A 12-year prospective study of childhood herpes simplex encephalitis: is there a broader spectrum of disease?

Primary herpes virus infection and ischemic stroke in childhood: a new association?

We describe, to our knowledge, the first case of arterial ischemic stroke after primary herpes simplex virus type 1 (HSV1) infection in a previously healthy child, without signs of encephalitis. A 10-year-old previously healthy girl was admitted to our hospital with acute left-sided hemiparesis which involved the lower half of her face. Submandibular lymphadenitis and oral vesicular lesions were present. MRI confirmed the suspicion of an acute ischemic stroke. Immunoglobulin M antibodies to HSV1 were detected. Cerebrospinal fluid polymerase chain reaction for herpes virus was negative. She was treated with aspirin (3mg/kg) and intravenous acyclovir (10mg/kg every 8 hours) for 21 days. Immunoglobulin G antibodies to HSV1 appeared 16 days after admission. Twelve months after her hospitalization the patient's examination was normal. Stroke should be considered a possible complication of HSV1 primary infection. Guidelines for the management of acute stroke in children are needed.

Long-term motor and cognitive outcome of acute encephalitis

OBJECTIVES

To examine the long-term motor and neurocognitive outcome of children with acute encephalitis and to look at possible prognostic factors.

METHODS

Children who were treated for acute encephalitis in 2000-2010 were reevaluated. All children and their parents were interviewed by using structured questionnaires, and the children underwent full neurologic examinations, along with comprehensive neurocognitive, attention, and behavioral assessments.

RESULTS

Of the 47 children enrolled, 1 died and 29 had neurologic sequelae, including motor impairment, mental retardation, epilepsy, and attention and learning disorders. Children with encephalitis had a significantly higher prevalence of attention-deficit/hyperactivity disorder (50%) and learning disabilities (20%) compared with the reported rate (5%-10%) in the general population of Israel (P < .05) and lower IQ scores. Lower intelligence scores and significantly impaired attention and learning were found even in children who were considered fully recovered at the time of discharge. Risk factors for long-term severe neurologic sequelae were focal signs in the neurologic examination and abnormal neuroimaging on admission, confirmed infectious cause, and long hospital stay.

CONCLUSIONS

Encephalitis in children may be associated with significant long-term neurologic sequelae. Significant cognitive impairment, attention-deficit/hyperactivity disorder, and learning disabilities are common, and even children who were considered fully recovered at discharge may be significantly affected. Neuropsychological testing should be recommended for survivors of childhood encephalitis.

Consensus guidelines on evaluation and management of suspected acute viral encephalitis in children in India

JUSTIFICATION

Viral encephalitis is an important cause of mortality and morbidity in children. The etiological agents are varied, and physicians treating such children often feel limited by the lack of uniform guidelines on evaluation and management of these critically ill children in resource-constrained settings.

PROCESS

An Expert Group Meeting on Viral Encephalitis in Children was held on 19th January, 2012 in Gurgaon, Haryana (under the aegis of PEDICON 2012, the National Conference of Indian Academy of Pediatrics). The invited experts included pediatricians and microbiologists with expertise in the relevant field. Various issues related to the subject were discussed and it was decided to bring out recommendations on the topic. The final recommendations were produced after circulating the draft document, and incorporating/discussing all changes, by email.

OBJECTIVES

To aid the pediatrician in the evaluation and management of children with suspected viral encephalitis and to assist the public health authorities in acute encephalitis surveillance. These guidelines do not cover viral encephalitis in the neonatal period and in immunocompromised children, Rabies encephalitis, and chronic viral encephalitis such as Subacute sclerosing panencephalitis (SSPE).

RECOMMENDATIONS

Recommendation for evaluation and management of suspected viral encephalitis in children are presented. In any acute encephalitis outbreak, pediatricians should be aware of the common viral causes of encephalitis in their area, what information and samples they should collect, and the contact details of the District Surveillance Unit. Pending specific diagnosis and therapy (which may or may not be possible), prompt empirical therapy and meticulous supportive care are important to prevent ongoing brain damage, and improve outcome.

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.

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

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

PCR for detection of herpes simplex virus in cerebrospinal fluid: alternative acceptance criteria for diagnostic workup

The determination of herpes simplex virus (HSV) infection using a PCR assay is one of the most commonly requested tests for analysis of cerebrospinal fluid (CSF), although only a very low proportion of results are positive. A previously reported study showed that selecting only those CSF samples with >5 leukocytes/mm(3) or a protein level of >50 mg/dl was adequate for the diagnostic workup. The aim of the present study was to assess the reliability of alternative acceptance criteria based on elevated CSF white blood cell counts (>10 cells/mm(3)). We analyzed all requests for HSV PCR received between January 2008 and December 2011. CSF samples were accepted for analysis if they had >10 cells/mm(3) or if the sample was from an immunocompromised patient or a child aged <2 years. In order to evaluate our selection criteria, we identified those CSF samples with a leukocyte count of 5 to 10 cells/mm(3) or protein levels of >50 mg/dl in order to test them for HSV type 1 and 2 (HSV-1 and HSV-2) DNA. During the study period, 466 CSF samples were submitted to the microbiology laboratory for HSV PCR. Of these, 268 (57.5%) were rejected, and 198 (42.5%) were tested according to our routine criteria. Of the tested samples, 11 (5.5%) were positive for HSV DNA (7 for HSV-1 and 4 for HSV-2). Of the 268 rejected specimens, 74 met the criteria of >5 cells/mm(3) and/or protein levels of >50 mg/dl. Of these, 70 (94.6%) were available for analysis. None of the samples yielded a positive HSV PCR result. Acceptance criteria based on CSF leukocyte counts, host immune status, and age can help to streamline the application of HSV PCR without reducing sensitivity.

Functional status of children with encephalitis in an inpatient rehabilitation setting: a case series

INTRODUCTION

Patterns and predictors of recovery from encephalitis are poorly understood.

METHODS

This study examined functional status and reviewed charts of all children who presented to a pediatric inpatient rehabilitation facility with encephalitis between 1996 and 2010. Functional status at admission and discharge from inpatient rehabilitation was evaluated using the Functional Independence Measure for Children (WeeFIM) Self-care, Mobility, Cognitive, and Total Developmental Functional Quotient scores (DFQ, % of age-appropriate function). Charts were reviewed to characterize key clinical features and findings.

RESULTS

Of the 13 children identified, the mean age was 9 years (range 5-16) with 54% males. Mean WeeFIM Total DFQ at admission was 37 (range: 15-90) and at discharge was 64 (range: 16-96). Average change in WeeFIM Total DFQ from admission to discharge was 26.7 (range 0-55, p < 0.001). WeeFIM domain scores improved between admission and discharge (Self-Care: p < 0.001, Cognition: p < 0.01, Mobility: p < 0.001). Eleven children displayed significant impairments in functional skills, defined as DFQ of < or =85, at discharge. Key clinical features and findings were diverse and not related to functional outcome.

CONCLUSIONS

Results suggest that significant functional improvement in children with encephalitis occurs during inpatient rehabilitation. Further research is necessary to identify predictors of outcome in children with encephalitis.

Should a hospitalized child receive empiric treatment with acyclovir?

Background

Herpes simplex encephalitis is associated with substantial morbidity and mortality and may be related to timely diagnosis and treatment. While awaiting the results of testing, hospitalization and empiric treatment with acyclovir is recommended, though the direct and indirect costs associated with this management are substantial. We sought to examine children hospitalized for possible herpes simplex encephalitis, following clinical and laboratory assessment in the emergency department, and empiric treatment with acyclovir, in order to describe the proportion receiving a complete course of treatment; and to identify the clinical variables which are associated with receiving a complete course, as compared with an incomplete course of acyclovir.

Methods

Hospitalized children prescribed acyclovir were included in this case control study. Clinical, laboratory and diagnostic variables were abstracted for children prescribed a complete (≥ 14 days) or an incomplete course (<14 days) of acyclovir. Odds ratios and 95% confidence intervals were calculated.

Results

289 children met eligibility criteria, 30 (10%) received a complete course and 259 (90%) received an incomplete course. A history of mucocutaneous herpes simplex virus infection (p < 0.01), Glasgow Coma Scale ≤ 13 (p = 0.02), focal neurologic findings (p = 0.001) and elevated cerebrospinal fluid white blood cell count (p = 0.05) were associated with a complete course of acyclovir.

Conclusions

Many children did not complete a full course of therapy. Unnecessary testing and treatment is burdensome to families and the health care system. Possible predictive variables include abnormal Glascow Coma Scale, focal neurologic findings and cerebrospinal fluid pleocytosis.

Herpes simplex serious neurological disease in young children: incidence and long-term outcome

OBJECTIVE

To determine the contribution of herpes simplex virus (HSV) to serious neurological disease.

SETTING AND PATIENTS

A 3-year prospective survey of children aged 2-23 months in Britain and Ireland.

RESULTS

19 children had HSV central nervous system (CNS) infection; 13 aged 2-11 months had focal neuroimaging abnormalities and 11 long-term neurological sequelae. Of six aged 12-35 months, one had abnormal neuroimaging and three long-term neurological sequelae. 17 of the 19 had serious neurological disease. HSV CNS infection accounted for 23% of serious neurological disease in children aged 2-11 months and 4.5% in older children.

CONCLUSIONS

The incidence of HSV-induced serious neurological disease in the UK was estimated at 1 in 64 000/year in younger children and 1 in 230 000 in older children. HSV CNS infection has clinical effects ranging from frank encephalitis to severe illness with fever and convulsions to milder disease lacking encephalopathy.

[Brainstem encephalitis in an 8-year-old girl]

Enzephalitiden sind häufig viral bedingt und können verschiedene Hirnareale betreffen. Ihre klinische Symptomatik ist sehr variabel. Gering symptomatische zerebrale (Begleit-)Infektionen bleiben bisweilen undiagnostiziert. Es können aber auch sehr schwere klinische Symptome (Lähmungen, Krämpfe) auftreten. Vorgestellt wird der Fall eines 8-jährigen Mädchens, das wenige Tage nach einem harmlosen Sturz auf den Hinterkopf zunehmend unter Kopfschmerzen und Erbrechen litt. Der Gesundheitszustand verschlechterte sich rasant und führte 7 Tage nach dem Sturz zur Vorstellung beim Kinderarzt. Nach weiterem foudroyantem Verlauf der Krankheit wurde das Mädchen 2 Tage später unter Krämpfen und pulmonaler Obstruktion in eine Klinik aufgenommen; hier musste es reanimiert werden. Im kranialen Computertomogramm (cCT) stellten sich temporal hypodense Areale und lokale Ödeme dar. Eine Herzechokardiographie ergab eine eingeschränkte linksventrikuläre Pumpfunktion, sodass der Verdacht auf eine Enzephalitis und eine Myokarditis gestellt wurde. Trotz antiviraler und antibiotischer Therapie verstarb das Kind 2 Tage nach Aufnahme in die Klinik an intravitalem Hirntod und Multiorganversagen. Bei der rechtsmedizinischen Sektion fanden sich keine knöchernen kranialen oder intrakranialen Verletzungen oder prädisponierende Erkrankungen. Histologische Untersuchungen ergaben eine nekrotisierende Hirnstammenzephalitis.

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.

Neurotropic viral infections leading to epilepsy: focus on Theiler's murine encephalomyelitis virus

Neurotropic viruses cause viral encephalitis and are associated with the development of seizures/epilepsy. The first infection-driven animal model for epilepsy, the Theiler's murine encephalomyelitis virus-induced seizure model is described herein. Intracerebral infection of C57BL/6 mice with Theiler's murine encephalomyelitis virus induces acute seizures from which the animals recover. However, once the virus is cleared, a significant portion of the animals that experienced acute seizures later develop epilepsy. Components of the innate immune response to viral infection, including IL-6 and complement component 3, have been implicated in the development of acute seizures. Multiple mechanisms, including neuronal cell destruction and cytokine activation, play a role in the development of acute seizures. Future studies targeting the innate immune response will lead to new therapies for seizures/epilepsy.

Pathology of tropical diseases

Tropical diseases affecting the central nervous system include infections, infestations, and nutritional deficiency disorders. This article discusses the commonly encountered diseases. The infections include bacterial, mycobacterial, fungal, parasitic, and viral infections with varied clinical manifestations. Imaging sensitivity and specificity for the prediction of the cause of infections has improved with application of advanced techniques. Microbial demonstration and histology remain the gold standard for diagnosis. Understanding the basis of imaging changes is mandatory for better evaluation of images. Nutritional disorders present with generalized and nonspecific imaging manifestations. The pathology of commonly encountered vitamin deficiencies is also discussed.

Infectious causes of seizures and epilepsy in the developing world

Central nervous system (CNS) infections are the main cause of seizures and acquired epilepsy in the developing world. Geographical variations determine the common causes in a particular region. Acute seizures are common in severe meningitis, viral encephalitis, malaria, and neurocysticercosis, and in most cases are associated with increased mortality and morbidity, including subsequent epilepsy. Neuronal excitability secondary to proinflammatory signals induced by CNS infections are an important common mechanism for the generation of seizures, in addition to various other specific mechanisms. Newer insights into the neurobiology of these infections and the associated epilepsy could help in developing neuroprotective interventions. Management issues include prompt treatment of acute seizures and the underlying CNS infection, correction of associated predisposing factors, and decisions regarding the appropriate choice and duration of antiepileptic therapy. Strategies for the prevention of epilepsy in CNS infections such as early anti-infective and anti-inflammatory therapy need scientific exploration. Prevention of CNS infections is the only definitive way forward to reduce the burden of epilepsy in developing countries.

Age-dependent Mendelian predisposition to herpes simplex virus type 1 encephalitis in childhood

OBJECTIVE

To test the hypothesis that predisposition to childhood herpes simplex virus (HSV) type 1 encephalitis (HSE) may be determined in part by human genetic factors.

STUDY DESIGN

A genetic epidemiologic survey of childhood HSE (onset at age 3 months to 15 years) over a 20-year period (1985-2004) was conducted throughout France (comprising 29 university hospital neuropediatric centers). A total of 85 children fulfilled the diagnostic criteria for inclusion. Family and personal histories were obtained by face-to-face interview for 51 patients.

RESULTS

No familial cases of HSE were identified in our survey; however, a high proportion (20%) of the children interviewed had a relevant family history: parental consanguinity (12% of patients), early-onset herpetic keratitis in a first-degree relative (6%), or both (2%). The narrow window of high susceptibility to HSE before age 3 years (62% of patients) further indicates that predisposition to HSE is tightly age-dependent.

CONCLUSIONS

This survey suggests that childhood HSE, although sporadic, may result from Mendelian predisposition (from autosomal recessive susceptibility in particular), at least in some children. There likely is incomplete penetrance, however, which may reflect, at least in part, the impact of age at the time of HSV-1 infection.

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.

Advances in pediatric neurovirology

Viral infections of the pediatric central nervous system (CNS) encompass a broad spectrum of both perinatally and postnatally acquired diseases with potentially devastating effects on the developing brain. In children, viral infections have been associated with chronic encephalopathy, encephalitis, demyelinating disease, tumors, and epilepsy. Older diagnostic techniques of biopsy, viral culture, electron microscopy, gel-based polymerase chain reaction (PCR), and viral titer quantification are being replaced with more rapid, sensitive, and specific real-time and microarray-based PCR technologies. Advances in neuroimaging technologies have provided for earlier recognition of CNS injury without elucidation of specific viral etiology. Although the mainstay therapy of many pediatric neurovirologic diseases, aside from HIV, includes intravenous acyclovir, much work is being done to develop novel antiviral immunotherapies aimed at both treating and preventing pediatric CNS viral disease.

Herpes simplex virus type-1 encephalitis and occipital ischemic stroke

Childhood ischemic stroke is a rare complication of herpes simplex virus type-1 encephalitis. We describe a previously healthy 3-year-old girl who presented with bilateral occipital ischemic stroke, attributable to herpes simplex virus type-1 encephalitis, highlighting the importance of viral diagnostics in cerebrospinal fluid.

Viral-like brain inflammation during development causes increased seizure susceptibility in adult rats

Viral infections of the CNS and their accompanying inflammation can cause long-term neurological effects, including increased risk for seizures. To examine the effects of CNS inflammation, we infused polyinosinic:polycytidylic acid, intracerebroventricularly to mimic a viral CNS infection in 14 day-old rats. This caused fever and an increase in the pro-inflammatory cytokine, interleukin (IL)-1beta in the brain. As young adults, these animals were more susceptible to lithium-pilocarpine and pentylenetetrazol-induced seizures and showed memory deficits in fear conditioning. Whereas there was no alteration in adult hippocampal cytokine levels, we found a marked increase in NMDA (NR2A and C) and AMPA (GluR1) glutamate receptor subunit mRNA expression. The increase in seizure susceptibility, glutamate receptor subunits, and hippocampal IL-1beta levels were suppressed by neonatal systemic minocycline. Thus, a novel model of viral CNS inflammation reveals pathophysiological relationships between brain cytokines, glutamate receptors, behaviour and seizures, which can be attenuated by anti-inflammatory agents like minocycline.

[Choreoathetosis after Herpes simplex encephalitis]

After Herpes simplex encephalitis, 25% of cases may have a relapse, rarely as a choreoathetosic movement disorder. The anatomic basis for herpes simplex virus encephalitis-associated movement disorders remains poorly understood, but the hypothesis is that it may be due to a post-infectious immune-mediated process. We report an 8-month-old boy, with herpes simplex encephalitis type 1, who started with an extrapyramidal Syndrome, presenting with choreoathetosis and ballistic movements, three weeks after onset. These new symptoms were attributed to a post-infectious immune-mediated process. We treated our patient with corticosteroids at high dose and gamma-globulins, in addition to a new course of Acyclovir. Sedation was required to control the intense choreoathetosic movements. Tetrabenazine was also tried, unsuccessfully. We studied a mutation on the toll like receptors (TLR3), which has been related to susceptibility for the disease, which was negative.

Viral encephalitis and epilepsy

Viral encephalitis presents with seizures not only in the acute stage but also increases the risk of late unprovoked seizures and epilepsy. Acute symptomatic and late unprovoked seizures in different viral encephalitides are reviewed here. Among the sporadic viral encephalitides, Herpes simplex encephalitis (HSE) is perhaps most frequently associated with epilepsy, which may often be severe. Seizures may be the presenting feature in 50% patients with HSE because of involvement of the highly epileptogenic frontotemporal cortex. The occurrence of seizures in HSE is associated with poor prognosis. In addition, chronic and relapsing forms of HSE have been described and these may be associated with antiepileptic drug-resistant seizures. Among the epidemic (usually due to flaviviruses) viral encephalitides, Japanese encephalitis (JE) is most common and is associated with acute symptomatic seizures, especially in children. The reported frequency of acute symptomatic seizures in JE is 7-46%. Encephalitis due to other flaviviruses such as equine, St. Louis, and West Nile viruses may also manifest with acute symptomatic seizures. In Nipah virus encephalitis, seizures are more common in relapsed and late-onset encephalitis in comparison to acute encephalitis (4% vs. 1.8%). Other viruses like measles, varicella, mumps, influenza, and entero-viruses may cause seizures depending on the area of brain involved. There is no comprehensive data regarding late unprovoked seizures in different viral encephalitides. Prospective studies are required to document the risk of late unprovoked seizures and epilepsy following viral encephalitis due to different viruses as well as to determine the clinical characteristics, course, and outcome of post-encephalitic epilepsy.

Craniectomy in herpetic encephalitis

The morbidity and mortality of herpes simplex encephalitis have decreased since the 1980s with the use of antivirals, but have remained stable in the last couple of years. One cause of morbidity is the development of focal hemorrhagic necrosis and edema in the temporal lobe, giving rise to space-occupying lesions, with a subsequent elevation of intracranial pressure. In some cases, the necrosis and edema can be refractory to medical treatment, with fatal outcome. Under these circumstances, some authors proposed decompressive craniectomy to treat severe intracranial hypertension and prevent serious neurologic deficits. We report the clinical outcomes of 2 adolescents affected with herpes simplex encephalitis who developed, during the course of their illness, severe intracranial hypertension refractory to medical treatment. Decompressive surgery was undertaken, with good outcomes in both patients.

Temporal lobectomy in acute complicated herpes simplex encephalitis: technical case report

OBJECTIVE

Herpes virus encephalitis is a rare, life-threatening complication of therapy in patients with brain tumors. A surgical therapeutic approach may be needed because the infection can be resistant to acyclovir in immunocompromised patients, and complications and long-term sequelae are frequent.

CLINICAL PRESENTATION

We present the case of a right-handed, 6-year-old girl with a brainstem tumor who had herpes virus encephalitis with refractory seizures while on immunosuppressive treatment. The virus was resistant to acyclovir but responded to gancyclovir. The patient developed local refractory brain edema with right uncal herniation.

INTERVENTION

To reduce the intracranial pressure, internal decompressive craniotomy was performed, which consisted of a right temporal lobectomy that allowed us to remove the focal necrotic-hemorrhagic tissue, decrease inflammation, and avoid subsequent chronic gliotic scarring. Clinical improvement was clear with prompt recovery and acute control of seizures. The only remaining deficits were mild memory and attention impairments. Seizures did not recur in the next 6 months.

CONCLUSION

Antiviral resistance should be suspected in immunocompromised patients with herpes virus encephalitis if there is no early response to acyclovir. If uncal herniation of the nondominant temporal lobe develops, temporal lobectomy, as an internal decompressive procedure, can be lifesaving. Lobectomy stopped the acute refractory seizures and can be considered a good approach to prevent later epilepsy, with only mild residual cognitive deficits.

The management of encephalitis: clinical practice guidelines by the Infectious Diseases Society of America

Guidelines for the diagnosis and treatment of patients with encephalitis were prepared by an Expert Panel of the Infectious Diseases Society of America. The guidelines are intended for use by health care providers who care for patients with encephalitis. The guideline includes data on the epidemiology, clinical features, diagnosis, and treatment of many viral, bacterial, fungal, protozoal, and helminthic etiologies of encephalitis and provides information on when specific etiologic agents should be considered in individual patients with encephalitis.

Central nervous system infections of herpesvirus family

Herpesviruses are one of the most common groups of pathogens causing central nervous system infections in humans. They mostly cause encephalitis, meningitis, or myelitis in immunocompetent and immunocompromised patients. Children, adults, and the elderly can all be affected. Although contrast-enhanced CT is more widely used for diagnosis, contrast-enhanced MR imaging combined with diffusion-weighted imaging is superior to CT in the detection of early changes and the real extent of the disease, and in assessing prognosis and monitoring response to antiviral treatment. More sophisticated techniques, such as MR spectroscopy and perfusion imaging, can aid in the differential diagnosis of herpesvirus infections from other tumoral, demyelinating, and ischemic processes.

Acute childhood encephalitis and encephalopathy associated with influenza: a prospective 11-year review

BACKGROUND

Influenza virus infection has been associated with a variety of neurologic complications. The objective of this study was to evaluate prospectively the role of influenza viruses in acute childhood encephalitis/encephalopathy (ACE).

METHODS

All children admitted to the Hospital for Sick Children, Toronto, during an 11-year period with ACE and evidence of acute influenza virus infection were included. Acute influenza virus infection was defined by detection of the organism in the nasopharynx by direct immunofluorescence microscopy or viral culture and/or by a 4-fold or greater rise in complement fixation titer.

RESULTS

A total of 311 children with ACE were evaluated; evidence of influenza infection was detected in 7% (22 of 311). Eight were excluded from the main analysis because of evidence implicating other potential pathogens. Eleven of the 14 included subjects were <5 years of age. A respiratory prodrome was documented in 93% of subjects. In 64% neurologic manifestations developed within 5 days of onset of respiratory symptoms. Neuroimaging abnormalities were more common in children <2 years of age. Neurologic sequelae occurred in more than one-half of subjects.

CONCLUSIONS

In this prospective registry, influenza virus infection was associated with 5% of ACE cases. The majority of children were <5 years of age and the prevalence of neuroimaging abnormalities was higher in children <2 years of age suggesting that younger children are predisposed to the neurologic complications of influenza. An acute rather than a postinfectious process was suggested by the briefness of the respiratory prodrome in most cases.

Clinical and laboratory features of neonatal herpes simplex virus infection: a case-control study

BACKGROUND

Neonatal herpes simplex virus (HSV) infection can cause significant morbidity and mortality but can be difficult to identify, particularly in neonates without vesicular rash.

OBJECTIVE

To determine the unique clinical and laboratory features of neonates with and without HSV infection admitted to Texas Children's Hospital during a 14-year period.

METHODS

An historic case-control study of all hospitalized neonates with laboratory-confirmed HSV infection and a restricted sample (ratio 1:4) of HSV test-negative hospitalized neonates. Univariate and multivariate analyses were performed to identify clinical and laboratory factors associated with neonatal HSV infection.

RESULTS

Forty cases and 160 comparison subjects were identified. The following factors were associated with neonatal HSV infection by univariate analysis: maternal primary HSV infection, maternal fever, vaginal delivery, prematurity, postnatal HSV contact, vesicular rash, hypothermia, lethargy, seizures, severe respiratory distress, hepatosplenomegaly, thrombocytopenia, elevated hepatic enzymes, and cerebrospinal fluid (CSF) pleocyosis and proteinosis. Factors not associated with neonatal HSV infection were fever, total peripheral white blood cell count, and red blood cells in the CSF. For neonates presenting without vesicular rash, maternal fever, respiratory distress requiring mechanical ventilation, and CSF pleocytosis were independently associated with HSV infection.

CONCLUSIONS

Inclusion of the newly appreciated features of maternal fever, respiratory distress, and thrombocytopenia might improve the detection of neonatal HSV infection. Clinical and laboratory factors typically associated with neonatal HSV infection were confirmed to be maternal primary HSV infection, vaginal delivery, prematurity, neonatal seizures, vesicular rash, elevated hepatic enzymes, and CSF pleocytosis.

The spectrum of herpes simplex encephalitis in children

Clinical and basic science research carried out in recent years into herpes simplex encephalitis (HSE) have shown that the concept of a "classical" picture of HSE in children is now outdated and that our current knowledge of the disease is probably only the tip of an iceberg. Indeed, increasing evidence supports the existence of a wider range of pathophysiological mechanisms, clinical presentations and disease progressions in paediatric HSE. This paper reviews the clinical, biological and radiological data available and redefines the spectrum of HSE in children. Full understanding of the condition should improve the management of suspected cases and decrease the morbidity and the mortality associated with this disease.

Use of prophylactic anticonvulsants in neurologic critical care: a critical appraisal

Seizures are commonly encountered in the setting of brain injury in neurologic critical care. Though seizure prophylaxis with the use of antiepileptic drugs is frequently utilized in variety of brain injury paradigms, it is often not based on evidence and is controversial. Significant difficulties arise from interpretation of supporting literature due to lack of definitions for early-vs.-late-seizures, variable end points with seizure prophylaxis, as well as methodologic inconsistencies for seizure detection. This descriptive review summarizes the existing literature on the use of prophylactic anticonvulsants in clinical paradigms commonly encountered in neurologic critical care and highlights the important controversies concerning their use.

Herpes simplex virus remodels T-cell receptor signaling, resulting in p38-dependent selective synthesis of interleukin-10

Herpes simplex virus (HSV)-specific T cells are essential for viral clearance. However, T cells do not prevent HSV latent infection or reactivation, suggesting that HSV has the potential to modulate T-cell function. T-cell receptor (TCR) stimulation is a potent and specific means of activating T cells. To investigate how HSV affects T-cell function, we have analyzed how HSV affects TCR-stimulated intracellular signaling and cytokine synthesis in mock-infected and HSV-infected T cells. Mock-infected T cells stimulated through the TCR synthesized a broad range of cytokines that included the proinflammatory cytokines tumor necrosis factor alpha, gamma interferon, and interleukin-2. In contrast, HSV-infected T cells stimulated through the TCR selectively synthesized interleukin-10, a cytokine that suppresses cellular immunity and favors viral replication. To achieve selective interleukin-10 synthesis, HSV differentially affected TCR signaling pathways. HSV inhibited TCR-stimulated formation of the linker for activation of the T-cell signaling complex, and HSV inhibited TCR-stimulated NF-kappaB activation. At the same time, HSV activated the p38 and JNK mitogen-activated protein kinases as well as the downstream transcription factors ATF-2 and c-Jun. HSV did not inhibit TCR-stimulated activation of STAT3, a transcription factor involved in interleukin-10 synthesis. The activation of p38 was required for interleukin-10 synthesis in HSV-infected T cells. The ability of HSV to differentially target intracellular signaling pathways and transform an activating stimulus into an immunosuppressive response represents a novel strategy for pathogen-mediated immune modulation. Selective, TCR-stimulated interleukin-10 synthesis may play an important role in HSV pathogenesis.