Acute encephalopathy with 2009 pandemic flu: comparison with seasonal flu

A nationwide survey of adenovirus-associated encephalitis/encephalopathy in Japan

BACKGROUND

Adenovirus is a major pathogen causing febrile illness among children. It may also cause acute encephalitis/encephalopathy. This study aimed to elucidate the clinical features of adenovirus-associated encephalitis/encephalopathy (AdVE) among children in Japan.

METHODS

A nationwide survey of children with AdVE was conducted. An initial survey was distributed among pediatricians to obtain information about children with AdVE treated between January 2014 and March 2019. A second survey was used to obtain the clinical information of children with AdVE from hospitals that responded to the initial survey and those identified from a literature search of the reported cases. We collected demographic data and information about symptoms of infection, neurological symptoms, laboratory parameters, treatment, and outcomes. Outcomes were determined using the Pediatric Cerebral Performance Category Score.

RESULTS

Clinical information was available for 23 children with a median age of 39 months. Two had preexisting neurological disorders and six had a history of febrile seizures. The outcome was good in 15 patients and poor in eight patients. Serum lactate dehydrogenase, glucose, and ammonia levels were higher among children with a poor outcome compared to those with a good outcome. Clinically mild encephalitis/encephalopathy with a reversible splenial lesion was the most common type (n = 8), followed by acute encephalopathy with biphasic seizures and late reduced diffusion (n = 7).

CONCLUSION

A prior history of febrile seizures was frequent in children with AdVE. Several different subtypes of acute encephalopathy were seen in children with AdVE, and the outcome was poor in those with acute encephalopathy with biphasic seizures and late reduced diffusion and hemorrhagic shock and encephalopathy syndrome. Elevated lactate dehydrogenase, glucose, and ammonia levels on admission were found to correlate with a poor outcome.

Neurologic Complications in Children Hospitalized With Influenza Infections: Prevalence, Risk Factors and Impact on Disease Severity

BACKGROUND

Influenza infection is a common cause of respiratory disease and hospitalization in children. Neurologic manifestations of the infection have been increasingly reported and may have an impact on the severity of the disease. The aim of this study is to describe neurologic events in pediatric patients hospitalized with influenza and identify associated risk factors.

METHODS

Retrospective cohort study which included all hospitalized patients with microbiologic confirmation of influenza disease over 4 epidemic seasons, focusing on neurologic complications. Demographic, laboratory and clinical data, as well as past history, were recorded. Descriptive and analytic statistical study was performed using SPSS and R statistical software.

RESULTS

Two hundred forty-five patients were included. Median age was 21 months (interquartile range, 6-57) and 47.8% had a previous underlying condition. Oseltamivir was administered to 86% of patients, median hospitalization was 4 days (interquartile range, 3-6), and pediatric intensive care unit admission rate 8.9%. Twenty-nine patients (11.8%) developed neurologic events, febrile seizures being the most frequent, followed by nonfebrile seizures and encephalopathy. Status epilepticus occurred in 4 children, and 69.6% of seizures recurred. Patients with a previous underlying condition were at greater risk of developing a neurologic complication [odds ratio (OR), 4.55; confidence interval (CI), 95% 1.23-16.81). Male sex (OR, 3.21; CI 95%, 1.22-8.33), influenza B virus (OR, 2.82; CI 95%, 1.14-7.14) and neurologic events (OR, 3.34; CI 95%, 1.10-10.19) were found to be risk factors for pediatric intensive care unit admission.

CONCLUSIONS

A significant proportion of influenza-related hospitalized patients develop neurologic complications, especially seizures which may be prolonged or recurrent. Previous underlying conditions pose the greatest risk to neurologic events, which increase disease severity.

Encephalitis after influenza and vaccination: a nationwide population-based registry study from Norway

Background

Influenza is known to be associated with various neurological complications, including encephalitis. We conducted a registry-based study to assess the risk of encephalitis after influenza and A(H1N1)pdm09 vaccine.

Methods

Data from Norwegian national health registries during 2008-14 were linked using the unique personal identifiers given to all Norwegian residents (N = 5 210 519). Cox proportional-hazard models with time-varying variables were fitted to estimate hazard ratios (HRs) of encephalitis after influenza and A(H1N1)pdm09 vaccine, using the risk windows 0-7, 0-14, 0-30, 0-60, 0-90 and 0-180 days.

Results

In Norway, 684 172 individuals received an influenza diagnosis and 2793 patients were hospitalized with encephalitis during 2008-14. The risk of encephalitis increased after influenza: HR, 7-day risk window: 47.8 (95% confidence interval (CI): 35.8-63.8), and the HR decreased for longer risk windows; HR, 180-day risk window: 3.8 (95% CI: 3.1-4.7). HR of encephalitis after influenza during the 2009 main pandemic wave using a 7-day risk window was 30.0 (95% CI: 10.8-83.2). We found no differences in the risk of encephalitis after the seasonal influenza compared with influenza during the 2009 main pandemic wave; HR, 7-day risk window: 1.3 (95% CI: 0.4-4.3). A(H1N1)pdm09 vaccine was not associated with the risk of encephalitis: HR, 14-day risk window: 0.6 (95% CI: 0.2-2.1).

Conclusions

There was an increased risk of encephalitis following influenza but not after A(H1N1)pdm09 vaccine. The risk of encephalitis was highest in the first few weeks after influenza.

The Spectrum and Burden of Influenza-Associated Neurological Disease in Children: Combined Encephalitis and Influenza Sentinel Site Surveillance From Australia, 2013-2015

Background

There are few longitudinal studies of seasonal influenza-associated neurological disease (IAND) and none from the Southern Hemisphere.

Methods

We extracted prospectively acquired Australian surveillance data from 2 studies nested within the Paediatric Active Enhanced Disease Surveillance (PAEDS) network: the Influenza Complications Alert Network (FluCAN) study and the Australian Childhood Encephalitis (ACE) study between 2013 and 2015. We described the clinical features and severity of IAND in children, including influenza-associated encephalitis/encephalopathy (IAE). We calculated the proportion of hospitalized influenza that is associated with IAND and IAE, and incidence of IAE.

Results

Over 3 influenza seasons, we identified 54 cases of IAND at 2 tertiary children's hospitals from Australia that accounted for 7.6% of hospitalized influenza. These included 10 cases of IAE (1.4% hospitalized influenza). The mean annual incidence of IAE among Australian children (aged ≤14 years) was 2.8 per 1000000. The spectrum of IAND was broad and included IAE (n = 10) including distinct acute encephalopathy syndromes, simple febrile seizures (n = 14), other seizures (n = 16), acute ataxia (n = 4), and other subacute syndromes (transverse myelitis [n = 1], opsoclonus myoclonus [n = 1]). Two-thirds of children with IAND were aged ≤4 years; less than half had preexisting neurological disease or other risk factors for severe influenza. IAE caused death or neurological morbidity in half of cases.

Conclusions

Seasonal influenza is an important cause of acute neurological disease in Australian children. The spectrum of seasonal IAND appears similar to that described during the 2009 H1N1 pandemic. IAE is associated with high morbidity and mortality.

Differential diagnosis of delirious behavior in children with influenza

Delirious behavior (DB) in children infected with influenza virus is an important symptom associated with encephalopathy. As children with influenza-associated DB with encephalopathy may require therapy whereas children with influenza-associated DB without encephalopathy do not, distinguishing between these conditions is essential. To clarify these differences and identify the most common features of acute encephalopathy, we retrospectively reviewed the clinical course, laboratory data, magnetic resonance imaging (MRI) and electroencephalography (EEG) findings, therapy, and prognosis of 48 children with influenza exhibiting DB. Of the 48 children, 37 and 11 were diagnosed with influenza A and B, respectively. Moreover, 40 were diagnosed with DB without encephalopathy (DBNE group) and 8, with DB with encephalopathy (DBE group). Reversible splenial lesion (RESLE) was detected in 7 patients in the DBNE group, mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) in 2 patients, and a mild form of acute encephalopathy with biphasic seizures and late reduced diffusion in 1 patient in the DBE group. Serum sodium levels <136mEq/L were observed in 28 cases. Disturbance of consciousness was observed in 25 cases, seizure in 20, and slow waves on EEG in 22. Methylprednisolone pulse therapy was administered in 8 cases. No cases of neurological sequelae were observed. Although most of the clinico-radiological features of the DBNE and DBE groups did not differ substantially, marked differences were observed in the age at onset, initial neurological symptoms, duration of DB, rate of seizure, and slowing of background activity on EEG. These differences should be considered when distinguishing between DBNE and DBE in children.

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.

Emerging infections of the central nervous system

Emerging infections affecting the central nervous system often present as encephalitis and can cause substantial morbidity and mortality. Diagnosis requires not only careful history taking, but also the application of newly developed diagnostic tests. These diseases frequently occur in outbreaks stemming from viruses that have mutated from an animal host and gained the ability to infect humans. With globalization, this can translate to the rapid emergence of infectious clusters or the establishment of endemicity in previously naïve locations. Since these infections are often vector borne and effective treatments are almost uniformly lacking, prevention is at least as important as prompt diagnosis and institution of supportive care. In this review, we focus on some of the recent literature addressing emerging and resurging viral encephalitides in the United States and around the world-specifically, West Nile virus, dengue, polio, and cycloviruses. We also discuss new, or "emerging," techniques for the precise and rapid diagnosis of encephalitides.

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.

Acute encephalopathy with pandemic (H1N1) 2009 virus infection

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.