Lipid droplets in Zika neuroinfection: Potential targets for intervention?

Lipid droplets (LD) are evolutionarily conserved lipid-enriched organelles with a diverse array of cell- and stimulus-regulated proteins. Accumulating evidence demonstrates that intracellular pathogens exploit LD as energy sources, replication sites, and part of the mechanisms of immune evasion. Nevertheless, LD can also favor the host as part of the immune and inflammatory response to pathogens. The functions of LD in the central nervous system have gained great interest due to their presence in various cell types in the brain and for their suggested involvement in neurodevelopment and neurodegenerative diseases. Only recently have the roles of LD in neuroinfections begun to be explored. Recent findings reveal that lipid remodelling and increased LD biogenesis play important roles for Zika virus (ZIKV) replication and pathogenesis in neural cells. Moreover, blocking LD formation by targeting DGAT-1 in vivo inhibited virus replication and inflammation in the brain. Therefore, targeting lipid metabolism and LD biogenesis may represent potential strategies for anti-ZIKV treatment development. Here, we review the progress in understanding LD functions in the central nervous system in the context of the host response to Zika infection.

Consensus for prevention and management of coronavirus disease 2019 (COVID-19) for neurologists

Coronavirus disease 2019 (COVID-19) has become a pandemic disease globally. Although COVID-19 directly invades lungs, it also involves the nervous system. Therefore, patients with nervous system involvement as the presenting symptoms in the early stage of infection may easily be misdiagnosed and their treatment delayed. They become silent contagious sources or 'virus spreaders'. In order to help neurologists to better understand the occurrence, development and prognosis, we have developed this consensus of prevention and management of COVID-19. It can also assist other healthcare providers to be familiar with and recognise COVID-19 in their evaluation of patients in the clinic and hospital environment.

Mechanisms of Pathogen Invasion into the Central Nervous System

CNS infections continue to rise in incidence in conjunction with increases in immunocompromised populations or conditions that contribute to the emergence of pathogens, such as global travel, climate change, and human encroachment on animal territories. The severity and complexity of these diseases is impacted by the diversity of etiologic agents and their routes of neuroinvasion. In this review, we present historical, clinical, and molecular concepts regarding the mechanisms of pathogen invasion of the CNS. We also discuss the structural components of CNS compartments that influence pathogen entry and recent discoveries of the pathways exploited by pathogens to facilitate CNS infections. Advances in our understanding of the CNS invasion mechanisms of different neurotropic pathogens may enable the development of strategies to control their entry and deliver drugs to mitigate established infections.

Blood and cerebrospinal fluid characteristics in neonates with a suspected central nervous system infection

Clinical signs and symptoms of central nervous system (CNS) infections in neonates are often nonspecific. Therefore, cerebrospinal fluid (CSF) analysis is performed to diagnose CNS infections. Data on combined microbiological results and their correlation with biochemical characteristics in CSF and blood in infants younger than 90 days are limited. This study provides an overview of microbiological test results, CSF- and hematological characteristics among infants with a clinically suspected CNS infection.This retrospective study included infants younger than 90 days, with a clinically suspected CNS infection who underwent a diagnostic lumbar puncture between January 2012 and January 2014. Data on the presence of microbiological pathogens in CSF, CSF inflammation markers (white blood cell [WBC] counts, protein levels and glucose CSF/serum ratio) and blood inflammatory responses (WBC count, C-reactive protein [CRP], neutrophil percentage) were collected by reviewing patient files.We included data from 576 infants (median age 12.5 days, interquartile range, 6-27 days) of whom 383 (66.5%) were born prematurely. In total, 16 bacterial pathogens (3.0%) and 21 viruses (5.5%) were detected in CSF. Escherichia coli was detected in 5 cases (1.0%), Enterovirus was detected in 12 cases (3.1%). Leucocytosis in CSF was associated with identification of a pathogen in CSF. Increased CRP was associated with the identification of a bacterial pathogen in CSF.Bacterial or viral pathogens were only identified in a small proportion of infants with a clinically suspected CNS infection. Leucocytosis in CSF was associated with CNS infection in infants. An increased CRP was indicative of bacterial meningitis.

Research advancements in the neurological presentation of flaviviruses

Owing to the large-scale epidemic of Zika virus disease and its association with microcephaly, properties that allow flaviviruses to cause nervous system diseases are an important area of investigation. At present, although potential pathogenic mechanisms of flaviviruses in the nervous system have been examined, they have not been completely elucidated. In this paper, we review the possible mechanisms of blood-brain barrier penetration, the pathological effects on neurons, and the association between virus mutations and neurotoxicity. A hypothesis on neurotoxicity caused by the Zika virus is presented. Clarifying the mechanisms of virulence of flaviviruses will be helpful in finding better antiviral drugs and optimizing the treatment of symptoms.

Pituitary function in children following infectious diseases of the central nervous system

Recent studies in adults suggest that pituitary deficiencies develop in a considerable proportion of patients who recover from infectious meningitis. The aim of this study was to evaluate pituitary function of children with a history of meningitis. Seventy-nine children were admitted to the Safra Children's Hospital due to meningitis between 2007 and 2010. Twenty-four families were lost for follow-up, 55 were interviewed by phone and 14 (9 males) participated in the study. Evaluation included medical history, physical examination, auxological measurements and basal levels of TSH, fT4, cortisol and IGF1. Children with abnormal results were followed for a year and dynamic testing was performed when indicated. Mean age at time of infectious meningitis was 3.8 ± 5.4 years (range 0.03-15.8), and at clinical evaluation 6.4 ± 6.4 (range 1.2-20). The interval between the acute event and evaluation was 2.7 ± 1.2 years. Thyroid function tests and basal cortisol levels were normal for all children. Three children had low IGF1 levels; however over a year of follow-up two of them had normal height and growth velocity, making growth hormone deficiency unlikely. One child had low height SDS, but exhibited a normal response to a growth hormone stimulation test. Pituitary dysfunction with overt clinical symptoms is not a frequent consequence of acute meningitis in children. Follow-up of growth and puberty of children post-meningitis by the primary care physician is probably sufficient. Invasive assessments should be reserved for selected cases where there is slow growth or other clinical suspicion of hypopituitarism.

The biological basis of injury and neuroprotection in the fetal and neonatal brain

A compromised intrauterine environment that delivers low levels of oxygen and/or nutrients, or is infected or inflammatory, can result in fetal brain injury, abnormal brain development and in cases of chronic compromise, intrauterine growth restriction. Preterm birth can also be associated with injury to the developing brain and affect the normal trajectory of brain growth. This review will focus on the effects that episodes of perinatal hypoxia (acute, chronic, associated with inflammation or as an antecedent of preterm birth) can have on the developing brain. In animal models of these conditions we have found that relatively brief (acute) periods of fetal hypoxemia can have significant effects on the fetal brain, for example death of susceptible neuronal populations (cerebellum, hippocampus, cortex) and cerebral white matter damage. Chronic placental insufficiency which includes fetal hypoxemia, nutrient restriction and altered endocrine status can result in fetal growth restriction and long-term deficits in neural connectivity in addition to altered postnatal function, for example in the auditory and visual systems. Maternal/fetal inflammation can result in fetal brain damage, particularly but not exclusively in the white matter; injury is more pronounced when associated with fetal hypoxemia. In the baboon, in which the normal trajectory of growth is affected by preterm birth, there is a direct correlation between a higher flux in oxygen saturation and a greater extent of neuropathological damage. Currently, the only established therapy for neonatal encephalopathy in full term neonates is moderate hypothermia although this only offers some protection to moderately but not severely affected brains. There is no accepted therapy for injured preterm brains. Consequently the search for more efficacious treatments continues; we discuss neuroprotective agents (erythropoietin, N-acetyl cysteine, melatonin, creatine, neurosteroids) which we have trialed in appropriate animal models. The possibility of combining hypothermia with such agents or growth factors is now being considered. A deeper understanding of causal pathways in brain injury is essential for the development of efficacious strategies for neuroprotection.

Microglial response to murine leukemia virus-induced encephalopathy is a good indicator of neuronal perturbations

The neuronal pathology caused by neonatal infection of rats with the PVC-211 murine leukemia virus (PVC-211 MuLV) and its underlying mechanisms are not well defined even though a loss of neurons and spongiform neurodegeneration has been reported to accompany the disease. Here we sought to identify sites of neurodegeneration using microglial reactivity as an indirect marker and to characterize microglial activation during disease progression. Using a panel of microglial antibodies including Iba1, OX-42, ED1, and anti-ferritin, we have studied the response of microglial cells to neonatal CNS infection with PVC-211 at post-infection survival times 7, 14, 21, and 28 days. We found that microglial activation occurred primarily in the spinal cord and brainstem where it gradually increased in intensity over the time course of this study. Other brain areas were relatively unremarkable in their microglial reaction to viral infection within this time frame. However, the presence of activated microglial cells was not correlated directly with the presence of viral glycoprotein (gp70), which was expressed in endothelial cells throughout the CNS. Although double-labeling of microglia with Iba1 and ED1 revealed numerous actively phagocytic microglia during disease progression, not all activated microglia were ED1-positive. In addition to the intense microglial activation, we found increased ferritin expression sporadically throughout the virus-infected brain. The ferritin-positive cells were mostly microglia that exhibited dystrophic changes and likely represented a degenerating subpopulation of microglial cells. Thus, activated microglia can co-exist with degenerating microglia in the same brain region. We attempted to localize degenerating neurons or neurites using Fluoro-Jade, anti-tau, and anti-alpha synuclein staining, but none of these procedures yielded results to indicate obvious neuronal pathology. We conclude that the visualization of microglial activation is a more sensitive measure of neuronal perturbations than direct detection of neuronal pathology which may be subtle and not produce overt degenerative changes.

[Efficacy of cytoflavin in therapy of encephalophathy in patients with neuroinfection]

The use of cytoflavin solution in complex therapy of patients with neuroinfection was studied. It showed a favourable effect on the disease clinical process, evident from less pronounced intoxication and meningeal signs by the 11th day of the treatment and improvement of the liquorological picture. The cytoflavin efficacy was also confirmed by normalization of the brain bioelectric activity evident from the electroencephalograms and by reduction of the level of antioxidants, such as metalloproteids and superoxidodismutase, that was in favour of the drug antiinflammatory and antioxidant effects. The use of cytoflavin tablets during in early convalescence period promoted earlier recovery of the intellectual and mnestic reactions. On the whole, the use of cytoflavin promoted favourable process and outcomes of neuroinfections and could be recommended for the use during the acute state and re habilitation of the patients.

Excretory-secretory products from Paragonimus westermani increase nitric oxide production in microglia in PKC-dependent and -independent manners

Excretory-secretory products (ESP) from helminthic parasites may play pivotal roles in the immune regulation in hosts. Previously, we reported that ESP produced from Paragonimus westermani induced morphological activation of microglial cells and markedly stimulated nitric oxide (NO) production via activation of mitogen-activated protein kinases (MAPKs). In the present study, we investigated the role of protein kinase C and protein kinase A in MAPKs-dependent NO production by ESP. We found that treatment with protein kinase C inhibitor Go6976 strongly inhibited the phosphorylation of p38 and JNK, but not ERK, of MAPKs and decreased the production of NO in ESP-stimulated microglial cells. Inhibition of ERK, p38 or PKC decreased the ESP-induced activation of NF-kappaB, an important transcription factor for iNOS expression. Furthermore, ESP increased the level of p-CREB in microglial cells. However, adenylyl cyclase activator (forskolin), adenylyl cyclase inhibitor (SQ22536), cAMP analogue (db-cAMP) or protein kinase A inhibitor (H89) was not able to change iNOS expression and NO production in ESP-treated microglial cells. It implies that the cAMP-PKA-CREB pathway is not implicated in the ESP-evoked NO production in microglial cells. Thus, our results indicate that ESP stimulates microglial expression of iNOS via both PKC-dependent and -independent MAPKs phosphorylation and NF-kappaB activation.

Characterization of human immunodeficiency virus (HIV)-infected cells in infiltrates associated with CNS opportunistic infections in patients with HIV clade C infection

Infection with human immunodeficiency virus (HIV) clade C is the most common HIV infection worldwide, yet its impact on the nervous system remains largely unknown. Autopsy studies from regions affected by this virus are scarce, and HIV dementia has only rarely been reported from these countries. Most patients who develop neurologic complications die of opportunistic infections. We thus conducted a neuropathologic study from a single institution in India to characterize the HIV-infected cells in the inflammatory infiltrates in a total of 15 cases (5 patients each who died of either CNS toxoplasmosis, tuberculosis, or cryptococcal meningitis). Nearly, all patients had HIV-infected cells in the brain, although these cells were most abundant in patients with toxoplasma encephalitis. Interestingly, none of the patients had any multinucleated giant cells. HIV-infected cells were found in the parenchyma, perivascular regions, and choroid plexus and found infiltrating the parenchyma from the meninges, suggesting multiple portals of entry into the brain. These findings suggest the possibility that patients, even if successfully treated for an opportunistic inflection, may be at high risk of developing HIV encephalitis and subsequent dementia.

Glial activation and matrix metalloproteinase release in cerebral malaria

Although neurological symptoms associated with cerebral malaria (CM) are largely reversible, recent studies suggest that lasting neurological sequelae can occur. This may be especially true for children, in whom persistent deficits include problems with memory and attention. Because the malaria parasite is not thought to enter the brain parenchyma, lasting deficits are likely related to factors including the host response to disease. Studies with a rodent model, and with human postmortem tissue, suggest that glial activation occurs with CM. In this review, the authors will highlight studies focused on such activation in CM. Likely causes will be discussed, which include ischemia and activation of blood brain barrier endothelial cells. The potential consequences of glial activation will also be discussed, highlighting the possibility that glial-derived proteinases contribute to structural damage of the central nervous system (CNS). Of note, for the purposes of this focused review, glial activation will refer to the activation of astrocytes and microglial cells; discussion of oligodendroglial cells will not be included. In addition, although events thought to be critical to the pathogenesis of CM and glial activation will be covered, a comprehensive review of cerebral malaria will not be presented. Excellent reviews are already available, including Coltel et al (2004; Curr Neurovasc Res 1: 91-110), Medana and Turner (2006; Int J Parasitol 36: 555-568), and Hunt et al (2006; Int J Parasitol 36: 569-582).

[Strokes caused by infection in the tropics]

INTRODUCTION

Almost three out of every four people in the world who suffer a fatal stroke live in developing countries. A number of different tropical diseases may appear in Europe in the coming years as a consequence of the demographic change that is being brought about by migratory flows. We review the main infectious causes of strokes in the tropics.

DEVELOPMENT

There are estimated to be 500 million cases of malaria every year. Cerebral malaria can cause cerebral oedema, diffuse or focal compromise of the subcortical white matter and cortical, cerebellar and pontine infarctions. Chagas disease is an independent risk factor for stroke in South America. At least 20 million people have the chronic form of Chagas disease. The main prognostic factors for Chagas-related stroke are the presence of apical aneurysms, arrhythmia and heart failure. Vascular complications of neurocysticercosis include transient ischemic attacks, ischemic strokes due to angiitis and intracranial haemorrhages. The frequency of cerebral infarction associated with neurocysticercosis varies between 2% and 12%. Gnathostomiasis is a cause of subarachnoid haemorrhage in south-east Asia. Other less common causes of stroke are viral haemorrhagic fevers due to arenavirus and flavivirus.

CONCLUSIONS

Several diseases that are endemic in the tropics can be responsible for up to 10% of the cases of strokes in adults.

[Cytomegalovirus infection--selected aspects of clinical pathology]

In this review short biological characteristics of human cytomegalovirus (CMV), the sources and its modes of transmission to human organisms, are presented. The authors described clinical pathology mainly of ocular organ and central nervous system in children with congenital cytomegalovirus infection and in acquired form of cytomegaly in adults with immunosupression (especially with HIV infection and AIDS). In review there are included contemporary diagnostic laboratory methods used in detection of CMV infection and in evaluation of clinical pathology.

Altered mental status and a retro-auricular mass

A 29-year-old woman was found lying unconscious in the shower. There was a two-day history of headache and dizziness. In the emergency room, she was initially stuporous (Glasgow Coma Scale 10/15), afebrile, bradycardic and hypertensive. She exhibited roving, conjugate eye movements, left facial paresis (including frontalis), left ptosis, diffuse hypotonia, extensor plantar responses bilaterally and a 1.5 cm warm, fluctuant mass with surrounding erythema behind the left ear (Figure 1). Otoscopy revealed a bulge in the posterior wall of the left external auditory canal.

Diffusion-weighted MR imaging: pediatric clinical applications

We have summarized the diffusion-weighed imaging (DWI) findings in a number of different cerebral disorders. In many cases, DWI with the accompanying apparent diffusion coefficient (ADC) map provides additional useful information to the standard imaging sequences. Pathophysiologic mechanisms resulting in baseline normal ADC values and changes with disease processes are not well understood; therefore, caution should be used when prognosticating the outcome of regions with abnormal ADCs. DWI should be used as an adjunct to routine imaging and interpreted in the context of the routine imaging findings and clinical scenario. As our understanding of ADC mechanisms increases and we begin to incorporate information about tissue organization from diffusion tensor imaging or diffusion spectrum imaging, the role of these methods in clinical diagnosis should continue to increase.

Viral induced demyelination

Viral induced demyelination, in both humans and rodent models, has provided unique insights into the cell biology of oligodendroglia, their complex cell-cell interactions and mechanisms of myelin destruction. They illustrate mechanisms of viral persistence, including latent infections in which no infectious virus is readily evident, virus reactivation and viral-induced tissue damage. These studies have also provided excellent paradigms to study the interactions between the immune system and the central nervous system (CNS). Although of interest in their own right, an understanding of the diverse mechanisms used by viruses to induce demyelination may shed light into the etiology and pathogenesis of the common demyelinating disorder multiple sclerosis (MS). This notion is supported by the persistent view that a viral infection acquired during adolescence might initiate MS after a long period of quiescence. Demyelination in both humans and rodents can be initiated by infection with a diverse group of enveloped and non-enveloped RNA and DNA viruses (Table 1). The mechanisms that ultimately result in the loss of CNS myelin appear to be equally diverse as the etiological agents capable of causing diseases which result in demyelination. Although demyelination can be a secondary result of axonal loss, in many examples of viral induced demyelination, myelin loss is primary and associated with axonal sparing. This suggests that demyelination induced by viral infections can result from: 1) a direct viral infection of oligodendroglia resulting in cell death with degeneration of myelin and its subsequent removal; 2) a persistent viral infection, in the presence or absence of infectious virus, resulting in the loss of normal cellular homeostasis and subsequent oligodendroglial death; 3) a vigorous virus-specific inflammatory response wherein the virus replicates in a cell type other than oligodendroglia, but cytokines and other immune mediators directly damage the oligodendroglia or the myelin sheath; or 4) infection initiates activation of an immune response specific for either oligodendroglia or myelin components. Virus-induced inflammation may be associated with the processing of myelin or oligodendroglial components and their presentation to the host's own T cell compartment. Alternatively, antigenic epitopes derived from the viral proteins may exhibit sufficient homology to host components that the immune response to the virus activates autoreactive T cells, i.e. molecular mimicry. Although it is not clear that each of these potential mechanisms participates in the pathogenesis of human demyelinating disease, analysis of the diverse demyelinating viral infections of both humans and rodents provides examples of many of these potential mechanisms.

Drug-induced aseptic meningitis in suspected central nervous system infections

This study presents eight patients with drug-induced aseptic meningitis (DIAM) admitted to our centre with an initial suspicion of central nervous system (CNS) infection. In all patients clinical findings, cerebrospinal fluid (CSF) examination, a cause-effect relationship according to the Naranjo adverse drug reactions probability scale and other diagnostic criteria required for DIAM recognition, were fulfilled. Nonsteroidal anti-inflammatory drugs were the most frequent cause of DIAM. In two cases, there was previous antimicrobial use. The time between use of the causative drug and onset of the symptoms ranged from 2 to 7 days. Clinical symptoms and CSF findings in patients with DIAM are indistinguishable from the early stage of infections of the CNS. Detailed anamnesis is essential, particularly related to medication use immediately prior to the appearance of symptoms of CNS impairment. In conclusion, the differential diagnosis of CNS infections should include DIAM.

Blood-brain barrier drug discovery for central nervous system infections

Central nervous system (CNS) infections are formidable diseases with high rates of morbidity and mortality. Since the majority of antimicrobial agents discovered so far do not cross the blood-brain barrier (BBB), the treatment of CNS infections is a major challenge issue. The development of drugs to treat those diseases requires consideration of achievable brain concentrations by targeting the following question. How can the chemistry and biology of the BBB, and infectomics be exploited for the development of drugs against CNS infections? To date drug targeting approaches, such as chemistry-based, biology-based, and infectomics-based, have been implicated in the development of drugs for treatment of CNS infections. The chemistry-based strategies rely on lipid-mediated BBB drug transport as substances that readily permeate the BBB. These usually include small molecular weight of lipophilic or hydrophobic molecules. The biology-based strategies depend on endogenous BBB transport systems, including carrier-mediated transport (CMT), active efflux transport (AET), and receptor-mediated transport (RMT). These transporters play important roles in the influxes and/or effluxes of drugs including antimicrobial agents in brain capillary endothelial cells that form the BBB. Both microbial and host signatures of infectomes, which can be dissected by infectomics, provide invaluable fountains in the search for novel antimicrobial therapies. Key markers associated with the mechanisms of neuronal injury may be identified, and thus, provide important targets for the prevention and treatment of CNS infections. This review focuses on the major BBB drug targeting strategies in the development of therapeutics for CNS infections. A combination of these strategies will ultimately lead to improved treatments.

Update on neuroimaging in infectious central nervous system disease

PURPOSE OF REVIEW

Neuroimaging constitutes an important component in the diagnosis of the underlying infectious agents in central nervous system infection. This review summarizes progress in the neuroimaging of infectious central nervous system disease since January 2003. It focuses on imaging of viral encephalitis, including that caused by exotic and emerging viruses, and on imaging in immunodeficient patients.

RECENT FINDINGS

Diffusion-weighted imaging has been shown to be superior to conventional magnetic resonance imaging for the detection of early signal abnormalities in herpes simplex virus encephalitis but also in enterovirus 71 encephalitis and in West Nile encephalitis. Several studies defined the pattern of magnetic resonance imaging signal changes in endemic diseases such as West Nile encephalitis, Murray Valley encephalitis, enterovirus 71 encephalitis and Japanese encephalitis, but also in encephalitides due to ubiquitous viruses such as measles virus and Lyssavirus (rabies). In patients with HIV infection, apparent diffusion coefficient ratios obtained by diffusion-weighted imaging were significantly greater in lesions due to Toxoplasma encephalitis than in primary central nervous system lymphomas.

SUMMARY

The diagnosis of unclear infectious central nervous system diseases remains a challenge. More recent magnetic resonance imaging techniques, such as diffusion-weighted imaging and magnetic resonance spectroscopy, provide additional helpful information. However, the mainstay of diagnosis remains the detection of viral DNA or serological markers of specific infectious agents within the cerebrospinal fluid.

Quantitative real time PCR detection of Varicella-zoster virus DNA in cerebrospinal fluid in patients with neurological disease

Varicella-zoster virus (VZV) reactivation can lead to the development of neurological disease. Diagnosis has been based on the detection of VZV DNA in cerebrospinal fluid (CSF) by PCR-based methods. The aim of this study was to determine whether the VZV DNA copy number in the CSF correlates with the course of the disease and to determine its prognostic relevance. VZV DNA was quantified in CSF samples obtained from 30 patients with neurological disease due to VZV reactivation using real time PCR, and the VZV DNA copy number was correlated to the clinical and laboratory findings for each case. Viral loads ranged from 50 copies/ml to 2.6 x 10(8) copies/ml. Significantly higher viral loads [geometric mean (GM): 7.2 x 10(4) copies/ml] were found in patients with encephalitis compared to patients with meningitis (GM: 4.1 x 10(3) copies/ml) (P=0.01, Mann-Whitney U test). In eight patients without zoster dermal lesions no significant difference in viral load (GM: 4.6 x 10(3)) was detected compared to patients exhibiting dermal lesions (GM: 2.2 x 10(4)) (P=0.14). High copy numbers of VZV DNA in CSF were clearly associated with the severity of neurological disease and none of the patients with a VZV viral load below 10(4) copies had a disease course which required intensive care.

Discriminatory features of acute transverse myelitis: a retrospective analysis of 45 patients

Acute transverse myelitis (ATM) is a pathogenetically heterogeneous inflammatory disorder of the spinal cord. Therefore, the identification of clinical and paraclinical features providing clues of the underlying etiologies is needed. The clinical presentation, blood and cerebrospinal fluid (CSF) findings as well as magnetic resonance imaging (MRI) and neurophysiological features were retrospectively analyzed in 45 unselected consecutive patients with ATM. Parainfectious ATM was diagnosed in 38% of patients. The underlying infectious agent, however, was identified only in a minority of patients. In 36% of patients, the etiology remained uncertain ("idiopathic" ATM) and in 22% ATM was the first manifestation of possible multiple sclerosis (ATM-MS) according to recently published diagnostic criteria. Spinal cord MRI showed signal alterations in 96% of the patients. In ATM-MS, monosegmental involvement of the spinal cord was most frequent while spinal cord involvement of two or more segments was more common in ATM of other etiologies. Of particular note, neurophysiological examinations showed evidence of peripheral nervous system (PNS) involvement in 27% of patients with ATM but not in patients with ATM-MS. Therefore, neurophysiological evidence of PNS involvement may provide additional discriminatory features between ATM-MS and ATM of other etiologies.

Cytomegalovirus glycoprotein B genotypes and central nervous system disease in AIDS patients

To investigate any association between cytomegalovirus glycoprotein B (CMV gB) subtypes and central nervous system (CNS) disease in AIDS patients, proportions of different gB genotypes detected in AIDS patients with CNS disease were compared with the gB genotypes detected in AIDS patients with no neurological disorder. The patients were matched by CD4+ cell counts. CMV was detected by PCR in cerebrospinal fluid (CSF) samples obtained from AIDS patients with CNS disease and from urine and saliva samples obtained from AIDS patients without CNS disease. CMV strains obtained were digested by restriction enzymes HinffI and RsaI to classify the genotypes. The CMV gB genotype was determined in 26 CSF samples. Of these, 11/26 (42.3%) typed as gB group 1, seven (26.9%) as gB2, four (15.4%) as gB3, and four (15.4%) as gB4. The CMV gB genotype frequency distribution in the 42 AIDS patients without CNS disease showed that 18/42 (42.8%) were classified as gB group 1, 10 (23.8%) as gB2, seven (16.6%) as gB3, and seven (16.6%) as gB4. In the present study, no association was found between CMV gB genotypes and CMV-related central nervous system disease.

Neopterin, biopterin, and nitric oxide concentrations in the cerebrospinal fluid of children with central nervous system infections

We measured neopterin, biopterin and nitric oxide (NO) concentrations in the cerebrospinal fluid of pediatric patients with central nervous system (CNS) infectious diseases. The nitric oxide and neopterin concentrations were significantly elevated in encephalitis patients, especially in two cases with serious neurological sequelae, while the biopterin levels were not elevated. The bacterial meningitis patients, on the contrary, had high cerebrospinal fluid concentrations of neopterin and biopterin, but not of NO. Although these findings are preliminary, it may suggest that cerebrospinal fluids nitric oxide would be a useful marker to prospect neurological prognoses in the CNS infections.

Complications of invasive monitoring used in intractable pediatric epilepsy

Invasive monitoring for intractable epilepsy is useful when the epileptogenic focus is in question even after an extensive noninvasive presurgical evaluation, or when the epileptogenic focus is located in or near eloquent cortex. From June 1989 to June 2001 at the Children's Hospital of Philadelphia, 64 children with intractable epilepsy underwent 67 invasive monitoring procedures as part of their presurgical evaluation. The average age at implantation was 10 years. In all but two cases, subdural strips and grids were used. Depth electrodes, when used, were placed stereotactically or under direct vision. The average duration of the monitoring period was 5.87 days. Every patient had intradural cultures sent during removal of the electrodes, and lumbar punctures were performed in 15 patients. Twenty-one patients had at least one episode of a CSF leak. Of the 67 patients, 10 had positive intradural cultures, only 1 of whom had a positive lumbar puncture and none of whom developed clinically significant meningitis. No clinically relevant hemorrhages occurred as a result of the invasive monitoring. One patient did have a transient visual field loss after placement of an occipital grid. While CSF leaks are common after invasive monitoring despite precautions, clinically significant CSF infections are uncommon and appear to be unrelated to the duration of monitoring, the occurrence of a CSF leak or the length of time the patient is on perioperative antibiotics. We conclude that invasive monitoring for intractable epilepsy is generally safe.

Characterization of microglial responses to Staphylococcus aureus: effects on cytokine, costimulatory molecule, and Toll-like receptor expression

Microglia participate in innate immune responses in the central nervous system (CNS). This work demonstrates that microglia can recognize heat-inactivated Staphylococcus aureus and its cell wall product peptidoglycan (PGN) through the elaboration of numerous proinflammatory cytokines and chemokines. Microglia also exhibited S. aureus bactericidal activity. Microglia constitutively expressed low levels of Toll-like receptor 1 (TLR1), TLR2, TLR6, and CD14, all of which were enhanced following S. aureus exposure. Activation of resident microglia by S. aureus may serve to amplify the CNS antibacterial immune response through the release of cytokines, chemokines, and induction of bactericidal activity.

Central nervous system infections in injection drug users

Central nervous system infections in injection drug users are often devastating in terms of excess morbidity and mortality. In injection drug users with infective endocarditis, embolization from infected valvular vegetations may cause cerebral infarction, intracranial hemorrhage, and the formation of brain abscess. Focal intracranial infections (i.e., brain abscess and spinal epidural abscess) may occur in the absence of infective endocarditis, resulting from bacteremia that seeds the brain or epidural space. Antimicrobial therapy, combined with surgical intervention, may be essential to improve outcome from these neurologic complications. Toxin-mediated diseases (especially tetanus and wound botulism) are also seen in injection drug users. Inoculation of Clostridium spp at injection sites may lead to toxin generation and disease. Clinicians must maintain a high level of suspicion for these diagnoses in injection drug users.

Infectious and inflammatory disorders of the circulatory system and stroke in childhood

The role of infectious and inflammatory causes of stroke is much more significant in children than in adults. Conversely, that of atherosclerotic disease, ischaemic heart disease and hypertensive haemorrhages has a lesser prominence in children. Bacterial meningitis caused by Streptococcus pneumoniae, Haemophilus influenzae, or Neiserria meningitidis has been known to cause stroke in children. The mechanism appears to be the spread of meningeal inflammation to involve the walls of intracranial vessels, resulting in arterial thrombosis with ischaemia or rupture with haemorrhage. Other infections caused by atypical bacterial agents such as Mycoplasma tuberculosis and viral agents such as varicella-zoster virus have also been well documented as causes of stroke. Non-infectious, inflammatory causes of stroke, such as collagen vascular disease and primary angiitis of the central nervous system, have been reported in children as well as adults. In this review, we will focus on recent advances in the field of childhood stroke caused by infectious and inflammatory disorders.

Blood brain barrier and infection

The blood brain barrier (BBB) is a highly dynamic structure and consists of endothelial cells, which are characterized by the presence of tight junctions and relative lack of endocytic vesicles. The tight junctions are reinforced by the foot processes of the astrocytes. The BBB functions through these specialised structures, to maintain the environment of the brain in a steady state by regulating the influx and efflux of substances. The protective effect of the BBB is however, lost during bacterial and viral infections. The primary mechanism operative are an increase in the permeability of the BBB and/or direct invasion of the brain by microorganisms. Since the BBB is relatively impermeable to chemotherapeutic agents the treatment of CNS infections is difficult. This paper aims to examine the various mechanisms by which infection spreads to the brain, and suggest measures for successful drug delivery into the brain during infections.

Blood-brain barrier function in cerebral malaria and CNS infections in Vietnam

BACKGROUND

The intraerythrocytic parasite Plasmodium falciparum induces the life-threatening neurologic syndrome of cerebral malaria (CM) from within cerebral blood vessels, without entering the brain parenchyma.

OBJECTIVES

1) To assess the use of CSF as an indicator of specific pathologic processes occurring in the brain during CM; 2) to compare this with other neurologic and infectious diseases to understand the distinct pathogenic features of CM; 3) to test the hypothesis that CM involves a specific functional breakdown of the blood-brain barrier (BBB).

METHODS

1) Radial immunodiffusion assays to detect albumin and IgG in matched plasma and CSF samples as indicators of BBB integrity and intrathecal IgG production; and 2) ELISA for soluble intracellular adhesion molecule-1 and sE-selectin, the cytokines tumor necrosis factor-alpha and transforming growth factor-beta1, and the matrix metalloproteinase MMP-9, to detect cellular activation and inflammatory responses within the brain.

RESULTS

Albumin and IgG indices implied only minimal degree of BBB breakdown in a few cases of CM, with most remaining within the normal range. In contrast, cryptococcal, tubercular, and acute bacterial meningitis produced detectable changes in the composition of the CSF and evidence of BBB breakdown.

CONCLUSIONS

CM appears to involve only subtle functional changes in BBB integrity with minimal intraparenchymal inflammatory responses compared with other neurologic infections. This focuses attention on local events within and around the cerebral microvasculature in CM, rather than indicating widespread parenchymal disease.

Motor evoked potentials in a rhesus macaque model of neuro-AIDS

Previous work using bone marrow passaged SIVmac239 (simian immunodeficiency virus) has shown that macrophage tropic strains of this virus enter the rhesus macaque brain early following inoculation (Sharma et al, 1992; Desrosiers et al, 1991; Zhu et al, 1995; and Narayan et al, 1997). As part of an effort to more fully characterize the extent of neurologic impairment associated with SIV infection of the brain, we used transcranial electrical stimulation of motor cortex and the spinal cord to evoke EMG potentials in two forelimb (EDC and APB) and two hindlimb (LG and AH) muscles. The latencies, magnitudes and thresholds of motor evoked potentials (MEPs) recorded from nine monkeys infected with neurovirulent SIVmac R71/17E were compared to pre-inoculation records from the same monkeys. Seven of nine monkeys developed simian AIDS within 4 months of inoculation and were euthanized. Two monkeys remained free of AIDS-related clinical illness for over 18 months following inoculation. Six of the seven monkeys with rapidly progressing disease showed post-inoculation latency increases ( > or = 2 s.d. of control) in at least one cortical MEP. Increases in cortical MEP latency ranged from 21-97% in different monkeys. All seven rapidly progressing animals showed post-inoculation increases in at least one spinal cord MEP latency. Maximum spinal cord MEP latency increases ranged from 22-147%. Increases in central conduction time (CCT) ranged up to 204% and exceeded two standard deviations of control in four monkeys. Neither of the two monkeys with slowly progressing disease showed significant increases in either cortical or spinal cord MEP latency or CCT. Only the monkeys with rapidly progressing disease exhibited classic AIDS-related neuropathology, although there was no consistent relationship between the severity of neuropathology and the extent of MEP abnormalities. In conclusion, our results demonstrate clear deficits in the functional integrity of both central and peripheral motor system structures associated with SIV infection and further support the use of SIV-infected rhesus macaques as a model of neuro-AIDS.

Perspective: virus infections and the death of neurons

Neuronotropic viruses induce apoptosis in neurons, and Bcl-2-related anti-apoptotic proteins and caspase inhibitors decrease mortality from acute viral encephalitis. Infected neurons develop cytoplasmic blebbing characteristic of apoptosis, but a paucity of apoptotic nuclear changes potentially indicates unique aspects of virus-induced neuronal apoptosis that remain to be discovered.