Burden of encephalitis-associated hospitalizations in the United States, 1988-1997

Innovative drug discovery strategies in epilepsy: integrating next-generation syndrome-specific mouse models to address pharmacoresistance and epileptogenesis

INTRODUCTION

Although there are numerous treatment options already available for epilepsy, over 30% of patients remain resistant to these antiseizure medications (ASMs). Historically, ASM discovery has relied on the demonstration of efficacy through the use of 'traditional' acute in vivo seizure models (e.g. maximal electroshock, subcutaneous pentylenetetrazol, and kindling). However, advances in genetic sequencing technologies and remaining medical needs for people with treatment-resistant epilepsy or special patient populations have encouraged recent efforts to identify novel compounds in syndrome-specific models of epilepsy. Syndrome-specific models, including Scn1a variant models of Dravet syndrome and APP/PS1 mice associated with familial early-onset Alzheimer's disease, have already led to the discovery of two mechanistically novel treatments for developmental and epileptic encephalopathies (DEEs), namely cannabidiol and soticlestat, respectively.

AREAS COVERED

In this review, the authors discuss how it is likely that next-generation drug discovery efforts for epilepsy will more comprehensively integrate syndrome-specific epilepsy models into early drug discovery providing the reader with their expert perspectives.

EXPERT OPINION

The percentage of patients with pharmacoresistant epilepsy has remained unchanged despite over 30 marketed ASMs. Consequently, there is a high unmet need to reinvent and revise discovery strategies to more effectively address the remaining needs of patients with specific epilepsy syndromes, including drug-resistant epilepsy and DEEs.

Investigation of acute encephalitis syndrome with implementation of metagenomic next generation sequencing in Nepal

BACKGROUND

The causative agents of Acute Encephalitis Syndrome remain unknown in 68-75% of the cases. In Nepal, the cases are tested only for Japanese encephalitis, which constitutes only about 15% of the cases. However, there could be several organisms, including vaccine-preventable etiologies that cause acute encephalitis, when identified could direct public health efforts for prevention, including addressing gaps in vaccine coverage.

OBJECTIVES

This study employs metagenomic next-generation-sequencing in the investigation of underlying causative etiologies contributing to acute encephalitis syndrome in Nepal.

METHODS

In this study, we investigated 90, Japanese-encephalitis-negative, banked cerebrospinal fluid samples that were collected as part of a national surveillance network in 2016 and 2017. Randomization was done to include three age groups (< 5-years; 5-14-years; >15-years). Only some metadata (age and gender) were available. The investigation was performed in two batches which included total nucleic-acid extraction, followed by individual library preparation (DNA and RNA) and sequencing on Illumina iSeq100. The genomic data were interpreted using Chan Zuckerberg-ID and confirmed with polymerase-chain-reaction.

RESULTS

Human-alphaherpes-virus 2 and Enterovirus-B were seen in two samples. These hits were confirmed by qPCR and semi-nested PCR respectively. Most of the other samples were marred by low abundance of pathogen, possible freeze-thaw cycles, lack of process controls and associated clinical metadata.

CONCLUSION

From this study, two documented causative agents were revealed through metagenomic next-generation-sequencing. Insufficiency of clinical metadata, process controls, low pathogen abundance and absence of standard procedures to collect and store samples in nucleic-acid protectants could have impeded the study and incorporated ambiguity while correlating the identified hits to infection. Therefore, there is need of standardized procedures for sample collection, inclusion of process controls and clinical metadata. Despite challenging conditions, this study highlights the usefulness of mNGS to investigate diseases with unknown etiologies and guide development of adequate clinical-management-algorithms and outbreak investigations in Nepal.

Diet composition and sterilization modifies intestinal microbiome diversity and burden of Theiler's virus infection-induced acute seizures

OBJECTIVE

Brain infection with Theiler's murine encephalomyelitis virus (TMEV) in C57BL/6J mice can induce acquired epileptogenesis. Diet alters acute seizure incidence in TMEV-infected mice; yet it is unclear whether intestinal dysbiosis may also impact acute or chronic behavioral comorbidities. This study thus assessed the impact of diet formulation and sterilization on acute seizure presentation, gut microbiome composition, and epilepsy-related chronic behavioral comorbidities.

METHODS

Baseline fecal samples were collected from male C57BL/6J mice (4- to 5-weeks-old; Jackson Labs) upon facility arrival. Mice were randomized to either autoclaved (AC) or irradiated diet (IR) (Prolab RMH 3000) or IR (Picolab 5053). Three days later, mice underwent intracerebral TMEV or phosphate-buffered saline (PBS) injection. Fecal samples were collected from a subset of mice at infection (Day 0) and Day 7 post-infection. Epilepsy-related working memory deficits and seizure threshold were assessed 6 weeks post-infection. Gut microbiome diversity was determined by 16S rRNA amplicon sequencing of fecal samples.

RESULTS

TMEV-infected mice displayed acute handling-induced seizures, regardless of diet: 28 of 57 IR Picolab 5053 (49.1%), 30 of 41 IR Prolab RMH 3000 (73.2%), and 47 of 77 AC Prolab RMH 3000 (61%) mice displayed seizures. The number of observed seizures differed significantly by diet: IR Picolab 5053 diet-fed mice had 2.2 ± 2.8 seizures (mean ± standard deviation), IR Prolab RMH 3000 diet-fed mice had 3.5 ± 2.9 seizures, and AC Prolab RMH 3000 diet-fed mice had 4.4 ± 3.8 seizures during the 7-day monitoring period. Gut microbiome composition differed significantly in TMEV-infected mice fed the AC Prolab RMH 3000 diet, with measured differences in gram-positive bacteria. These mice also displayed worsened long-term working memory deficits.

SIGNIFICANCE

Diet-induced differences in intestinal dysbiosis in the TMEV model are associated with marked changes in acute seizure presentation, symptomatic recovery, and onset of chronic behavioral comorbidities of epilepsy. Our study reveals a novel disease-modifying impact of dietary manipulation on intestinal bacterial species after TMEV-induced acute seizures.

Utilization of a Meningitis/Encephalitis PCR panel at the University Hospital Basel - a retrospective study to develop a diagnostic decision rule

Background

The Biofire® FilmArray® Meningitis/Encephalitis (ME) PCR panel covers 14 viral, bacterial, and fungal pathogens and has been implemented in many institutions worldwide. Post-marketing studies indicate a reduced sensitivity and overutilization underscoring the need for a more targeted usage. The aim of our study is to describe the utilization of the ME panel and to develop a diagnostic-stewardship based decision rule.

Materials

Adult patients, who underwent CSF analysis with the ME panel between August 2016 and June 2021 at the University Hospital Basel, were included. Demographic, clinical, microbiological, and laboratory data were extracted from the electronic health record. Factors associated with a positive ME panel result were identified, and a decision rule was developed to potentially optimize the diagnostic yield and reduce the number of unnecessary tests.

Results

1,236 adult patients received at least one panel in the observed period, of whom 106 panels tested positive (8.6%). The most frequently observed pathogens were Varicella Zoster Virus (VZV, 27%), Streptococcus pneumoniae (19%), Enterovirus (16%), Herpes simplex Virus 1/2 (16%), and Human Herpesvirus 6 (HHV-6, 13%). Fever, vomiting, headache, and photophobia were more frequently present in test positive patients as were significantly higher CSF leukocytes and protein concentrations. When simulating a decision rule based on CSF leukocytes and protein concentration, only 35% of all patients would have qualified for a ME panel tests, thereby increasing the positivity rate to 22.7%. 10 of 106 positive ME panels would have been missed, only involving HHV-6 and VZV (6 and 4 cases, respectively). As these subjects were either severely immunocompromised or had clinical features of shingles we propose extending the testing algorithm by including those criteria.

Conclusion

The ME panel positivity rate at our institution was similar as previously published. Our results highlight the need for diagnostic-stewardship interventions when utilizing this assay by implementing a stepwise approach based on a limited number of clinical and laboratory features. This decision rule may improve the pretest probability of a positive test result, increase the quality of test utilization, and reduce costs.

Outcome and Sequelae of Infectious Encephalitis

Acute infectious encephalitis is a widely studied clinical syndrome. Although identified almost 100 years ago, its immediate and delayed consequences are still neglected despite their high frequency and possible severity. We reviewed the available data on sequelae and persisting symptoms following infectious encephalitis with the aim of characterizing the clinical picture of these patients at months to years after hospitalization. We searched PubMed for case series involving sequelae after infectious encephalitis. We carried out a narrative review of the literature on encephalitis caused by members of the Herpesviridae family (herpes simplex virus, varicella zoster virus, and human herpesvirus-6), members of the Flaviviridae family (West Nile virus, tick-borne encephalitis virus, and Japanese encephalitis virus), alphaviruses, and Nipah virus. We retrieved 41 studies that yielded original data involving 3,072 adult patients evaluated after infectious encephalitis. At least one of the five domains of cognitive outcome, psychiatric disorders, neurological deficits, global functioning, and quality of life was investigated in the reviewed studies. Various tests were used in the 41 studies and the investigation took place at different times after hospital discharge. The results showed that most patients are discharged with impairments, with frequent deficits in cognitive function such as memory loss or attention disorders. Sequelae tend to improve within several years following flavivirus or Nipah virus infection, but long-term data are scarce for other pathogens. Further research is needed to better understand the extent of sequelae after infectious encephalitis, and to propose a standardized assessment method and assess the rehabilitation efficacy in these patients.

Diet composition and sterilization modifies intestinal microbiome diversity and burden of Theiler's virus infection-induced acute seizures

Objective

Central nervous system infection with Theiler's murine encephalomyelitis virus (TMEV) in C57BL/6J mice can model acquired epileptogenesis. Diet alters the acute seizure incidence in TMEV-infected mice; yet it is unclear whether intestinal dysbiosis may also impact acute or chronic behavioral comorbidities. This study thus assessed the impact of diet sterilization in a specific pathogen-free vivarium on acute seizure presentation, the composition of the gut microbiome, and chronic behavioral comorbidities of epilepsy.

Methods

Baseline fecal samples were collected from male C57BL/6J mice (4-5 weeks-old; Jackson Labs) upon arrival. Mice were randomized to either autoclaved (AC) or irradiated (IR) diet (Prolab RMH 3000 - UU diets) or IR (Picolab 5053 - UW IR diet). Mice then underwent intracerebral TMEV or PBS injection three days later. Fecal samples were collected from a subset of mice at infection (Day 0) and Day 7 post-infection. Epilepsy-related working memory deficits and seizure threshold were assessed 6 weeks post-infection. Gut microbiome diversity was determined by 16S rRNA amplicon sequencing of fecal samples.

Results

TMEV-infected mice displayed acute handling-induced seizures, regardless of diet: 28/57 UW IR (49.1%), 30/41 UU IR (73.2%), and 47/77 UU AC (61%) mice displayed seizures. The number of observed seizures significantly differed: UW IR mice had 2.2±2.8 seizures (mean±standard deviation), UU IR mice had 3.5±2.9 seizures, and UU AC mice had 4.4±3.8 seizures during the 7-day monitoring period. The composition of the gut microbiome significantly differed in TMEV-infected mice fed the UU AC diet, with most measured differences occurring in Gram-positive bacteria. TMEV-infected mice fed the UU AC diet displayed worsened chronic working memory.

Significance

Intestinal dysbiosis evokes stark differences in acute seizure presentation in the TMEV model and vastly influences the trajectory of post-TMEV infection-induced behavioral comorbidities of epilepsy. Our study reveals a novel disease-modifying contribution of intestinal bacterial species after TMEV-induced acute seizures.

Rapid and sensitive single-sample viral metagenomics using Nanopore Flongle sequencing

The ability of viral metagenomic Next-Generation Sequencing (mNGS) to unbiasedly detect nucleic acids in a clinical sample is a powerful tool for advanced diagnosis of viral infections. When clinical symptoms do not provide a clear differential diagnosis, extensive laboratory testing with virus-specific PCR and serology can be replaced by a single viral mNGS analysis. However, widespread diagnostic use of viral mNGS is thus far limited by long sample-to-result times, as most protocols rely on Illumina sequencing, which provides high and accurate sequencing output but is time-consuming and expensive. Here, we describe the development of an mNGS protocol based on the more cost-effective Nanopore Flongle sequencing with decreased turnaround time and lower, yet sufficient sequencing output to provide sensitive virus detection. Sample preparation (6 h) and sequencing (2 h) times are substantially reduced compared to Illumina mNGS and allow detection of DNA/RNA viruses at low input (up to 33-38 cycle threshold of specific qPCR). Although Flongles yield lower sequencing output, direct comparison with Illumina mNGS on diverse clinical samples showed similar results. Collectively, the novel Nanopore mNGS approach is specifically tailored for use in clinical diagnostics and provides a rapid and cost-effective mNGS strategy for individual testing of severe cases.

Seasonal Trends in the Prevalence and Incidence of Viral Encephalitis in Korea (2015-2019)

Viral infections are a common cause of encephalitis. This study investigated the relationship between the incidence of encephalitis and that of respiratory and enteric viral infections in all age groups from 2015 to 2019, using the Health Insurance Review and Assessment (HIRA) Open Access Big Data Platform. We identified monthly incidence patterns and seasonal trends using the autoregressive integrated moving average (ARIMA). The Granger causality test was used to analyze correlations between encephalitis incidence and the positive detection rate (PDR) at 1-month intervals. A total of 42,775 patients were diagnosed with encephalitis during the study period. The incidence of encephalitis was highest in the winter (26.8%). The PDRs for respiratory syncytial virus (HRSV) and coronavirus (HCoV) were associated with the trend in encephalitis diagnosis in all age groups, with a 1-month lag period. In addition, an association with norovirus was observed in patients aged over 20 years, and with influenza virus (IFV) in patients aged over 60 years. This study found that HRSV, HCoV, IFV, and norovirus tended to precede encephalitis by 1 month. Further research is required to confirm the association between these viruses and encephalitis.

Cerebrospinal fluid proteomics indicates immune dysregulation and neuronal dysfunction in antibody associated autoimmune encephalitis

Autoimmune Encephalitis (AE) spans a group of non-infectious inflammatory conditions of the central nervous system due to an imbalanced immune response. Aiming to elucidate the pathophysiological mechanisms of AE, we applied an unsupervised proteomic approach to analyze the cerebrospinal fluid (CSF) protein profile of AE patients with autoantibodies against N-methyl-d-aspartate receptor (NMDAR) (n = 9), leucine-rich glioma-inactivated protein 1 (LGI1) (n = 9), or glutamate decarboxylase 65 (GAD65) (n = 8) compared to 9 patients with relapsing-remitting multiple sclerosis as inflammatory controls, and 10 patients with somatic symptom disorder as non-inflammatory controls. We found a dysregulation of the complement system, a disbalance between pro-inflammatory and anti-inflammatory proteins on the one hand, and dysregulation of proteins involved in synaptic transmission, synaptogenesis, brain connectivity, and neurodegeneration on the other hand to a different extent in all AE subtypes compared to non-inflammatory controls. Furthermore, elevated levels of several proteases and reduction in protease inhibitors could be detected in all AE subtypes compared to non-inflammatory controls. Moreover, the different AE subtypes showed distinct protein profiles compared to each other and inflammatory controls which may facilitate future identification of disease-specific biomarkers. Overall, CSF proteomics provides insights into the complex pathophysiological mechanisms of AE, including immune dysregulation, neuronal dysfunction, neurodegeneration, and altered protease function.

Acute bacterial encephalitis complicated with recurrent nasopharyngeal carcinoma associated with Elizabethkingia miricola infection: A case report

Elizabethkingia miricola (E. miricola) is an extremely rare pathogenic bacterium, which causes serious infections in patients with primary immunodeficiency or tumors, and it is often misdiagnosed. E. miricola has rarely been known to cause a neurologic infection. We describe the first case of acute bacterial encephalitis associated with E. miricola infection in a man with recurrent nasopharyngeal carcinoma, which was successfully cured by antibiotics. The patient initially presented with recurrent episodes of fever and later showed impaired consciousness but these symptoms were alleviated with antibiotic therapy including cefoperazone/sulbactam. This study highlights that rapid and accurate pathogen detection via metagenomic next-generation sequencing and early use of appropriate antibiotics can improve the prognosis of patients with suspected neurologic E. miricola infection. Early treatment for underlying primary diseases can also significantly improve the outcomes of patients.

Viral aetiology of acute central nervous system infections in children, Iran

Introduction. Viral infections are increasingly an important cause of central nervous system (CNS) complications.

Hypothesis/Gap Statement. There is no comprehensive insight about CNS infections due to viral agents among Iranian children.

Aim. This study aimed to investigate the viral aetiology, clinical and epidemiological profile of children with acute infections of the CNS.

Methodology. A prospective study was conducted on children at the referral hospital in Isfahan, Iran, from June 2019 to June 2020. A multiplex PCR assay was used to detect the viral causative agent in cerebrospinal fluid and throat/rectal swab samples.

Results. Among 103 patients with eligible criteria, a confirmed or probable viral aetiology was detected in 41 (39.8 %) patients, including enteroviruses – 56.1 %, herpes simplex virus 1/2 (HSV-1/2) – 31.7 %, Epstein-Barr virus – 17.1 %, varicella-zoster virus (VZV) – 9.7 %, influenza A virus (H1N1) –4.9 % and mumps – 2.4 %. There was a higher proportion of PCR-positive samples in infants than in other age groups. Encephalitis and meningoencephalitis were diagnosed in 68.3 % (28/41) and 22 % (9/41) PCR-positive cases, respectively.

Conclusion. The findings of this research provide insights into the clinical and viral aetiological patterns of acute CNS infections in Iran, and the importance of molecular methods to identify CNS viruses. HSV and VZV were identified as important causes of encephalitis in young children.

Inconsistency analysis between metagenomic next-generation sequencing results of cerebrospinal fluid and clinical diagnosis with suspected central nervous system infection

Background

Recently, with the rapid progress of metagenomic next-generation sequencing (mNGS), inconsistency between mNGS results and clinical diagnoses has become more common. There is currently no reasonable explanation for this, and the interpretation of mNGS reports still needs to be standardised.

Methods

A retrospective analysis was conducted on 47 inpatients with suspected central nervous system (CNS) infections, and clinical data were recorded. The final diagnosis was determined by an expert group based on the patient’s clinical manifestation, laboratory examination, and response to treatment. mNGS results were compared with the final diagnosis, and any inconsistencies that occurred were investigated. Finally, the credibility of mNGS results was evaluated using the integral approach, which consists of three parts: typical clinical features, positive results with the traditional method, and cerebrospinal fluid cells ≥ 100 (× 10⁶/L) or protein ≥ 500 mg/L, with one point for each item.

Results

Forty-one patients with suspected CNS infection were assigned to infected (ID, 31/41, 75.61%) and non-infected groups (NID, 10/41, 24.39%) after assessment by a panel of experts according to the composite diagnostic criteria. For mNGS-positive results, 20 of the 24 pathogens were regarded as contaminants when the final score was ≤ 1. The remaining 11 pathogens detected by mNGS were all true positives, which was consistent with the clinical diagnosis when the score was ≥ 2. For mNGS negative results, when the score was ≥ 2, the likelihood of infection may be greater than when the score is ≤ 1.

Conclusion

The integral method is effective for evaluating mNGS results. Regardless of whether the mNGS result was positive or negative, the possibility of infection was greater when the score was ≥ 2. A negative mNGS result does not necessarily indicate that the patient was not clinically infected, and, therefore, clinical features are more important.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-022-07729-0.

Cytokines and chemokines profile in encephalitis patients: A meta-analysis

BACKGROUND

Encephalitis is caused by autoimmune or infectious agents marked by brain inflammation. Investigations have reported altered concentrations of the cytokines in encephalitis. This study was conducted to determine the relationship between encephalitis and alterations of cytokine levels in cerebrospinal fluid (CSF) and serum.

METHODS

We found possibly suitable studies by searching PubMed, Embase, Scopus, and Web of Science, systematically from inception to August 2021. 23 articles were included in the meta-analysis. To investigate sources of heterogeneity, subgroup analysis and sensitivity analysis were conducted. The protocol of the study has been registered in PROSPERO with a registration ID of CRD42021289298.

RESULTS

A total of 23 met our eligibility criteria to be included in the meta-analysis. A total of 12 cytokines were included in the meta-analysis of CSF concentration. Moreover, 5 cytokines were also included in the serum/plasma concentration meta-analysis. According to the analyses, patients with encephalitis had higher CSF amounts of IL-6, IL-8, IL-10, CXCL10, and TNF-α than healthy controls. The alteration in the concentration of IL-2, IL-4, IL-17, CCL2, CXCL9, CXCL13, and IFN-γ was not significant. In addition, the serum/plasma levels of the TNF-α were increased in encephalitis patients, but serum/plasma concentration of the IL-6, IL-10, CXCL10, and CXCL13 remained unchanged.

CONCLUSIONS

This meta-analysis provides evidence for higher CSF concentrations of IL-6, IL-8, IL-10, CXCL10, and TNF-α in encephalitis patients compared to controls. The diagnostic and prognostic value of these cytokines and chemokines should be investigated in future studies.

Infectious Meningitis and Encephalitis

Infectious meningitis and encephalitis are associated with significant morbidity and mortality worldwide. Acute bacterial meningitis is rapidly fatal and early recognition and institution of therapy are imperative. Viral meningitis is typically a benign self-limited illness. Chronic meningitis (defined as presenting with >4 weeks of symptoms) is most often caused by tuberculosis and fungal infection. Because the diagnostic testing for tuberculous meningitis is insensitive and cultures often take weeks to grow, therapy is often initiated empirically when the diagnosis is suspected. Human simplex virus encephalitis is the most common cause of encephalitis and requires prompt treatment with intravenous acyclovir.

Clinical use of steroids in viral central nervous system (CNS) infections: three challenging cases

The role of adjunctive corticosteroids in reducing morbidity and mortality of viral CNS infections remains poorly defined. Clinicians are often left in a quagmire regarding steroid use in complex and rapidly evolving viral CNS infections. Limited studies have explored the underlying mechanisms behind the potential benefit of steroids. Here, we describe steroid use in three cases of viral CNS disease: varicella zoster virus (VZV), Powassan virus, and influenza A-associated acute necrotizing encephalopathy.

Procalcitonin measurement in West Nile virus neuroinvasive disease: A first case series

West Nile virus neuroinvasive disease (WNV-NID) is challenging to diagnose. Procalcitonin (PCT) is a useful diagnostic test to identify bacterial infections. We present four cases of WNV-NID with serum PCT measurements.

METHODS

Daily (days 1-7) serum PCT (bioMérieux) was examined for critically ill patients with sepsis enrolled in a provincial sepsis study. Patients with identified WNV-NID are descriptively analyzed in this case series. PCT values of ≥0.5 ng/mL were suggestive of bacterial infection.

RESULTS

Four patients with WNV-NID were identified. Those with viral infections alone had consistently low PCT values ranging from 0.09 ng/mL to 0.34 ng/mL. Those with documented bacterial co-infections had initially elevated PCT levels that decreased by more than 50% with antimicrobial therapy.

CONCLUSION

These cases are the first to report serial PCT measurements in confirmed cases of WNV-NID and support a low serum PCT in WNV-NID.

Cerebrospinal Fluid Analysis for Viruses by Metagenomic Next-Generation Sequencing in Pediatric Encephalitis: Not Yet Ready for Prime Time?

BACKGROUND

Metagenomic next-generation sequencing offers an unbiased approach to identifying viral pathogens in cerebrospinal fluid of patients with meningoencephalitis of unknown etiology.

METHODS

In an 11-month case series, we investigated the use of cerebrospinal fluid metagenomic next-generation sequencing to diagnose viral infections among pediatric hospitalized patients presenting with encephalitis or meningoencephalitis of unknown etiology. Cerebrospinal fluid from patients with known enterovirus meningitis were included as positive controls. Cerebrospinal fluid from patients with primary intracranial hypertension were included to serve as controls without known infections.

RESULTS

Cerebrospinal fluid metagenomic next-generation sequencing was performed for 37 patients. Among 27 patients with encephalitis or meningoencephalitis, 4 were later diagnosed with viral encephalitis, 6 had non-central nervous system infections with central nervous system manifestations, 6 had no positive diagnostic tests, and 11 were found to have a noninfectious diagnosis. Metagenomic next-generation sequencing identified West Nile virus (WNV) in the cerebrospinal fluid of 1 immunocompromised patient. Among the 4 patients with known enterovirus meningitis, metagenomic next-generation sequencing correctly identified enteroviruses and characterized the viral genotype. No viral sequences were detected in the cerebrospinal fluid of patients with primary intracranial hypertension. Metagenomic next-generation sequencing also identified sequences of nonpathogenic torque Teno virus in cerebrospinal fluid specimens from 13 patients.

CONCLUSIONS

Our results showed viral detection by cerebrospinal fluid metagenomic next-generation sequencing only in 1 immunocompromised patient and did not offer a diagnostic advantage over conventional testing. Viral phylogenetic characterization by metagenomic next-generation sequencing could be used in epidemiologic investigations of some viral pathogens, such as enteroviruses. The finding of torque Teno viruses in cerebrospinal fluid by metagenomic next-generation sequencing is of unknown significance but may merit further exploration for a possible association with noninfectious central nervous system disorders.

Multicenter prospective surveillance study of viral agents causing meningoencephalitis

The frequency of bacterial factors causing central nervous system infections has decreased as a result of the development of our national immunization program. In this study, it is aimed to obtain the data of our local surveillance by defining the viral etiology in cases diagnosed with meningoencephalitis for 1 year. Previously healhty 186 children, who applied with findings suggesting viral meningoencephalitis to 8 different tertiary health centers between August 2018 and August 2019, in Istanbul, were included. The cerebrospinal fluid (CSF) sample was evaluated by polymerase chain reaction. The M:F ratio was 1.24 in the patient group, whose age ranged from 1 to 216 months (mean 40.2 ± 48.7). Viral factor was detected in 26.8%. Enterovirus was the most common agent (24%) and followed by Adenovirus (22%) and HHV type 6 (22%). In the rest of the samples revealed HHV type 7 (10%), EBV (6%), CMV (6%), HSV type 1 (6%), Parvovirus (4%) and VZV (2%). The most common symptoms were fever (79%) and convulsions (45.7%). Antibiotherapy and antiviral therapy was started 48.6% and 4% respectively. Mortality and sequela rate resulted 0.53% and 3.7%, respectively. This highlights the importance of monitoring trends in encephalitis in Turkey with aview to improving pathogen diagnosis for encephalitis and rapidly identifying novel emerging encephalitis-causing pathogens that demand public health action especially in national immunisation programme.

Epidemiology, Pathophysiology, Diagnosis, and Management of Cerebral Toxoplasmosis

Toxoplasma gondii is known to infect a considerable number of mammalian and avian species and a substantial proportion of the world's human population. The parasite has an impressive ability to disseminate within the host's body and employs various tactics to overcome the highly regulatory blood-brain barrier and reside in the brain. In healthy individuals, T. gondii infection is largely tolerated without any obvious ill effects. However, primary infection in immunosuppressed patients can result in acute cerebral or systemic disease, and reactivation of latent tissue cysts can lead to a deadly outcome. It is imperative that treatment of life-threatening toxoplasmic encephalitis is timely and effective. Several therapeutic and prophylactic regimens have been used in clinical practice. Current approaches can control infection caused by the invasive and highly proliferative tachyzoites but cannot eliminate the dormant tissue cysts. Adverse events and other limitations are associated with the standard pyrimethamine-based therapy, and effective vaccines are unavailable. In this review, the epidemiology, economic impact, pathophysiology, diagnosis, and management of cerebral toxoplasmosis are discussed, and critical areas for future research are highlighted.

Clinical utility of the FilmArray meningitis/encephalitis panel in children at a tertiary center in South Korea

BACKGROUND

We retrospectively evaluated the pathogens in the cerebrospinal fluid (CSF) of pediatric meningitis/encephalitis (M/E) by FilmArray meningitis/encephalitis panel (FA-MEP), and the characteristics of children showing positive and negative FA-MEP results.

METHOD

FA-MEP along with conventional tests (bacterial/viral cultures, and polymerase chain reaction tests) was performed in children who presented symptoms of M/E. Clinical and laboratory data were reviewed to evaluate the characteristics of children with pathogens detected by FA-MEP.

RESULTS

The CSF specimens from 110 pediatric M/E patients were enrolled. Mean age of the patients was 5.9 ± 5.2 years. Overall positive rate of FA-MEP was 46.4% (51/110). The pathogens detected in the patients were enterovirus (23/51, 45.1%), parechovirus (10/51, 19.6%), S. pneumoniae (7/51, 13.7%), human herpesvirus type 6 (6/51, 11.8%), S. agalactiae (3/51, 5.9%), herpes simplex virus type 2 (1/51, 2.0%), and E. coli (1/51, 2.0%). Aseptic meningitis (OR, 3.24, 95% CI, 1.18-12.73) and a duration of <2 days from onset of symptoms to CSF test (OR, 3.56, 95% CI, 0.1-0.91) significantly contributed to detection of pathogens by the FA-MEP. Among the 14 children who were administered empiric antibiotics before the CSF test, the detection rate was significantly higher in the FA-MEP than in the conventional test (28.6 vs. 0.0%, p = 0.031).

CONCLUSIONS

FA-MEP had a higher detection rate in children with M/E compared with conventional tests, particularly aseptic meningitis, and in case of shorter duration of time-to-test. This test was more effective than the conventional test in pediatric M/E patients that had been administered empiric antibiotics.

Retrospective Review of Clinical Utility of Shotgun Metagenomic Sequencing Testing of Cerebrospinal Fluid from a U.S. Tertiary Care Medical Center

Shotgun metagenomic sequencing can detect nucleic acids from bacteria, fungi, viruses, and/or parasites in clinical specimens; however, little data exist to guide its optimal application to clinical practice. We retrospectively reviewed results of shotgun metagenomic sequencing testing requested on cerebrospinal fluid samples submitted to an outside reference laboratory from December 2017 through December 2019. Of the 53 samples from Mayo Clinic patients, 47 were requested by neurologists, with infectious diseases consultation in 23 cases. The majority of patients presented with difficult-to-diagnose subacute or chronic conditions. Positive results were reported for 9 (17%) Mayo Clinic patient samples, with 6 interpreted as likely contamination. Potential pathogens reported included bunyavirus, human herpesvirus 7, and enterovirus D-68, ultimately impacting care in two cases. Twenty-seven additional samples were submitted from Mayo Clinic Laboratories reference clients, with positive results reported for three (11%): two with potential pathogens (West Nile virus and Toxoplasma gondii) and one with Streptococcus species with other bacteria below the reporting threshold (considered to represent contamination). Of 68 negative results, 10 included comments on decreased sensitivity due to high DNA background (n = 5), high RNA background (n = 1), insufficient RNA read depth (n = 3), or quality control (QC) failure with an external RNA control (n = 1). The overall positive-result rate was 15% (12/80), with 58% (7/12) of these interpreted as being inconsistent with the patient's clinical presentation. Overall, potential pathogens were found in a low percentage of cases, and positive results were often of unclear clinical significance. Testing was commonly employed in cases of diagnostic uncertainty and when immunotherapy was being considered.

Diagnostic value of real-time PCR of brain mass lesion in HIV-associated toxoplasmic encephalitis: a case series

BACKGROUND

Toxoplasmic encephalitis (TE) is a leading cause of brain mass lesions (BML) in human immunodeficiency viruses (HIV)-infected patients. Yet, so far, no accurate diagnostic approach for TE has been developed. Herein, we presented a case series (9 HIV-infected patients with TG confirmed by RT-PCR of BML) to assess the diagnostic value of reverse transcription-polymerase chain reaction (RT-PCR) on TE.

METHODS

A total of 9 HIV-infected patients with TE confirmed by RT-PCR of BML were included in this study. Clinical data, including clinical symptoms, blood and CSF analysis, neuroimaging features, histopathological characteristics, treatment, and prognosis, were assessed in all patients. According to the results of RT-PCR of BML, all the patients received oral administration of trimethoprim-sulfamethoxazole combined with antiretroviral therapy (ART). Patients were followed up by telephone or outpatient service.

RESULTS

There were 8 male and 1 female patients; their age ranged from 26 to 56 years-old. The main symptom was intracranial hypertension (6/9). Six patients presented multiple brain lesions, which were mainly located in the supratentorial area (7/9). CD₄⁺ count ranged from 11 to 159 cells/μl (median 92 cells/μl), and serological HIV viral load 0-989190 copies/ml (median 192836 copies/ml). IgG and IgM against serum TG were positive in 7 and 1 patients, respectively. Moreover, regarding CSF, IgG against TG was positive in 3 patients, while all patients were negative for IgM. The neuroimaging features on MRI showed no specificity. Four patients were diagnosed with TE by histopathological findings. After receiving anti-Toxoplasma therapy, 8 (8/9) patients improved clinically to a considerable extent.

CONCLUSIONS

The application of RT-PCR of BML, together with conventional methods, may significantly improve the diagnostic efficiency of TE.

Predicting Inpatient Mortality Among Encephalitis Patients: A Novel Admission Risk Score

Background

Identifying underlying commonalities among all-cause encephalitis cases can be extraordinarily useful in predicting meaningful risk factors associated with inpatient mortality.

Methods

A retrospective cohort of patients with encephalitis was derived from a clinical chart review of adult patients (age ≥18 years) across 16 different hospitals in Houston, Texas, between January 2005 and July 2015. Clinical features at admission were assessed for their correlation with inpatient mortality and used to derive a final risk score prediction tool.

Results

The study included a total of 273 adult patients with all-cause encephalitis, 27 (9.9%) of whom died during hospitalization. A limited number of clinical features were substantially different between patients who survived and those who died (Charlson score, Glasgow coma scale [GCS], immunosuppression, fever on admission, multiple serologic studies, and abnormal imaging). A final multivariable logistic model was derived with the following risk factors, which were transformed into a scoring system: 1 point was assigned to the presence of a Charlson score >2, thrombocytopenia, or cerebral edema, and 2 points for a GCS value <8. Patients were then classified into different risk groups for inpatient mortality: 0 points (0%), 1 point (7%), 2 points (10.9%), 3 points (36.8%), and ≥4 points (81.8%).

Conclusions

The risk score developed from this study shows a high predictive value. This can be highly beneficial in alerting care providers to key clinical risk factors associated with in-hospital mortality in adults with encephalitis.

Direct economic burden of patients with autoimmune encephalitis in western China

Objective

To analyze the cost of autoimmune encephalitis (AE) in China for the first time.

Methods

Patients who were newly diagnosed with antibody-positive AE (anti-NMDA receptor [NMDAR], anti-γ aminobutyric acid type B receptor [GABA_BR], antileucine-rich glioma-inactivated 1 [LGI1], and anticontactin-associated protein-2 [CASPR2]) at West China Medical Center between June 2012 and December 2018 were enrolled, and a cost-of-illness study was performed retrospectively. Data on clinical characteristics, costs, and utilization of sources were collected from questionnaires and the hospital information system.

Results

Of the 208 patients reviewed, the mean direct cost per patient was renminbi (RMB) 94,129 (United States dollars [USD] 14,219), with an average direct medical cost of RMB 88,373 (USD 13,349). The average inpatient cost per patients with AE was RMB 86,810 (USD 13,113). The direct nonmedical cost was much lower than the direct medical cost, averaging RMB 5,756 (USD 869). The direct cost of anti-LGI1/CASPR2 encephalitis was significantly lower than that of anti-NMDAR encephalitis and anti-GABA_BR encephalitis. The length of stay in the hospital was significantly associated with the direct cost.

Conclusions

The financial burden of AE is heavy for Chinese patients, and there are significant differences between different types of AE.

Infectious and Autoimmune Causes of Encephalitis in Children

BACKGROUND AND OBJECTIVES

Encephalitis can result in neurologic morbidity and mortality in children. Newly recognized infectious and noninfectious causes of encephalitis have become increasingly important over the past decade.

METHODS

We retrospectively reviewed medical records from pediatric patients in Houston diagnosed with encephalitis in both an urban and rural catchment area between 2010 and 2017. We conducted an investigation to understand the etiology, clinical characteristics, and diagnostic testing practices in this population.

RESULTS

We evaluated 231 patients who met the case definition of encephalitis, among which 42% had no recognized etiology. Among those with an identified etiology, the most common were infectious (73; 31%), including viral (n = 51; 22%), with the most frequent being West Nile virus (WNV; n = 12), and bacterial (n = 19; 8%), with the most frequent being Bartonella henselae (n = 7). Among cases of autoimmune encephalitis (n = 60; 26%), the most frequent cause was anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis (n = 31). Autoimmune causes were seen more commonly in female (P < .01) patients. Testing for herpes simplex virus and enterovirus was nearly universal; testing for anti-NMDAR encephalitis, WNV, and Bartonella was less common.

CONCLUSIONS

WNV was the most common infectious cause of encephalitis in our pediatric population despite lower testing frequency for WNV than herpes simplex virus or enterovirus. Increasing testing for anti-NMDAR encephalitis resulted in frequent identification of cases. Increased awareness and testing for WNV and Bartonella would likely result in more identified causes of pediatric encephalitis. Earlier etiologic diagnosis of encephalitides may lead to improve clinical outcomes.

The longitudinal health economic impact of viral encephalitis in the United States

Introduction. Previous studies of viral encephalitis have focused on acute costs, estimating incidence at 7.3 per 100 000 and total US annual charges at $2 billion in 2010.Aim. We aim to quantify the most updated longitudinal health economic impact of viral encephalitis in the USA from 2008 to 2015.Methodology. Data on patients diagnosed with viral encephalitis were obtained from the Truven Health Analytics MarketScan database. Patients with a primary diagnosis of viral encephalitis, from herpetic viruses and other viral aetiologies (e.g. West Nile fever) were included in the analysis. Data concerning healthcare resource utilization, inpatient mortality, length of stay and accrued healthcare costs were collected for up to 5 years.Results. Among 3985 patients with continuous enrolment for 13 months prior to the encephalitis diagnosis, more non-herpes simplex encephalitis (61.7 %) than herpes simplex encephalitis (HSE; 38.3 %) cases were recorded, with the majority concentrated in the southern USA (29.2 %). One-year inpatient mortality was 6.2 %, which over a 5-year period rose to 8.9 % for HSE and 5.8 % for all other viral encephalitides. HSE resulted in longer cumulative stays in the hospital (11 days vs. 4 days; P=0.0025), and accrued 37 % higher first-year costs, after adjusting for known confounders [P<0.001, cost ratio=1.37, 95 % confidence interval (1.20, 1.57)]. Additionally, HSE was associated with greater 5-year cumulative median charges ($125 338 vs. $82 317, P=0.0015).Conclusion. The health economic impact and long-term morbidity of viral encephalitis in the USA are substantial.

Understanding and managing acute encephalitis

Encephalitis is an important cause of morbidity, mortality, and permanent neurologic sequelae  globally. Causes are diverse and include viral and non-viral infections of the brain as well as autoimmune processes. In the West, the autoimmune encephalitides are now more common than any single infectious cause, but, in Asia, infectious causes are still more common. In 2006, the World Health Organization coined the term "acute encephalitis syndrome", which simply means acute onset of fever with convulsions or altered consciousness or both. In 2013, the International Encephalitis Consortium set criteria for diagnosis of encephalitis on basis of clinical and laboratory features. The most important infectious cause in the West is herpes simplex virus, but globally Japanese encephalitis (JE) remains the single largest cause. Etiologic diagnosis is difficult because of the large number of agents that can cause encephalitis. Also, the responsible virus may be detectable only in the brain and is either absent or transiently found in blood or cerebrospinal fluid (CSF). Virological diagnosis is complex, expensive, and time-consuming. Different centres could make their own algorithms for investigation in accordance with the local etiologic scenarios. Magnetic resonance imaging (MRI) and electroencephalography are specific for few agents. Clinically, severity may vary widely. A severe case may manifest with fever, convulsions, coma, neurologic deficits, and death. Autoimmune encephalitis (AIE)  includes two major categories: (i) classic paraneoplastic limbic encephalitis (LE) with autoantibodies against intracellular neuronal antigens (Eg: Hu and Ma2) and (ii) new-type AIE with autoantibodies to neuronal surface or synaptic antigens (Eg: anti-N-methyl-D-aspartate receptor). AIE has prominent psychiatric manifestations: psychosis, aggression, mutism, memory loss, euphoria, or fear. Seizures, cognitive decline, coma, and abnormal movements are common. Symptoms may fluctuate rapidly. Treatment is largely supportive. Specific treatment is available for herpesvirus group and non-viral infections. Various forms of immunotherapy are used for AIE.

Exploratory analysis of the potential for advanced diagnostic testing to reduce healthcare expenditures of patients hospitalized with meningitis or encephalitis

Objective

To estimate healthcare expenditures that could be impacted by advanced diagnostic testing for patients hospitalized with meningitis or encephalitis

Methods

Patients hospitalized with meningitis (N = 23,933) or encephalitis (N = 7,858) in the U.S. were identified in the 2010–2014 Truven Health MarketScan Commercial Claims and Encounters Database using ICD-9-CM diagnostic codes. The database included an average of 40.8 million commercially insured enrollees under age 65 per year. Clinical, demographic and healthcare utilization criteria were used to identify patient subgroups early in their episode who were at risk to have high inpatient expenditures. Healthcare expenditures of patients within each subgroup were bifurcated: those expenditures that remained five days after the patient could be classified into the subgroup versus those that had occurred previously.

Results

The hospitalization episode rate per 100,000 enrollee-years for meningitis was 13.0 (95% CI: 12.9–13.2) and for encephalitis was 4.3 (95% CI: 4.2–4.4), with mean inpatient expenditures of $36,891 (SD = $92,636) and $60,181 (SD = $130,276), respectively. If advanced diagnostic testing had been administered on the day that a patient could be classified into a subgroup, then a test with a five-day turnaround time could impact the following mean inpatient expenditures that remained by subgroup for patients with meningitis or encephalitis, respectively: had a neurosurgical procedure ($83,337 and $56,020), had an ICU stay ($34,221 and $46,051), had HIV-1 infection or a previous organ transplant ($37,702 and $62,222), were age <1 year ($35,371 and $52,812), or had a hospital length of stay >2 days ($18,325 and $30,244).

Discussion

Inpatient expenditures for patients hospitalized with meningitis or encephalitis were substantial and varied widely. Patient subgroups who had high healthcare expenditures could be identified early in their stay, raising the potential for advanced diagnostic testing to lower these expenditures.

Diagnostic Practices for Suspected Community-Acquired Central Nervous System Infection in the Post-Conjugate Vaccine Era

OBJECTIVE

The aim of this study was to evaluate diagnostic practices for suspected community-acquired central nervous system (CNS) infection in an urban pediatric population.

METHODS

This is an observational, retrospective single-center review of cerebrospinal fluid (CSF) studies in children, 1 month to 21 years old, evaluated for suspected CNS infection from 2004 to 2014. Cases of suspected nosocomial meningitis were excluded. The frequency of N-methyl-D-aspartate receptor antibody (NMDAR ab) encephalitis was analyzed from 2010 to 2014.

RESULTS

A total of 940 unique patient visits with CSF studies were included in the final analysis. There were 940 bacterial cultures sent; 4 (0.42%) grew suspected CSF bacterial pathogens, and 18 (1.9%) grew organisms that were suspected contaminants. Bacterial pathogens included late-onset group B Streptococcus in 3 infants younger than 3 months and Streptococcus pneumoniae in an unvaccinated 9-year-old child. Viral CNS infection was 7.5 times more frequent than bacterial infection. Enterovirus was the only virus isolated. Five cases positive for NMDAR ab were identified since 2010.

CONCLUSIONS

Bacterial studies were performed more frequently than viral and other studies. Cerebrospinal fluid bacterial culture was nearly 5 times more likely to yield a contaminant than a pathogen. The frequency of viral infection was likely underestimated as only 20% were tested, mainly by culture, which is suboptimal. These data suggest diagnostic practices for the evaluation of suspected community-acquired CNS infections in children need to be modified to reflect current epidemiology and highlight the need for greater accessibility to polymerase chain reaction for viral diagnostics. Furthermore, NMDAR ab-mediated encephalitis should be considered early in children presenting with suggestive symptoms.

Clinical Metagenomic Sequencing for Diagnosis of Meningitis and Encephalitis

BACKGROUND

Metagenomic next-generation sequencing (NGS) of cerebrospinal fluid (CSF) has the potential to identify a broad range of pathogens in a single test.

METHODS

In a 1-year, multicenter, prospective study, we investigated the usefulness of metagenomic NGS of CSF for the diagnosis of infectious meningitis and encephalitis in hospitalized patients. All positive tests for pathogens on metagenomic NGS were confirmed by orthogonal laboratory testing. Physician feedback was elicited by teleconferences with a clinical microbial sequencing board and by surveys. Clinical effect was evaluated by retrospective chart review.

RESULTS

We enrolled 204 pediatric and adult patients at eight hospitals. Patients were severely ill: 48.5% had been admitted to the intensive care unit, and the 30-day mortality among all study patients was 11.3%. A total of 58 infections of the nervous system were diagnosed in 57 patients (27.9%). Among these 58 infections, metagenomic NGS identified 13 (22%) that were not identified by clinical testing at the source hospital. Among the remaining 45 infections (78%), metagenomic NGS made concurrent diagnoses in 19. Of the 26 infections not identified by metagenomic NGS, 11 were diagnosed by serologic testing only, 7 were diagnosed from tissue samples other than CSF, and 8 were negative on metagenomic NGS owing to low titers of pathogens in CSF. A total of 8 of 13 diagnoses made solely by metagenomic NGS had a likely clinical effect, with 7 of 13 guiding treatment.

CONCLUSIONS

Routine microbiologic testing is often insufficient to detect all neuroinvasive pathogens. In this study, metagenomic NGS of CSF obtained from patients with meningitis or encephalitis improved diagnosis of neurologic infections and provided actionable information in some cases. (Funded by the National Institutes of Health and others; PDAID ClinicalTrials.gov number, NCT02910037.).

Laboratory validation of a clinical metagenomic sequencing assay for pathogen detection in cerebrospinal fluid

Metagenomic next-generation sequencing (mNGS) for pan-pathogen detection has been successfully tested in proof-of-concept case studies in patients with acute illness of unknown etiology but to date has been largely confined to research settings. Here, we developed and validated a clinical mNGS assay for diagnosis of infectious causes of meningitis and encephalitis from cerebrospinal fluid (CSF) in a licensed microbiology laboratory. A customized bioinformatics pipeline, SURPI+, was developed to rapidly analyze mNGS data, generate an automated summary of detected pathogens, and provide a graphical user interface for evaluating and interpreting results. We established quality metrics, threshold values, and limits of detection of 0.2-313 genomic copies or colony forming units per milliliter for each representative organism type. Gross hemolysis and excess host nucleic acid reduced assay sensitivity; however, spiked phages used as internal controls were reliable indicators of sensitivity loss. Diagnostic test accuracy was evaluated by blinded mNGS testing of 95 patient samples, revealing 73% sensitivity and 99% specificity compared to original clinical test results, and 81% positive percent agreement and 99% negative percent agreement after discrepancy analysis. Subsequent mNGS challenge testing of 20 positive CSF samples prospectively collected from a cohort of pediatric patients hospitalized with meningitis, encephalitis, and/or myelitis showed 92% sensitivity and 96% specificity relative to conventional microbiological testing of CSF in identifying the causative pathogen. These results demonstrate the analytic performance of a laboratory-validated mNGS assay for pan-pathogen detection, to be used clinically for diagnosis of neurological infections from CSF.

Clinical Utilization of the FilmArray Meningitis/Encephalitis (ME) Multiplex Polymerase Chain Reaction (PCR) Assay

Objective: To assess the clinical utilization and performance of the FilmArray® Meningitis/Encephalitis (ME) multiplex polymerase chain reaction (PCR) panel in a hospital setting.

Background: Rapid diagnosis and treatment of central nervous system (CNS) infections are critical to reduce morbidity and mortality. The ME panel is a Food and Drug Administration (FDA) approved rapid multiplex PCR assay that targets 14 bacteria, viruses, and fungi. Previous studies show an overall agreement of 93–99% between the ME panel and conventional diagnostic testing. However, few studies have evaluated the clinical implementation of the ME assay, which is available for routine use at our institution.

Methods: We performed a single center retrospective chart review of inpatients who underwent ME panel testing from August 2016 to May 2017. Clinical, radiologic, and laboratory data were reviewed to determine the clinical significance of results. Indication for lumbar puncture (LP), time to results of the ME panel, and duration of antimicrobial therapy were evaluated.

Results: Seven hundred and five inpatients underwent ME testing, of whom 480 (68.1%) had clinical suspicion for CNS infection with 416 (59.0%) receiving empiric antimicrobial treatment for CNS infection. The median time-to-result of the ME panel was 1.5 h (IQR, 1.4–1.7). Overall agreement between the ME panel results and clinico-laboratory assessment was 98.2%. Forty-five patients tested positive by ME, of which 12 (26.6%) were determined likely to be clinically insignificant.

Conclusions: Routine availability of the ME panel led to overutilization of diagnostic test ordering, as demonstrated by the fact that over one-third of ME panel tests performed were ordered for patients with little or no suspicion for CNS infection. The median time from LP to ME panel result was 1.5 h (IQR, 1.4–1.7). The ME panel's rapid turn-around time contributed to the overuse of the test. Approximately one-quarter of positive ME results were deemed clinically insignificant, though the impact of these positive results requires additional evaluation. Twenty-four and forty-eight hours after the ME panel resulted, 68 and 25% of patients started on empiric therapy remained on antibiotics, respectively. The median time from diagnosis to discontinuation and/or narrowing of antibiotic coverage was 25.6 h (IQR, 3.6–42.5). Further consideration of the appropriate indications for use of the ME panel in clinical settings is required.

High burden and low awareness of toxoplasmosis in the United States

Toxoplasmosis, a disease with diverse clinical manifestations, caused by infection with the Apicomplexan parasite, Toxoplasma gondii (T. gondii), is a major source of morbidity and mortality in the United States. Although toxoplasmosis prevalence and mortality have declined over the past two decades, the CDC considers this disease a neglected parasitic infection requiring public health action. Here, we overview the literature to bring attention to the prevalence of the disease in the United States, and high economic burden associated with the disease. The conclusions to be drawn are clear: there is low awareness and underestimation of the disease burden amongst healthcare professionals; a high economic burden associated with the disease; relapse rates to treatment represent additional mortality and morbidity and further costs for the healthcare system; and better treatments are necessary to combat this public health threat.

Patient and treatment pathways for toxoplasmosis in the United States: data analysis of the Vizient Health Systems Data from 2011 to 2017

Toxoplasmosis causes substantial morbidity and mortality in the United States (US). Clinical manifestations to toxoplasmosis vary and there is limited information on incidence or treatment patterns in the US. Treatment pathways for pyrimethamine-based regimens and trimethoprim-sulfamethoxazole (TMP-SMX) for toxoplasmosis hospitalizations were investigated using the Vizient Health Systems inpatient and outpatient data. Between January 1^st, 2011 and December 31^st, 2017, 10,273 hospital visits from 4,736 unique patients received a primary or secondary ICD-9/ICD-10 diagnosis for toxoplasmosis. The projected annual hospital visits with a diagnosis of toxoplasmosis was 68,821, corresponding to a total annual incidence of 9,832 comprising ocular toxoplasmosis of 2,169, toxoplasmic encephalitis of 1,399, unspecified toxoplasmosis of 4,368, congenital toxoplasmosis of 381, multisystemic toxoplasmosis of 69 and other toxoplasmosis of 1,446. Only 16.3% of the study population received treatment with pyrimethamine-based regimens or TMP-SMX. Pyrimethamine-based regimens were used significantly more often than TMP-SMX in toxoplasmic encephalitis (88.7% vs 79.6%, p = 0.01), other toxoplasmosis (85.0% vs 79.2%, p = 0.04), and unspecified toxoplasmosis (87.6% vs 77.9%, p = 0.03) in hospitals with 300 beds or more. A significantly higher percentage of visits with TMP-SMX as first-line treatment switched to pyrimethamine-based regimens compared to visits initiated on pyrimethamine-based treatments (26.7% vs 4.1%, p < .001). Ocular toxoplasmosis patients receiving pyrimethamine-based therapy were more likely to be discharged home compared to TMP-SMC at rates of 72.4% and 55.2%, respectively. Our analysis of commercial insurance records suggest toxoplasmosis is undertreated. Overall, pyrimethamine-based regimens are favored over TMP-SMX, have higher rates of discharge home, and have lower switch rates.

Limited Correlation of Shotgun Metagenomics Following Host Depletion and Routine Diagnostics for Viruses and Bacteria in Low Concentrated Surrogate and Clinical Samples

The etiologic cause of encephalitis, meningitis or meningo-encephalitis is unknown in up to 70% of cases. Clinical shotgun metagenomics combined with host depletion is a promising technique to identify infectious etiologies of central nervous system (CNS) infections. We developed a straightforward eukaryotic host nucleic acid depletion method that preserves intact viruses and bacteria for subsequent shotgun metagenomics screening of clinical samples, focusing on cerebrospinal fluid (CSF). A surrogate CSF sample for a CNS infection paradigm was used to evaluate the proposed depletion method consisting of selective host cell lysis, followed by enzymatic degradation of the liberated genomic DNA for final depletion with paramagnetic beads. Extractives were subjected to reverse transcription, followed by whole genome amplification and next generation sequencing. The effectiveness of the host depletion method was demonstrated in surrogate CSF samples spiked with three 1:100 dilutions of Influenza A H3N2 virus (qPCR Ct-values 20.7, 28.8, >42/negative). Compared to the native samples, host depletion increased the amount of the virus subtype reads by factor 7127 and 132, respectively, while in the qPCR negative sample zero vs. 31 (1.4E-4 %) virus subtype reads were detected (native vs. depleted). The workflow was applied to thirteen CSF samples of patients with meningo-/encephalitis (two bacterial, eleven viral etiologies), a serum of an Andes virus infection and a nose swab of a common cold patient. Unlike surrogate samples, host depletion of the thirteen human CSF samples and the nose swab did not result in more reads indicating presence of damaged pathogens due to, e.g., host immune response. Nevertheless, previously diagnosed pathogens in the human CSF samples (six viruses, two bacteria), the serum, and the nose swab (Human rhinovirus A31) were detected in the depleted and/or the native samples. Unbiased evaluation of the taxonomic profiles supported the diagnosed pathogen in two native CSF samples and the native and depleted serum and nose swab, while detecting various contaminations that interfered with pathogen identification at low concentration levels. In summary, damaged pathogens and contaminations complicated analysis and interpretation of clinical shotgun metagenomics data. Still, proper consideration of these issues may enable future application of metagenomics for clinical diagnostics.

Defining diagnostic approaches and outcomes in patients with inflammatory CSF: A retrospective cohort study

OBJECTIVE

Define the etiologies, clinical features, time to diagnosis, and outcomes of patients that present with cerebral spinal fluid (CSF) pleocytosis.

PATIENTS AND METHODS

This is retrospective cohort study of patients with CSF pleocytosis, defined as WBC count >5 cells/mm³ in the CSF, from July 2015 to June 2016 at a large tertiary care hospital. The proportion of patients within specific diagnostic categories were analyzed for differences in diagnostic testing and outcomes.

RESULTS

53% of patients had CSF pleocytosis due to an unknown etiology. The leading known cause of neuroinflammation was CNS infection (n = 43/244, 18%), followed by malignancy (n = 28/244, 11%). Mean time to diagnosis was 125 days in patients with autoimmune neuroinflammation and was 16 days in patients with an infection or malignancy. CSF parameters and peripheral white blood cell counts did not distinguish between categories of disease. The presence of CSF oligoclonal bands or a positive biopsy result most commonly supported a diagnosis of an autoimmune disease or malignancy, respectively. Neuroimaging changes were present in only 44% of infections but were found in 80-90% of other categories of neuroinflammation. Patients presenting with a severe neurologic deficit had 22.29 higher odds of a severe deficit at the last neurologic assessment, and mortality was highest (29%) in patients with malignancy-associated neuroinflammation.

CONCLUSIONS

This study to defines general diagnostic categories of neuroinflammatory disease in patients and provides new insight on the value of specific diagnostic testing, time to diagnosis, and outcomes in these patient populations.

Epidemiology and clinical outcomes of viral central nervous system infections

BACKGROUND

Central nervous system (CNS) viral infections are an important cause of morbidity and mortality. No data are available regarding their epidemiology in Qatar.

DESIGN

We retrospectively evaluated all cerebrospinal fluid findings from January 2011-March 2015 at Hamad Medical Corporation. Those with abnormal CSF finding were included in our study. We excluded those with missing medical records, no clinical evidence of viral CNS infection, or proven bacterial, fungal or tuberculosis CNS infection. CNS clinical findings were classified as meningitis, encephalitis or myelitis.

RESULTS

Among 7690 patients with available CSF results, 550 cases met the inclusion criteria (meningitis 74.7%; encephalitis 25%; myelitis 0.4%). Two-thirds (65%) were male and 50% were between 16-60 years old. Viral etiology was confirmed in 38% (enterovirus, 44.3%; Epstein-Barr virus, 31%; varicella zoster virus, 12.4%). The estimated incidence was 6.4 per 100,000 population. Two persons died and the rest were discharged to home. Among those with confirmed viral etiology, 83.8% received ceftriaxone (mean duration 7.3±5.2 days), 38% received vancomycin (mean duration 2.7±5.4 days) and 38% received at least one other antibiotic. Intravenous acyclovir was continued for more than 48h in patients with confirmed negative viral etiology (mean duration 5±5.6 days).

CONCLUSION

Viral etiology is not uncommon among those evaluated for CNS infection in Qatar. Clinical outcomes are excellent in this group of patients. Antibiotics and acyclovir are overly used even when a viral etiology is confirmed. There is a need for clinician education regarding etiology and treatment of viral CNS infections.

Systematic review of rehabilitation intervention outcomes of adult and paediatric patients with infectious encephalitis

OBJECTIVE

Although a range of rehabilitation interventions have been applied to restore function after infectious encephalitis, there is a lack of literature summarising the benefits of these interventions. This systematic review aims to synthesise current scientific knowledge on outcome measures following rehabilitative interventions among children and adults with infectious encephalitis, with a specific focus on the influence of the age, sex, baseline status and intervention type.

SEARCH STRATEGY

Five scholarly databases (MEDLINE, Embase, PsycINFO, CINAHL and Cochrane Central Register of Controlled Trials), three sources of grey literature (Google, Google Scholar and Grey Matters) and reference lists of included publications were systematically searched. Literature published before 15 December 2017 and focused on patients with infectious encephalitis in any rehabilitation setting were included. Quality assessment was completed using the Downs and Black rating scale.

RESULTS

Of the 12 737 reference titles screened, 20 studies were included in this review. All of the studies had sample sizes of less than 25 patients and received a score of less than 15 out of 31 points on the Downs and Black rating scale. Findings showed a variety of interventions has been applied to alleviate sequelae from infectious encephalitis, including using cognitive therapy (nine studies), behavioural therapy (five studies), physical therapy (two studies) or two or more therapies (four studies). There was inconclusive evidence on the effect of sex, age and baseline functional abilities on outcomes. Due to clinical and methodological heterogeneity between studies, meta-analyses were not performed.

CONCLUSION

Evidence suggests the potential for a beneficial effect of rehabilitation interventions in patients with infectious encephalitis. Future research is required to identify all effect modifiers and to determine the effect of time in the natural course of recovery. An enhanced set of known effect modifiers will support the process of future evaluation of a client-centred rehabilitation intervention.

TRIAL REGISTRATION NUMBER

CRD42015029217.

Increased serum vascular endothelial growth factor is associated with acute viral encephalitis in Bangladeshi children

Encephalitis causes significant global morbidity and mortality. A large number of viruses cause encephalitis, and their geographic and temporal distributions vary. In many encephalitis cases, the virus cannot be detected, even after extensive testing. This is one challenge in management of the encephalitis patient. Since cytokines are pivotal in any form of inflammation and vary according to the nature of the inflammation, we hypothesized cytokine levels would allow us to discriminate between encephalitis caused by viruses and other aetiologies. This pilot study was conducted in a tertiary care hospital in Dhaka, Bangladesh. Viral detection was performed by polymerase chain reaction using patient cerebrospinal fluid. Acute phase reactants and cytokines were detected in patient serum. Of the 29 biomarkers assessed using the Wilcoxon rank-sum test, only vascular endothelial growth factor (VEGF) was significantly higher (P = 0.0015) in viral-positive compared with virus–negative encephalitis patients. The area under the curve (AUC) for VEGF was 0.82 (95% confidence interval: 0.66–0.98). Serum VEGF may discriminate between virus-positive and virus-negative encephalitis. Further study will be needed to confirm these findings.

Intravenous immunoglobulin for the treatment of childhood encephalitis

BACKGROUND

Encephalitis is a syndrome of neurological dysfunction due to inflammation of the brain parenchyma, caused by an infection or an exaggerated host immune response, or both. Attenuation of brain inflammation through modulation of the immune response could improve patient outcomes. Biological agents such as immunoglobulin that have both anti-inflammatory and immunomodulatory properties may therefore be useful as adjunctive therapies for people with encephalitis.

OBJECTIVES

To assess the efficacy and safety of intravenous immunoglobulin (IVIG) as add-on treatment for children with encephalitis.

SEARCH METHODS

The Cochrane Multiple Sclerosis and Rare Diseases of the CNS group's Information Specialist searched the following databases up to 30 September 2016: CENTRAL, MEDLINE, Embase, CINAHL, ClinicalTrials.gov, and the WHO ICTRP Search Portal. In addition, two review authors searched Science Citation Index Expanded (SCI-EXPANDED) & Conference Proceedings Citation Index - Science (CPCI-S) (Web of Science Core Collection, Thomson Reuters) (1945 to January 2016), Global Health Library (Virtual Health Library), and Database of Abstracts of Reviews of Effects (DARE).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing IVIG in addition to standard care versus standard care alone or placebo.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected articles for inclusion, extracted relevant data, and assessed quality of trials. We resolved disagreements by discussion among the review authors. Where possible, we contacted authors of included studies for additional information. We presented results as risk ratios (RR) or mean differences (MD) with 95% confidence intervals (CI).

MAIN RESULTS

The search identified three RCTs with 138 participants. All three trials included only children with viral encephalitis, one of these included only children with Japanese encephalitis, a specific form of viral encephalitis. Only the trial of Japanese encephalitis (22 children) contributed to the primary outcome of this review and follow-up in that study was for three to six months after hospital discharge. There was no follow-up of participants in the other two studies. We identified one ongoing trial.For the primary outcomes, the results showed no significant difference between IVIG and placebo when used in the treatment of children with Japanese encephalitis: significant disability (RR 0.75, 95% CI 0.22 to 2.60; P = 0.65) and serious adverse events (RR 1.00, 95% CI 0.07 to 14.05; P = 1.00).For the secondary outcomes, the study of Japanese encephalitis showed no significant difference between IVIG and placebo when assessing significant disability at hospital discharge (RR 1.00, 95% CI 0.60 to 1.67). There was no significant difference (P = 0.53) in Glasgow Coma Score at discharge between IVIG (median score 14; range 3 to 15) and placebo (median 14 score; range 7 to 15) in the Japanese encephalitis study. The median length of hospital stay in the Japanese encephalitis study was similar for IVIG-treated (median 13 days; range 9 to 21) and placebo-treated (median 12 days; range 6 to 18) children (P = 0.59).Pooled analysis of the results of the other two studies resulted in a significantly lower mean length of hospital stay (MD -4.54 days, 95% CI -7.47 to -1.61; P = 0.002), time to resolution of fever (MD -0.97 days, 95% CI -1.25 to -0.69; P < 0.00001), time to stop spasms (MD -1.49 days, 95% CI -1.97 to -1.01; P < 0.00001), time to regain consciousness (MD -1.10 days, 95% CI -1.48 to -0.72; P < 0.00001), and time to resolution of neuropathic symptoms (MD -3.20 days, 95% CI -3.34 to -3.06; P < 0.00001) in favour of IVIG when compared with standard care.None of the included studies reported other outcomes of interest in this review including need for invasive ventilation, duration of invasive ventilation, cognitive impairment, poor adaptive functioning, quality of life, number of seizures, and new diagnosis of epilepsy.The quality of evidence was very low for all outcomes of this review.

AUTHORS' CONCLUSIONS

The findings suggest a clinical benefit of adjunctive IVIG treatment for children with viral encephalitis for some clinical measures (i.e. mean length of hospital stay, time (days) to stop spasms, time to regain consciousness, and time to resolution of neuropathic symptoms and fever. For children with Japanese encephalitis, IVIG had a similar effect to placebo when assessing significant disability and serious adverse events.Despite these findings, the risk of bias in the included studies and quality of the evidence make it impossible to reach any firm conclusions on the efficacy and safety of IVIG as add-on treatment for children with encephalitis. Furthermore, the included studies involved only children with viral encephalitis, therefore findings of this review cannot be generalised to all forms of encephalitis. Future well-designed RCTs are needed to assess the efficacy and safety of IVIG in the management of children with all forms of encephalitis. There is a need for internationally agreed core outcome measures for clinical trials in childhood encephalitis.

Neuroinflammation in epileptogenesis: Insights and translational perspectives from new models of epilepsy

Animal models have provided a wealth of information on mechanisms of epileptogenesis and comorbidogenesis, and have significantly advanced our ability to investigate the potential of new therapies. Processes implicating brain inflammation have been increasingly observed in epilepsy research. Herein we discuss the progress on animal models of epilepsy and comorbidities that inform us on the potential role of inflammation in epileptogenesis and comorbidity pathogenesis in rodent models of West syndrome and the Theiler's murine encephalomyelitis virus (TMEV) mouse model of viral encephalitis-induced epilepsy. Rat models of infantile spasms were generated in rat pups after right intracerebral injections of proinflammatory compounds (lipopolysaccharides with or without doxorubicin, or cytokines) and were longitudinally monitored for epileptic spasms and neurodevelopmental and cognitive deficits. Anti-inflammatory treatments were tested after the onset of spasms. The TMEV mouse model was induced with intracerebral administration of TMEV and prospective monitoring for handling-induced seizures or seizure susceptibility, as well as long-term evaluations of behavioral comorbidities of epilepsy. Inflammatory processes are evident in both models and are implicated in the pathogenesis of the observed seizures and comorbidities. A common feature of these models, based on the data so far available, is their pharmacoresistant profile. The presented data support the role of inflammatory pathways in epileptogenesis and comorbidities in two distinct epilepsy models. Pharmacoresistance is a common feature of both inflammation-based models. Utilization of these models may facilitate the identification of age-specific, syndrome- or etiology-specific therapies for the epilepsies and attendant comorbidities, including the drug-resistant forms.

Epidemiology of infectious encephalitis causes in 2016

We performed a literature search in the Medline database, using the PubMed website. The incidence of presumably infectious encephalitis is estimated at 1.5-7 cases/100,000 inhabitants/year, excluding epidemics. Infectious encephalitis and immune-mediated encephalitis share similar clinical signs and symptoms. The latter accounts for a significant proportion of presumably infectious encephalitis cases without any established etiological diagnosis; as shown from a prospective cohort study where 21% of cases were due to an immune cause. Several infectious agents are frequently reported in all studies: Herpes simplex virus (HSV) is the most frequent pathogen in 65% of studies, followed by Varicella-zoster virus (VZV) in several studies. Enteroviruses are also reported; being the most frequent viruses in two studies, and the 2nd or 3rd viruses in five other studies. There are important regional differences, especially in case of vector-borne transmission: Asia and the Japanese encephalitis virus, Eastern and Northern Europe/Eastern Russia and the tick-borne encephalitis virus, Northern America and Flavivirus or Alphavirus. Bacteria can also be incriminated: Mycobacterium tuberculosis and Listeria monocytogenes are the most frequent, after HSV and VZV, in a French prospective study. The epidemiology of encephalitis is constantly evolving. Epidemiological data may indicate the emergence and/or dissemination of new causative agents. The dissemination and emergence of causative agents are fostered by environmental, social, and economical changes, but prevention programs (vaccination, vector controls) help reduce the incidence of other infectious diseases and associated encephalitis (e.g., measles).

Cost-Effectiveness Study of Criteria for Screening Cerebrospinal Fluid To Determine the Need for Herpes Simplex Virus PCR Testing

The absence of markers of inflammation in the cerebrospinal fluid (CSF) commonly predicts the absence of herpes simplex virus (HSV) central nervous system (CNS) infection. Consequently, multiple authors have proposed and validated criteria for deferring HSV PCR testing of CSF in immunocompetent hosts with normal CSF white blood cell and protein levels (≤5 cells/mm³ and ≤50 mg/dl, respectively). Hosts are considered immunocompetent if they are ≥2 years old and have not had HIV or an organ transplant. Adoption of the criteria may erroneously exclude HSV-infected persons from a necessary diagnostic test or, alternatively, reduce the costs associated with HSV tests with minimal to no effect on patient care. Little is known about the cost-effectiveness of this approach. A decision analysis model was developed to evaluate the adoption of criteria for screening HSV tests of CSF. Estimates of input parameter values combined available literature with a multiyear multisite review at two of the largest health care systems in the United States. Adoption of criteria to screen for HSV test need proved cost-effective when less than 1 in 200 patients deferred from testing truly had an HSV CNS infection. Similar to prior studies, none of the deferred cases had HSV encephalitis (n = 3120). Adoption of these criteria in the United States would save an estimated $127 million ($95 million to $158 million [±25%]) annually. The model calculations remained robust to variation in test cost, prevalence of HSV infection, and random variation to study assumptions. The adoption of criteria to screen HSV PCR tests in CSF represents a cost-effective approach.

Encephalitis, Ontario, Canada, 2002-2013

The epidemiology of encephalitis in Ontario is remarkably similar to that in England.

Encephalitis, a brain inflammation leading to severe illness and often death, is caused by >100 pathogens. To assess the incidence and trends of encephalitis in Ontario, Canada, we obtained data on 6,463 Ontario encephalitis hospitalizations from the hospital Discharge Abstract Database for April 2002–December 2013 and analyzed these data using multiple negative binomial regression. The estimated crude incidence of all-cause encephalitis in Ontario was ≈4.3 cases/100,000 persons/year. Incidence rates for infants <1 year of age and adults >65 years were 3.9 and 3.0 times that of adults 20–44 years of age, respectively. Incidence peaks during August–September in 2002 and 2012 resulted primarily from encephalitis of unknown cause and viral encephalitis. Encephalitis occurred more frequently in older age groups and less frequently in women in Ontario when compared to England, but despite differences in population, vector-borne diseases, climate, and geography, the epidemiology was overall remarkably similar in the two regions.

Herpes Simplex Virus-1 Encephalitis in Adults: Pathophysiology, Diagnosis, and Management

Herpetic infections have plagued humanity for thousands of years, but only recently have advances in antiviral medications and supportive treatments equipped physicians to combat the most severe manifestations of disease. Prompt recognition and treatment can be life-saving in the care of patients with herpes simplex-1 virus encephalitis, the most commonly identified cause of sporadic encephalitis worldwide. Clinicians should be able to recognize the clinical signs and symptoms of the infection and familiarize themselves with a rational diagnostic approach and therapeutic modalities, as early recognition and treatment are key to improving outcomes. Clinicians should also be vigilant for the development of acute complications, including cerebral edema and status epilepticus, as well as chronic complications, including the development of autoimmune encephalitis associated with antibodies to the N-methyl-D-aspartate receptor and other neuronal cell surface and synaptic epitopes. Herein, we review the pathophysiology, differential diagnosis, and clinical and radiological features of herpes simplex virus-1 encephalitis in adults, including a discussion of the most common complications and their treatment. While great progress has been made in the treatment of this life-threatening infection, a majority of patients will not return to their previous neurologic baseline, indicating the need for further research efforts aimed at improving the long-term sequelae.

Potential clinical impact of the film array meningitis encephalitis panel in children with suspected central nervous system infections

The FilmArray Meningitis Encephalitis Panel, a multiplex PCR for testing of cerebrospinal fluid, was compared to conventional diagnostic methods in children with suspected central nervous system infections. The panel had comparable diagnostic yield (96% agreement) and improved time-to-diagnosis by 10.3 hours with potential for more judicious antimicrobial use, particularly acyclovir.

Encephalitis Surveillance through the Emerging Infections Program, 1997-2010

A 3-state syndromic surveillance system documented reduction and emergence of neurologic infectious diseases.

Encephalitis is a devastating illness that commonly causes neurologic disability and has a case fatality rate >5% in the United States. An etiologic agent is identified in <50% of cases, making diagnosis challenging. The Centers for Disease Control and Prevention Emerging Infections Program (EIP) Encephalitis Project established syndromic surveillance for encephalitis in New York, California, and Tennessee, with the primary goal of increased identification of causative agents and secondary goals of improvements in treatment and outcome. The project represents the largest cohort of patients with encephalitis studied to date and has influenced case definition and diagnostic evaluation of this condition. Results of this project have provided insight into well-established causal pathogens and identified newer causes of infectious and autoimmune encephalitis. The recognition of a possible relationship between enterovirus D68 and acute flaccid paralysis with myelitis underscores the need for ongoing vigilance for emerging causes of neurologic disease.

Diagnostics and Discovery in Viral Central Nervous System Infections

The range of viruses implicated in central nervous system disease continues to grow with globalization of travel and trade, emergence and reemergence of zoonoses and investments in discovery science. Diagnosis of viral central nervous system infections is challenging in that brain tissue, where the pathogen concentration is likely to be highest, is not readily obtained and sensitive methods for molecular and serological detection of infection are not available in most clinical microbiology laboratories. Here we review these challenges and discuss how they may be addressed using advances in molecular, proteomic and immunological methods.

Herpes Simplex Encephalitis: An Uncommon Presentation

Herpes Simplex Virus (HSV) encephalitis is an uncommon illness, with about 2 cases per 250,000 per year. Most are caused by HSV-1, with 10% having HSV-2 as the aetiologic factor. We present a case of Herpes simplex type1encephalitis in a 70 year old male with an uncommon presentation. The patient was a known case of endogenous depression with no medical records and on no treatment for the same, reported with acute changes in mental state for the past five days. He was talking irrelevantly, had hallucinations and was unduly aggressive and violent. He was subjected to a thorough clinical and diagnostic work-up which included cerebrospinal fluid analysis, CT head and MRI brain. MRI brain was suggestive of mild subdural effusion which hinted towards infectious cause of encephalitis. The cerebrospinal fluid viral serology panel detected herpes simplex type 1 virus (HSV1) that was later confirmed by CSF Polymerase Chain Reaction (PCR) technique. Hence, acyclovir was initiated by intravenous route at a dosage of 10mg/kg body weight and continued for two weeks. This case holds significance in view of the fact that organic causes must be excluded in suspected cases of psychiatric illness especially in the absence of fever. Also, CSF-PCR testing plays a pivotal role in diagnosing herpes simplex encephalitis.