Manifestations of Influenza A(H3N2) Infection in Children During the 2016-2017 Season

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.

Deep cerebral venous thrombosis mimicking influenza-associated acute necrotizing encephalopathy: a case report

Background

Acute necrotizing encephalopathy is one of the most devastating neurological complications of influenza virus infection. Acute necrotizing encephalopathy preferentially affects the thalamus bilaterally, as does deep cerebral venous thrombosis, which can lead to misdiagnosis.

Case presentation

A 52-year-old Japanese woman infected with seasonal influenza B virus presented to the emergency care unit in our hospital with progressive alteration of her level of consciousness. Bilateral thalamic lesions were demonstrated by magnetic resonance imaging, leading to a tentative diagnosis of acute necrotizing encephalopathy. However, she had deep cerebral venous thrombosis, and the presence of diminished signal and enlargement of deep cerebral veins on T2*-weighted imaging contributed to a revised diagnosis of deep cerebral venous thrombosis. Anticoagulant therapy was initiated, leading to her gradual recovery, with recanalization of the deep venous system and straight sinus.

Conclusions

To the best of our knowledge, these results represent the first report of deep cerebral venous thrombosis associated with influenza infection. It is clinically important to recognize that deep cerebral venous thrombosis, although rare, might be one of the neurological complications of influenza infection. In the presence of bilateral thalamic lesions in patients with influenza infection, deep cerebral venous thrombosis should be considered in addition to acute necrotizing encephalopathy. Delays in diagnosis and commencement of anticoagulant therapy can lead to unfavorable outcomes.

Successful Treatment of Influenza-Associated Acute Necrotizing Encephalitis in an Adult Using High-Dose Oseltamivir and Methylprednisolone: Case Report and Literature Review

A case of influenza-associated acute necrotizing encephalitis (ANE) is described in an otherwise healthy adult. The patient was treated successfully with a combination of high-dose methylprednisolone and high-dose oseltamivir. The patient relapsed after discontinuing 150 mg twice daily oseltamivir but quickly improved and eventually recovered after reinitiation of high-dose oseltamivir for an additional 2 weeks. The clinical presentation, pathogenesis, and treatment of influenza-associated ANE is reviewed. The use of high-dose oseltamivir in combination with methylprednisolone may offer additional therapeutic benefit for this rare and poorly understood complication of influenza infection.

Successful Treatment of Influenza-Associated Acute Necrotizing Encephalitis in an Adult Using High-Dose Oseltamivir and Methylprednisolone: Case Report and Literature Review

A case of influenza-associated acute necrotizing encephalitis (ANE) is described in an otherwise healthy adult. The patient was treated successfully with a combination of high-dose methylprednisolone and high-dose oseltamivir. The patient relapsed after discontinuing 150 mg twice daily oseltamivir but quickly improved and eventually recovered after reinitiation of high-dose oseltamivir for an additional 2 weeks. The clinical presentation, pathogenesis, and treatment of influenza-associated ANE is reviewed. The use of high-dose oseltamivir in combination with methylprednisolone may offer additional therapeutic benefit for this rare and poorly understood complication of influenza infection.

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 necrotizing encephalopathy: an underrecognized clinicoradiologic disorder

Acute necrotizing encephalopathy (ANE) is a rare but distinctive type of acute encephalopathy with global distribution. Occurrence of ANE is usually preceded by a virus-associated febrile illness and ensued by rapid deterioration. However, the causal relationship between viral infections and ANE and the exact pathogenesis of ANE remain unclear; both environmental and host factors might be involved. Most cases of ANE are sporadic and nonrecurrent, namely, isolated or sporadic ANE; however, few cases are recurrent and with familial episodes. The recurrent and familial forms of ANE were found to be incompletely autosomal-dominant. Further the missense mutations in the gene encoding the nuclear pore protein Ran Binding Protein 2 (RANBP2) were identified. Although the clinical course and the prognosis of ANE are diverse, the hallmark of neuroradiologic manifestation of ANE is multifocal symmetric brain lesions which are demonstrated by computed tomography (CT) or magnetic resonance imaging (MRI). The treatment of ANE is still under investigation. We summarize the up-to-date knowledge on ANE, with emphasis on prompt diagnosis and better treatment of this rare but fatal disease.

Neurological events related to influenza A (H1N1) pdm09

OBJECTIVES

To review neurological complications after the influenza A (H1N1) pdm09, highlighting the clinical differences between patients with post-vaccine or viral infection.

DESIGN

A search on Medline, Ovid, EMBASE, and PubMed databases using the keywords “neurological complications of Influenza AH1N1” or “post-vaccine Influenza AH1N1.”

SETTING

Only papers written in English, Spanish, German, French, Portuguese, and Italian published from March 2009 to December 2012 were included.

SAMPLE

We included 104 articles presenting a total of 1636 patient cases. In addition, two cases of influenza vaccine-related neurological events from our neurological care center, arising during the period of study, were also included.

MAIN OUTCOME MEASURES

Demographic data and clinical diagnosis of neurological complications and outcomes: death, neurological sequelae or recovery after influenza A (H1N1) pdm09 vaccine or infection.

RESULTS

The retrieved cases were divided into two groups: the postvaccination group, with 287 patients, and the viral infection group, with 1349 patients. Most patients in the first group were adults. The main neurological complications were Guillain-Barre syndrome (GBS) or polyneuropathy (125), and seizures (23). All patients survived. Pediatric patients were predominant in the viral infection group. In this group, 60 patients (4.7%) died and 52 (30.1%) developed permanent sequelae. A wide spectrum of neurological complications was observed.

CONCLUSIONS

Fatal cases and severe, permanent, neurological sequelae were observed in the infection group only. Clinical outcome was more favorable in the post-vaccination group. In this context, the relevance of an accurate neurological evaluation is demonstrated for all suspicious cases, as well as the need of an appropriate long-term clinical and imaging follow-up of infection and post-vaccination events related to influenza A (H1N1) pdm09, to clearly estimate the magnitude of neurological complications leading to permanent disability.

Clinical and MRI features of neurological complications after influenza A (H1N1) infection in critically ill children

BACKGROUND

Influenza A (H1N1) can cause severe neurological complications.

OBJECTIVE

The purpose of this study was to analyze clinical and MRI features of neurological complications after H1N1 infection in critically ill children.

MATERIALS AND METHODS

We retrospectively analyzed clinical and neuroimaging findings in 17 children who were hospitalized in an intensive care unit with severe neurological complications after H1N1 infection in South China between September 2009 and December 2011. All children underwent pre- and post-contrast-enhanced brain MRI. Postmortem studies were performed in two children.

RESULTS

Six children died, five because of acute necrotizing encephalopathy (ANE) and one because of intracranial fungal infection. Eleven recovered; their manifestations of H1N1 were meningitis (3), encephalitis (1) and influenza encephalopathy (7). MRI features of ANE included multiple symmetrical brain lesions demonstrating prolonged T1 and T2 signal in the thalami, internal capsule, lenticular nucleus and pontine tegmentum. Postmortem MRI in two children with acute necrotizing encephalopathy showed diffuse prolonged T1 and T2 signal in the bilateral thalami, brainstem deformation and tonsillar herniation.

CONCLUSION

Fatal neurological complications in children after H1N1 infection include ANE and opportunistic fungal infection. MRI is essential for identification of neurological complications and for clinical evaluation.

Novel Influenza A (H1N1)-Associated Acute Necrotizing Encephalopathy: A Case Report

Several cases of acute necrotizing encephalopathy (ANE) with influenza A (H1N1) have been reported to date. The prognosis of ANE associated with H1N1 is variable; some cases resulted in severe neurologic complication, whereas other cases were fatal. Reports mostly focused on the diagnosis of ANE with H1N1 infection, rather than functional recovery. We report a case of ANE with H1N1 infection in a 4-year-old Korean girl who rapidly developed fever, seizure, and altered mentality, as well as had neurologic sequelae of ataxia, intentional tremor, strabismus, and dysarthria. Brain magnetic resonance imaging showed lesions in the bilateral thalami, pons, and left basal ganglia. To our knowledge, this is the first report of ANE caused by H1N1 infection and its long-term functional recovery in Korea.

Management of influenza infection in solid-organ transplant recipients: consensus statement of the Group for the Study of Infection in Transplant Recipients (GESITRA) of the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC) and the Spanish Network for Research in Infectious Diseases (REIPI)

BACKGROUND

Solid organ transplant (SOT) recipients are at greater risk than the general population for complications and mortality from influenza infection.

METHODS

Researchers and clinicians with experience in SOT infections have developed this consensus document in collaboration with several Spanish scientific societies and study networks related to transplant management. We conducted a systematic review to assess the management and prevention of influenza infection in SOT recipients. Evidence levels based on the available literature are given for each recommendation. This article was written in accordance with international recommendations on consensus statements and the recommendations of the Appraisal of Guidelines for Research and Evaluation II (AGREE II).

RESULTS

Recommendations are provided on the procurement of organs from donors with suspected or confirmed influenza infection. We highlight the importance of the possibility of influenza infection in any SOT recipient presenting upper or lower respiratory symptoms, including pneumonia. The importance of early antiviral treatment of SOT recipients with suspected or confirmed influenza infection and the necessity of annual influenza vaccination are emphasized. The microbiological techniques for diagnosis of influenza infection are reviewed. Guidelines for the use of antiviral prophylaxis in inpatients and outpatients are provided. Recommendations for household contacts of SOT recipients with influenza infection and health care workers in close contact with transplant patients are also included. Finally antiviral dose adjustment guidelines are presented for cases of impaired renal function and for pediatric populations.

CONCLUSIONS

The latest scientific information available regarding influenza infection in the context of SOT is incorporated into this document.

Cortical vision loss as a prominent feature of H1N1 encephalopathy

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.

Severe form of encephalopathy associated with 2009 pandemic influenza A (H1N1) in Japan

BACKGROUND

Every year, an estimated 200-500 children in Japan develop influenza-associated encephalopathy (IAE), and 10-30% of these children die.

OBJECTIVE

To clarify the clinical features of a severe form of acute encephalopathy seen with 2009 pandemic influenza A (H1N1).

STUDY DESIGN

This retrospective survey examined 20 children with acute encephalopathy associated with the 2009 pandemic influenza A (H1N1) who died or were in a prolonged deep coma with a flat electroencephalogram tracing and loss of spontaneous respiration. We obtained demographic, clinical, laboratory, and neuroimaging data through interviews with the attending physicians and chart reviews.

RESULTS

Subjects were 13 boys and seven girls. Their median age was 45 (range 11-200) months. Five patients had one or more pre-existing conditions. Acute encephalopathy developed within 2 days after influenza onset in 16 patients. As the initial neurological symptom, delirious behavior was seen in six children, and brief seizures in six. Eighteen patients were comatose within 6h of the onset of encephalopathy. Marked brain edema on computed tomography (CT) was seen in all but one patient. Brainstem lesions on CT were recognized in 12 patients. Sixteen patients died 0-45 (median 2.5) days after the onset of acute encephalopathy, and the others remained in deep comas without spontaneous respiration.

CONCLUSIONS

The clinical course of the patients was characterized by an onset with mild neurological symptoms and rapid deterioration of consciousness into coma. Head CT revealed marked cerebral edema, often associated with brainstem lesions.

Post-marketing assessment of neuropsychiatric adverse events in influenza patients treated with oseltamivir: an updated review

A 2008 review by our group concluded that the risk of neuropsychiatric adverse events (NPAEs) in influenza patients was not increased by oseltamivir exposure, and did not identify any mechanism by which oseltamivir or its metabolites could cause or worsen such events. The current article reviews new information on this topic. Between September 16, 2007 and May 15, 2010, 1,805 spontaneously-reported NPAEs were identified in 1,330 patients receiving oseltamivir: 767 (42.5%) from Japan, 296 (16.4%) from the USA, and 742 (41.1%) from other countries. NPAEs were more common in children: 1,072 (59.4%) events were in those aged ≤16 years. NPAEs often occurred within 48 h of treatment initiation (953 events; 52.8%). Nearly half of the events were serious in nature (838; 46.4%). The three largest categories of events were abnormal behavior (457 events, 25.3%), miscellaneous psychiatric events (370; 20.5%), and delusions/perceptual disturbances (316 events, 17.5%). A total of 1,545 events (85.6%) in eight different categories were considered to be delirium or delirium-like. Twenty-eight suicide-related events were reported. A US healthcare claims database analysis showed that the risk of NPAEs in 7,798 oseltamivir-treated patients was no higher than that in 10,411 patients not on antivirals, but a study on oseltamivir and abnormal behavior in Japan was less conclusive. NPAE frequency in oseltamivir-exposed Japanese and Taiwanese children with influenza was the same as in unexposed children. New analysis of the UK General Practice Research Database showed that the relative adjusted risk of NPAEs in influenza patients was 2.18-times higher than in the general population. Other epidemiology studies report frequent occurrence of encephalitis and similar disorders in influenza patients independently of oseltamivir exposure. The new data support the findings of the original assessment. Evidence suggests that influenza-related encephalopathies are caused by influenza-induced inflammatory responses, but more work is needed to confirm the underlying mechanisms.

Neurologic complications of influenza A(H1N1)pdm09: surveillance in 6 pediatric hospitals

OBJECTIVE

We sought to determine the range and extent of neurologic complications due to pandemic influenza A (H1N1) 2009 infection (pH1N1'09) in children hospitalized with influenza.

METHODS

Active hospital-based surveillance in 6 Australian tertiary pediatric referral centers between June 1 and September 30, 2009, for children aged <15 years with laboratory-confirmed pH1N1'09.

RESULTS

A total of 506 children with pH1N1'09 were hospitalized, of whom 49 (9.7%) had neurologic complications; median age 4.8 years (range 0.5-12.6 years) compared with 3.7 years (0.01-14.9 years) in those without complications. Approximately one-half (55.1%) of the children with neurologic complications had preexisting medical conditions, and 42.8% had preexisting neurologic conditions. On presentation, only 36.7% had the triad of cough, fever, and coryza/runny nose, whereas 38.7% had only 1 or no respiratory symptoms. Seizure was the most common neurologic complication (7.5%). Others included encephalitis/encephalopathy (1.4%), confusion/disorientation (1.0%), loss of consciousness (1.0%), and paralysis/Guillain-Barré syndrome (0.4%). A total of 30.6% needed intensive care unit (ICU) admission, 24.5% required mechanical ventilation, and 2 (4.1%) died. The mean length of stay in hospital was 6.5 days (median 3 days) and mean ICU stay was 4.4 days (median 1.5 days).

CONCLUSIONS

Neurologic complications are relatively common among children admitted with influenza, and can be life-threatening. The lack of specific treatment for influenza-related neurologic complications underlines the importance of early diagnosis, use of antivirals, and universal influenza vaccination in children. Clinicians should consider influenza in children with neurologic symptoms even with a paucity of respiratory symptoms.

Influenza A H1N1 Related Acute Necrotizing Encephalopathy: Radiological Findings in Adulthood

In 2009 a novel swine-origin Influenza A H1N1 virus was identified in Mexico and Southern California. Since it was first recognized, neurological complications including acute necrotizing encephalopathy (ANE) have been globally documented in association with this viral infection. ANE is mostly known to occur in the paediatric population. We describe a fatal case of ANE in a previously healthy 40-year-old man infected with influenza A H1N1 virus presenting with severe neurologic decline. Computed tomography (CT) scan and magnetic resonance imaging (MRI) findings were consistent with ANE. CT and MR findings typically documented in paediatric cases of ANE - including bilateral thalamic necrosis with petechial hemorrhage - have been seldom described in adulthood.

Acute disseminated encephalomyelitis following 2009 H1N1 influenza vaccine

Acute disseminated encephalomyelitis (ADEM) is an immune-mediated inflammatory disorder of the central nervous system. We describe a previously healthy 2-year-old boy with ADEM, who exhibited high fever, lethargy, and recurrent seizures at 25 days after H1N1 influenza vaccination. To our knowledge, there has been only one report of ADEM following the 2009 H1N1 influenza vaccine, although such vaccination is accompanied with optic neuritis apart from this case. Thus, this is the first case of ADEM without optic neuritis, following the 2009 H1N1 influenza vaccination. Although vaccine-associated ADEM remains rare, the increasing number of influenza vaccinations might increase the incidence of ADEM. We still need to pay attention to the occurrence of ADEM and treat patients with steroid therapy.

Acute encephalopathy with 2009 pandemic flu: comparison with seasonal flu

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.

Influenza virus pathophysiology and brain invasion in mice with functional and dysfunctional Mx1 genes

Mice with a dysfunctional myxovirus resistance-1 (dMx1) gene transport intranasally-instilled PR8 influenza virus to the olfactory bulb (OB) within 4 h post-infection. To determine if the presence of a functional Mx1 (fMx1) gene would influence this brain viral localization and/or disease, we infected mature C57BL/6 dMx1 and fMx1 mice under the same conditions and observed sickness behaviors, viral nucleoprotein (NP) RNA expression and innate immune mediator (IIM) mRNA expression in selected tissues at 15 and 96 h post-infection. Virus invaded the OB and lungs comparably in both sub-strains at 15 and 96 h as determined by nested PCR. In contrast, virus was present in blood and somatosensory cortex of dMx1, but not fMx1 mice at 96 h. At 15 h, sickness behaviors were comparable in both sub-strains. By 96 h dMx1, but not fMx1, were moribund. In both 15 and 96 h lungs, viral NP was significantly elevated in the dMx1 mice compared to the fMx1 mice, as determined by quantitative PCR. OB expression of most IIM mRNAs was similar at both time periods in both sub-strains. In contrast, lung IIM mRNAs were elevated in fMx1 at 15 h, but by 96 h were consistently reduced compared to dMx1 mice. In conclusion, functional Mx1 did not alter OB invasion by virus but attenuated illness compared to dMx1 mice. Inflammation was similar in OBs and lungs of both strains at 15 h but by 96 h it was suppressed in lungs, but not in OBs, of fMx1 mice.

Fatal H1N1-Related Acute Necrotizing Encephalopathy in an Adult

Acute necrotizing encephalopathy (ANE) is a severe neurological complication of influenza infection, including H1N1 influenza. Many cases of ANE have been reported in the pediatric literature, but very few cases have been described in adults. The cause of ANE remains unknown-the influenza virus is not known to be neurotropic, and evidence of direct viral involvement of the central nervous system (CNS) has not been demonstrated in the limited cases of ANE in which pathological specimens have been obtained. Here we report a fatal case of ANE from H1N1 influenza infection in an adult. Neuroimaging and postmortem analysis both showed widespread brain edema, necrosis, and hemorrhage, but molecular studies and postmortem pathology revealed no evidence of direct viral involvement of the CNS. This case of fatal ANE in an adult is consistent with the hypothesis generated from pediatric cases that the host immune response, and not direct viral invasion of the CNS, is responsible for pathogenesis of ANE.

Neurological complications and pandemic influenza A (H1N1) virus infection

AIM

To report on a different clinical course of pandemic influenza A (H1N1) infection among children who were neurologically impaired before the acute onset of the disease, in comparison with children who were neurologically intact.

METHODS

In a period of 6 months, six children with neurological complications associated with pandemic A (H1N1) infection were identified in a single institution paediatric emergency room. The children suffered from seizures or altered mental status during pandemic A (H1N1) infection. All children underwent extensive clinical and laboratory assessment. Three children were neurologically impaired before the acute onset of the H1N1 infection. The other three were neurologically intact before the acute viral infection.

RESULTS

In all six patients, pandemic influenza A (H1N1) viral RNA was detected in nasopharyngeal specimens but none in the cerebrospinal fluid. Five children fully recovered or returned to baseline at discharge. The clinical course of the disease and recovery were different between the children who were neurologically impaired before the acute viral infection and those who were neurologically intact.

CONCLUSIONS

It is possible that children with various neurological conditions are in a higher risk to develop further neurological complications during pandemic influenza A (H1N1) infection.

Neurological complications of pandemic influenza A H1N1 2009 infection: European case series and review

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.

Pediatric neurological complications of 2009 pandemic influenza A (H1N1)

OBJECTIVE

To analyze the spectrum of neurological manifestations in children hospitalized with pandemic influenza A H1N1 virus of 2009 (pH1N1).

DESIGN

Retrospective case series of children hospitalized from May 1, 2009, through November 30, 2009.

SETTING

Tertiary-care children's hospital in Colorado.

PATIENTS

All hospitalized patients with pH1N1 with neurological consult or diagnosis, lumbar puncture, electroencephalogram, or neuroimaging were selected as suspected cases. These were systematically reviewed and selected for final analysis if confirmed by pre-established definitions as a neurological complication.

RESULTS

Of 307 children with pH1N1, 59 were selected as having suspected cases of neurological complications. Twenty-three children were confirmed to have a neurological complication. Of these 23, 15 (65%) required intensive care monitoring. The median length of stay was 4 days. Seventeen (74%) had a preexisting neurological diagnosis. The most common manifestation was seizure with underlying neurological disease (in 62% of cases) followed by encephalopathy with or without neuroimaging changes (in 26% of cases). Results from a lumbar puncture showed elevated protein levels in 3 of 6 patients but no significant pleocytosis. Seven of the 9 electroencephalograms showed diffuse slowing, and findings from magnetic resonance imaging were abnormal in 5 of 6 children. Deaths occurred in 13% of patients, and short-term disability in 22%.

CONCLUSIONS

Children infected with pH1N1 presented with a wide spectrum of neurological manifestations, which occurred primarily in individuals with preexisting neurological conditions. These individuals had a severe disease course, evidenced by need for intensive care services and relatively high rates of mortality or neurological disability. Children with underlying neurological conditions should be particularly targeted for influenza prevention and aggressive supportive treatment at the onset of influenzalike symptoms.

The interplay of infection and genetics in acute necrotizing encephalopathy

PURPOSE OF REVIEW

Acute necrotizing encephalopathy (ANE) presents with fulminant encephalopathy and characteristic brain lesions following viral infection. The rarity and unpredictability of the disorder have significantly impaired its study. Growing recognition of ANE and the discovery of causative missense mutations in the nuclear pore gene RANBP2 give promising steps toward unraveling this disease. This review summarizes recent advances of clinical and scientific understanding of ANE.

RECENT FINDINGS

Inflammatory factors participate in the pathogenesis of ANE, but the lack of difference between influenza and noninfluenza ANE focuses attention on the abnormal host response as causative. Early treatment with steroids provides the best outcome for patients who do not have brainstem lesions. Missense mutations in RANBP2 cause the majority of familial and recurrent ANE cases, but other single-gene causes of ANE are possible for familial, recurrent, and sporadic cases.

SUMMARY

Early recognition and systematic evaluation of ANE are necessary. Modeling ANE as a genetic disorder may provide the most immediate gains in the understanding and treatment of ANE and related disorders.