In search of encephalitis etiologies: diagnostic challenges in the California Encephalitis Project, 1998-2000

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

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

Use of clinical and neuroimaging characteristics to distinguish temporal lobe herpes simplex encephalitis from its mimics

BACKGROUND

We describe the spectrum of etiologies associated with temporal lobe (TL) encephalitis and identify clinical and radiologic features that distinguish herpes simplex encephalitis (HSE) from its mimics.

METHODS

We reviewed all adult cases of encephalitis with TL abnormalities on magnetic resonance imaging (MRI) from the California Encephalitis Project. We evaluated the association between specific clinical and MRI characteristics and HSE compared with other causes of TL encephalitis and used multivariate logistic modeling to identify radiologic predictors of HSE.

RESULTS

Of 251 cases of TL encephalitis, 43% had an infectious etiology compared with 16% with a noninfectious etiology. Of infectious etiologies, herpes simplex virus was the most commonly identified agent (n = 60), followed by tuberculosis (n = 8) and varicella zoster virus (n = 7). Of noninfectious etiologies, more than half (n = 21) were due to autoimmune disease. Patients with HSE were older (56.8 vs 50.2 years; P = .012), more likely to be white (53% vs 35%; P = .013), more likely to present acutely (88% vs 64%; P = .001) and with a fever (80% vs 49%; P < .001), and less likely to present with a rash (2% vs 15%; P = .010). In a multivariate model, bilateral TL involvement (odds ratio [OR], 0.38; 95% confidence interval [CI], .18-.79; P = .010) and lesions outside the TL, insula, or cingulate (OR, 0.37; 95% CI, .18-.74; P = .005) were associated with lower odds of HSE.

CONCLUSIONS

In addition to HSE, other infectious and noninfectious etiologies should be considered in the differential diagnosis for TL encephalitis, depending on the presentation. Specific clinical and imaging features may aid in distinguishing HSE from non-HSE causes of TL encephalitis.

Influence of Malnutrition on Adverse Outcome in Children with Confirmed or Probable Viral Encephalitis: A Prospective Observational Study

A prospective observational study was conducted in a tertiary care teaching hospital from August 2008 to August 2009 to explore the independent predictors of adverse outcome in the patients with confirmed/probable viral encephalitis. The primary outcome variable was the incidence of adverse outcomes defined as death or severe neurological deficit such as loss of speech, motor deficits, behavioural problems, blindness, and cognitive impairment. Patients with confirmed or probable viral encephalitis were classified into two groups based on their Z-score of weight-for-age as per WHO growth charts. Group I. Patients with confirmed or probable viral encephalitis with weight-for-age (W/A) Z-scores below −2SD were classified as undernourished. Group II. Patients with confirmed or probable viral encephalitis were classified as having normal nutritional status (weight-for-age Z-score >−2SD). A total of 114 patients were classified as confirmed or probable viral encephalitis based on detailed investigations. On multivariate logistic regression, undernutrition (adjusted OR: 5.05; 95% CI: 1.92 to 13.44) and requirement of ventilation (adjusted OR: 6.75; 95% CI: 3.63 to 77.34) were independent predictors of adverse outcomes in these patients. Thus, the results from our study highlight that the association between undernutrition and adverse outcome could be extended to the patients with confirmed/probable viral encephalitis.

Child and adult forms of human herpesvirus 6 encephalitis: looking back, looking forward

PURPOSE OF REVIEW

This review evaluates publications on human herpesvirus 6 (HHV-6) encephalitis recognizing firstly that HHV-6A and HHV-6B are separate species with differing properties, and secondly the phenomenon of chromosomal integration; this occurs in a minority of persons and the complete viral genome of either HHV-6A or HHV-6B is present in every nucleated cell in the body. Although chromosomal integration has not been associated with disease, the resulting very high level of viral DNA in human tissues and blood has sometimes been wrongly misinterpreted as active infection.

RECENT FINDINGS

No disease has been linked to HHV-6A, whereas HHV-6B may cause encephalitis. Encephalitis due to primary HHV-6B infection in young children is commonly reported from Japan, but very rarely elsewhere in the world, suggesting a genetic predisposition. Reports of HHV-6A or HHV-6B encephalitis in immunocompetent older children/adults are most likely due to chromosomal integration and not active infection. HHV-6B reactivation is well established as causing limbic encephalitis after haematopoietic stem cell transplantation, particularly after receipt of cord blood; the outcome is poor and preventive strategies are ineffective.

SUMMARY

Understanding the pathophysiology of HHV-6B encephalitis remains incomplete, especially regarding young children. Clinical trials of antiviral therapy are warranted for treatment and prevention of HHV-6B encephalitis after transplantation.

Neuroepidemiology and the epidemiology of viral infections of the nervous system

The field of neurovirology will undoubtedly experience evolution and change in the years to come. The epidemiology of viral CNS diseases continues to change, and as our understanding of the pathogenesis and pathophysiology associated with viral agents grows, so does our understanding of the behavior of these pathogens among populations. The appearance of viral pathogens in newsettings, new or unrecognized modes of transmission,and the emergence of previously unrecognized pathogens will continue to challenge our laboratory diagnostic and epidemiologic capabilities. However, each lesson that is learned from this evolving epidemiology will hopefully result in improved surveillance, diagnostic,and treatment and prevention capabilities.

Herpes simplex encephalitis in Iceland 1987-2011

Herpes simplex encephalitis (HSE) is a serious disease with 10-20% mortality and high rate of neuropsychiatric sequelae. This study is a long-term, nationwide study in a single country, Iceland. Clinical data were obtained from patient records and from DNA PCR and antibody assays of CSF. Diagnosis of HSE was classified as definite, possible or rejected based on symptoms, as well as virological, laboratory and brain imaging criteria. A total of 30 definite cases of HSE were identified during the 25 year period 1987-2011 corresponding to incidence of 4.3 cases/106 inhabitants/year. Males were 57% of all patients, median age 50 years (range, 0-85). Fever (97%), cognitive deficits (79%), impaired consciousness (79% with GCS < 13), headache (55%) and seizures (55%) were the most common symptoms. Brain lesions were found in 24 patients (80%) by MRI or CT. All patients received intravenous acyclovir for a mean duration of 20 days. Three patients (10%) died within one year and 21/28 pts (75%) had a Karnofsky performance score of <70% with memory loss (59%), dysphasia (44%), frontal symptoms (44%) and seizures (30%) as the most frequent sequelae. Mean delay from onset of symptoms to treatment was 6 days; this was associated with adverse outcome. In conclusion, the incidence of `HSE is higher than recently reported in a national registry study from Sweden. Despite advances in rapid diagnosis and availability of treatment of HSE, approximately three of every four patients die or are left with serious neurological impairment.

Trends in encephalitis-associated deaths in the United States, 1999-2008

BACKGROUND

While encephalitis may be caused by numerous infectious, immune and toxic processes, the etiology often remains unknown.

METHODS

We analyzed multiple cause-of-death mortality data during 1999-2008 for the USA, using the 10th revision of International Classification of Diseases codes for encephalitis, listed anywhere on the death record, including 'specified' and 'unspecified' encephalitis. Annual and average annual age-adjusted and age-specific death rates were calculated.

RESULTS

For 1999-2008, 12,526 encephalitis-associated deaths were reported with 68.5% as unspecified encephalitis. The average annual age-adjusted encephalitis-associated death rate was 4.3 per 1 million persons, 1.3 for specified and 2.9 for unspecified encephalitis. Annual encephalitis-associated death rates had a significant downward trend (p < 0.01). The most common specified encephalitis deaths were herpesviral encephalitis (36.7%), Toxoplasma meningoencephalitis (27.8%) and Listeria meningitis/meningoencephaltis (6.8%). HIV was colisted with 15.0% of encephalitis-associated deaths, 58.4% of these with a specified code.

CONCLUSION

Encephalitis-associated death rates decreased during 1999-2008, and herpesvirus was the most commonly identified infectious agent associated with encephalitis deaths. The high proportion of unspecified encephalitis deaths highlights the continued challenge of laboratory confirmation for causes of encephalitis and the importance of monitoring trends to assess the impact of new diagnostics and guide potential interventions.

Actionable diagnosis of neuroleptospirosis by next-generation sequencing

A 14-year-old boy with severe combined immunodeficiency presented three times to a medical facility over a period of 4 months with fever and headache that progressed to hydrocephalus and status epilepticus necessitating a medically induced coma. Diagnostic workup including brain biopsy was unrevealing. Unbiased next-generation sequencing of the cerebrospinal fluid identified 475 of 3,063,784 sequence reads (0.016%) corresponding to leptospira infection. Clinical assays for leptospirosis were negative. Targeted antimicrobial agents were administered, and the patient was discharged home 32 days later with a status close to his premorbid condition. Polymerase-chain-reaction (PCR) and serologic testing at the Centers for Disease Control and Prevention (CDC) subsequently confirmed evidence of Leptospira santarosai infection.

Better tests, better care: improved diagnostics for infectious diseases

In this IDSA policy paper, we review the current diagnostic landscape, including unmet needs and emerging technologies, and assess the challenges to the development and clinical integration of improved tests. To fulfill the promise of emerging diagnostics, IDSA presents recommendations that address a host of identified barriers. Achieving these goals will require the engagement and coordination of a number of stakeholders, including Congress, funding and regulatory bodies, public health agencies, the diagnostics industry, healthcare systems, professional societies, and individual clinicians.

Deep sequencing to identify the causes of viral encephalitis

Deep sequencing allows for a rapid, accurate characterization of microbial DNA and RNA sequences in many types of samples. Deep sequencing (also called next generation sequencing or NGS) is being developed to assist with the diagnosis of a wide variety of infectious diseases. In this study, seven frozen brain samples from deceased subjects with recent encephalitis were investigated. RNA from each sample was extracted, randomly reverse transcribed and sequenced. The sequence analysis was performed in a blinded fashion and confirmed with pathogen-specific PCR. This analysis successfully identified measles virus sequences in two brain samples and herpes simplex virus type-1 sequences in three brain samples. No pathogen was identified in the other two brain specimens. These results were concordant with pathogen-specific PCR and partially concordant with prior neuropathological examinations, demonstrating that deep sequencing can accurately identify viral infections in frozen brain tissue.

Meningoencephalitis due to adenovirus in a healthy infant mimicking severe bacterial sepsis

We present the case of a previously healthy 15-month-old girl with acute adenovirus infection who had features of severe bacterial sepsis and meningitis. Real-time qPCR done on cerebrospinal fluid identified adenovirus as the causative agent allowing stopping antibiotic treatment. The patient subsequently recovered without sequelae. An overview of published and unpublished data on adenovirus central nervous system infection in immunocompetent children is presented.

Acute disseminated encephalomyelitis following meningoencephalitis: case report and literature review

Meningoencephalitis and acute disseminated encephalomyelitis (ADEM) are both neurological disease processes, but there have been few cases of meningoencephalitis progressing to ADEM in the pediatric population. A case of a 4-year-old girl with an initial diagnosis of meningoencephalitis is presented here, whose initial presentation was manifested by prolonged fever, gray matter signal abnormality on brain magnetic resonance imaging, cerebrospinal fluid pleocytosis, and a markedly irritable mental status. As her neurological examination changed with focal abnormalities, a repeat magnetic resonance imaging demonstrated new areas of both gray and white matter signal abnormality, consistent with ADEM. Her symptoms and imaging findings completely resolved with a course of methylprednisolone. Based on the literature and this current case, it is our recommendation to consider ADEM as a diagnosis if meningoencephalitis is not improving.

The role of continuous electroencephalography in childhood encephalitis

BACKGROUND

Seizures are a known complication of encephalitis. We sought to determine the incidence of seizures and the relative utility of routine and continuous electroencephalography in children with suspected encephalitis.

METHODS

Records from all 217 children (ages 0-20 years, enrolled 2004-2011) from our institution who had diagnostic samples sent to the California Encephalitis Project were reviewed.

RESULTS

One hundred children (46%) had at least one seizure observed clinically or recorded on electroencephalography. Diffuse abnormalities (e.g., generalized slowing) were more common than focal or epileptiform abnormalities (88.9% vs 63.2% and 57.3%, respectively; P < 0.0001), but focal and epileptiform abnormalities were more correlated with seizures (91.0% [P = 0.04] and 89.2% [P = 0.05], respectively vs 76.9%). Fifty-four patients (25%) had at least 1 day of continuous electroencephalography. When used, continuous electroencephalography recorded a seizure in more than half of patients. Six children had no recognized seizure (clinical or electrographic) before continuous electroencephalography was performed. Twenty-two children (10%) had a seizure recorded by continuous electroencephalography after routine electroencephalography did not record a seizure. Overall, continuous electroencephalography was more likely to capture a seizure, capture a subclinical seizure, or rule out a concerning event as a seizure than routine electroencephalography (all comparisons P < 0.0001).

CONCLUSIONS

Children with suspected encephalitis are at high risk for seizures. Continuous electroencephalography is better able than routine electroencephalography to determine whether seizures are present. Further, continuous electroencephalography can guide treatment by classifying a clinical event as seizure or seizure-mimic. Our findings support the expanded use of continuous electroencephalography in children with suspected encephalitis.

Encephalitis-associated hospitalizations among American Indians and Alaska Natives

Encephalitis produces considerable morbidity in the United States, but morbidity rates among American Indian/Alaska Native (AI/AN) people have not been described. Hospitalization records listing an encephalitis diagnosis were analyzed by using Indian Health Service direct/contract inpatient data. For 1998-2010, there were 436 encephalitis-associated hospitalizations among AI/AN people, an average annual age-adjusted hospitalization rate of 3.1/100,000 population. The rate for infants (11.9) was more than double that for any other age group. Death occurred for 4.1% of hospitalizations. Consistent with reports for the general U.S. population, the rate was high among infants and most (53.9%) hospitalizations were of unexplained etiology. The average annual rate during the study period appeared lower than for the general U.S. population, due particularly to lower rates in the elderly. Future community-based surveillance and mortality studies are needed to confirm these findings and examine reasons underlying the low rates of encephalitis in AI/AN people.

Clinical features, outcomes, and cerebrospinal fluid findings in adult patients with central nervous system (CNS) infections caused by varicella-zoster virus: comparison with enterovirus CNS infections

Varicella-zoster virus (VZV) is known to be associated with central nervous system (CNS) infections in adults. However, the clinical characteristics of VZV CNS infections are not well characterized. The aim of this study was to compare the clinical manifestations, outcomes, and cerebrospinal fluid (CSF) findings in patients with VZV CNS infections with those in patients with enterovirus (EV) CNS infections. This retrospective cohort study was performed at a 2,700-bed tertiary care hospital. Using a clinical microbiology computerized database, all adults with CSF PCR results positive for VZV or EV that were treated between January 1999 and February 2013 were identified. Thirty-eight patients with VZV CNS infection and 68 patients with EV CNS infection were included in the study. Compared with the EV group, the median age in the VZV group was higher (VZV, 35 years vs. EV, 31 years; P = 0.02), and showed a bimodal age distribution with peaks in the third and seventh decade. Encephalitis was more commonly encountered in the VZV group (VZV, 23.7% vs. EV, 4.4%; P = 0.01). The median lymphocyte percentage in the CSF (VZV, 81% vs. EV, 36%; P < 0.001) and the CSF protein level (VZV, 100 mg/dl vs. EV, 46 mg/dl; P < 0.001) were higher in the VZV group. Compared with patients with EV CNS infection, patients with VZV CNS infection developed encephalitis more often and exhibited more intense inflammatory reaction. Nevertheless, both VZV and EV CNS infections were associated with excellent long-term prognosis.

Nervous System Complications of Systemic Viral Infections

Invasion of the central nervous system (CNS) by viral agents typically produces a meningoencephalitis in which either meningitis or encephalitis may predominate. Viruses may also infect cranial or spinal blood vessels to produce ischemic injury. Viral and other infections may also elicit a host immune response which is cross-reactive with components of the neural tissue, resulting in encephalomyelitis, transverse myelitis, injury to peripheral nerves, or optic neuritis. This chapter discusses the pathogenesis of CNS viral infections and reviews clinical features of these disorders, major agents responsible in immunocompromised and immunocompetent individuals, and treatment. Prion diseases and postinfectious viral CNS syndromes including postinfectious encephalomyelitis, acute hemorrhagic leukoencephalitis, cerebellar ataxia, and transverse myelitis are also discussed.

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.

Autoimmune causes of encephalitis syndrome in Thailand: prospective study of 103 patients

Background

Data on encephalitis in Thailand have not been completely described. Etiologies remain largely unknown. We prospectively analyzed 103 Thai patients from 27 provinces for the causes of encephalitis using clinical, microbiological and neuroimaging indices; caseswithout a diagnosis were evaluated for autoimmune causes of encephalitis.

Methods

Patients with encephalitis and/or myelitis were prospectively studied between October 2010 and August 2012. Cases associated with bacterial, rickettsial and mycobacterial diseases were excluded. Herpes viruses 1-6 and enteroviruses infection was diagnosed using PCR evaluation of CSF; dengue and JE viruses infection, by serology. The serum of test-negative patients was evaluated for the presence of autoantibodies.

Results

103 patients were recruited. Fifty-three patients (52%) had no etiologies identified. Twenty-five patients (24%) were associated with infections. Immune encephalitis was found in 25 (24%); neuropsychiatric lupus erythematosus (4), demyelinating diseases (3), Behcet’s disease (1) and the remaining had antibodies to NMDAR (5), ANNA-2 (6), Yo (2), AMPA (1), GABA (1), VGKC (1) and NMDA coexisting with ANNA-2 (1). Presenting symptoms in the autoimmune group included behavioral changes in 6/25 (versus 12/25 in infectious and 13/53 in unknown group) and as psychosis in 6/25 (versus 0/25 infectious and 2/53 unknown). Seizures were found in 6/25 autoimmune, 4/25 infectious and 19/53 unknown group. Two patients with anti-ANNA-2 and one anti-Yo had temporal lobe involvement by magnetic resonance imaging. Two immune encephalitis patients with antibodies to NMDAR and ANNA-2 had ovarian tumors.

Conclusions

Autoantibody-associated encephalitis should be considered in the differential diagnosis and management algorithm regardless of clinical and neuroimaging features.

Two novel circo-like viruses detected in human feces: complete genome sequencing and electron microscopy analysis

The application of viral metagenomic techniques and a series of PCRs in a human fecal sample enabled the detection of two novel circular unisense DNA viral genomes with 92% nucleotide similarity. The viruses were tentatively named circo-like virus-Brazil (CLV-BR) strains hs1 and hs2 and have genome lengths of 2526 and 2533 nucleotides, respectively. Four major open reading frames (ORFs) were identified in each of the genomes, and differences between the two genomes were primarily observed in ORF 2. Only ORF 3 showed significant amino acid similarities to a putative rolling circle replication initiator protein (Rep), although with low identity (36%). Our phylogenetic analysis, based on the Rep protein, demonstrated that the CLV-BRs do not cluster with members of the Circoviridae, Nanoviridae or Geminiviridae families and are more closely related to circo-like genomes previously identified in reclaimed water and feces of a wild rodent and of a bat. The CLV-BRs are members of a putative new family of circular Rep-encoding ssDNA viruses. Electron microscopy revealed icosahedral (~23 nm) structures, likely reflecting the novel viruses, and rod-shaped viral particles (~65-460 × 21 × 10 nm in length, diameter, and axial canal, respectively). Circo-like viruses have been detected in stool samples from humans and other mammals (bats, rodents, chimpanzees and bovines), cerebrospinal fluid and sera from humans, as well as samples from many other sources, e.g., insects, meat and the environment. Further studies are needed to classify all novel circular DNA viruses and elucidate their hosts, pathogenicity and evolutionary history.

Variability in the Diagnosis of Encephalitis by Pediatric Subspecialists: The Need For a Uniform Definition

Research definitions of encephalitis vary widely. When surveyed on the criteria used in clinical diagnosis, 88 pediatric specialists demonstrated diverse responses, with pediatric neurologists and pediatric infectious disease specialists differing significantly in their consideration of cerebrospinal fluid pleocytosis and abnormal neuroimaging. Results emphasize the need for a uniform definition.

Predictors of outcome in acute encephalitis

OBJECTIVE

To investigate predictors of outcome in patients with all-cause encephalitis receiving care in the intensive care unit.

METHODS

A retrospective analysis of encephalitis cases at The Johns Hopkins Hospital and Johns Hopkins Bayview Medical Center was performed. Using multivariate logistic regression analysis, we examined mortality and predictors of good outcome (defined as modified Rankin Scale scores of 1-3) and poor outcome (scores 4 and 5) in those surviving to hospital discharge.

RESULTS

In our cohort of 103 patients, the median age was 52 years (interquartile range 26), 52 patients (50.49%) were male, 28 patients (27.18%) had viral encephalitis, 19 (18.45%) developed status epilepticus (SE), 15 (14.56%) had cerebral edema, and 19 (18.45%) died. In our multivariate logistic regression analysis, death was associated with cerebral edema (odds ratio [OR] 18.06, 95% confidence interval [CI] 3.14-103.92), SE (OR 8.16, 95% CI 1.55-43.10), and thrombocytopenia (OR 6.28, 95% CI 1.41-28.03). Endotracheal intubation requirement with ventilator support was highly correlated with death (95%). In addition, in those patients who survived, viral, nonviral, and unknown causes of encephalitis were less likely to have a poor outcome at hospital discharge compared with an autoimmune etiology (viral encephalitis: OR 0.09, 95% CI 0.01-0.57; nonviral encephalitis: OR 0.02, 95% CI 0.01-0.31; unknown etiology: OR 0.18, 95% CI 0.04-0.91).

CONCLUSIONS

Our study suggests that predictors of death in patients with encephalitis comprise potentially reversible conditions including cerebral edema, SE, and thrombocytopenia. Further prospective studies are needed to determine whether aggressive management of these complications in patients with encephalitis improves outcome.

Paediatric autoimmune encephalopathies: clinical features, laboratory investigations and outcomes in patients with or without antibodies to known central nervous system autoantigens

OBJECTIVE

To report the clinical and investigative features of children with a clinical diagnosis of probable autoimmune encephalopathy, both with and without antibodies to central nervous system antigens.

METHOD

Patients with encephalopathy plus one or more of neuropsychiatric symptoms, seizures, movement disorder or cognitive dysfunction, were identified from 111 paediatric serum samples referred from five tertiary paediatric neurology centres to Oxford for antibody testing in 2007-2010. A blinded clinical review panel identified 48 patients with a diagnosis of probable autoimmune encephalitis whose features are described. All samples were tested/retested for antibodies to N-methyl-D-aspartate receptor (NMDAR), VGKC-complex, LGI1, CASPR2 and contactin-2, GlyR, D1R, D2R, AMPAR, GABA(B)R and glutamic acid decarboxylase.

RESULTS

Seizures (83%), behavioural change (63%), confusion (50%), movement disorder (38%) and hallucinations (25%) were common. 52% required intensive care support for seizure control or profound encephalopathy. An acute infective organism (15%) or abnormal cerebrospinal fluid (32%), EEG (70%) or MRI (37%) abnormalities were found. One 14-year-old girl had an ovarian teratoma. Serum antibodies were detected in 21/48 (44%) patients: NMDAR 13/48 (27%), VGKC-complex 7/48(15%) and GlyR 1/48(2%). Antibody negative patients shared similar clinical features to those who had specific antibodies detected. 18/34 patients (52%) who received immunotherapy made a complete recovery compared to 4/14 (28%) who were not treated; reductions in modified Rankin Scale for children scores were more common following immunotherapies. Antibody status did not appear to influence the treatment effect.

CONCLUSIONS

Our study outlines the common clinical and paraclinical features of children and adolescents with probable autoimmune encephalopathies. These patients, irrespective of positivity for the known antibody targets, appeared to benefit from immunotherapies and further antibody targets may be defined in the future.

Viral pathogen discovery

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Pathogen discovery is critically important to infectious diseases and public health.

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Nearly all new outbreaks are caused by the emergence of novel viruses.

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Genomic tools for pathogen discovery include consensus PCR, microarrays, and deep sequencing.

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Downstream studies are often necessary to link a candidate novel virus to a disease.

Viral pathogen discovery is of critical importance to clinical microbiology, infectious diseases, and public health. Genomic approaches for pathogen discovery, including consensus polymerase chain reaction (PCR), microarrays, and unbiased next-generation sequencing (NGS), have the capacity to comprehensively identify novel microbes present in clinical samples. Although numerous challenges remain to be addressed, including the bioinformatics analysis and interpretation of large datasets, these technologies have been successful in rapidly identifying emerging outbreak threats, screening vaccines and other biological products for microbial contamination, and discovering novel viruses associated with both acute and chronic illnesses. Downstream studies such as genome assembly, epidemiologic screening, and a culture system or animal model of infection are necessary to establish an association of a candidate pathogen with disease.

Laboratory diagnosis of CNS infections by molecular amplification techniques

The initial presentation of symptoms and clinical manifestations of CNS infectious diseases often makes a specific diagnosis difficult and uncertain, and the emergence of polymerase chain reaction-led molecular techniques have been used in improving organism-specific diagnosis. These techniques have not only provided rapid, non-invasive detection of microorganisms causing CNS infections, but also demonstrated several neurologic disorders linked to infectious pathogens. Molecular methods performed on cerebrospinal fluid are recognized as the new 'gold standard' for some of these infections caused by microorganisms that are difficult to detect and identify. Although molecular techniques are predicted to be widely used in diagnosing and monitoring CNS infections, the limitations as well as strengths of these techniques must be clearly understood by both clinicians and laboratory personnel.

Encephalitis

Encephalitis is a serious and potentially treatable infection of the central nervous system. A pathogen is identified in less than 50% of cases. The differential diagnosis includes acute infection, immune-mediated causes, and other central nervous system processes. Emergent investigations include blood work, cerebrospinal fluid analysis, and neuroimaging. Empiric acyclovir and antibiotics should be started immediately to maximize the child's chance of neurologic recovery.

Viral infections of the central nervous system in Spain: a prospective study

The aim of the study was to determine the incidence of viruses causing aseptic meningitis, meningoencephalitis, and encephalitis in Spain. This was a prospective study, in collaboration with 17 Spanish hospitals, including 581 cases (CSF from all and sera from 280): meningitis (340), meningoencephalitis (91), encephalitis (76), febrile syndrome (7), other neurological disorders (32), and 35 cases without clinical information. CSF were assayed by PCR for enterovirus (EV), herpesvirus (herpes simplex [HSV], varicella-zoster [VZV], cytomegalovirus [CMV], Epstein-Barr [EBV], and human herpes virus-6 [HHV-6]), mumps (MV), Toscana virus (TOSV), adenovirus (HAdV), lymphocytic choriomeningitis virus (LCMV), West Nile virus (WNV), and rabies. Serology was undertaken when methodology was available. Amongst meningitis cases, 57.1% were characterized; EV was the most frequent (76.8%), followed by VZV (10.3%) and HSV (3.1%; HSV-1: 1.6%; HSV-2: 1.0%, HSV non-typed: 0.5%). Cases due to CMV, EBV, HHV-6, MV, TOSV, HAdV, and LCMV were also detected. For meningoencephalitis, 40.7% of cases were diagnosed, HSV-1 (43.2%) and VZV (27.0%) being the most frequent agents, while cases associated with HSV-2, EV, CMV, MV, and LCMV were also detected. For encephalitis, 27.6% of cases were caused by HSV-1 (71.4%), VZV (19.1%), or EV (9.5%). Other positive neurological syndromes included cerebellitis (EV and HAdV), seizures (HSV), demyelinating disease (HSV-1 and HHV-6), myelopathy (VZV), and polyradiculoneuritis (HSV). No rabies or WNV cases were identified. EVs are the most frequent cause of meningitis, as is HSV for meningoencephalitis and encephalitis. A significant number of cases (42.9% meningitis, 59.3% meningoencephalitis, 72.4% encephalitis) still have no etiological diagnosis.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Epidemiology of infectious encephalitis, differences between a prospective study and hospital discharge data

The French epidemiology of infectious encephalitis has been described in a 2007 prospective study. We compared these results with available data (demographic features, causative agents, case-fatality ratio) obtained through the French national hospital discharge 2007 database (PMSI), in order to evaluate it as a surveillance tool for encephalitis. Causative agents were identified in 52% of cases in the study, and 38% in PMSI (P < 0·001). The incidence of encephalitis in France in 2007 was estimated as 2·6 cases/100 000 inhabitants. HSV and VZV were the most frequent aetiological agents in both databases with similar rates. Listeria monocytogenes and Mycobacterium tuberculosis were less frequent in PMSI than in the study (Listeria: 2% vs. 5%, P = 0·001; Mycobacterium: 2% vs. 8%, P < 0·001). The case-fatality ratios were similar, except for Listeria (46% in the study vs. 16%). Nevertheless, despite the absence of case definitions and a possible misclassification weakening PMSI data, we suggest that PMSI may be used as a basic surveillance tool at a limited cost.

Infectious encephalitis: a description of a Norwegian cohort

BACKGROUND

Prompt recognition and rapid initiation of adequate treatment are important for the outcome of encephalitis. Despite extensive diagnostic testing, the causative agent often remains unknown. The aim of this study was to investigate in how many patients the causative agent was found.

METHODS

Adults (≥ 18 y) diagnosed with ICD codes indicating encephalitis between 2000 and 2009 at Oslo University Hospital, Ullevål were retrospectively studied. Causative agents, clinical presentation, and demographic characteristics were registered. Those with an identified causative agent were compared to those for whom no agent could be found.

RESULTS

Of 136 registered patients, 70 were included in the study. Sixty-six did not fulfil our inclusion criteria or were diagnosed with other, more probable conditions. The causative agent was found in 30/70 (43%) patients; herpes simplex type 1 (10/70, 14%) and varicella zoster virus (6/70, 9%) were the most frequently identified agents. A bacterial cause was found in 6/70 (9%). Patients with an identified agent were more often men and had been ill longer than those for whom no agent could be found. Computed tomography and magnetic resonance imaging were more likely to be abnormal in those patients where a causative agent was found. Five of the 70 (7%) patients died of the infection. The identification rate did not increase during the study period.

CONCLUSIONS

The diagnosis of encephalitis remains a challenge, and in many patients no causative agent is found. Clinically, immune-mediated encephalitis cannot be differentiated from infectious encephalitis and represents an important differential diagnosis. More knowledge is needed to improve our diagnostic skills.

Computational tools for viral metagenomics and their application in clinical research

There are 100 times more virions than eukaryotic cells in a healthy human body. The characterization of human-associated viral communities in a non-pathological state and the detection of viral pathogens in cases of infection are essential for medical care and epidemic surveillance. Viral metagenomics, the sequenced-based analysis of the complete collection of viral genomes directly isolated from an organism or an ecosystem, bypasses the “single-organism-level” point of view of clinical diagnostics and thus the need to isolate and culture the targeted organism. The first part of this review is dedicated to a presentation of past research in viral metagenomics with an emphasis on human-associated viral communities (eukaryotic viruses and bacteriophages). In the second part, we review more precisely the computational challenges posed by the analysis of viral metagenomes, and we illustrate the problem of sequences that do not have homologs in public databases and the possible approaches to characterize them.

Rapidly progressive dementia: prion diseases and other rapid dementias

Dementias that occur over weeks to months require a different differential than the slowly progressive dementias that occur over years. Because of the rapidity of decline in cognition, the evaluation of the patient is usually urgent and requires an extensive workup with multiple tests running in parallel. Creutzfeldt-Jakob disease, perhaps the prototypic rapidly progressive dementia (RPD), is often the first diagnosis many neurologists consider when faced with a patient with rapid cognitive decline. Many conditions other than prion disease, however, can present with RPD. Other etiologies include autoimmune conditions, cancers, uncommon presentations of other more common neurodegenerative dementias, and others. This chapter discusses some of the major etiologies for RPDs and offers an algorithm for diagnosis. Some topics, such as other neurodegenerative dementias and autoimmune dementias, are covered in other chapters in this issue, and will be mentioned here only briefly.

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.

Serious invasive Saffold virus infections in children, 2009

This virus might have caused previously unexplained cerebral infections and deaths in children.

The first human virus in the genus Cardiovirus was described in 2007 and named Saffold virus (SAFV). Cardioviruses can cause severe infections of the myocardium and central nervous system in animals, but SAFV has not yet been convincingly associated with disease in humans. To study a possible association between SAFV and infections in the human central nervous system, we designed a real-time PCR for SAFV and tested cerebrospinal fluid (CSF) samples from children <4 years of age. SAFV was detected in 2 children: in the CSF and a fecal sample from 1 child with monosymptomatic ataxia caused by cerebellitis; and in the CSF, blood, and myocardium of another child who died suddenly with no history of illness. Virus from each child was sequenced and shown to be SAFV type 2. These findings demonstrate that SAFV can cause serious invasive infection in children.

Epidemiology of acute encephalopathy in Japan, with emphasis on the association of viruses and syndromes

A research committee supported by the Japanese government conducted a nationwide survey on the epidemiology of acute encephalopathy in Japan using a questionnaire. A total of 983 cases reportedly had acute encephalopathy during the past 3 years, 2007-2010. Among the pathogens of the preceding infection, influenza virus was the most common, followed by human herpesvirus-6 (HHV-6) and rotavirus. Among syndromes of acute encephalopathy, acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) was the most frequent, followed by clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS), acute necrotizing encephalopathy (ANE) and hemorrhagic shock and encephalopathy syndrome (HSES). Influenza virus was strongly associated with ANE and MERS, HHV-6 with AESD, and rotavirus with MERS. Mortality was high in ANE and HSES, but was low in AESD, MERS and HHV-6-associated encephalopathy. Neurologic sequelae were common in AESD and ANE, but were absent in MERS.

[Two cases of autoimmune encephalitis with antibodies to N-methyl-D-aspartate receptor in intensive care]

We report here two cases of autoimmune encephalitis associated with antibodies against the N-methyl-D-aspartate receptor. The primary cause was an ovarian teratoma in one case. The outcomes were good. The first case was a late diagnosis, despite a typical clinical presentation. The clinical presentation of this disease remains unknown, especially in the intensive care unit. The treatment was recently codified and transformed the prognosis of this encephalitis. The second case was early treated in the course of the disease, due to the experience related to the previous case. In case of unexplained acute or subacute encephalitis or psychiatric-like disorders without prior medical history, the determination of the level of expression of antibodies against the N-methyl-D-aspartate receptors and other antineuroreceptors antibodies can help to identify this diagnosis. The initial picture of the disease, its variability and the unawareness of the recent reports on this encephalitis may lead to a wrong diagnosis and inappropriate management.