Chronic encephalitis and epilepsy (Rasmussen's encephalitis): detection of cytomegalovirus and herpes simplex virus 1 by the polymerase chain reaction and in situ hybridization

Rasmussen's Encephalitis: A Literary Review

Usually affecting one hemisphere of the brain, Rasmussen's encephalitis (RE) is a persistent inflammatory disease of unclear origin. Rasmussen and colleagues presumed a viral etiology of the sickness in their first description. Later, the condition was linked to autoantibodies that were in the blood. Recently, it was shown that the cause of RE was a cytotoxic T-cell reaction to neurons. RE may be identified histopathologically by cortical inflammation, neuronal degeneration, and cerebral hemispheric-specific gliosis. The hemisphere is affected by increasing multilocular inflammation. To diagnose patients sooner and to evaluate whether the aforementioned phenomena are primary or secondary, it is essential to continue the search for a primary immunological or viral component. This information is crucial for determining the effectiveness of immunotherapy. RE-related seizures can only now be managed surgically. The only procedure that works is complete hemispheric disconnection (hemidisconnection), which may be done as either a (functional) hemispherectomy or hemispherectomy. Although thalidomide has been anecdotally reported, its safety profile prevents it from being used as a first-line treatment despite having a noticeable effect on the frequency and severity of seizures. Finding the disease's root causes more quickly by combining descriptive clinical studies, genetic testing, and early histological evaluation of RE tissue specimens to check for viral and autoimmune pathogenesis. Creating appropriate in vitro or animal models will enable the study of causality, perhaps directing clinical trials.

Progress in pathogenesis and therapy of Rasmussen's encephalitis

Rasmussen's encephalitis (RE) is a rare condition of unknown etiology that causes a severe chronically neurological disorder with mostly affecting children. The main clinical feature of RE includes frequent seizures with drug-resistant, unilateral hemispheric atrophy, and progressive neurological deficits. In this review, we summarized five pathogenesis on the basis of the current research including virus infection, antibody-mediated degeneration, cell-mediated immunity, microglia-induced degeneration, and genetic mutations. So far, no exact virus in RE brain tissue or definite antigen in humoral immune system was confirmed as the determined etiology. The importance of cytotoxic CD8⁺ T lymphocytes and activated microglial and the role of their immune mechanism in RE development are gradually emerging with the deep study. Genetic researches support the notion that the pathogenesis of RE is probably associated with single nucleotide polymorphisms on immune-related genes, which is driven by affecting inherent antiretroviral innate immunity. Recent advances in treatment suggest immunotherapy could partially slows down the progression of RE according to the histopathology and clinical presentation, which aimed at the initial damage to the brain by T cells and microglia in the early stage. However, the cerebral hemispherectomy is an effective means to controlling the intractable seizure, which is accompanied by neurological complications inevitably. So, the optimal timing for surgical intervention is still a challenge for RE patient. On the contrary, exploration on other aspects of pathogenesis such as dysfunction of adenosine system may offer a new therapeutic option for the treatment of RE in future.

Fundamental mechanistic insights from rare but paradigmatic neuroimmunological diseases

The pathophysiology of complex neuroimmunological diseases, such as multiple sclerosis and autoimmune encephalitis, remains puzzling - various mechanisms that are difficult to dissect seem to contribute, hampering the understanding of the processes involved. Some rare neuroimmunological diseases are easier to study because their presentation and pathogenesis are more homogeneous. The investigation of these diseases can provide fundamental insights into neuroimmunological pathomechanisms that can in turn be applied to more complex diseases. In this Review, we summarize key mechanistic insights into three such rare but paradigmatic neuroimmunological diseases - Susac syndrome, Rasmussen encephalitis and narcolepsy type 1 - and consider the implications of these insights for the study of other neuroimmunological diseases. In these diseases, the combination of findings in humans, different modalities of investigation and animal models has enabled the triangulation of evidence to validate and consolidate the pathomechanistic features and to develop diagnostic and therapeutic strategies; this approach has provided insights that are directly relevant to other neuroimmunological diseases and applicable in other contexts. We also outline how next-generation technologies and refined animal models can further improve our understanding of pathomechanisms, including cell-specific and antigen-specific CNS immune responses, thereby paving the way for the development of targeted therapeutic approaches.

Clonally Focused Public and Private T Cells in Resected Brain Tissue From Surgeries to Treat Children With Intractable Seizures

Using a targeted transcriptomics approach, we have analyzed resected brain tissue from a cohort of 53 pediatric epilepsy surgery cases, and have found that there is a spectrum of involvement of both the innate and adaptive immune systems as evidenced by the differential expression of immune-specific genes in the affected brain tissue. The specimens with the highest expression of immune-specific genes were from two Rasmussen encephalitis cases, which is known to be a neuro-immunological disease, but also from tuberous sclerosis complex (TSC), focal cortical dysplasia, and hemimegalencephaly surgery cases. We obtained T cell receptor (TCR) Vβ chain sequence data from brain tissue and blood from patients with the highest levels of T cell transcripts. The clonality indices and the frequency of the top 50 Vβ clonotypes indicated that T cells in the brain were clonally restricted. The top 50 Vβ clonotypes comprised both public and private (patient specific) clonotypes, and the TCR Vβ chain third complementarity region (CDR3) of the most abundant public Vβ clonotype in each brain sample was strikingly similar to a CDR3 that recognizes an immunodominant epitope in either human cytomegalovirus or Epstein Barr virus, or influenza virus A. We found that the frequency of 14 of the top 50 brain Vβ clonotypes from a TSC surgery case had significantly increased in brain tissue removed to control recurrent seizures 11 months after the first surgery. Conversely, we found that the frequency in the blood of 18 of the top 50 brain clonotypes from a second TSC patient, who was seizure free, had significantly decreased 5 months after surgery indicating that T cell clones found in the brain had contracted in the periphery after removal of the brain area associated with seizure activity and inflammation. However, the frequency of a public and a private clonotype significantly increased in the brain after seizures recurred and the patient underwent a second surgery. Combined single cell gene expression and TCR sequencing of brain-infiltrating leukocytes from the second surgery showed that the two clones were CD8 effector T cells, indicating that they are likely to be pathologically relevant.

HCMV infection and IFITM3 rs12252 are associated with Rasmussen's encephalitis disease progression

OBJECTIVE

Rasmussen's encephalitis (RE) is a rare and severe progressive epileptic syndrome with unknown etiology. Infection by viruses such as human cytomegalovirus (HCMV) has been hypothesized to be a potential trigger for RE. Interferon-induced transmembrane protein-3 (IFITM3) single-nucleotide polymorphism (SNP) rs12252 is associated with the severity of viral infection disease. This study aimed to address the possibility that HCMV infection and IFITM3 rs12252 might be associated with RE disease progression.

METHODS

The expression of HCMV and IFITM3 was detected with immunohistochemical staining, in situ hybridization and immunofluorescence double staining. The genotype of IFITM3 rs12252 was detected using the Sanger sequencing method. A genetic association analysis was carried out for this SNP and HCMV antigen expression. The relationship between this SNP and the clinical characteristics of these patients was further analyzed. In in vitro study, HCMV replication in SH-SY5Y cells with overexpressed IFITM3 variant was detected by immunofluorescence and real-time RT-PCR.

RESULTS

Elevated expression of HCMV and IFITM3 was observed in the brain tissue of RE patients. Moreover, the IFITM3 polymorphism rs12252-C was found to associate with HCMV high detection and rapid disease progression in RE patients with the IFITM3 rs12252-CC genotype. In vitro study showed the overexpressed IFITM3 variant was associated with HCMV high infection level.

CONCLUSION

These results suggest that the IFITM3 rs12252-C is associated with the disease progression of RE patients via facilitating persistent HCMV infection in brain tissue and provides new insight into understanding the pathogenesis of RE.

The Dilemma of Hemispherectomy for Rasmussen's Encephalitis in a Neurologically Intact Child

Rasmussen's encephalitis is a rare drug-resistant focal epilepsy characterized by progressive hemiparesis, hemianopia, and cognitive decline. Hemispherectomy is currently the only known treatment that can be curative, though expected to cause postoperative motor and visual deficits in children and adolescents. To date, medical treatment with antiseizure medications and immunosuppressive agents can only offer partial, delayed, or temporary alleviation of symptoms. Hence, patients and families are often faced with the difficult decision to consider the possibility of seizure freedom at the cost of incurring permanent deficits. Here, we discussed the unique ethical issues when faced with a cure that can cause harm, and also discussed a shared decision-making approach guided by informed consent, principles of autonomy, and patient-centered values.

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen's Encephalitis

Rasmussen's encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.

Proliferative hippocampal activity in a group of patients with Rasmussen's encephalitis: Neuronal, glial, and BDNF tissue expression correlations

Rasmussen's encephalitis (RE) is a rare and devastating unilateral inflammatory brain disease that causes severe and intractable partial epilepsy. It has been shown that epilepsy and subsequent inflammation have deleterious influence on hippocampal cell survival and neurogenesis, but this still has not been systematically explored in human tissue. In this study, we investigated the correlation between inflammation and epilepsy as well as the rates of hippocampal gliogenesis and neurogenesis in a pediatric group of six patients with RE and six control cases. The dentate gyrus (DG) samples were obtained from patients who underwent surgery for intractable RE. Sections were processed for immunohistochemistry using antibodies against sex determining region Y-box 2 (Sox2), nestin, human protein encoded by MKI67 gen (Ki67), and brain-derived neurotrophic factor (BDNF). There was an increase in the number of Ki67-positive granule cells in the DG of patients with RE in comparison with the autopsy control group, but no statistical difference for Sox2-positive cells was observed between these groups. Nestin immunolabeling was less intense in the RE group while BDNF expression was increased. Neurons that were BDNF-positive were found in DG from patients with RE but not in the control group. In patients with RE, few nestin-positive cells in DG were also positive for BDNF, unlike in controls which showed no colocalization for these two markers. These results suggest a proliferation activity in the DG subfield of patients with RE, and also future studies are necessary to address the role of new cells in the hippocampus of patients with RE.

Humanized mouse model of Rasmussen's encephalitis supports the immune-mediated hypothesis

Rasmussen's encephalitis (RE) is a chronic inflammatory brain disorder that causes frequent seizures and unilateral hemispheric atrophy with progressive neurological deficits. Hemispherectomy remains the only treatment that leads to seizure freedom for this refractory epileptic syndrome. The absence of an animal model of disease has been a major obstacle hampering the development of effective therapies. Here, we describe an experimental mouse model that shares several clinical and pathological features with the human disease. Immunodeficient mice injected with peripheral blood mononuclear cells from RE patients and monitored by video electroencephalography developed severe seizures of cortical origin and showed intense astrogliosis and accumulation of human IFN-γ- and granzyme B-expressing T lymphocytes in the brain compared with mice injected with immune cells from control subjects. We also provide evidence for the efficacy of α4 integrin blockade, an approved therapy for the treatment of multiple sclerosis and Crohn's disease, in reducing inflammatory markers associated with RE in the CNS. This model holds promise as a valuable tool for understanding the pathology of RE and for developing patient-tailored experimental therapeutics.

Phenotypic and functional complexity of brain-infiltrating T cells in Rasmussen encephalitis

Objective:

To characterize the brain-infiltrating immune cell repertoire in Rasmussen encephalitis (RE) with special focus on the subsets, clonality, and their cytokine profile.

Methods:

The immune cell infiltrate of freshly isolated brain tissue from RE was phenotypically and functionally characterized using immunohistology, flow cytometry, and T-cell receptor (TCR) deep sequencing. Identification of clonally expanded T-cell clones (TCCs) was achieved by combining flow cytometry sorting of CD4⁺ and CD8⁺ T cells and high-throughput TCR Vβ-chain sequencing. The most abundant brain-infiltrating TCCs were isolated and functionally characterized.

Results:

We found that CD4⁺, CD8⁺, and also γδ T cells infiltrate the brain tissue in RE. Further analysis surprisingly revealed that not only brain-infiltrating CD8⁺ but also CD4⁺ T cells are clonally expanded in RE. All 3 subsets exhibited a Tc1/Th1 phenotype characterized by the production of interferon (IFN)-γ and TNF. Broad cytokine profiling at the clonal level showed strong production of IFN-γ and TNF and also secretion of interleukin (IL)-5, IL-13, and granzyme B, both in CD4⁺ and CD8⁺ T cells.

Conclusions:

CD8⁺ T cells were until now considered the central players in the immunopathogenesis of RE. Our study adds to previous findings and highlights that CD4⁺ TCCs and γδ T cells that secrete IFN-γ and TNF are also involved. These findings underline the complexity of T-cell immunity in RE and suggest a specific role for CD4⁺ T cells in orchestrating the CD8⁺ T-cell effector immune response.

Elevated expression of EBV and TLRs in the brain is associated with Rasmussen's encephalitis

Rasmussen's encephalitis (RE) is a rare pediatric neurological disorder, the etiology of which remains unclear. It has been speculated that the immunopathogenesis of RE involves damage to neurons, which eventually leads to the occurrence of RE. Viral infection may be a critical factor in triggering RE immunopathogenesis. In this study, we analyzed the expression of Epstein-Barr virus (EBV) antigens as well as of Toll-like receptor 3 (TLR3), TLR9, and downstream adapter TIRdomain-containing adapter-inducing interferon-β (TRIF) in the brain tissues of 26 patients with RE and 16 control individuals using immunohistochemistry (IHC). In the RE group, EBV antigens were detected in 53% of individuals at various expression levels. In contrast, there was no detectable EBV antigen expression in control brain tissues. Moreover, we found marked increases in the expression of TLR3, TLR9, and TRIF in the brain tissues of RE patients compared with levels in the control group. Furthermore, among RE cases, EBV expression and high TLR3 expression were associated with more severe brain atrophy. Our results suggest that the elevated expression of EBV and TLRs may be involved in RE occurrence through the activation of downstream molecules.

Expression of human cytomegalovirus components in the brain tissues of patients with Rasmussen's encephalitis

Rasmussen’s encephalitis (RE) is a rare and severe progressive epileptic syndrome with unknown etiology. Infection by viruses, including human cytomegalovirus (HCMV), has been speculated to be a potential trigger for RE. However, no viral antigens have been detected in the brains of patients with RE; thus, a possible clinical linkage between viral infections and RE has not been firmly established. In this study, we evaluated the expression of HCMV pp65 antigen in brain sections from 26 patients with RE and 20 non-RE patients by immunohistochemistry and in situ hybridization, and assessed the associations between HCMV infection and clinical parameters. Elevated expression of HCMV pp65 protein and DNA was observed in 88.5% (23/26) and 69.2% (18/26) of RE cases, respectively. In the non-RE group, HCMV pp65 antigen was detected only in two cases (10%), both of which were negative for DNA staining. Additionally, the intensity of HCMV pp65 staining was correlated with a shorter duration of the prodromal stage, younger age of seizure onset, and more severe unilateral cortical atrophy. Elevated expression of HCMV pp65 was observed in RE brain tissue and was correlated with the clinical features of RE disease. In summary, our results suggested that HCMV infection may be involved in the occurrence and progression of RE disease. Thus, further studies are needed to determine whether early treatment with anti-HCMV antibodies could modulate the course of RE.

Elevated expression of human papillomavirus antigen in brain tissue of patients with Rasmussen's encephalitis

OBJECTS

To investigate the expression of human papillomavirus (HPV)-specific antigen in the brain tissue of patients with Rasmussen's Encephalitis (RE) and its possible link to the clinical manifestation of RE.

METHODS

The correlation between RE and HPV antigen expression in brain tissue sections was investigated using immunohistochemical (IHC) staining, pathological examination, MRI and clinical manifestations.

RESULTS

HPV antigen expression was elevated in three out of four patients with RE, whereas there were no detectable HPV antigens in six control patients. Significant staining for HPV antigen was located mainly around or in the nucleus and cytoplasm of neurons. Among these RE patients, three with elevated expression of HPV antigens had obvious hemisphere atrophy, whereas the patient with negative staining for HPV antigens had mild atrophy.

CONCLUSIONS

Elevated expression of HPV antigens was observed in the brain tissue of RE patients, which may correlate with hemisphere atrophy. Thus, our results may suggest that HPV infection or being a carrier of HPV may play a role in the initiation and progression of RE.

Autoimmunity to Glutamate Receptors in Rasmussen's Encephalitis: A Rare Finding or The Tip of an Iceberg?

Neurological disorders demonstrate remarkable specificity in afflicting precise brain regions. They are most frequently sporadic in origin and they are devastating because of the progressive impairment of cognitive and/or motor functions. Our studies have found that some neurological diseases may actually reflect a dysfunction of the immune system in which highly specific autoantibodies are generated that bind neuronal glutamate receptors and directly affect their function in normal neurotransmission. Understanding at the molecular level how the immune system participates in neurological disease will ultimately lead to more effective therapeutic approaches to some of these disorders with presently unknown etiology. NEURO SCIENTIST 4:373-379, 1998

Anti-N-Methyl-D-Aspartate Receptor Encephalitis In A Young Child With Histological Evidence On Brain Biopsy Of Coexistent Herpes Simplex Virus Type 1 Infection

We report a 3-year-old boy with anti-N-methyl-D-aspartate receptor encephalitis with a typical syndrome of movement disorder and encephalopathy and evidence of herpes simplex virus (HSV) type 1 infection on brain biopsy. HSV type 1 infection and anti-N-methyl-D-aspartate receptor encephalitis are temporally linked in some cases: this case suggests that prodromal HSV type-1 infection may be clinically subtle and easily missed.

Evidence for Resident Memory T Cells in Rasmussen Encephalitis

Rasmussen encephalitis (RE) is a rare pediatric neuroinflammatory disease of unknown etiology characterized by intractable seizures, and progressive atrophy usually confined to one cerebral hemisphere. Surgical removal or disconnection of the affected cerebral hemisphere is currently the only intervention that effectively stops the seizures. Histopathological evaluation of resected brain tissue has shown that activated brain resident macrophages (microglia) and infiltrating T cells are involved in the inflammatory reaction. Here, we report that T cells isolated from seven RE brain surgery specimens express the resident memory T cell (T_RM) marker CD103. CD103 was expressed by >50% of CD8⁺ αβ T cells and γδ T cells irrespective of the length of time from seizure onset to surgery, which ranged from 0.3 to 8.4 years. Only ~10% of CD4⁺ αβ were CD103⁺, which was consistent with the observation that few CD4⁺ T cells are found in RE brain parenchyma. Clusters of T cells in brain parenchyma, which are a characteristic of RE histopathology, stained for CD103. Less than 10% of T cells isolated from brain specimens from eight surgical cases of focal cortical dysplasia (FCD), a condition that is also characterized by intractable seizures, were CD103⁺. In contrast to the RE cases, the percent of CD103⁺ T cells increased with the length of time from seizure onset to surgery. In sections of brain tissue from the FCD cases, T cells were predominantly found around blood vessels, and did not stain for CD103. The presence of significant numbers of T_RM cells in RE brain irrespective of the length of time between clinical presentation and surgical intervention supports the conclusion that a cellular immune response to an as yet unidentified antigen(s) occurs at an early stage of the disease. Reactivated T_RM cells may contribute to disease progression.

Autoimmune encephalitis and its relation to infection

Encephalitis, an inflammatory condition of the brain that results in substantial morbidity and mortality, has numerous causes. Over the past decade, it has become increasingly recognized that autoimmune conditions contribute significantly to the spectrum of encephalitis causes. Clinical suspicion and early diagnosis of autoimmune etiologies are of particular importance due to the need for early institution of immune suppressive therapies to improve outcome. Emerging clinical observations suggest that the most commonly recognized cause of antibody-mediated autoimmune encephalitis, anti-N-methyl-D-aspartate (NMDA) receptor encephalitis, may in some cases be triggered by herpes virus infection. Other conditions such as Rasmussen's encephalitis (RE) and febrile infection-related epilepsy syndrome (FIRES) have also been posited to be autoimmune conditions triggered by infectious agents. This review focuses on emerging concepts in central nervous system autoimmunity and addresses clinical and mechanistic findings linking autoimmune encephalitis and infections. Particular consideration will be given to anti-NMDA receptor encephalitis and its relation to herpes simplex encephalitis.

Mechanisms of epileptogenesis in pediatric epileptic syndromes: Rasmussen encephalitis, infantile spasms, and febrile infection-related epilepsy syndrome (FIRES)

The mechanisms of epileptogenesis in pediatric epileptic syndromes are diverse, and may involve disturbances of neurodevelopmental trajectories, synaptic homeostasis, and cortical connectivity, which may occur during brain development, early infancy, or childhood. Although genetic or structural/metabolic factors are frequently associated with age-specific epileptic syndromes, such as infantile spasms and West syndrome, other syndromes may be determined by the effect of immunopathogenic mechanisms or energy-dependent processes in response to environmental challenges, such as infections or fever in normally-developed children during early or late childhood. Immune-mediated mechanisms have been suggested in selected pediatric epileptic syndromes in which acute and rapidly progressive encephalopathies preceded by fever and/or infections, such as febrile infection-related epilepsy syndrome, or in chronic progressive encephalopathies, such as Rasmussen encephalitis. A definite involvement of adaptive and innate immune mechanisms driven by cytotoxic CD8(+) T lymphocytes and neuroglial responses has been demonstrated in Rasmussen encephalitis, although the triggering factor of these responses remains unknown. Although the beneficial response to steroids and adrenocorticotropic hormone of infantile spasms, or preceding fever or infection in FIRES, may support a potential role of neuroinflammation as pathogenic factor, no definite demonstration of such involvement has been achieved, and genetic or metabolic factors are suspected. A major challenge for the future is discovering pathogenic mechanisms and etiological factors that facilitate the introduction of novel targets for drug intervention aimed at interfering with the disease mechanisms, therefore providing putative disease-modifying treatments in these pediatric epileptic syndromes.

Rasmussen's encephalitis: clinical features, pathobiology, and treatment advances

Rasmussen's encephalitis is a rare chronic neurological disorder, characterised by unilateral inflammation of the cerebral cortex, drug-resistant epilepsy, and progressive neurological and cognitive deterioration. Neuropathological and immunological studies support the notion that Rasmussen's encephalitis is probably driven by a T-cell response to one or more antigenic epitopes, with potential additional contribution by autoantibodies. Careful analysis of the association between histopathology and clinical presentation suggests that initial damage to the brain is mediated by T cells and microglia, suggesting a window for treatment if Rasmussen's encephalitis can be diagnosed early. Advances in neuroimaging suggest that progression of the inflammatory process seen with MRI might be a good biomarker in Rasmussen's encephalitis. For many patients, families, and doctors, choosing the right time to move from medical management to surgery is a real therapeutic dilemma. Cerebral hemispherectomy remains the only cure for seizures, but there are inevitable functional compromises. Decisions of whether or when surgery should be undertaken are challenging in the absence of a dense neurological deficit, and vary by institutional experience. Further, the optimum time for surgery, to give the best language and cognitive outcome, is not yet well understood. Immunomodulatory treatments seem to slow rather than halt disease progression in Rasmussen's encephalitis, without changing the eventual outcome.

Differential expression of interferon-γ and chemokine genes distinguishes Rasmussen encephalitis from cortical dysplasia and provides evidence for an early Th1 immune response

Background

Rasmussen encephalitis (RE) is a rare complex inflammatory disease, primarily seen in young children, that is characterized by severe partial seizures and brain atrophy. Surgery is currently the only effective treatment option. To identify genes specifically associated with the immunopathology in RE, RNA transcripts of genes involved in inflammation and autoimmunity were measured in brain tissue from RE surgeries and compared with those in surgical specimens of cortical dysplasia (CD), a major cause of intractable pediatric epilepsy.

Methods

Quantitative polymerase chain reactions measured the relative expression of 84 genes related to inflammation and autoimmunity in 12 RE specimens and in the reference group of 12 CD surgical specimens. Data were analyzed by consensus clustering using the entire dataset, and by pairwise comparison of gene expression levels between the RE and CD cohorts using the Harrell-Davis distribution-free quantile estimator method.

Results

Consensus clustering identified six RE cases that were clearly distinguished from the CD cases and from other RE cases. Pairwise comparison showed that seven mRNAs encoding interferon-γ, CCL5, CCL22, CCL23, CXCL9, CXCL10, and Fas ligand were higher in the RE specimens compared with the CD specimens, whereas the mRNA encoding hypoxanthine-guanine phosphoribosyltransferase was reduced. Interferon-γ, CXCL5, CXCL9 and CXCL10 mRNA levels negatively correlated with time from seizure onset to surgery (P <0.05), whereas CCL23 and Fas ligand transcript levels positively correlated with the degree of tissue destruction and inflammation, respectively (P <0.05), as determined from magnetic resonance imaging (MRI) T2 and FLAIR images. Accumulation of CD4⁺ lymphocytes in leptomeninges and perivascular spaces was a prominent feature in RE specimens resected within a year of seizure onset.

Conclusions

Active disease is characterized by a Th1 immune response that appears to involve both CD8⁺ and CD4⁺ T cells. Our findings suggest therapeutic intervention targeting specific chemokine/chemokine receptors may be useful in early stage RE.

Bilateral Rasmussen encephalitis

Rasmussen encephalitis (RE) is a rare, chronic, inflammatory neurological disorder that usually affects one hemisphere of the brain. RE is characterized by frequent and severe seizures, progressive neurological dysfunction, and unilateral brain atrophy. This article documents a case of RE with bilateral involvement occurring at the age of 2. The patient's seizures consisted of focal motor seizures (epilepsia partialis continua in the fingers on the right hand); tonic convulsions of the right arm and head turning to the right with impairment of consciousness; and secondarily generalized tonic-clonic seizures. Antiepileptic drugs did not effectively control the seizures. The pathology of the left frontoparietal lobe biopsy of the abnormal MRI signal showed typical neuronal loss, abundant lymphocytic infiltration into the perivascular space, and numerous microglial nodules. Bipolar electrocoagulation on functional cortexes, which failed to alter the course of the illness, was followed by high-dose prednisone (about 2 weeks worth), without improvement. Both functional hemispherectomies and anatomical hemispherectomies failed to halt the course of the illness, and contralateral seizures developed and became apparent after the operation, suggesting bilateral RE.

Chronic active herpes simplex type 2 encephalitis in an asymptomatic immunocompetent child

A unique form of chronic, active, granulomatous herpes simplex type 2 encephalitis is described in an asymptomatic, immunocompetent 8-year-old girl who acquired the virus as a neonate. The extensive, bilateral cerebral parenchymal involvement was discovered incidentally. Diagnosis was confirmed by a combination of serial neuroimaging, brain biopsy, and quantitative polymerase chain reaction targeted to DNA sequences in the glycoprotein G gene, allowing differentiation between herpes simplex virus types 1 and 2. The clinical course over a 5-year period, treatment with intermittent intravenous steroids, and daily valacyclovir, diagnostic imaging, and laboratory studies are reviewed in detail. This form of herpes simplex virus type 2 encephalitis hasn't been described previously and is significant because of its prolonged indolent course, absence of neurological findings or suggestive history, and benign behavior in this child, who is now 14 years old. The authors believe this entity can be unsuspected and underdiagnosed in the general pediatric population, especially in those with a prior maternal history of herpes simplex virus type 2 infection.

Rasmussen's encephalitis: update on pathogenesis and treatment

Rasmussen's encephalitis is a devastating disease characterized by refractory epilepsy and progressive atrophy of one cerebral hemisphere. The only treatment option able to prevent seizures is the surgical disconnection of the affected hemisphere. The etiology of the disease remains unknown, but several laboratory findings have recently indicated the involvement of the immune system. Whether these findings represent an initiating event or the consequence of a not yet identified trigger factor must be elucidated. Nevertheless, these observations suggest the use of different immunomodulatory approaches (including corticosteroids, plasmapheresis, intravenous immunoglobulins and immunosuppressive drugs) that proved to be of variable efficacy in some patients, confirming the potential role of the immune system, at least in the perpetuation of the disease.

Correlation between magnetic resonance imaging and histopathologic grades in Rasmussen syndrome

The aim of this study was to investigate the correlation between magnetic resonance imaging (MRI) and histopathologic findings in Rasmussen syndrome. Serial MRIs were obtained for five patients who had histologically proven Rasmussen syndrome. The histopathologic grades of the lesions were subdivided into phases: active 1-3, resolving 1-3, and chronic inflammatory. The images were then correlated with histopathologic findings. Neuropathologic findings in the central areas on MRI demonstrated only the chronic and resolving grades, but active inflammatory abnormalities were present not only at the margins of the lesions, but also in areas of subtle signal abnormality on MRI. Atrophic areas on MRI exhibited all grades of histopathologic abnormalities, but chronic and resolving grades were predominant. Seizure duration of less than 6 months was associated with very active grades, duration of 1-2 years with variable grades, and duration greater than 6 years with chronic and resolving grades only. The MRI images correlated highly with histopathologic analysis. These findings suggest that the lesions initially arise from one site in the brain, and so support the centrifugal spreading theory of this disease. Findings also suggest that the margin rather than the center of the MRI abnormality may be the most ideal site for biopsy.

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.

Investigation of HSV-1, HSV-2, CMV, HHV-6 and HHV-8 DNA by real-time PCR in surgical resection materials of epilepsy patients with mesial temporal lobe sclerosis

OBJECTIVE

The objective of this study is to investigate the presence of viral DNAs of HSV-1, HSV-2, HHV-6, HHV-8, and CMV in hippocampus of the patients with mesial temporal lobe epilepsy (MTLE) syndrome.

METHODS

Pathological specimens were obtained from 33 patients with MTLE undergone temporal lobectomy with amygdalo-hippocampectomy due to intractable seizures. Autopsy materials from the hippocampus of 7 patients without neurological disease were used as controls. The data was also correlated with the clinical history of patients including febrile convulsions, age, and history of CNS infections. Real-time polymerase chain reaction method was performed for detection of DNAs of these viruses.

RESULTS

HHV-6, HSV-1 and HHV-8 were detected in the hippocampus of 3, 2 and 1 patients with MTLE respectively. None of the hippocampus of patients with MTLE was positive for DNA of HSV-2 and/or CMV. Three patients with positive HHV-6 DNAs had febrile convulsions and family history for epilepsy. None of our control specimens showed PCR positivity to any of the 5 tested viruses.

CONCLUSIONS

Our study is the first to report the presence of HHV-8 viral genome in the brain tissue of patient with MTLE. Viral DNAs were detected in a total of 18% of the patients in this study; we can conclude that activity of the latent virus in patients with hippocampal sclerosis should be more extensively studied to establish its role in active infection.

Detection of herpes simplex virus type 1 DNA in bilateral human trigeminal ganglia and optic nerves by polymerase chain reaction

Herpes simplex virus type 1 (HSV-1) DNA was extracted from human trigeminal ganglia of 121 cadavers aged between 3 months and 94 years, and its PCR amplification was performed for the RL2 HSV-1 sequence using two pairs of primers. The HSV-1 DNA was detected in 74 of 121 patients (61%); 70/74 bilaterally, 3/74 only on the left side, and 1/74 only on the right side. Although the PCR-positive rate was significantly higher in advanced age, the correlation between the PCR-positive rate and gender was unclear. Additionally, HSV-1 DNA was not detected in any of the 50 optic nerve samples.

Neue Erkenntnis zur Rasmussen-Enzephalitis

Rasmussen encephalitis (RE) is a severe and at the same time pathophysiologically fascinating condition. The chronic inflammation affects one of the two cerebral hemispheres and destroys it during the disease process that lasts from months to years. The patients -- mostly children -- suffer from frequent pharmacoresistant seizures, often in the form of epilepsia partialis continua. In parallel to the atrophy of the affected hemisphere, the neurological functions associated with it decline continuously. This results in a final stage with a usually high-grade sensorimotor hemisyndrome, hemianopia, cognitive impairment and -- if the language-dominant hemisphere is affected -- aphasia. Research results in the last 5 years have contributed to a deeper understanding of the pathogenesis of this condition. Formal diagnostic criteria have been proposed, and new therapeutic options have emerged by which the disease progression can be slowed or stopped. This article summarizes the current research results on the background of older data and gives recommendations regarding diagnostic and therapeutic procedures in RE patients.

[Recent advances in pathogenic concepts and therapeutic strategies in Rasmussen's encephalitis]

Rasmussen's encephalitis (RE) is a rare inflammatory brain disease mainly affecting children and characterised by intractable epilepsy involving a single hemisphere that undergoes progressive atrophy. RE is characterized by refractory focal seizures, often associated with epilepsia partialis continua, progressive unilateral motor defect, slow EEG activity over the entire contralateral hemisphere, with focal white matter hyperintensity and insular cortical atrophy on neuroimaging. Surgical exclusion of the affected hemisphere is the only treatment that interrupts progression of the disease. Pathogenic concepts have considered viruses, autoimmune antibodies and autoimmune cytotoxic T lymphocytes that might contribute to the initiating or perpetuating events in the central nervous system. Based on these concepts, different therapeutic strategies have been pursued, such as antiviral agents, plasmapheresis, immuno-adsorption, immunosuppression or immunomodulation with intravenous immunoglobulins. However, due to the lack of large studies, to date there is no established therapeutic strategy for this devastating condition. In this review, we give an overview of the current state of immunopathogenic concepts for Rasmussen's encephalitis and discuss the different therapeutic options for future perspectives.

Herpesviral DNA in brain tissue from patients with temporal lobe epilepsy

OBJECTIVES

Presence of DNA from six herpesviruses were examined in brain tissue from patients operated for temporal lobe epilepsy.

MATERIAL AND METHODS

A total of 19 Canadian patients (I) with a median age of 22 years, 17 Swedish patients (II) with a median age of 14 years and a reference group comprising 12 individuals were studied. Presence of herpesviral DNA was detected by nested polymerase chain reaction.

RESULTS

Of three children with Rasmussen's encephalitis, Cytomegalovirus (CMV) DNA was found in two, and human herpesvirus type 6 DNA in two. In six children with ganglioglioma, Epstein-Barr virus (EBV) was detected in four. CMV DNA was found significantly more in group I compared with II, while the reverse occurred with EBV DNA. Malformations of cortical development were found significantly more in group II compared with I.

CONCLUSION

Detection of DNA from some herpesviruses in epileptic brain tissue may possibly be associated with distinct clinical conditions, but factors such as age and malformations of cortical development should also be considered.

Rasmussen syndrome and long-term response to thalidomide

We report a 13-year-old female who experienced symptoms and signs of Rasmussen encephalitis for the first time at the age of 5 years. Various therapeutic procedures, including conventional and new antiepileptic drugs, steroids, immunoglobulin, plasma exchanges, and partial hemispherectomy, were applied, but their results were unsatisfactory. During one of the exacerbations, when the patient's life was endangered, thalidomide was administered. Frequency and intensity of epileptic seizures were reduced significantly, and the quality of her life improved. Except for moderate neutropenia, the other adverse effects were not recognized. In our opinion, thalidomide is not a first-choice drug for Rasmussen encephalitis but is a good alternative only for cases refractory to other well-known and accepted therapeutic procedures.

Virological and immunological aspects of seizure disorders

The brain is a symptom-producing organ, and one of the symptoms due to a basic brain dysfunction is epilepsy. The pathophysiologic background is in most epilepsies multifactorial, as different pre-, peri-, and postnatal triggers or environmental conditions influence one or several genetic factors, where also gender is of importance. One of the genetic factors is immunodysfunction, and the trigger mechanism may be a virus infection. Viruses are the most common agents to which the human being is exposed throughout life. The herpes virus group is of special interest with respect to complications of the central nervous system. Herpes viruses, especially herpes simplex virus type 1 (HSV-1), human herpes virus type 6 (HHV-6), cytomegalovirus (CMV) and Epstein-Barr virus (EBV), are capable of establishing latent infection and reactivating under a variety of stimuli. In this review especially HHV-6 will be emphasized, as well as CMV in relation to Rasmussen's syndrome. The immunological aspects will focus on immunoglobulins, antibodies, especially the glutamate receptors, human leukocyte antigens, T- and B-lymphocytes, and their respective interaction with the antigen presenting cell. This course of events concerns the 'immunological synapse'. Finally, reports on herpes virus genomes in the human brain are discussed. A study on herpes viral DNA in brain tissue from patients operated for focal epilepsy is briefly mentioned.

A longitudinal MRI study in children with Rasmussen syndrome

The aim of this study was to identify the presence of any neuroimaging patterns of Rasmussen syndrome using magnetic resonance imaging (MRI). This was a prospective study evaluating brain MRIs in seven children with neuropathologically proven Rasmussen syndrome. All patients were unresponsive to conventional antiepileptics; five patients subsequently underwent functional hemispherectomy, and two patients underwent cortical resection. Three to eight (mean = 4.7) MRIs per patient were performed, and neuropathologic examination of the brain was available. Serial MRIs were obtained between 12 months before and 9 months after the onset of epilepsia partialis continua. The most common region of initial MRI signal change was the frontocentral region (six patients). Three patterns of neuroimaging abnormalities were observed as follows: (1) normal MRI followed by increased signal intensity with progressive cortical atrophy over time, (2) initial increased focal signal intensity followed by decrease in spatial extent and degree of signal intensity; (3) initially increased signal intensity without further changes on follow-up scans. This observation suggests three possible distinct patterns of MRI changes in patients with Rasmussen syndrome and that the differences in these neuroimaging patterns may reflect inherent differences in the pathogenesis of Rasmussen syndrome.

Advances in pathogenic concepts and therapeutic agents in Rasmussen's encephalitis

Rasmussen's encephalitis is a rare inflammatory brain disease which occurs mainly in children and is characterised by affection of only one hemisphere. Pathogenetic concepts have considered three different, not mutually exclusive, key factors contributing to the initiating or perpetuating events in the central nervous system. These include viruses, autoimmune antibodies and autoimmune cytotoxic T lymphocytes. Based on these concepts, different therapeutic strategies have been pursued, such as antiviral agents, plasmapheresis, immuno-adsorption, immunosuppression or immunomodulation with intravenous immunoglobulins. However, due to the lack of larger studies, to date there is no established therapeutic strategy of this devastating disease. An overview of the current state of immunepathogenic concepts for Rasmussen's encephalitis is given and past and present treatment attempts are discussed, including an outline of future perspectives. An opinion on symptomatic treatment with anticonvulsive drugs is included.

Rasmussen encephalitis: a clinicopathologic and immunohistochemical study of seven patients

We retrospectively reviewed the clinicopathologic features and immunohistochemical profiles of 7 patients with Rasmussen encephalitis (age range, 3.5-15 years at surgery). All had medically intractable seizures (6 months' to 7 years' duration); all but 1 developed unilateral hemiparesis. Histologically, all cases were characterized by leptomeningeal and parenchymal perivascular chronic inflammation consisting primarily of T lymphocytes (CD3+, CD5+, CD7+). In all but 1 case, a predominance of CD8+ T-cytotoxic/suppressor lymphoid cells over CD4+ cells was observed. All cases had rare B lymphocytes (CD79a+, CD20+). Rare CD10+ and no CD56+ cells were noted. All cases were marked by diffuse proliferation of microglial cells, highlighted on CD68 immunostaining. Focal microglial nodule formations were observed in 4 cases and focal cortical atrophy in 5 cases. Viral inclusions were not noted. There was no evidence of Epstein-Barr virus by LMP-1 antibody immunostaining. The histologic findings of Rasmussen encephalitis resemble those of viral meningoencephalitis. The pathologicfindings may be only focally present, and missed, if diagnosis is made or confirmed with biopsy alone. Most lymphoid cells have a T-cell immunophenotype, with a predominance of CD8+ cells in most cases.

Patterns of cerebral glucose metabolism in early and late stages of Rasmussen's syndrome

Rasmussen's syndrome is a chronic encephalitis characterized by intractable focal epilepsy and progressive neurologic deterioration with lateralized brain destruction. In the early stages of the disease, the diagnosis can be difficult to make, and brain biopsy is often performed. We evaluated the patterns of cerebral glucose metabolism using 2-deoxy-2-[18F]-fluoro-D-glucose positron emission tomography (PET) in 15 children (age range 2.9-15.4 years, mean age 8.7 +/- 4.3 years) with Rasmussen's syndrome. In 6 patients evaluated early (< or = 1 year of onset of seizures), the PET scan showed areas of abnormal metabolism restricted mostly to the frontal and temporal regions, whereas the posterior cortex was preserved. Pathologic changes seen in the resected cortex were more pronounced in cortical areas of abnormal metabolism than in regions showing normal metabolism. In 9 patients evaluated later (>1 year after onset of seizures), the PET scan showed more diffuse hemispheric metabolic abnormalities including the occipital cortex, but the abnormalities remained highly lateralized. These patterns of glucose metabolic abnormalities in the early and late stages of the disease may facilitate the diagnosis of Rasmussen's syndrome and assist guidance of biopsy in early cases, when structural neuroimaging is still normal.

Polymerase chain reaction as a diagnostic adjunct in herpesvirus infections of the nervous system

Polymerase chain reaction (PCR) is a powerful technique that allows detection of minute quantities of DNA or RNA in cerebrospinal fluid (CSF), vesicle and endoneurial fluids, blood, fresh-frozen, and even formalin-fixed tissues. Various infectious agents can be detected with high specificity and sensitivity, including bacteria, parasites, rickettsia and viruses. PCR analysis of CSF has revolutionized the diagnosis of nervous system viral infections, particularly those caused by human herpesviruses (HHV), and has now replaced brain biopsy as the gold standard for diagnosis of herpes simplex virus (HSV) encephalitis. PCR analysis of both CSF and nervous system tissues has also broadened our understanding of the spectrum of disease caused by HSV-1 and -2, cytomegalovirus (CMV), Epstein-Barr virus (EBV), varicella zoster virus (VZV), and HHV-6. Nonetheless, positive tissue PCR results must be interpreted cautiously, especially in cases that lack corroborating clinical and neuropathologic evidence of infection. Moreover, positive PCR results from tissues do not distinguish latent from productive (lytic) viral infections. In several neurological diseases, negative PCR results have provided strong evidence against a role for herpesviruses as the causative agents. This review focuses on the use of PCR tests to diagnose HSV and VZV infections of the nervous system.

Rasmussen's syndrome: intractable epilepsy and progressive neurological deterioration from a unilateral central nervous system

Rasmussen's syndrome (chronic encephalitis with epilepsy) is a rare neurological disorder of unknown cause characterized by severe epilepsy, hemiplegia, dementia, and inflammation of the brain, and progressive functional and structural destruction of a single cerebral hemisphere. While one mechanism underlying the pathogenesis of Rasmussen's encephalitis has been hypothesized to be mediated by production of excitotoxic GluR3 autoantibodies to the a-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor, other neuropathological etiologies have also been indicated. Proposed therapies have included antiepileptics, steroids, antiviral agents, alpha-interferon, and immunoglobulin. The mainstay of therapy is surgical hemispherectomy. To date, no medical therapies have permanently halted neurologic deterioration.

Establishment of a cytokine-producing anaplastic large-cell lymphoma cell line containing the t(2;5) translocation: potential role of cytokines in clinical manifestations

A permanent cell line, HSC-M1, was established from a child with advanced CD30 (Ki-1)+ anaplastic large-cell lymphoma (ALCL). Clinical features included irritability, fever, weight loss, tender lymphadenopathy, pneumonitis, neutrophilia, and bone marrow erythrophagocytosis. While HSC-M1 cells exhibited an immunophenotype characteristic of ALCL of T-cell lineage, the cell line also demonstrated features of monocyte-macrophage lineage. Cytogenetic and polymerase chain reaction (PCR) analysis of the HSC-M1 cell line and involved bone marrow demonstrated the characteristic non-random chromosomal translocation t(2:5)(p23:q35). Reverse transcriptase PCR for mRNA expression of cytokines and cytokine receptors showed that HSC-M1 cells expressed the message for multiple cytokines and their receptors. Measurement of cytokine levels in serum samples using enzyme-linked immunosorbent assays showed increased concentrations of several cytokines. The increased levels of some cytokines correlated with disease activity and clinical symptoms. Although spontaneous production by HSC-M1 cells of some of these cytokines was demonstrated, the production of others was only detectable after stimulation with exogenous CD30 ligand. With few exceptions, there was good correlation between serum cytokine levels and cytokines produced by HSC-M1 cells. These findings indicate that cytokine production is a feature of ALCL cells and that some of the clinical manifestations in ALCL may result from cytokines produced by either the malignant or accessory cells.

Rolandic encephalopathy and epilepsia partialis continua following bone marrow transplant

Epilepsia partialis continua (EPC) is a condition defined by prolonged focal myoclonus. Often resistant to therapy, EPC in children is frequently present in Rasmussen encephalitis, a form of chronic encephalitis of uncertain etiology. We discuss a child who developed bilateral EPC 5 months after a bone marrow transplant. Neuroimaging studies showed signal abnormalities on both sensory-motor areas. An extensive search failed to reveal the etiology of the disorder, but treatment with a broad-spectrum anti-viral agent was associated with resolution of the process. An unidentified infectious agent may be responsible for an encephalitis of the motor strip in immunosuppressed patients.

[Probable Rasmussen's syndrome. Case report]

The syndrome of chronic encephalitis with epilepsy (Rasmussen's syndrome) typically occurs in children and is characterized by the development of intractable focal seizures, progressive hemiparesis and intellectual deterioration. The etiology is unknown, and the pathological abnormalities vary. We report the case of a 17-year-old boy, presenting with clinical features typical of probable Rasmussen's syndrome. We discuss the etiology and treatment for this pathology.

Immunoglobulin G and complement immunoreactivity in the cerebral cortex of patients with Rasmussen's encephalitis

OBJECTIVE

To provide evidence that complement (C')-dependent processes may be involved in Rasmussen's encephalitis (RE).

BACKGROUND

RE is a rare, progressive, childhood epilepsy syndrome associated with inflammation and neuronal cell loss in a single cerebral hemisphere. Recent work suggests an autoimmune immunoglobulin (Ig) G-mediated process is important in disease pathogenesis.

METHODS

Brain samples from RE and complex partial epilepsy control patients were analyzed immunohistochemically. Sections were stained for IgG and the C' factors C4, C8, and the membrane attack complex (MAC).

RESULTS

Brain samples from three of five patients with active, progressive RE but neither of two chronic RE nor five control epilepsy patients demonstrated immunoreactivity for IgG, C4, C8, and MAC on discrete patches of cerebrocortical neurons. Intensely activated glial fibrillary acid protein-positive astrocytes were found in areas overlapping these patches.

CONCLUSION

Focally distributed IgG- and C'-positive neurons were found to colocalize with activated astrocytes, suggesting focal IgG-dependent classical C' cascade pathway activation with attendant tissue damage in this subset of RE patients. Intraparenchymal C' activation triggered by pathogenic antibodies may contribute to the development of focal inflammation, neuronal cell loss, and pharmacoresistant seizures in some patients with this disease. This process may be an important component in the initial, active phase of RE.

Histopathologic findings in 37 cases of functional hemispherectomy

Hemispherectomy procedures are performed in patients for whom focal cortical resection would be predicted to produce a significant reduction in seizures. The functional hemispherectomy procedure consists of disconnecting the hemispheres while attempting, in some cases, to preserve parenchyma. This study retrospectively reviews the histopathologic findings in 37 cases of functional hemispherectomy performed between 1990 and 1998 at a major epilepsy center. Procedures were performed in 20 males and 17 females who ranged in age from 3 months to 37 years (mean age, 9.6 years). In all but two cases, more than half or all the material submitted for pathologic testing was examined histologically. Cortical dysplasias or hemimegalencephaly were identified in 14 patients. The most common patterns of dysplasia observed included architectural disorganization (n = 13), increased molecular layer neurons (n = 11), and neuronal cytomegaly (n = 11). One patient was known to have epidermal nevus syndrome. Six patients had Sturge-Weber syndrome. Remote infarct/ischemic damage was identified as the etiology of seizures in six patients; four of these patients had mild associated secondary cortical architectural abnormalities. Three patients demonstrated pathology consistent with Rasmussen's encephalitis; one additional patient had chronic encephalitis changes, not otherwise specified. In two cases, changes consistent with hippocampal sclerosis were identified; additionally, hippocampal neuronal loss and gliosis was focally identified in three patients. Most of these patients had coexistent cortical dysplasia or radiographic evidence of remote infarct. One specimen demonstrated areas of infarct following resection of an arteriovenous malformation. In two specimens, significant histopathologic findings were not identified; both of these patients had radiographic evidence of remote infarct. The spectrum of pathologic conditions that may be encountered in the setting of a functional hemispherectomy is varied and in this study most frequently included cortical dysplasia, Sturge-Weber syndrome remote infarct, and Rasmussen's encephalitis.

Autoimmunity and neurological disease: antibody modulation of synaptic transmission

Over the past three decades, compelling evidence has emerged that the immune system can attack the nervous system with devastating consequences for human health. Either cell-mediated or humoral (antibody-mediated) autoimmune mechanisms may predominate in effecting a given disease, and either glia or neurons may fall under immune attack. A subset of these diseases has been particularly useful for understanding fundamental neuroscience as well as mechanisms of human disease. This subset involves humoral autoimmune attack on cell surface molecules subserving transmembrane signaling of excitable cells; special emphasis is placed here on proteins involved in synaptic transmission. We begin by reviewing the prototypic humoral autoimmune disease of synaptic transmission, myasthenia gravis. This provides a context for insights obtained from the study of diseases targeting molecules that regulate synaptic transmission at the neuromuscular junction and in the central nervous system. We also explore a disease where autoimmunity produces agonist antibodies acting at two distinct G-protein-coupled receptors. We conclude with an exploration of the vital issue of access of antibodies to targets within the central nervous system and the implications that such access may have in the pathogenesis of poorly understood idiopathic central nervous system diseases.

Viral diagnosis of neurological infection by RT multiplex PCR: a search for entero- and herpesviruses in a prospective study

The diagnosis of a wide range of different neurological syndromes was established by a reverse transcription multiplex PCR assay. The presence of enterovirus and herpesviruses was studied in cerebrospinal fluid samples collected prospectively from 200 patients hospitalized with neurological diseases suspected of viral infection. Positive PCR results for enterovirus and neurotropic herpesvirus (herpes simplex, HSV, and varicella zoster, VZV) were obtained among the immunocompetent patients (55/156, 35%) who presented aseptic meningitis or encephalitis. Among immunocompromised patients the yield of positive PCR results was 41% (18/44), predominantly lymphotropic herpesviruses (15/44, 34%). Cytomegalovirus (CMV) DNA was detected in patients with several clinical syndromes, including encephalitis, chronic meningitis, retinitis, ventriculitis, polyradiculomyelitis, and myeloradiculitis. Epstein-Barr (EBV) and VZV-specific DNA sequences were detected in patients with either encephalitis, aseptic meningitis, and chronic meningitis. Dual infections of CMV and HSV or CMV and EBV were established in two AIDS patients with encephalitis and polyradiculomyelitis, respectively. The applications of this RT multiplex PCR assay are extensive and may prove to be particularly valuable for the rapid and sensitive diagnosis of neurological diseases in both immunocompetent and immunocompromised patients.

Rasmussen's encephalitis with concomitant cortical dysplasia: the role of GluR3

The role of the glutamate receptor GluR3 in Rasmussen's encephalitis is actively under investigation. Autoimmune processes with this receptor as the target are currently theorized. We provide an additional case of pathologically proved Rasmussen's encephalitis (with concomitant cortical dysplasia) in the presence of antibodies against the GluR3 receptor.