Viral encephalitis: a review of diagnostic methods and guidelines for management

Respiratory syncytial virus-related encephalitis: magnetic resonance imaging findings with diffusion-weighted study

INTRODUCTION

Respiratory syncytial virus (RSV) is a common pathogen causing acute respiratory infection in children. Herein, we describe the incidence and clinical and magnetic resonance imaging (MRI) findings of RSV-related encephalitis, a major neurological complication of RSV infection.

METHODS

We retrospectively reviewed the medical records and imaging findings of the patients over the past 7 years who are admitted to our medical center and are tested positive for RSV-RNA by reverse transcriptase PCR. In total, 3,856 patients were diagnosed with RSV bronchiolitis, and 28 of them underwent brain MRI for the evaluation of neurologic symptoms; 8 of these 28 patients had positive imaging findings. Five of these 8 patients were excluded because of non-RSV-related pathologies, such as subdural hemorrhage, brain volume loss due to status epilepticus, periventricular leukomalacia, preexisting ventriculomegaly, and hypoxic brain injury.

RESULTS

The incidence of RSV-related encephalitis was as follows: 3/3,856 (0.08 %) of the patients are positive for RSV RNA, 3/28 (10.7 %) of the patient underwent brain MRI for neurological symptom, and 3/8 (37.5 %) of patients revealed abnormal MR findings. The imaging findings were suggestive of patterns of rhombenmesencephalitis, encephalitis with acute disseminated encephalomyelitis, and limbic encephalitis. They demonstrated no diffusion abnormality on diffusion-weighted image and symptom improvement on the follow-up study.

CONCLUSION

Encephalitis with RSV bronchiolitis occurs rarely. However, on brain MRI performed upon suspicion of neurologic involvement, RSV encephalitis is not infrequently observed among the abnormal MR findings and may mimic other viral and limbic encephalitis. Physicians should be aware of this entity to ensure proper diagnosis and neurologic care of RSV-positive patients.

Herpesvirus-associated central nervous system diseases after allogeneic hematopoietic stem cell transplantation

Herpesvirus infections of the central nervous system (CNS) are associated with encephalitis/myelitis and lymphoproliferative diseases in immunocompromised individuals. As of now, data of herpesvirus-associated CNS diseases in transplant recipients is limited. Hence, in this prospective study, we investigated the incidence of herpesvirus-associated CNS diseases and explored the diagnosis of these diseases in 281 allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. Herpesvirus-DNA and cerebrospinal fluid (CSF) cells were sampled from 58 recipients with herpesvirus-associated diseases or with unexplainable CNS manifestations. Results showed that 23 patients were diagnosed as herpesvirus-associated CNS diseases, including 15 Epstein-Barr virus (EBV)-associated diseases (4 encephalitis and 11 lymphoproliferative diseases), 5 herpes simplex virus type 1 encephalitis, 2 cytomegalovirus encephalitis/myelitis and 1 varicella zoster virus encephalitis. The median time of diseases onset was 65 (range 22-542) days post-transplantation. The 3-year cumulative incidence of herpesvirus-associated encephalitis/myelitis and post-transplant lymphoproliferative disorder (PTLD) was 6.3% ±1.9% and 4.1% ±1.2%, respectively. Of the evaluable cases, CSF cells mainly consisted of CD19⁺CD20⁺ B cells (7/11) and had clonal rearrangement of immunoglobulin genes (3/11) in patients with CNS-PTLD. On the contrary, in patients with encephalitis/myelitis, CSF cells were comprised of different cell populations and none of the gene rearrangement was detected. Herpesvirus-associated CNS diseases are common in the early stages of allo-HSCT, wherein EBV is the most frequent causative virus. The immunophenotypic and clonal analysis of CSF cells might be helpful in the differential diagnosis between encephalitis and lymphoproliferative diseases.

Case definitions, diagnostic algorithms, and priorities in encephalitis: consensus statement of the international encephalitis consortium

BACKGROUND

Encephalitis continues to result in substantial morbidity and mortality worldwide. Advances in diagnosis and management have been limited, in part, by a lack of consensus on case definitions, standardized diagnostic approaches, and priorities for research.

METHODS

In March 2012, the International Encephalitis Consortium, a committee begun in 2010 with members worldwide, held a meeting in Atlanta to discuss recent advances in encephalitis and to set priorities for future study.

RESULTS

We present a consensus document that proposes a standardized case definition and diagnostic guidelines for evaluation of adults and children with suspected encephalitis. In addition, areas of research priority, including host genetics and selected emerging infections, are discussed.

CONCLUSIONS

We anticipate that this document, representing a synthesis of our discussions and supported by literature, will serve as a practical aid to clinicians evaluating patients with suspected encephalitis and will identify key areas and approaches to advance our knowledge of encephalitis.

A proposed roadmap for inpatient neurology quality indicators

BACKGROUND/PURPOSE

In recent years, there has been increasing pressure to measure and report quality in health care. However, there has been little focus on quality measurement in the field of neurology for conditions other than stroke and transient ischemic attack. As the number of evidence-based treatments for neurological conditions grows, so will the demand to measure the quality of care delivered. The purpose of this study was to review essential components of hospital performance measures for neurological disease and propose potential quality indicators for commonly encountered inpatient neurological diagnoses.

METHODS

We determined the most common inpatient neurological diagnoses at a major tertiary care medical center by reviewing the billing database. We then searched PubMed and the National Guidelines Clearinghouse to identify treatment guidelines for these conditions. Guideline recommendations with class I/level A evidence were evaluated as possible quality indicators.

RESULTS

We found 94 guidelines for 14 inpatient neurological conditions other than stroke and transient ischemic attack. Of these, 36 guidelines contained at least 1 recommendation with class I evidence. Based on these, potential quality indicators for intracerebral hemorrhage, subarachnoid hemorrhage, pneumococcal meningitis, coma following cardiac arrest, encephalitis, Guillain-Barre syndrome, multiple sclerosis, and benign paroxysmal positional vertigo are proposed.

CONCLUSIONS

There are several inpatient neurological conditions with treatments or diagnostic test routines supported by high levels of evidence that could be used in the future as quality indicators.

Pitfalls associated with the diagnosis of herpes simplex encephalitis

Herpes simplex encephalitis (HSE) still remains a serious illness with high morbidity and mortality. The characteristic presentation of HSE usually consists of fever, headache, and altered mental function. We present three patients with atypical features of HSE. First, a 48-year-old man with symptomatic posttraumatic epilepsy, who developed a gastrointestinal infection, seizures, and fever. After significant clinical improvement, the patient had fever again and developed a status epilepticus, which led to the diagnosis of HSE. Second, an 84-year-old woman with hyperactive delirium after levofloxacin intake. Cranial computed tomography (CCT) revealed hypodense temporal changes, prompting lumbar puncture and diagnosis of HSE. Third, a 51-year-old diabetic woman presented with fever and acute confusion. As CCT and cell count of cerebrospinal fluid (CSF) were normal, infection and hyperglycemia as initial diagnoses were postulated. Due to aphasic symptoms, the differential diagnosis of a stroke was taken into account. Thus a second lumbar puncture led to the correct diagnosis of HSE. These atypical presentations need a high grade of suspicion and a high willingness to reconsider the initial working diagnosis, in order to prevent a diagnostic delay.

Human cord blood-derived mononuclear cell transplantation for viral encephalitis-associated cognitive impairment: a case report

INTRODUCTION

Herpes simplex virus is the most common cause of sporadic viral encephalitis. Cognitive impairments persist in most patients who survive herpes simplex virus-caused encephalitis after undergoing currently available treatments. This is the first report on the development of human cord blood-derived mononuclear cell transplantation as a new treatment intervention to improve the prognosis of sequelae of viral encephalitis.

CASE PRESENTATION

An 11-year-old Han Chinese boy developed sequelae of viral encephalitis with cognitive, mental and motor impairments in the 8 months following routine treatments. Since receiving allogeneic cord blood-derived mononuclear cell transplantation combined with comprehensive rehabilitation therapies 7 years ago, the patient's health has significantly improved and remained stable.

CONCLUSIONS

Human cord blood-derived mononuclear cell transplantation may be a potential therapeutic strategy for treating the neuropsychiatric and neurobehavioral sequelae of viral encephalitis.

Recent issues in herpes simplex encephalitis

Herpes simplex encephalitis (HSE) remains the most important cause of fatal sporadic encephalitis in man. Caused by herpes simplex virus type 1 (HSV-1), and more rarely by HSV-2, it can have devastating clinical consequences for the patient, especially when the instigation of acyclovir therapy has been delayed by more than 2 days or more. Even with acyclovir treatment, nearly a third of patients may die or suffer significant morbidity. Both host and viral factors may interact to affect the clinical phenotype. Here we consider some of the recently published management guidelines for HSE and comment on various current issues of contention. The latter includes the timing and frequency of cerebrospinal fluid examinations for the polymerase chain reaction detection of HSV, decisions regarding acyclovir therapy including the consequences of delay in its initiation, and the use of corticosteroids in the disease.

Herpes simplex encephalitis following microvascular decompression for trigeminal neuralgia

The authors present the first reported case of herpes simplex encephalitis (HSE) precipitated by trigeminal nerve microvascular decompression (MVD). The presentation of this specific case together with the pathogenesis and management of HSE are discussed, with a relevant literature review. This 29-year-old woman with treatment-resistant trigeminal neuralgia underwent a successful elective MVD of the right trigeminal nerve. She was discharged but was readmitted 1 week postoperatively with clinical signs and symptoms of meningitis. A CSF sample was obtained through lumbar puncture before she was treated initially with ceftriaxone. The polymerase chain reaction test of CSF was later positive for herpes simplex virus Type 1, at which point the patient was switched to a 2-week course of intravenous acyclovir before being discharged. Although this disease is rare, to avoid a delay in antiviral treatment the authors suggest that HSE should be considered in any patient presenting with a meningoencephalitic picture following MVD.

Decompressive craniectomy for encephalitis with brain herniation: case report and review of the literature

BACKGROUND

Decompressive craniectomy (DC) has been sporadically used in cases of infectious encephalitis with brain herniation. Like for other indications of DC, evidence is lacking regarding the beneficial or detrimental effects for this pathology.

METHODS

We reviewed all the cases of viral and bacterial encephalitis treated with decompressive craniectomy reported in the literature. We also present one case from our institution. These data were analyzed to determine the relation between clinical and epidemiological variables and outcome in surgically treated patients.

RESULTS

Of 48 patients, 39 (81.25 %) had a favorable functional recovery and 9 (18.75 %) had a negative course. Only two patients (4 %) died after surgical treatment. A statistically significant association was found between diagnosis (viral and bacterial encephalitis) and outcome (GOS) in surgically treated patients. Viral encephalitis, usually caused by herpes simplex virus (HSV), has a more favorable outcome (92.3 % with GOS 4 or 5) than bacterial encephalitis (56.2 % with GOS 4 or 5).

CONCLUSIONS

Based on this literature review, we consider that, due to the specific characteristics of infectious encephalitis, especially in case of viral infection, decompressive craniectomy is probably an effective treatment when brain stem compression threatens the course of the disease. In patients with viral encephalitis, better prognosis can be expected when surgical decompression is used than when only medical treatment is provided.

[Acute encephalitis]

Acute encephalitis can be due to many causes, although most are viral, and is a medical emergency. A significant percentage remains without a definitive diagnosis due to the large number of etiologic agents. The single most frequent cause of sporadic encephalitis around the world is herpes simplex virus type 1, although in certain locations diverse local agents should be considered such as West Nile virus or tick-borne encephalitis, among others. Patients with encephalitis require intense care measures with special emphasis on respiratory problems secondary to a depressed level of consciousness, seizures, and intracranial hypertension due to cerebral edema. Herpes encephalitis has an incidence of 4 cases per million inhabitants. Clinical presentation, together with electroencephalography, magnetic resonance imaging and cerebrospinal fluid (CSF) findings are critical to establish a diagnosis. Polymerase chain reaction (PCR) in CSF is highly sensitive and specific (> 95%), but the results can be negative during the first 3 days of the disease. The treatment of choice is currently acyclovir 10 mg/kg/8 h for 10-21 days. Whenever resistance is suspected, foscarnet is an alternative. The family of arboviruses represents another important etiologic group of encephalities. These are zoonotic diseases transmitted by mosquitoes or ticks and include alphaviruses, bunyaviruses (Toscana virus and others) and flaviviruses. The West Nile virus belongs to the latter group. There is no specific therapy and diagnosis is based on serology and PCR depending on the suspected virus.

Management of suspected viral encephalitis in adults--Association of British Neurologists and British Infection Association National Guidelines

In the 1980s the outcome of patients with herpes simplex encephalitis was shown to be dramatically improved with aciclovir treatment. Delays in starting treatment, particularly beyond 48 h after hospital admission, are associated with a worse prognosis. Several comprehensive reviews of the investigation and management of encephalitis have been published. However, their impact on day-to day clinical practice appears to be limited. The emergency management of meningitis in children and adults was revolutionised by the introduction of a simple algorithm as part of management guidelines. In February 2008 a group of clinicians met in Liverpool to begin the development process for clinical care guidelines based around a similar simple algorithm, supported by an evidence base, whose implementation is hoped would improve the management of patients with suspected encephalitis.

Prolonged detection of herpes simplex virus type 2 (HSV-2) DNA in cerebrospinal fluid despite antiviral therapy in a patient with HSV-2-associated radiculitis

Herpes simplex virus type 2 (HSV-2) can cause radiculo-myelitis as a neurological manifestation. We report a case of ongoing HSV-2 DNA positivity in the cerebrospinal fluid (CSF) of at least eight weeks under antiviral therapy with acyclovir in a highly immunocompromised hemato-oncologic patient with HSV-2-associated radiculitis. Upon admission, the patient presented with pain, leg paresis, and urinary incontinence, as well as pleocytosis in the CSF. Quantitative real-time PCR of the CSF at day 3 after admission revealed HSV-2 with a concentration of 2.0×10(5) copies/ml and treatment with acyclovir intravenously and prednisolone by mouth was started. Clinical symptoms resolved almost completely after approximately 3 weeks of antiviral therapy. However, CSF samples of day 12, 19, 26, 33, 39, 48 and 54 after admission showed a slow decline of HSV-2 DNA concentrations. HSV-2 DNA was still detectable (1.6×10(4) copies/ml) at day 54 after admission. Genotypic resistance testing showed, as far as available, no mutations indicative for acyclovir resistance. Since an increasing specific antibody index for HSV was observed, we speculate that the prolonged detectability of HSV-2 DNA in the CSF might not necessarily indicate ongoing viral replication but neutralized virus. Other hypotheses and the consequences on treatment are discussed. To our knowledge this is the first report about the long-term viral load kinetics of HSV-2 in the CSF of a patient with radiculitis under antiviral therapy, highlighting the need for further studies on HSV DNA kinetics in the CSF and their significance for an appropriate antiviral treatment.

Management of suspected viral encephalitis in children - Association of British Neurologists and British Paediatric Allergy, Immunology and Infection Group national guidelines

In the 1980s the outcome of patients with herpes simplex encephalitis was shown to be dramatically improved with aciclovir treatment. Delays in starting treatment, particularly beyond 48 h after hospital admission, are associated with a worse prognosis. Several comprehensive reviews of the investigation and management of encephalitis have been published. However, their impact on day-to-day clinical practice appears to be limited. The emergency management of meningitis in children and adults was revolutionised by the introduction of a simple algorithm as part of management guidelines. In February 2008 a group of clinicians met in Liverpool to begin the development process for clinical care guidelines based around a similar simple algorithm, supported by an evidence base, whose implementation is hoped would improve the management of patients with suspected encephalitis.

Diagnostic strategy used to establish etiologies of encephalitis in a prospective cohort of patients in England

The laboratory diagnostic strategy used to determine the etiology of encephalitis in 203 patients is reported. An etiological diagnosis was made by first-line laboratory testing for 111 (55%) patients. Subsequent testing, based on individual case reviews, resulted in 17 (8%) further diagnoses, of which 12 (71%) were immune-mediated and 5 (29%) were due to infection. Seventy-five cases were of unknown etiology. Sixteen (8%) of 203 samples were found to be associated with either N-methyl-d-aspartate receptor or voltage-gated potassium channel complex antibodies. The most common viral causes identified were herpes simplex virus (HSV) (19%) and varicella-zoster virus (5%), while the most important bacterial cause was Mycobacterium tuberculosis (5%). The diagnostic value of testing cerebrospinal fluid (CSF) for antibody was assessed using 139 samples from 99 patients, and antibody was detected in 46 samples from 37 patients. Samples collected at 14 to 28 days were more likely to be positive than samples taken 0 to 6 days postadmission. Three PCR-negative HSV cases were diagnosed by the presence of virus-specific antibody in the central nervous system (CNS). It was not possible to make an etiological diagnosis for one-third of the cases; these were therefore considered to be due to unknown causes. Delayed sampling did not contribute to these cases. Twenty percent of the patients with infections with an unknown etiology showed evidence of localized immune activation within the CNS, but no novel viral DNA or RNA sequences were found. We conclude that a good standard of clinical investigation and thorough first-line laboratory testing allows the diagnosis of most cases of infectious encephalitis; testing for CSF antibodies allows further cases to be diagnosed. It is important that testing for immune-mediated causes also be included in a diagnostic algorithm.

Enterovirus and herpesviridae family as etiologic agents of lymphomonocytary meningitis, Southern Brazil

Viral meningitis is a common infectious disease of the central nervous system (CNS) that occurs worldwide. The aim of this study was to identify the etiologic agent of lymphomonocytary meningitis in Curitiba, PR, Brazil. During the period of July 2005 to December 2006, 460 cerebrospinal fluid (CSF) samples with lymphomonocytary meningitis were analyzed by PCR methodologies. Fifty nine (12.8%) samples were positive. Enteroviruses was present in 49 (83%) samples and herpes virus family in 10 (17%), of these 6 (10%) herpes simplex virus, 1 (2%) Epstein Barr virus, 2 (3%) human herpes virus type 6 and 1 (2%) mixed infection of enterovirus and Epstein Barr virus. As conclusion enterovirus was the most frequent virus, with circulation during summer and was observed with higher frequency between 4 to 17 years of age. PCR methodology is an important method for rapid detection of RNA enterovirus and DNA herpesvirus in CSF.

Is West Nile virus a potential cause of central nervous system infection in Brazil?

Meningitis and encephalitis are complications of West Nile virus (WNV) infection. Although WNV is endemic in North America, the virus has recently been reported in Colombia and Argentina. Investigation of WNV in Brazil is important since this virus has never been studied previously in this country.

OBJECTIVE

To investigate the presence of WNV infection in viral encephalitis/meningitis cases of unknown etiology in the city of Rio de Janeiro, Brazil.

METHOD

Thirty-seven adults with viral meningitis/encephalitis had their serum and CSF tested for WNV antibodies using the ELISA method.

RESULTS

Only one case was WNV-positive, but this case was also positive for dengue. The plaque reduction neutralization test distinguished infections, and was negative for WNV.

CONCLUSION

WNV can be confused with dengue infection. Their symptoms and neurological picture are similar. We did not find WNV in any patients with encephalitis and meningitis in the city of Rio de Janeiro. Up to now, it has not been detected in Brazil.

Review of the etiologies of viral meningitis and encephalitis in a dengue endemic region

OBJECTIVES

To evaluate the etiology of viral meningitis and encephalitis in adults and adolescents living in areas affected by dengue.

METHODS

Over two years, adults and adolescents with diagnoses of viral encephalitis or meningitis were selected for study in Brazil. PCRs for dengue, enterovirus, HSV1 and 2 and cytomegalovirus were performed in CSF samples. Serum and CSF samples were tested for the presence of anti-dengue IgM antibodies.

RESULTS

The etiologies of encephalitis and meningitis were determined in 70% of cases (30/47). Dengue was the leading cause of encephalitis (47%) with normal CSF cellularity in 75% of these patients. HSV1 was found in 17.6% of the cases, two of which had mild encephalitis. Enterovirus was the most common cause of meningitis (50%), followed by HSV1 (15%), cytomegalovirus and dengue (10%, each).

CONCLUSIONS

We identified the viral agents causing encephalitis and meningitis in a higher proportion of cases than has been reported in other studies. Dengue was the most frequent cause of encephalitis, which surpassed HSV. In endemic areas, dengue should be investigated as an important cause of encephalitis. Normal CSF cellularity should not exclude dengue encephalitis. Enterovirus is known to be the leading cause of meningitis in children, but here we found it was also the main cause of the disease in adults. HSV1 should be investigated in patients with mild forms of encephalitis and meningitis.

Neuroinfection survey at a neurological ward in a Brazilian tertiary teaching hospital

OBJECTIVES

This study was undertaken to characterize the neuroinfection profile in a tertiary neurological ward.

INTRODUCTION

Neuroinfection is a worldwide concern and bacterial meningitis, tetanus and cerebral malaria have been reported as the commonest causes in developing countries.

METHODS

From 1999 to 2007, all patients admitted to the Neurology Ward of Hospital das Clínicas, São Paulo University School of Medicine because of neuroinfection had their medical records reviewed. Age, gender, immunological status, neurological syndrome at presentation, infectious agent and clinical outcome were recorded.

RESULTS

Three hundred and seventy four cases of neuroinfectious diseases accounted for 4.2% of ward admissions and the identification of infectious agent was successful in 81% of cases. Mean age was 40.5 + 13.4 years, 63.8% were male, 19.7% were immunocompromised patients and meningoencephalitis was the most common clinical presentation despite infectious agent. Viruses and bacteria were equally responsible for 29.4% of neuroinfectious diseases; parasitic, fungal and prion infections accounted for 28%, 9.6% and 3.5% respectively. Human immunodeficiency virus (HIV), herpes simplex virus 1 (HSV1), Mycobacterium tuberculosis, Treponema pallidum, Taenia solium, Schistosoma mansoni, Cryptococcus neoformans and Histoplasma capsulatum were the more common infectious pathogens in the patients. Infection mortality rate was 14.2%, of which 62.3% occurred in immunocompetent patients.

CONCLUSION

Our institution appeared to share some results with developed and developing countries. Comparison with literature may be considered as quality control to health assistance.

Should there be a standardised approach to the diagnostic workup of suspected adult encephalitis? A case series from Australia

BACKGROUND

The clinical diagnosis of encephalitis is often difficult and identification of a causative organism is infrequent. The encephalitis syndrome may herald the emergence of novel pathogens with outbreak potential. Individual treatment and an effective public health response rely on identifying a specific pathogen. In Australia there have been no studies to try to improve the identification rate of encephalitis pathogens. This study aims to review the diagnostic assessment of adult suspected encephalitis cases.

METHODS

A retrospective clinical audit was performed, of all adult encephalitis presentations between July 1998 and December 2007 to the three hospitals with adult neurological services in the Hunter New England area, northern New South Wales, Australia. Case notes were examined for evidence of relevant history taking, clinical features, physical examination, laboratory and neuroradiology investigations, and outcomes.

RESULTS

A total of 74 cases were included in the case series. Amongst suspected encephalitis cases, presenting symptoms and signs included fever (77.0%), headache (62.1%), altered consciousness (63.5%), lethargy (32.4%), seizures (25.7%), focal neurological deficits (31.1%) and photophobia (17.6%). The most common diagnostic laboratory test performed was cerebrospinal fluid (CSF) analysis (n = 67, 91%). Herpes virus polymerase chain reaction (n = 53, 71.6%) and cryptococcal antigen (n = 46, 62.2%) were the antigenic tests most regularly performed on CSF. Neuroradiological procedures employed were computerized tomographic brain scanning (n = 68, 91.9%) and magnetic resonance imaging of the brain (n = 35, 47.3%). Thirty-five patients (47.3%) had electroencephalograms. The treating clinicians suspected a specific causative organism in 14/74 cases (18.9%), of which nine (12.1%) were confirmed by laboratory testing.

CONCLUSIONS

The diagnostic assessment of patients with suspected encephalitis was not standardised. Appropriate assessment is necessary to exclude treatable agents and identify pathogens warranting public health interventions, such as those transmitted by mosquitoes and those that are vaccine preventable. An algorithm and guidelines for the diagnostic workup of encephalitis cases would assist in optimising laboratory testing so that clinical management can be best tailored to the pathogen, and appropriate public health measures implemented.

High-throughput automated image analysis of neuroinflammation and neurodegeneration enables quantitative assessment of virus neurovirulence

Historically, the safety of live attenuated vaccine candidates against neurotropic viruses was assessed by semi-quantitative analysis of virus-induced histopathology in the central nervous system of monkeys. We have developed a high-throughput automated image analysis (AIA) for the quantitative assessment of virus-induced neuroinflammation and neurodegeneration. Evaluation of the results generated by AIA showed that quantitative estimates of lymphocytic infiltration, microglial activation, and neurodegeneration strongly and significantly correlated with results of traditional histopathological scoring. In addition, we show that AIA is a targeted, objective, accurate, and time-efficient approach that provides reliable differentiation of virus neurovirulence. As such, it may become a useful tool in establishing consistent analytical standards across research and development laboratories and regulatory agencies, and may improve the safety evaluation of live virus vaccines. The implementation of this high-throughput AIA will markedly advance many fields of research including virology, neuroinflammation, neuroscience, and vaccinology.

Acute central nervous system infections in adults--a retrospective cohort study in the NHS North West region

BACKGROUND

Over the last 15 years, bacterial meningitis has received considerable attention, including national guidelines, whilst viral central nervous system (CNS) infections have been relatively neglected. A recent pilot study suggested that management of patients with suspected viral encephalitis was often suboptimal.

AIM

To examine the relative incidence, clinical features and management of suspected acute CNS infections in adults across the NHS North West Region.

DESIGN

A multicentre cross-sectional retrospective cohort study at 10 hospitals across the region over 3 months (from September to December 2007). Following a screen of all patients who had cerebrospinal fluid (CSF) analysis or received intravenous aciclovir and/or third-generation cephalosporin, those with clinical features suspicious of a CNS infection were included. Management was compared with the national meningitis and regional encephalitis guidelines.

RESULTS

Three hundred and eighty-five patients were screened; 217 patients had a suspected CNS infection and 44 (20%) had a CNS infection: 18 aseptic meningitis (one herpes simplex virus [HSV]-2), 13 purulent meningitis (four Streptococcus pneumoniae) and 13 encephalitis (three HSV-1). The median (range) time from admission to suspicion of CNS infection and to LP was longer for patients with encephalitis than meningitis [4 (0.3-312) vs. 0.3 (0.1-12) h, P<0.001, and 23 (4-360) vs. 12 (2-48) h, P=0.042, respectively]; and the median time to treatment was longer for aciclovir than cephalosporin [7 (0.5-312) vs. 3 (0.3-312) h, P=0.002].

DISCUSSION

Encephalitis was as common as purulent meningitis, and HSV as common as Streptococcus pneumoniae. However, the management of patients with encephalitis was worse than meningitis. National encephalitis guidelines are needed.

High-dose ganciclovir in HHV-6 encephalitis of an immunocompetent child

Encephalitis and other neurologic complications, including acute necrotizing encephalopathy, are associated with human herpesvirus-6 infection. Antiviral treatment against human herpesvirus-6 infection is indicated only for immunocompromised patients. We describe a 15-month-old immunocompetent child with severe human herpesvirus-6-induced encephalitis. The primary infection was characterized by human herpesvirus-6 DNA in cerebrospinal fluid and serum, the presence of serum human herpesvirus-6 immunoglobulin M antibodies, and a rise in serum human herpesvirus-6 immunoglobulin G antibodies. Magnetic resonance imaging demonstrated multiple, partly symmetric, necrotic lesions in the pons, medulla oblongata, thalamus, external capsules, and occipital subcortical and cortical areas. High-dose ganciclovir (18 mg/kg/day) was used as antiviral treatment, without side effects. A pharmacokinetic analysis of ganciclovir was performed. The initial recovery from severe disease was good. At 3-year follow-up, neurologic sequelae included epilepsy and ataxia. This case suggests that treatment with ganciclovir should be considered in human herpesvirus-6 central nervous system infections because the neurologic sequelae may otherwise be severe. Controlled, prospective, clinical trials are warranted, to analyze the pharmacokinetics of ganciclovir in infants.

Herpes simplex type 1 encephalitis restricted to the brainstem in a pediatric patient

Herpes simplex encephalitis is a potentially fatal infection of central nervous system that typically involves frontal and temporal lobes. Occasionally, it presents an extratemporal involvement and in rarer cases, it is limited to the brainstem. We describe a case of an adolescent who presented with fever, sore throat, and vertigo. Clinical picture evolved to lethargy, tetraparesis, consciousness impairment, and respiratory failure. MRI showed lesions restricted to the brainstem. PCR of CSF was positive for herpes simplex type 1.

Novel swine-origin influenza A (H1N1) viral encephalitis

The World Health Organization declared that a new strain of novel swine-origin influenza A (H1N1) virus was responsible for the pandemic infection in June 2009. We report a case of encephalitis diagnosed as the H1N1 virus infection. We describe a 17-year-old patient who had a seizure attack, diagnosed with a H1N1 virus infection via real time reverse-transcriptase polymerase chain reaction (RT-PCR). The H1N1 virus infection can be causative of the encephalitis, as with other influenza virus infections. Careful monitoring is essential for reducing complications.

Fatal herpetic encephalitis during brain radiotherapy in a cerebral metastasized breast cancer patient

Herpes simplex encephalitis (HSE) is a life-threatening condition with high mortality. The pathogenesis underlying the reactivation of latent herpes simplex virus (HSV) remains undefined. We present the case of a 55-year-old female who developed HSE type 1 during brain irradiation and antioedematous dexamethasone treatment for leptomeningeal metastasized breast tumor with epileptic seizures. During the radiotherapy (RT), after a total of 32 Gray administrated in 16 fractions, our patient developed cognitive impairment and partial epileptic status without fever. Two days later the patient's clinical conditions had deteriorated and high fever manifested. A diagnosis of HSE type 1 was made by a positive cerebrospinal fluid polymerase chain reaction. Antiviral therapy with high doses of acyclovir was practiced for four weeks but the comatose state persisted. The patient died 59 days after the last RT fraction. The temporal relationship of RT to the occurrence of HSE suggests that cranial irradiation may play a role in the reactivation of latent HSV. Although antiviral therapy resistance is infrequent in immunocompetent patients, it is one of the main problems in immunocompromized patients.

Conventional and molecular diagnostic testing for the acute neurologic patient

OBJECTIVE

The aim of this review is to describe and evaluate both conventional and molecular diagnostic testing utilized in dogs and cats with acute neurologic diseases. Various types of polymerase chain reaction (PCR) are explored along with novel molecular diagnostic testing that ultimately may prove useful in the critical care setting.

DATA SOURCES

PUBMED was searched to obtain relevant references material using keywords: 'canine OR feline meningitis AND meningoencephalitis,''feline infectious peritonitis,''canine distemper,''canine OR feline AND toxoplasma,''canine neospora,''canine OR feline AND rickettsia,''granulomatous meningoencephalitis,''steroid responsive meningitis arteritis,''necrotizing encephalitis,''novel neurodiagnostics,''canine OR feline AND CNS borrelia,''canine OR feline AND CNS bartonella,''canine OR feline AND CNS fungal,''nested OR multiplex OR degenerate OR consensus OR CODEHOP AND PCR.' Research findings from the authors' laboratory and current veterinary textbooks also were utilized.

HUMAN DATA SYNTHESIS

Molecular diagnostic testing including conventional, real-time, and consensus and degenerate PCR and microarray analysis are utilized routinely for the antemortem diagnosis of infectious meningoencephalitis (ME) in humans. Recently, PCR using consensus degenerate hybrid primers (CODEHOP) has been used to identify and characterize a number of novel human viruses.

VETERINARY DATA SYNTHESIS

Molecular diagnostic testing such as conventional and real-time PCR aid in the diagnosis of several important central nervous system infectious agents including canine distemper virus, Toxoplasma gondii, Neospora caninum, rickettsial species, and others. Recently, broadly reactive consensus and degenerate PCR reactions have been applied to canine ME including assays for rickettsial organisms, Borrelia spp. and Bartonella spp., and various viral families.

CONCLUSIONS

In the acute neurologic patient, there are several key infectious diseases that can be pursued by a combination of conventional and molecular diagnostic testing. It is important that the clinician understands the utility, as well as the limitations, of the various neurodiagnostic tests that are available.

Etiology of encephalitis in Australia, 1990-2007

Unexplained disease etiology in hospitalized patients highlights the importance of surveillance to detect emerging novel pathogens.

Encephalitis is a clinical syndrome commonly caused by emerging pathogens, which are not under surveillance in Australia. We reviewed rates of hospitalization for patients with encephalitis in Australia’s most populous state, New South Wales, from January 1990 through December 2007. Encephalitis was the primary discharge diagnosis for 5,926 hospital admissions; average annual hospitalization rate was 5.2/100,000 population. The most commonly identified pathogen was herpes simplex virus (n = 763, 12.9%). Toxoplasma encephalitis and subacute sclerosing panencephalitis showed notable declines. The average annual encephalitis case-fatality rate (4.6%) and the proportion of patients hospitalized with encephalitis with no identified pathogen (69.8%, range 61.5%–78.7%) were stable during the study period. The nonnotifiable status of encephalitis in Australia and the high proportion of this disease with no known etiology may conceal emergence of novel pathogens. Unexplained encephalitis should be investigated, and encephalitis hospitalizations should be subject to statutory notification in Australia.

Neurologic varicella complications before routine immunization in Germany

Varicella is an acute febrile, highly infectious disease. We describe the incidence and types of neurologic complications in children up to 16 years old. Hospitalized varicella cases were prospectively captured by active nationwide surveillance through the German Pediatric Surveillance Unit for Rare Diseases from January 2003 to December 2004. Neurologic complications occurred in 232 (25.4%) of 918 hospitalized children with varicella, and were the most frequent reason for hospitalization. The median age was 4.2 years (interquartile range 2.5-5.9). The median duration of hospital stay was 6 days (interquartile range 3-11). Neurologic complications were more frequent (P=0.054) in immunocompetent (32%) than immunocompromised (4%) children. The most frequent diagnoses comprised acute cerebellar ataxia in 72 (31.0%), febrile convulsion in 69 (29.7%), meningoencephalitis in 52 (22.4%), cerebral convulsions in 21 (9.1%), syncope in 9 (3.9%), and cerebral vasculitis/infarction in 6 (2.6%) of all children with neurologic complications. Twenty-eight (12%) demonstrated sequelae (18 with ataxia, four with epilepsy, two with hemiparesis, three with cerebral nerve palsy, and one with dysesthesia). Three patients died. The yearly incidence of neurologic varicella-associated hospitalizations was estimated at 2.4 neurologic complications per 100,000 children, corresponding to about one neurologic complication in 2000 varicella cases.

Herpes simplex type I (HSV-1) infection of the nervous system: is an immune response a good thing?

Herpes simplex virus type 1 (HSV-1) can induce a robust immune response initially thru the activation of pattern recognition receptors and subsequent type I interferon production that then shapes, along with other innate immune components, the adaptive immune response to the insult. While this response is necessary to quell virus replication, drive the pathogen into a "latent" state, and likely hinder viral reactivation, collateral damage can ensue with demonstrable cell death and foci of tissue pathology in the central nervous system (CNS) as a result of the release of inflammatory mediators including reactive oxygen species. Although rare, HSV-1 is the leading cause of frank sporadic encephalitis that, if left untreated, can result in death. A greater understanding of the contribution of resident glial cells and infiltrating leukocytes within the CNS in response to HSV-1 invasion is necessary to identify candidate molecules as targets for therapeutic intervention to reduce unwarranted inflammation coinciding with the maintenance of the anti-viral state.

Quantitation of cerebrospinal fluid lactic acid in infectious and non-infectious neurological diseases

BACKGROUND

The differential diagnosis between bacterial and viral meningitis is not easy in some cases. Cerebrospinal fluid (CSF) analysis is essential for establishing this diagnosis. The objectives were to quantitate lactic acid (LA) concentrations in bacterial and viral meningitis, and other central nervous system (CNS) diseases in order to evaluate the diagnostic utility of CSF LA for discriminating bacterial from viral meningitis.

METHODS

CSF LA was measured in 139 CSF samples from seven groups: viral meningitis with classic CSF; suspicion of viral meningitis with neutrophils in CSF; bacterial meningitis; non-infectious neurological diseases; chronic meningitis; traumatic lumbar puncture (LP) and normal CSF.

RESULTS

CSF LA was higher in bacterial meningitis 8.7 + 5.4 mmol/L compared with viral meningitis (1.9 + 0.6) and the other groups (p < 0.0001). CSF LA in the groups with viral meningitis was not different compared to groups with non-infectious CNS diseases and chronic meningitis. The ability of CSF LA to discriminate bacterial from viral meningitis showed a sensitivity of 80% and specificity of 97%, positive predictive value (PPV) of 94%, and negative predictive value (NPV) of 89%.

CONCLUSIONS

CSF LA is a powerful test to discriminate bacterial from viral meningitis with high sensitivity, specificity and predictive values. CSF LA can help in the cases with diagnostic uncertainty.

Autoimmune limbic encephalitis

Autoimmune limbic encephalitis (LE) can arise both by paraneoplastic and non-paraneoplastic mechanisms. Patients with LE usually have a subacute onset of memory impairment, disorientation and agitation, but can also develop seizures, hallucinations and sleep disturbance. The following investigations may aid the diagnosis: analysis of cerebrospinal fluid (CSF), electroencephalography, magnetic resonance imaging, fluorodeoxyglucose positron emission tomography and neuronal antibodies in the serum and CSF. Neuronal antibodies are sometimes, but not always, pathogenic. Autoimmune LE may respond to corticosteroids, intravenous IgG (IVIG) or plasma exchange. The cornerstone of paraneoplastic LE therapy is resection of the tumour and/or oncological treatment. Several differential diagnoses must be excluded, among them herpes simplex encephalitis.

Differential diagnosis of acute central nervous system infections in children using modern microbiological methods

AIM

Except bacterial meningitis, the agents causing acute central nervous system (CNS) infections in children are disclosed in only approximately half of the cases, and even less in encephalitis. We studied the potential of modern microbiological assays to improve this poor situation.

METHODS

In a prospective study during 3 years, all children attending hospital with suspected CNS infection were examined using a wide collection of microbiological tests using samples from the cerebrospinal fluid, serum, nasal swabs and stool.

RESULTS

Among 213 patients, 66 (31%) cases suggested CNS infection and specific aetiology was identified in 56 patients. Of these microbiologically confirmed cases, viral meningitis/encephalitis was diagnosed in 25 (45%), bacterial meningitis in 21 (38%) and neuroborreliosis in 9 (16%) cases while 1 child had fungal infection. In meningitis patients, the causative agent was identified in 85% (35/41) cases and in encephalitis in 75% (12/16). The most common bacteria were Streptococcus agalactiae, Streptococcous pneumonie and Neisseria meningitidis, while the most frequently detected viruses were enteroviruses and varicella zoster virus.

CONCLUSION

In 75% to 85% of paediatric CNS infections, specific microbiological diagnosis was obtained with modern laboratory techniques. The results pose a basis for prudent approach to these potentially serious diseases.

Management of suspected herpes simplex virus encephalitis in adults in a U.K. teaching hospital

The outcome of herpes simplex virus (HSV) encephalitis is improved with prompt initiation of aciclovir treatment. Delays are common, but there is little understanding of why they occur. The case notes of 21 adults admitted with suspected HSV encephalitis over one year were reviewed. The median (range) duration of illness was 2.5 (1-99) days. Seventeen (81%) patients had a lumbar puncture (LP) performed, at a median (range) time of 24 (2-114) hours after encephalitis was suspected. Lumbar puncture was delayed for a computed tomography (CT) scan in 15 patients, but only one of these had contraindications to an immediate LP. The median (range) time from presentation to starting aciclovir was 48 (2-432) hours. HSV-PCR (polymerase chain reaction) was requested on cerebrospinal fluid from 12 patients, one of whom was positive. Five (24%) patients were given the wrong dose of aciclovir. Overall the management of suspected HSV encephalitis was often sub-optimal, with delays in LP occurring due to unnecessary CT scans, and the wrong aciclovir dose administered. Guidelines for the management of suspected encephalitis are needed.

Multiplex real-time PCR for the simultaneous detection of herpes simplex virus, human herpesvirus 6, and human herpesvirus 7

A simultaneous detection system to quantify HSV, HHV-6, and HHV-7 DNA via multiplex real-time PCR using different fluorochromes was developed. The minimum quantitative level established via this multiplex assay was four copies per reaction for HSV type 1, four copies for HHV-6, and three copies for HHV-7, respectively. The dynamic range encompassed at least six orders of magnitude. The system was specific and reproducible even in the presence of large amounts of other viral DNA. We then applied this multiplex real-time PCR assay to 105 CSF specimens obtained from subjects less than 15 years old in whom a diagnosis of viral encephalitis/encephalopathy was suspected on clinical grounds. The detection rate for each viral DNA was 6.7% for HSV, 9.5% for HHV-6, and 1.9% for HHV-7. These results indicate that our system is reliable and may be useful for the rapid diagnosis of viral encephalitis/encephalopathy.

A case of maternal herpes simplex virus encephalitis during late pregnancy

BACKGROUND

A pregnant 25-year-old woman at 32 weeks' gestation was admitted to an emergency unit after her husband had found her drowsy and with her tongue bitten. The day before admission, the patient had developed a fever of 39 degrees C, was suffering from headaches, was nauseated and had vomited. On admission, she had anterograde and retrograde amnesia, but no somatic neurological deficits were detected.

INVESTIGATIONS

Routine laboratory testing, lumbar puncture, cerebrospinal fluid analysis, routine bacteriology, brain MRI, and polymerase chain reaction testing for neurotropic viruses including herpes simplex virus types 1 and 2.

DIAGNOSIS

Maternal herpes simplex virus type 1 encephalitis.

MANAGEMENT

Antiviral and anticonvulsive therapy, supportive treatment, and cesarean section.

Central nervous system involvement after herpes zoster ophthalmicus

PURPOSE

To report central nervous system involvement after varicella zoster virus infection.

METHODS

We evaluated the frequency and type of neurological complications in patients initially presenting with ophthalmic herpes zoster at an ophthalmological department in a Danish university hospital, over a 7-year period.

RESULTS

Of the 110 immunocompetent patients who presented with initial ophthalmic zoster, six (5.5%) suffered from neurological complications other than post-herpetic neuralgia. Four experienced isolated cranial motor nerve palsies, one patient had meningitis with a favourable outcome and one patient had severe encephalitis with a poor clinical outcome.

CONCLUSIONS

Central nervous system involvement after varicella zoster virus infection is an uncommon, but potentially life-threatening, complication. Early recognition of neurological complications prompts acute, appropriate antiviral treatment.

Herpes simplex encephalitis after craniopharyngioma surgery

A 13-year-old girl exhibited rapid deterioration in mental status 15 days after surgery for craniopharyngioma. Serial CT scanning detected progression of a low-density lesion on the left frontotemporal lobe. The serum level of C-reactive protein was elevated and polymerase chain reaction identified herpes simplex virus DNA in the cerebrospinal fluid. Antiviral therapy with high-dose acyclovir (10 mg/kg 3 times daily) was begun. She recovered and could speak short sentences, but dysphasia and right hemiparesis remained. Early diagnosis and active treatment of herpes simplex encephalitis is essential for improving prognosis and saving lives.