Neuronal surface antibody-mediated autoimmune encephalitis

Clinical features, cerebrospinal fluid changes, and prognosis in Chinese patients with autoimmune encephalitis

INTRODUCTION

Autoimmune encephalitis (AE) is a rare, treatable disease of the central nervous system (CNS) caused by an antibody-related immune response. This study is to investigate the correlation of clinical features, cerebrospinal fluid (CSF) characteristics, and prognosis in patients with AE.

METHODS

A total of 71 patients diagnosed with antibody-positive AE were retrospectively analyzed. The patients were divided into three groups: anti-NMDAR group, anti-LGI1 group, and other types. Clinical data were collected to analyze clinical features and CSF results, and prognosis was determined by modified Rankin Scale (mRS).

RESULTS

There was statistical difference in the incidences of decreased consciousness level (P < 0.001), memory loss (P = 0.017), speech disorders (P = 0.035), and dyskinesia (P = 0.001) in different antibodies groups. Younger age (P = 0.018), elevated CSF chloride content (P = 0.006), and white blood cells > 50/mm3 (P = 0.026) were highly correlated with ICU admission. Anti-LGI1 encephalitis had a relatively small risk for ICU admission (P = 0.034), and a lower risk of poor functional recovery (P = 0.048) and recurrence (P = 0.041). Patients with first-line treatment failure (P = 0.021) had an increased risk of poor functional recovery. Delayed treatment (P = 0.011) would increase the risk of recurrence.

CONCLUSION

There are differences in age, gender, clinical characteristics, and CSF results in different subtypes of AE. First-line therapy failure would have poor functional recovery, and delayed therapy would increase the risk of relapse. Chloride ion content and white blood cell count in cerebrospinal fluid are positively correlated with the patient's exacerbation and admission to ICU. These indicators have certain clinical value for the prognosis of AE patients.

Anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor encephalitis developed after ovarian cancer cytoreduction surgery: a case report and literature review

BACKGROUND

Anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis, a rare subtype of autoimmune encephalitis (AE), is often found associated with tumors such as thymoma, lung cancer, ovarian tumors, and breast cancer, and the tumors were generally detected during the screening process after the encephalitis initiated. The tumor is considered a trigger of AE, but the mechanism remains unclear.

CASE PRESENTATION

A 53-year-old woman presented short-term memory loss two days after the primary cytoreduction for high-grade serous ovarian cancer (HGSOC, FIGO stage IC3). Cell-based assay found AMPAR CluA2 IgG positive in both serum (1:3.2) and cerebrospinal fluid (1:32). Moreover, mild AMPAR GluA1 and strong GluA2 expressions were also found positive in the paraffin sections of ovarian tumor tissue, indicating the ovarian cytoreduction surgery might stimulate the release of receptor antigens into the circulation system. The patient's condition deteriorated within two weeks, developing consciousness and autonomic dysfunction, leading to ICU admission. With oral steroids, intravenous immunoglobulin, plasmapheresis, and rituximab treatment, the patient's consciousness markedly improved after three months.

CONCLUSION

We presented the first case of anti-AMPAR encephalitis developed right after the primary cytoreduction of a patient with HGSOC and retrieved paraneoplastic anti-AMPAR encephalitis cases (n = 66). Gynecologists should pay attention to patients who develop cognitive dysfunction or psychiatric symptoms shortly after the ovarian tumor resection and always include AE in the differentiation diagnosis.

Presence of neural surface and onconeural autoantibodies in cerebrospinal fluid and serum in neurological diseases presents a potential risk for misdiagnosis

BACKGROUND AND PURPOSE

Autoantibodies have been found to contribute to pathology and are used in the diagnosis of some neurological diseases. We examined the prevalence of autoantibodies in patients with various neurological diseases and whether patients who had autoantibodies differed in age, sex, or disability from those who did not.

METHODS

We examined the prevalence of neural surface and onconeural autoantibodies in cerebrospinal fluid (CSF) and serum from patients with multiple sclerosis (n = 64), Parkinson disease plus atypical parkinsonism (n = 150), amyotrophic lateral sclerosis (n = 43), or autoimmune encephalitis (positive control; n = 7) and a healthy control group (n = 37). A total of 12 onconeural autoantibodies and six neural surface autoantibodies were tested in all participants.

RESULTS

Autoantibodies were present in all cohorts. The prevalence of autoantibodies was high (>80%) in the autoimmune encephalitis cohort but low (<20%) in all other cohorts. When comparing patients within cohorts who were positive for autoantibodies to patients who were not, there was no difference in age, sex, and disability. This was apart from the multiple sclerosis and Parkinson disease plus atypical parkinsonism cohorts, where those with positivity for autoantibodies in the CSF were significantly older.

CONCLUSIONS

The presence of the autoantibodies examined does not appear to have a substantial clinical impact within the diseases examined in this study. The presence of autoantibodies in all cohorts presents a risk for misdiagnosis when the method is used incorrectly on patients with atypical clinical presentation.

Autoimmune Encephalitis-A Multifaceted Pathology

Autoimmune encephalitis is a complex and multifaceted pathology that involves immune-mediated inflammation of the brain. It is characterized by the body's immune system attacking the brain tissue, leading to a cascade of inflammatory processes. What makes autoimmune encephalitis vast is the wide range of causes, mechanisms, clinical presentations, and diagnostic challenges associated with the condition. The clinical presentations of autoimmune encephalitis are broad and can mimic other neurological disorders, making it a challenging differential diagnosis. This diverse clinical presentation can overlap with other conditions, making it crucial for healthcare professionals to maintain a high level of suspicion for autoimmune encephalitis when evaluating patients. The diagnostic challenges associated with autoimmune encephalitis further contribute to its vastness. Due to the variable nature of the condition, there is no definitive diagnostic test that can confirm autoimmune encephalitis in all cases. In this context, personalized patient management is crucial for achieving favorable outcomes. Each patient's treatment plan should be tailored to their specific clinical presentation, underlying cause, and immune response. Our objective is to raise awareness about the frequent yet underdiagnosed nature of autoimmune encephalitis by sharing five cases we encountered, along with a brief literature review.

Fire acupuncture for anti-LGI1 antibody autoimmune encephalitis: a case report

Autoimmune encephalitis, a class of encephalitis, is clinically characterized by multifocal or diffuse brain injury, including aberrant mental behavior, convulsions, and near-event memory impairment. In this article, we describe a female patient with autoimmune encephalitis who tested positive for leucine-rich glioma inactivated 1 (LGI1) antibodies and had hippocampal inflammatory edema in the lesion area. During the first 3 months of her illness, the patient primarily experienced memory loss, the onset of rigid twitching in her extremities that lasted for 1 min while in remission, and incontinence. After gamma globulin administration, methylprednisolone shock, and other symptomatic therapies during hospitalization, the patient's psychiatric symptoms and seizures improved considerably; however, she did not fully recover her memory. After receiving fire acupuncture for 6 months, the patient's understanding, orientation, and calculation skills improved considerably. Her memory and mental state were also improved at the follow-up visit. In this case, the use of fire acupuncture for the treatment of autoimmune encephalitis resulted in favorable outcomes with important benefits for conditions affecting the central nervous system; however, more convincing data are required to support the effectiveness of this treatment method.

Autoimmune Encephalitis: A Physician’s Guide to the Clinical Spectrum Diagnosis and Management

The rapidly expanding spectrum of autoimmune encephalitis in the last fifteen years is largely due to ongoing discovery of many neuronal autoantibodies. The diagnosis of autoimmune encephalitis can be challenging due to the wide spectrum of clinical presentations, prevalence of psychiatric features that mimic primary psychiatric illnesses, frequent absence of diagnostic abnormalities on conventional brain MR-imaging, non-specific findings on EEG testing, and the lack of identified IgG class neuronal autoantibodies in blood or CSF in a subgroup of patients. Early recognition and treatment are paramount to improve outcomes and achieve complete recovery from these debilitating, occasionally life threatening, disorders. This review is aimed to provide primary care physicians and hospitalists who, together with neurologist and psychiatrists, are often the first port of call for individuals presenting with new-onset neuropsychiatric symptoms, with up-to-date data and evidence-based approach to the diagnosis and management of individuals with neuropsychiatric disorders of suspected autoimmune origin.

Pathophysiology and Clinical Management of Autoimmune Encephalitis-Associated Seizures

Seizures are a very common manifestation of autoimmune encephalitis (AE), ranging from 33% to 100% depending on the antigen, most often accompanied by other clinical features such as behavioral changes, movement disorders, memory deficits, autoimmune disturbances, and altered levels of consciousness. Unusual seizure frequency, resistance to antiepileptic treatment, and often, definitive response to immunotherapy emphasize the importance for neurologists to consider the probable etiology of immune disorders. Studies on pathogenic mechanisms of autoantibodies have improved the understanding of different pathophysiologies and clinical characteristics of different AE groups. In encephalitis with antibodies to neuronal extracellular antigens, autoantibodies play a direct role in disease pathogenesis. They have access to target antigens and can potentially alter the structure and function of antigens but induce relatively little neuronal death. Prompt immunotherapy is usually very effective, and long-term antiepileptic treatment may not be needed. In contrast, in encephalitis with antibodies against intracellular antigens, autoantibodies may not be directly pathogenic but serve as tumor markers. These autoantibodies cannot reach intracellular target antigens and are considered to result from a T-cell-mediated immune response against antigens released by apoptotic tumor cells, which contain nerve tissue or express neuronal proteins. Neuronal loss is frequently described and predominantly induced through cytotoxic T-cell mechanisms. They often exhibit an inadequate response to immunotherapy and require early tumor treatment. Long-term antiepileptic treatment is usually needed. In conclusion, each neural autoantibody can specifically precipitate seizures. Early proper management of these cases may help prevent neurological deterioration and manage the occurrence of seizures. Consequently, confirmation of the presence of neuronal autoantibodies is strongly recommended even in patients with confirmed AE, as they are not only essential in achieving a good outcome but also may provide evidence for underlying neoplasia.

Speech, Language, and Communication Deficits and Intervention in a Single Case of Pediatric Autoimmune Encephalitis

Purpose The current literature on pediatric autoimmune encephalitis (AE) focuses on medical identification/diagnosis and medical treatments. Data about the identification and treatment of communication disorders in these children are limited. This clinical focus article provides an example of the speech, language, and communication characteristics, intervention, and recovery of a single child with medical diagnoses of pediatric AE and pediatric acute-onset neuropsychiatric syndrome (PANS) and special education eligibility under the autism spectrum disorder category. Method This is an in-depth illustrative/descriptive case study. Medical, educational, and speech-language documentation of one child diagnosed with AE at age 7 years was reviewed. Methods included interviews with family members, teachers, and the school speech-language pathologist and reviews of documentation including evaluations, reports, and Individualized Education Programs. Results This child received special education and therapy services through his public school and a university speech-language clinic. He concurrently received medical treatment for AE and PANS. Comprehensive augmentative and alternative communication (AAC) intervention included the use of core words, modeling, parallel talk, self-talk, expansive recasts, shared book reading, family counseling, and collaboration with the parents and the school speech-language pathologist. The child made progress on all goals despite irregular attendance to therapy due to medical complications. Discussion Because experimental research including this population is currently limited, this descriptive case study provides valuable information to clinicians, educators, pediatricians, medical diagnosticians, and anyone providing services to a child with a complex neuropsychological disorder like AE. Future research is needed with more children who have AE, especially experimental investigations of the intervention methods utilized here. Additional research of more children with AE can provide information about the scope and severity of speech, language, and communication needs and the trajectory of recovery given AAC intervention.

Short- and Long-Lived Autoantibody-Secreting Cells in Autoimmune Neurological Disorders

As B cells differentiate into antibody-secreting cells (ASCs), short-lived plasmablasts (SLPBs) are produced by a primary extrafollicular response, followed by the generation of memory B cells and long-lived plasma cells (LLPCs) in germinal centers (GCs). Generation of IgG4 antibodies is T helper type 2 (Th2) and IL-4, -13, and -10-driven and can occur parallel to IgE, in response to chronic stimulation by allergens and helminths. Although IgG4 antibodies are non-crosslinking and have limited ability to mobilize complement and cellular cytotoxicity, when self-tolerance is lost, they can disrupt ligand-receptor binding and cause a wide range of autoimmune disorders including neurological autoimmunity. In myasthenia gravis with predominantly IgG4 autoantibodies against muscle-specific kinase (MuSK), it has been observed that one-time CD20⁺ B cell depletion with rituximab commonly leads to long-term remission and a marked reduction in autoantibody titer, pointing to a short-lived nature of autoantibody-secreting cells. This is also observed in other predominantly IgG4 autoantibody-mediated neurological disorders, such as chronic inflammatory demyelinating polyneuropathy and autoimmune encephalitis with autoantibodies against the Ranvier paranode and juxtaparanode, respectively, and extends beyond neurological autoimmunity as well. Although IgG1 autoantibody-mediated neurological disorders can also respond well to rituximab induction therapy in combination with an autoantibody titer drop, remission tends to be less long-lasting and cases where titers are refractory tend to occur more often than in IgG4 autoimmunity. Moreover, presence of GC-like structures in the thymus of myasthenic patients with predominantly IgG1 autoantibodies against the acetylcholine receptor and in ovarian teratomas of autoimmune encephalitis patients with predominantly IgG1 autoantibodies against the N‐methyl‐d‐aspartate receptor (NMDAR) confers increased the ability to generate LLPCs. Here, we review available information on the short-and long-lived nature of ASCs in IgG1 and IgG4 autoantibody-mediated neurological disorders and highlight common mechanisms as well as differences, all of which can inform therapeutic strategies and personalized medical approaches.

Failed, Interrupted, or Inconclusive Trials on Immunomodulatory Treatment Strategies in Multiple Sclerosis: Update 2015-2020

In the past decades, multiple sclerosis (MS) treatment has experienced vast changes resulting from major advances in disease-modifying therapies (DMT). Looking at the overall number of studies, investigations with therapeutic advantages and encouraging results are exceeded by studies of promising compounds that failed due to either negative or inconclusive results or have been interrupted for other reasons. Importantly, these failed clinical trials are informative experiments that can help us to understand the pathophysiological mechanisms underlying MS. In several trials, concepts taken from experimental models were not translatable to humans, although they did not lack a well-considered pathophysiological rationale. The lessons learned from these discrepancies may benefit future studies and reduce the risks for patients. This review summarizes trials on MS since 2015 that have either failed or have been interrupted for various reasons. We identify potential causes of failure or inconclusiveness, looking at the path from basic animal experiments to clinical trials, and discuss the implications for our current view on MS pathogenesis, clinical practice, and future study designs. We focus on anti-inflammatory treatment strategies, without including studies on already approved and effective DMT. Clinical trials addressing neuroprotective and alternative treatment strategies are presented in a separate article.

Neuronal Surface Antibody-Medicated Autoimmune Encephalitis (Limbic Encephalitis) in China: A Multiple-Center, Retrospective Study

Objective: The epidemiological characteristics of patients with antibody-medicated autoimmune encephalitis in China remain unclear, and a large-scale epidemiological survey is necessary.

Methods: A multiple-center retrospective study was performed. We collected 1,047 patients with suspected autoimmune encephalitis and ultimately enrolled 778 defined patients across centers in China. All patients were positive for serum [or cerebrospinal fluid (CSF)] antibodies. Demographic information and clinical data from January 2014 to January 2019 from 22 centers in China were reviewed.

Results: A total of 778 patients with autoimmune encephalitis were enrolled in the study. In general, the ratio of males to females was ~1.2:1. The main subtypes of autoimmune encephalitis were NMDAR-AE (61.35%), LGI-1-AE (20.61%), and GABAbR-AE (12.40%). According to the characteristics of age of onset, the incidence of autoimmune encephalitis showed a “double peak” distribution entailing a 20-year-old age group and a 60-year-old age group. We next analyzed the proportion of patients with tumors in this cohort. More specifically, there were 34 patients with tumors and 85 with tumor marker positivity. Relapse occurred in 81 patients within at least 1 year's follow up study: 52 with NMDAR-AE (18.2%); 19 with LGI-1-AE (16.8%); 5 with GABAbR-AE (9%); and 3 with CASPR2-AE.

Interpretation: Due to the vast differences in demographic features, the incidence of cancer and the genetic characteristics between the populations in China and Western countries, the demographics, sex distribution, concomitant tumor rate, clinical features, and relapse characteristics associated with autoimmune encephalitis in China shows a similar profile with Western countries with some minor differences.

Neuropsychiatric Disorders Due to Limbic Encephalitis: Immunologic Aspect

Limbic encephalitis (LE) is a rare cause of encephalitis presenting as an acute and subacute onset of neuropsychiatric manifestations, particularly with memory deficits and confusion as core features, along with seizure occurrence, movement disorders, or autonomic dysfunctions. LE is caused by neuronal antibodies targeting the cellular surface, synaptic, and intracellular antigens, which alter the synaptic transmission, especially in the limbic area. Immunologic mechanisms involve antibodies, complements, or T-cell-mediated immune responses in different degree according to different autoantibodies. Sensitive cerebrospinal fluid markers of LE are unavailable, and radiographic findings may not reveal a typical mesiotemporal involvement at neurologic presentations; therefore, a high clinical index of suspicions is pivotal, and a neuronal antibody testing is necessary to make early diagnosis. Some patients have concomitant tumors, causing paraneoplastic LE; therefore, tumor survey and treatment are required in addition to immunotherapy. In this study, a review on the molecular and immunologic aspects of LE was conducted to gain awareness of its peculiarity, which we found quite different from our knowledge on traditional psychiatric illness.

Steroid-Responsive Encephalitis in Coronavirus Disease 2019

Coronavirus disease 2019 (COVID-19) infection has the potential for targeting the central nervous system, and several neurological symptoms have been described in patients with severe respiratory distress. Here, we described the case of a 60-year-old patient with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection but only mild respiratory abnormalities who developed an akinetic mutism attributable to encephalitis. Magnetic resonance imaging was negative, whereas electroencephalography showed generalized theta slowing. Cerebrospinal fluid analyses during the acute stage were negative for SARS-CoV-2, positive for pleocytosis and hyperproteinorrachia, and showed increased interleukin-8 and tumor necrosis factor-α concentrations. Other infectious or autoimmune disorders were excluded. A progressive clinical improvement along with a reduction of cerebrospinal fluid parameters was observed after high-dose steroid treatment, thus arguing for an inflammatory-mediated brain involvement related to COVID-19. ANN NEUROL 2020;88:423-427.

Anti-NMDAR Encephalitis Following Herpes Simplex Virus Encephalitis: 2 Cases From Portugal

Herpes simplex virus encephalitis (HSVE) usually presents as a monophasic disease. Symptomatic HSVE relapsing with seizures, encephalopathy, or involuntary movements associated with anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis have been recently reported. We report 2 cases of adult post-HSVE anti-NMDAR encephalitis from Portugal. Two female patients aged 50 years and 30 years were diagnosed with herpes simplex virus type 2 and type 1 encephalitis, respectively. After the initial improvement with specific treatment and despite virologic negativization, both patients suffered clinical, electroencephalographic, and imaging deterioration. The autoimmune encephalitis hypothesis was confirmed with the demonstration of anti-NMDAR antibodies in both cerebrospinal fluid and serum. Both responded to human immunoglobulin and methylprednisolone, with progressive gain of autonomy along the follow-up period. Thymectomy for thymic hyperplasia diagnosed during follow-up was performed in 1 patient. Although being rare, post-HSVE anti-NMDAR encephalitis should be considered in all cases of symptomatic recrudescence after HSVE, since adequate immune-modulating treatment improves the outcome. The role of thyme hyperplasia in autoimmune encephalitis pathogenesis needs better understanding.

Is rat hippocampus section immunostaining an indicator for immunotherapy in cryptogenic adult new-onset refractory status epilepticus (NORSE)?

PURPOSE

To evaluate the meaning of immunostaining of rat hippocampus with respect to clinical manifestations, Status epilepticus(SE)severity, treatment, and prognosis of New-Onset Refractory Status Epilepticus(NORSE) patients.

METHODS

Consecutive patients with cryptogenic NORSE admitted to the neuro-intensive care unit (NICU) between January 2015 and October 2018 were screened, and those who had serum and cerebrospinal fluid (CSF) immunostaining were included. Subsequently, the patients were classified into positive and negative immunostain groups. Immunotherapy was initiated in patients who progressed to super-RSE (SRSE). The demographic, and clinical, and immunostaining data were collected. The prognosis was evaluated by modified Rankin scale (mRS) at discharge (short-term prognosis) and 6 months (long-term prognosis), with mRS score ≤2 defined as the favorable outcome. The clinical manifestations, treatment response, and prognosis were compared between the patients with positive and negative immunostains.

RESULTS

4/18 patients had positive immunostaining on both CSF and serum, 8 (had positive immunostaining on serum only, while 6 had negative immunostaining on serum and CSF. Twelve (66.7 %) patients progressed to SRSE, with no difference between the positive and negative immunostaining groups (P = 1.000). 7/18 patients had a favorable outcome at discharge and 11/18 after 6 months. No significant difference on the prognosis was detected between patients with positive and negative serum/CSF immunostaining and between the patients with or without immunotherapy at discharge or 6-month follow-up (P = 0.657/P = 0.502, P = 0.445/P = 0.829, P = 0.622, P = 0.567, respectively).

CONCLUSIONS

The immunostaining on serum and/or CSF from NORSE patients did not indicate the progression to SRSE and clinical outcomes.

The immunobiology of autoimmune encephalitides

Autoimmune encephalitides, with an estimated incidence of 1.5 per million population per year, although described only 15 years ago, have already had a remarkable impact in neurology and paved the field to autoimmune neuropsychiatry. Many patients traditionally presented with aberrant behavior, especially of acute or subacute onset, and treated with anti-psychotic therapies, turn out to have a CNS autoimmune disease with pathogenic autoantibodies against synaptic antigens responding to immunotherapies. The review describes the clinical spectrum of these disorders, and the pathogenetic role of key autoantibodies directed against: a) cell surface synaptic antigens and receptors, including NMDAR, GABAa, GABAb, AMPA and glycine receptors; b) channels such as AQP4 water-permeable channel or voltage-gated potassium channels; c) proteins that stabilize voltage-gated potassium channel complex into the membrane, like the LGI1 and CASPR2; and d) enzymes that catalyze the formation of neurotransmitters such as Glutamic Acid Decarboxylase (GAD). These antibodies, effectively target excitatory or inhibitory synapses in the limbic system, basal ganglia or brainstem altering synaptic function and resulting in uncontrolled neurological excitability disorder clinically manifested with psychosis, agitation, behavioral alterations, depression, sleep disturbances, seizure-like phenomena, movement disorders such as ataxia, chorea and dystonia, memory changes or coma. Some of the identified triggering factors include: viruses, especially herpes simplex, accounting for the majority of relapses occurring after viral encephalitis, which respond to immunotherapy rather than antiviral agents; tumors especially teratoma, SCLC and thymomas; and biological cancer therapies (immune-check-point inhibitors). As anti-synaptic antibodies persist after viral infections or tumor removal, augmentation of autoreactive B cells which release autoantigens to draining lymph nodes, molecular mimicry and infection-induced bystander immune activation products play a role in autoimmunization process or perpetuating autoimmune neuroinflammation. The review stresses the importance of early detection, clinical recognition, proper antibody testing and early therapy initiation as these disorders, regardless of a known or not trigger, are potentially treatable responding to systemic immunotherapy with intravenous steroids, IVIg, rituximab or even bortezomid.

A Practical Primer on Prion Pathology

Prion diseases comprise a group of transmissible degenerative encephalopathies resulting from propagation of a misfolded cellular protein of uncertain function. As is generally the case with rare diseases, lack of institutional experience compromises individual familiarity with the varying, and apparently protean, manifestations of prion diseases, both clinically and pathologically. Coupled with the documented transmissibility of these diseases both within and between species, the Centers for Disease Control and Prevention (CDC) has established the National Prion Disease Pathology Surveillance Center to both aid with diagnosis of prion disease and to survey the United States for evidence of zoonotic transmission. We have assembled this primer with the hope that our accumulated experience will enable the neuropathological community to help the CDC "save lives and protect people."

Novel Object Recognition in Rats With NMDAR Dysfunction in CA1 After Stereotactic Injection of Anti-NMDAR Encephalitis Cerebrospinal Fluid

Purpose: Limbic encephalitis associated with autoantibodies against N-methyl D-aspartate receptors (NMDARs) often presents with memory impairment. NMDARs are key targets for memory acquisition and retrieval, and have been mechanistically linked to its underlying process, synaptic plasticity. Clinically, memory deficits are largely compatible with a pre-dominantly hippocampus-dependent phenotype, which, in rodents, is principally involved in spatial memory. Previous studies confirmed the impaired spatial memory in the rat model of anti-NMDAR encephalitis. Here, we hypothesized that non-spatial memory functions, such as object recognition might also be affected in this model.

Methods: We performed stereotactic intrahippocampal bolus injection of human cerebrospinal fluid (CSF) from anti-NMDAR encephalitis and control patients into the hippocampus of the anesthetized rat. After recovery for 1–8 days, hippocampal slices were prepared from these animals and NMDAR-dependent long-term potentiation was assessed at the Schaffer collateral-CA1 synapse. In addition, we performed behavioral analyses using the open field and novel object recognition tasks.

Results: NMDAR-dependent long-term potentiation in the hippocampal CA1 area was significantly suppressed, indicating successful NMDAR dysfunction in this subfield. Spontaneous locomotor activity as well as anxiety-related behavior in the open field did not differ between NMDAR-CSF-treated and control animals. In the novel object recognition task, there were no differences in the motivation to approach objects. In contrast, we observed a significantly preferred exploration of the novel object only in control, but not in NMDAR-CSF-treated rats.

Conclusion: These results indicate that NMDAR dysfunction obtained by intrahippocampal stereotactic injection does not alter locomotor or anxiety-related behavior. In addition, approach to an object or exploratory behavior in general are not affected either, but intact initial NMDAR-dependent processes might be involved in novel object recognition.

A review of EEG in anti-NMDA receptor encephalitis

Anti-N-methyl-d-aspartate receptor encephalitis (anti-NMDARE) is common among autoimmune encephalitides (AE) and can present with protean features and nonspecific laboratory and neuroimaging results. Antibody testing is specific, but results are often delayed, and prompt diagnosis and treatment is vital given associated morbidity and mortality. Electroencephalography (EEG) may be a useful tool given ease of performance and short turn-around time for results. As such, we performed a systematic review of the literature on anti-NMDARE and EEG characteristics. We found that EEG is often pathologic in anti-NMDAR encephalitis, though at times nonspecific. A stronger focus on common EEG features in patient with this type of encephalitis and an effort to identify when these features are present in the course of the disease may allow for improved diagnosis, description and differentiation of anti-NMDARE.

Structural mapping of hot spots within human CASPR2 discoidin domain for autoantibody recognition

Accumulating evidence has showed that anti-CASPR2 autoantibodies occur in a long list of neurological immune disorders including limbic encephalitis (LE). Belonging to the well-known neurexin superfamily, CASPR2 has been suggested to be a central node in the molecular networks controlling neurodevelopment. Distinct from other subfamilies in the neurexin superfamily, the CASPR subfamily features a unique discoidin (Disc) domain. As revealed by our and others' recent studies, CASPR2 Disc domain bears a major epitope for autoantibodies. However, structural information on CASPR2 recognition by autoantibodies has been lacking. Here, we report the crystal structure of human CASPR2 Disc domain at a high resolution of 1.31 Å, which is the first atomic-resolution structure of the CASPR subfamily members. The Disc domain adopts a total β structure and folds into a distorted jellyroll-like barrel with a conserved disulfide-bond interlocking its N- and C-termini. Defined by four loops and located in one end of the barrel, the "loop-tip surface" is totally polar and easily available for protein docking. Based on structure-guided epitope prediction, we generated nine mutants and evaluated their binding to autoantibodies of cerebrospinal fluid from twelve patients with limbic encephalitis. The quadruple mutant G69N/A71S/S77N/D78R impaired CASPR2 binding to autoantibodies from eleven LE patients, which indicates that the loop L1 in the Disc domain bears hot spots for autoantibody interaction. Structural mapping of autoepitopes within human CASPR2 Disc domain sheds light on how autoantibodies could sequester CASPR2 ectodomain and antagonize its functionalities in the pathogenic processes.

Post-malaria neurological syndrome: Imported case series and literature review to unscramble the auto-immune hypothesis

Post-malaria neurological syndrome (PMNS) is a complication that occurs after recovery from a severe Plasmodium falciparum attack. Over the past two decades, the description of several imported cases has confirmed that this syndrome is a clearly distinct entity, different from other post malarial neurological disorders. However, the underlying mechanisms are not yet elucidated. Herein, we present five imported PMNS cases managed in Marseille, France. The detection of neuronal surface antibodies to an encephalitic syndrome of unknown origin allowed us to reveal positivity of anti Voltage-Gated-Potassium Channel antibodies (anti VGKC) in one of them. Using treatment options from other autoimmune encephalitis has to be explored in patients with PMNS.

Peptide ligand-based ELISA reagents for antibody detection

Detection of specific antibodies has numerous research, therapeutic and diagnostic applications. Short peptide ligands that bind specifically to antibodies with continuous epitopes can be derived from epitope mapping experiments. Short peptide ligands (mimotopes) specific to antibodies with discontinuous epitopes can be identified by screening complex peptide libraries. In an effort to enhance practical utility of such peptide ligands, we describe here a simple approach to turn such target antibody-specific peptide ligands into specific ELISA detection reagents. We show that a simple addition of biotinylated peptide ligands to commonly available horseradish peroxidase (HRP)-labeled streptavidin (or HRP-anti-biotin antibody), or digoxigenin-labeled peptides to HRP-anti-digoxigenin antibody detection reagents transformed these generic detection reagents into sensitive target antibody-specific reagents. ELISA assays performed using these reagents exhibited excellent analytical properties indicating their practical utility for antibody detection. One generic detection reagent can be readily transformed into many different specific ELISA reagents by a simple mix and match design using an appropriate target-specific peptide ligand. Simplicity of preparation of these ELISA reagents for detecting antibodies should facilitate their practical applications.

Differentially Altered NMDAR Dependent and Independent Long-Term Potentiation in the CA3 Subfield in a Model of Anti-NMDAR Encephalitis

Purpose: Autoantibodies against NMDA receptors (NMDAR) in the cerebrospinal fluid (CSF) from anti-NMDAR encephalitis patients have been suggested to be pathogenic since in previous studies using patient CSF, NMDAR-dependent processes such as long-term potentiation (LTP) were compromised. However, autoantibodies may represent a family of antibodies targeted against different epitopes, and CSF may contain further autoantibodies. Here, we tested the specificity of the autoantibody by comparing NMDAR-dependent and NMDAR-independent LTP within the same hippocampal subfield, CA3, using CSF samples from four anti-NMDAR encephalitis patients and three control patients.

Methods: We performed a stereotactic injection of patient-derived cell-free CSF with proven presence or absence of NMDAR-antibodies into the rat hippocampus in vivo. Hippocampal brain slices were prepared 1–8 days after intrahippocampal injection, and NMDAR-dependent LTP at the associational-commissural (A/C) fiber-CA3 synapse was compared to NMDAR-independent LTP at the mossy fiber (MF)-CA3 synapse.

Results: The LTP magnitude at A/C fiber-CA3 synapses in slices from control-CSF-treated animals (168 ± 8% n = 54) was significantly higher than LTP in slices from NMDAR-CSF-treated animals (139 ± 9%, n = 40; P = 0.015), although there was some variation between the individual CSF samples. We found residual LTP in NMDAR-CSF-treated tissue which could be abolished by the NMDAR inhibitor D-AP5. Moreover, the CA3 field excitatory postsynaptic potential (fEPSP) was followed by epileptiform afterpotentials in 5% of slices (4/78) from control-CSF-treated animals, but in 26% of slices (12/46) from NMDAR-CSF-treated animals (P = 0.002). Application of the LTP-inducing paradigm increased the proportion of slices with epileptiform afterpotentials, but D-AP5 significantly reduced the occurrence of epileptiform afterpotentials only in NMDAR-CSF-treated, but not in control tissue. At the MF synapse, no significant difference in LTP values of control-CSF and in NMDAR-CSF-treated tissue was observed indicating that NMDAR-independent MF-LTP is intact in NMDAR-CSF-treated tissue.

Conclusion: These findings indicate that anti-NMDAR containing CSF impairs LTP at the A/C fiber-CA3 synapse, although there is substantial variation among CSF samples suggesting different epitopes among patient-derived antibodies. The differential inhibition of LTP at this synapse in contrast to the MF-CA3 synapse suggests the specificity and underlines the pathophysiological role of the NMDAR-antibody.

Predictors of neural-specific autoantibodies and immunotherapy response in patients with cognitive dysfunction

Recognition of autoimmunity as a cause of encephalopathy has increased. Recent studies have validated the use of Antibody-Prevalence-in-Epilepsy (APE) and Responsive-to-immunotherapy-in-Epilepsy (RITE) scores in the evaluation and management of autoimmune-epilepsy. We aim to assess the utility of these models for patients with cognitive dysfunction. Among the evaluated patients, 17% had antibodies universally associated with autoimmune-encephalopathy. NMDA-R-IgG and LGI1-IgG were the most common antibody specificities. Antibody-Prevalence-in-Epilepsy-and-Encephalopathy (APE²) score ≥ 4 was 99% sensitive and 93% specific for neural-specific-antibodies. Responsive-to-immunotherapy-in-Epilepsy-and-Encephalopathy (RITE²) score ≥ 7 had 96% sensitivity and 86% specificity for favorable initial immunotherapy response. Application of these models may optimize autoantibody evaluations and immunotherapeutic trials.

A Simple Cell-based Immunofluorescence Assay to Detect Autoantibody Against the N-Methyl-D-Aspartate (NMDA) Receptor in Blood

The presence of anti-NMDA receptor autoantibody can cause various neuropsychiatric symptoms in the affected patients, termed anti-NMDA receptor autoimmune encephalitis. Detection of the specific autoantibody against the NMDA receptor in the blood or cerebrospinal fluid (CSF) is essential for the accurate diagnosis of this condition. The NMDA receptor is an ion channel protein complex that contains four subunits, including two mandatory NMDA receptor subunit 1 (NR1) and one or two NMDA receptor subunit 2A (NR2A), NMDA receptor subunit 2B (NR2B), NMDA receptor subunit 2C (NR2C), or NMDA receptor subunit 2D (NR2D). The epitope of anti-NMDA receptor autoantibody was reported to be present at the extracellular N-terminal domain of the NR1 subunit of the NMDA receptor. The goal of this study is to develop a simple cell-based immunofluorescence assay that can be used as a screening test to detect the presence of autoantibodies against NR1 subunit of the NMDA receptor in the blood to facilitate the clinical and basic research of anti-NMDA receptor autoimmune encephalitis.

Differential diagnosis with other rapid progressive dementias in human prion diseases

Prion diseases are unique in medicine as in humans they occur in sporadic, genetic, and acquired forms. The most common human prion disease is sporadic Creutzfeldt-Jakob disease (CJD), which commonly presents as a rapidly progressive dementia (RPD) with behavioral, cerebellar, extrapyramidal, and some pyramidal features, with the median survival from symptom onset to death of just a few months. Because human prion diseases, as well as other RPDs, are relatively rare, they can be difficult to diagnose, as most clinicians have seen few, if any, cases. Not only can prion diseases mimic many other conditions that present as RPD, but some of those conditions can present similarly to prion disease. In this article, the authors discuss the different etiologic categories of conditions that often present as RPD and also present RPDs that had been misdiagnosed clinically as CJD. Etiologic categories of conditions are presented in order of the mnemonic used for remembering the various categories of RPDs: VITAMINS-D, for vascular, infectious, toxic-metabolic, autoimmune, mitochondrial/metastases, iatrogenic, neurodegenerative, system/seizures/sarcoid, and demyelinating. When relevant, clinical, imaging, or other features of an RPD that overlap with those of CJD are presented.

Seroprevalence survey of selective anti-neuronal autoantibodies in patients with first-episode schizophrenia and chronic schizophrenia

Autoimmune encephalopathy caused by autoantibodies against neuronal cell-surface proteins in the brain is a newly discovered disease category associated with psychiatric disorders. Correct diagnosis of this condition relies on the detection of specific autoantibodies in the blood or cerebral spinal fluid in addition to the clinical presentations. The study aimed to understand the seroprevalence of selective anti-neuronal autoantibodies in our patients with schizophrenia. First, we screened for six anti-neuronal autoantibodies in an archived blood sample collected from patients with the first-episode schizophrenia. The six autoantibodies including antibodies against N-methyl-d-aspartate (NMDA) receptor, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors 1 and 2, γ-butyric acid receptor type B1 (GABARB1), leucine-rich glioma inactivated-1 (LGI1) protein, and contactin-associated protein-like 2 (CASPR2) protein. A total of 78 plasma samples (46 males and 32 females) were investigated; however, no positive case was identified. In this second study, we screened anti-NMDA receptor autoantibodies in a blood sample of 234 patients with chronic schizophrenia (133 females and 101 males) including 48 patients defined as treatment resistance. None of this sample was detected as positive. The negative findings in this study suggest that the seroprevalence of autoantibodies against neuronal surface proteins might be low in patients diagnosed with schizophrenia.

Pathogenic potential of antibodies to the GABAB receptor

GABA_B receptor (GABA_BR) autoantibodies have been detected in the serum of immunotherapy-responsive patients with autoimmune encephalitis. This study aimed to investigate the effect of immunoglobulin G (IgG) from a patient with GABA_BR antibodies on primary neuronal cultures and acute slices of entorhinal cortex. Primary hippocampal neuronal cultures were incubated with serum immunoglobulin from patients with GABA_BR or AMPA receptor (AMPAR) antibodies for up to 72 h to investigate their effect on receptor surface expression. Whole-cell patch-clamp recordings from layer III pyramidal cells of the medial entorhinal cortex were used to examine the effect on neuronal activity. GABA_BR surface expression was unaltered by incubation with GABA_BR antibodies. By contrast, after 24 h application of AMPAR antibodies, AMPARs were undetectable. However, acute application of GABA_BR IgG decreased both the duration of network UP states and the spike rate of pyramidal cells in the entorhinal cortex. GABA_BR antibodies do not appear to affect GABA_BRs by internalization but rather reduce excitability on the medial temporal lobe networks. This unusual mechanism of action may be exploited in rational drug development strategies.

Advances in Autoimmune Epilepsy Associated with Antibodies, Their Potential Pathogenic Molecular Mechanisms, and Current Recommended Immunotherapies

In this comprehensive article, we present an overview of some most common autoimmune antibodies believed to be potentially pathogenic for autoimmune epilepsies and elaborate their pathogenic mode of action in molecular levels based on the existing knowledge. Findings of the studies of immunemodulatory treatments for epilepsy are also discussed, and guidelines for immunotherapy are sorted out. We aim to summarize the emerging understanding of different pathogenic mechanisms of autoantibodies and clinical immunotherapy regimens to open up therapeutic possibilities for future optimum therapy. We conclude that early diagnosis of autoimmune epilepsy is of great significance, as early immune treatments have useful disease-modifying effects on some epilepsies and can facilitate the recovery.

Diagnostic Value of 18F-FDG PET/CT Versus MRI in the Setting of Antibody-Specific Autoimmune Encephalitis

Diagnosis of autoimmune encephalitis presents some challenges in the clinical setting because of varied clinical presentations and delay in obtaining antibody panel results. We examined the role of neuroimaging in the setting of autoimmune encephalitides, comparing the utility of ¹⁸F-FDG PET/CT versus conventional brain imaging with MRI. Methods: A retrospective study was performed assessing the positivity rate of MRI versus ¹⁸F-FDG PET/CT during the initial workup of 23 patients proven to have antibody-positive autoimmune encephalitis. ¹⁸F-FDG PET/CT studies were analyzed both qualitatively and semiquantitatively. Areas of cortical lobar hypo (hyper)-metabolism in the cerebrum that were 2 SDx from the mean were recorded as abnormal. Results: On visual inspection, all patients were identified as having an abnormal pattern of ¹⁸F-FDG uptake. In semiquantitative analysis, at least 1 region of interest with metabolic change was identified in 22 of 23 (95.6%) patients using a discriminating z score of 2. Overall, ¹⁸F-FDG PET/CT was more often abnormal during the diagnostic period than MRI (10/23, 43% of patients). The predominant finding on brain ¹⁸F-FDG PET/CT imaging was lobar hypometabolism, being observed in 21 of 23 (91.3%) patients. Hypometabolism was most commonly observed in the parietal lobe followed by the occipital lobe. An entire subset of antibody-positive patients, anti-N-methyl-d-aspartate receptor (5 patients), had normal MRI results and abnormal ¹⁸F-FDG PET/CT findings whereas the other subsets demonstrated a greater heterogeneity. Conclusion: Brain ¹⁸F-FDG PET/CT may play a significant role in the initial evaluation of patients with clinically suspected antibody-mediated autoimmune encephalitis. Given that it is more often abnormal when compared with MRI in the acute setting, this molecular imaging technique may be better positioned as an early biomarker of disease so that treatment may be initiated earlier, resulting in improved patient outcomes.

Survey of the diagnostic and therapeutic approach to new-onset refractory status epilepticus

PURPOSE

We conducted a survey of providers to assess for practice patterns in diagnosing and treating new-onset refractory status epilepticus (NORSE). NORSE is the occurrence of prolonged seizures that are not responsive to initial therapies in otherwise healthy individuals without obvious cause on initial presentation. This entity is thought to have multiple etiologies, including autoimmune.

METHOD

A 29-question electronic survey was sent to providers included in the Neurocritical Care Society emailing list. Questions regarded responders' demographics, existing institutional practice protocols, diagnostic work-up, therapeutic management and expected outcomes in NORSE. Responses were collected from October 23, 2014, to November 25, 2014.

RESULTS

There were 107 respondents out of 1334 (8%). CT head, continuous EEG, lumbar puncture and microbe serologies were suggested within 24h of presentation as part of a diagnostic work-up. MRI brain, autoimmune work-up (systemic and anti-neuronal antibodies) and cytology/flow cytometry were favored later in the course. About 25% of providers would never perform an autoimmune work-up in this setting. Initial treatment included up to 3 anticonvulsants (including one anesthetic), followed by additional anticonvulsants/anesthetics along with antimicrobials, followed by steroids, plasma exchange, hypothermia and ketogenic diet. Many respondents would never use IV immunoglobulin or steroid-sparing immunosuppressants (29% and 42%, respectively) for NORSE.

CONCLUSIONS

This survey could serve as the foundation for development of a standardized approach for the diagnosis and treatment of NORSE.

EEG Findings May Serve as a Potential Biomarker for Anti-NMDA Receptor Encephalitis

Objective To determine if an electroencephalographic (EEG) characteristic, beta:delta power ratio (BDPR), is significantly higher for N-methyl-d-aspartate receptor encephalitis (NMDARE) patients than for non-NMDARE patients on presenting EEG. Identification of an additional EEG biomarker with significant specificity for NMDARE (in the absence of frank delta brush) could potentially allow for early identification of at-risk patients. Methods Single center retrospective comparison of NMDARE and non-NMDARE consecutive cases of encephalitis, collated over a 6-year period (from 2008 to 2014). Results None of the 10 NMDARE patients displayed the extreme delta brush pattern on EEG previously described, but the ratio of BDPR was significantly higher for NMDARE patients (P < .005). There was no significant relationship between BDPR and the time of recording from symptom onset. Additional analysis of clinical characteristics also indicated that the patients with NMDARE (median age 19.5 years) were younger than the 5 patients with non-NMDARE (median age 36 years). Encephalopathy, seizure, and psychiatric complaints were the most common diagnoses at time of first health care presentation and did not favor a single etiology, though the latter was present only in the NMDARE population (50% at T₀). Prodromal illness featuring headache was more common in the non-NMDARE population. Outcomes, as measured by the Modified Rankin Scale, were globally better in the NMDARE group. Conclusions Patients with NMDARE had a significantly higher BDPR on EEG when compared with non-NMDARE patients even in the absence of extreme delta brush. This suggests that early EEG characteristics may be helpful in distinguishing NMDARE from non-NMDARE.

Brain Correlates of Human Leukocyte Antigen (HLA) Protection in Gulf War Illness (GWI)

BACKGROUND

We recently reported that six alleles from class II genes of the Human Leukocyte Antigen (HLA) confer protection from Gulf War Illness (GWI) (Georgopoulos et al., 2015). The most significant effect is exerted on Neurological-Cognitive-Mood (NCM), Pain, and Fatigue symptoms, such that higher number of copies of the protective alleles are associated with lower symptom severity. Here we tested the hypothesis that this effect is exerted by modulating the strength of neural synchronicity.

METHODS

Eighty-one Gulf War veterans (65 with GWI and 16 healthy controls) underwent a magnetoencephalography (MEG) scan to assess the strength of brain synchronicity by computing zero-lag crosscorrelations (and their Fisher z transforms) between prewhitened MEG time series. A high-resolution HLA genotyping determined the number of copies, k, of the 6 protective alleles above in each participant. We tested the hypothesis above by regressing NCM, Pain and Fatigue symptom severity against the interaction term, k×z (HLA-related effect), while including z (non-HLA-related effect), gender and age as covariates. The k×z and z terms assessed HLA- and non-HLA-related effects, respectively, of neural synchronicity on symptom severity. The distributions of these effects in sensor space were visualized using statistical heatmaps.

FINDINGS

We found significant, graded HLA- and non-HLA-related effects: (a) NCM>Pain>Fatigue for HLA-related effects, (b) NCM>Fatigue>Pain for non-HLA-related effects, and (c) HLA-related>non-HLA-related effects for all symptoms. These effects had widespread but distinct distributions in sensor space that allowed the orderly separation of the 6 terms (3 symptom domains×2 HLA factors) in a multidimensional plot, where one dimension separated the symptoms and the other the HLA relation.

INTERPRETATION

These findings demonstrate the presence of substantial, widespread, distinct and orderly HLA- and non-HLA-related neural influences on NCM, Pain and Fatigue symptom severity in GWI.

FUNDING

U.S. Department of Veterans Affairs and University of Minnesota.

The Clinical Approach to Encephalitis

Encephalitis has various etiologies, but viral infections and autoimmune disorders are the most commonly identified. Clinical signs, geographical clues, and diagnostic testing-including cerebrospinal fluid abnormalities and magnetic resonance imaging abnormalities-can be helpful in identifying the cause. Certain forms of encephalitis have specific treatments; hence, establishing a diagnosis rapidly and accurately is crucial. Here, we describe the clinical approach to diagnosing several common etiologies of encephalitis as well as treatment strategies.

CSF herpes virus and autoantibody profiles in the evaluation of encephalitis

Objective:

To report the frequency of coexisting herpes viruses (herpes simplex virus 1 [HSV-1] or HSV-2, varicella zoster virus, Epstein-Barr virus [EBV], cytomegalovirus, or human herpes virus 6 [HHV-6]) and autoantibodies in patients with encephalitis (herpes or autoimmune) in clinical laboratory service.

Methods:

Three groups were evaluated for herpes viruses and antibodies: group 1—patients whose CSF was positive for a herpes virus by real-time PCR over a period of 6 months; group 2—patients whose CSF was positive for an autoimmune encephalitis–associated antibody over 5 years (e.g., NMDA receptor [NMDA-R] antibody), and the same number of controls without autoimmune/infectious disease; and group 3—incidental autoimmune parainfectious encephalitis cases encountered over 1 year.

Results:

In group 1, antibodies were detected in 27 of 100 herpes PCR-positive CSF specimens (CSFs), either unclassified neural or nonneural in all but one patient with NMDA-R antibody detected after EBV infection. Antibodies were also detected in 3 of 7 CSFs submitted for repeat PCR testing (unclassified, 2; AMPA receptor, 1). In group 2, herpes viruses were detected in 1 of 77 controls (HHV-6) and 4 of 77 patients with autoimmune encephalitis (EBV, 2; HHV-6, 2); autoantibodies targeted NMDA-R in 3/4 and GABA_B-R in 1/4. In group 3, NMDA-R antibody was detected in 7 patients post–HSV-1 encephalitis. Of the remaining 3 patients, 2 had unclassified neural antibodies detected, and one had GABA_B-R autoimmunity. Concomitant neoplasms were discovered in 2 patients each from groups 2 and 3.

Conclusions:

Autoantibodies and herpes virus DNA frequently coexist in encephalitic CSF. Some patients develop parainfectious autoimmunity following viral CNS infection (usually HSV-1 encephalitis). The significance of detecting herpes nucleic acids in others remains unclear.

Progress in autoimmune epileptic encephalitis

PURPOSE OF REVIEW

Autoimmune epileptic encephalopathy is a potentially treatable neurological syndrome characterized by the coexistence of a neuronal antibody in serum and, often, cerebrospinal fluid. Patients present with combinations of seizures, neuropsychiatric features, movement disorder, and cognitive decline, but some patients have isolated seizures either at first presentation or during their illness. This review summarizes our current understanding of the roles of specific neuronal antibodies in epilepsy-related syndromes and aims to aid the clinician in diagnosis and treatment.

RECENT FINDINGS

Antigen discovery methods in three neuroimmunology centres independently identified antibodies to different subunits of the γ amino butyric acid-A receptor; high levels of these antibodies were found mainly in patients with severe refractory seizures. These and other antibodies were also found in a proportion (<10%) of children and adults with epilepsy. A clinical study comparing immunotherapy in patients with autoantibodies or without an identified target antigen found neuroinflammatory features were predictive of a therapeutic response. New in-vitro and in-vivo studies, and spontaneous animal models, have confirmed the pathogenicity and epileptogenicity of neuronal antibodies and their relevance to other mammals.

SUMMARY

Neuronal antibodies are an important cause of autoimmune epileptic encephalopathy, early recognition is important as there may be an underlying tumour, and early treatment is associated with a better outcome. In the absence of an antibody, the clinician should adopt a pragmatic approach and consider a trial of immunotherapy when other causes have been excluded.

Motor cortex and hippocampus are the two main cortical targets in LGI1-antibody encephalitis

Encephalitis associated with antibodies against leucine-rich glioma-inactivated 1 (LGI1) protein is increasingly recognized as an auto-immune disorder associated with characteristic tonic-dystonic seizures. The cortical or subcortical origin of these motor events is not clear. Some patients also present with different epileptic seizures and with cognitive impairment. The frequency of these features and their timing during the natural history of this encephalitis have not been fully described. We therefore reviewed data from 34 patients harbouring antibodies against LGI1 protein (21-81 years, median age 64) referred to the French Reference Centre for Neurological Paraneoplastic Syndrome. Three types of evidence suggested tonic-dystonic seizures were of cortical origin: (i) a slow, unilateral, frontal electroencephalographic wave, of duration ∼580 ms and amplitude ∼71 µV, preceded the contralateral tonic-dystonic seizures in simultaneous electroencephalographic and myographic records from seven of seven patients tested; (ii) 18-Fluorodeoxyglucose imaging revealed a strong hypermetabolism in primary motor cortex, controlateral to the affected limb, during encephalitis for five patients tested, as compared with data from the same patients after remission or from 16 control subjects; and (iii) features of polymyographic records of tonic-dystonic seizure events pointed to a cortical origin. Myoclonic patterns with brief, rhythmic bursts were present in three of five patients tested and a premyoclonic potential was identified in the cortex of one patient. Initially during encephalitis, 11 of 34 patients exhibited tonic-dystonic seizures (32%). Distinct epileptic syndromes were evident in 13 patients (38%). They were typically simple, focal seizures from the temporal lobe, consisting of vegetative symptoms or fear. At later stages, 22 of 32 patients displayed tonic-dystonic seizures (68%) and 29 patients presented frequent seizures (91%) including status epilepticus. Cognitive impairment, either anterograde amnesia or confusion was evident in 30 of 34 patients (88%). Brain imaging was normal in patients with isolated tonic-dystonic seizures; in patients with limbic symptoms it revealed initially a hippocampal hyperintensity in 8 of 19 patients (42%) and 17 of 24 patients (70%) at later stages. Our data suggest that the major signs of LGI1-antibody encephalitis can be linked to involvement of motor cortex and hippocampus. They occur in parallel with striatum involvement. One of these cortical targets is involved, often unilaterally at disease onset. As the encephalitis progresses, in the absence of immunomodulatory treatment, the second cortical target is affected and effects become bilateral. Progression to the second cortical target occurs with a variable delay of days to several months.

Prevalence of antineuronal antibodies in patients with encephalopathy of unknown etiology: Data from a nationwide registry in Korea

We aimed to evaluate the prevalence of antineuronal antibodies in a nationwide cohort of patients with encephalopathy of unknown etiology. We screened 1699 patients with idiopathic encephalopathy who were referred from 70 hospitals across Korea for autoimmune synaptic and classic paraneoplastic antibodies. Those with cerebellar degeneration, sensory polyneuropathy or other paraneoplastic syndromes without encephalopathy were not included in this study. One-hundred and four patients (6.12%) had antibody-associated autoimmune encephalopathy. Autoimmune synaptic antibodies were identified in 89 patients (5.24%) and classic paraneoplastic antibodies were identified in 16 patients (0.94%). The patients with antibody-associated autoimmune encephalopathy comprised a small but significant portion of the total number of patients with encephalopathy of unknown cause.

Insufficient disease inhibition by intrathecal rituximab in progressive multiple sclerosis

Objective

Inaccessibility of the inflammation compartmentalized to the central nervous system (CNS) may underlie the lack of efficacy of immunomodulatory treatments in progressive multiple sclerosis (MS). The double blind combination of Rituximab by IntraVenous and IntraThecAl injection versus placebo in patients with Low‐Inflammatory SEcondary progressive MS (RIVITALISE; NCT01212094) trial was designed to answer: (1) Whether an induction dose of intravenous and intrathecal rituximab efficiently depletes CNS B cells? and (2) If so, whether this leads to global inhibition of CNS inflammation and slowing of CNS tissue destruction?

Methods

Patients aged 18–65 years were randomly assigned to rituximab or placebo. Protocol‐stipulated interim analysis quantified the efficacy of B‐cell depletion.

Results

The efficacy on cerebrospinal fluid (CSF) biomarkers failed to reach criteria for continuation of the trial. B‐cell‐related CSF biomarkers (sCD21 and B‐cell activating factor) changed only in the active‐treatment arm. While CSF B cells were killed robustly (median −79.71%, P = 0.0176), B cells in CNS tissue were depleted inadequately (~−10–20%, P < 0.0001). Consequently, the T‐cell‐specific CSF biomarker sCD27 decreased slightly (−10.97%, P = 0.0005), while axonal damage marker, neurofilament light chain did not change. Insufficient saturation of CD20, lack of lytic complement, and paucity of cytotoxic CD56^dimNK cells contribute to decreased efficacy of rituximab in the CNS.

Interpretation

Biomarker studies reliably quantified complementary pharmacodynamic effects of rituximab in the CNS, exposed causes for poor efficacy and determined that RIVITALISE trial would be underpowered to measure efficacy on clinical outcomes. Identified mechanisms for poor efficacy are applicable to all CNS‐inflammation targeting monoclonal antibodies.

Epidemiology and outcomes of acute encephalitis

PURPOSE OF REVIEW

This review seeks to describe recent advances in the epidemiology, outcomes, and prognostic factors in acute encephalitis.

RECENT FINDINGS

Infectious causes continue to account for the largest proportion of encephalitis cases in which a cause is identified, although autoimmune causes are increasingly recognized. Type-A gamma-aminobutyric acid (GABAa) receptor antibodies have been recently identified in encephalitis with refractory seizures, whereas the roles of antibodies to the glycine receptor and dipeptidyl peptidase-like protein 6 have been defined in progressive encephalomyelitis with rigidity and myoclonus. Recent findings in the US cases of encephalomyelitis presenting with acute flaccid paralysis raise the possibility that enterovirus D68, a common respiratory pathogen, may cause central nervous system disease. Mortality from acute encephalitis occurs in about 10% of cases, with a large proportion of survivors suffering from cognitive or physical disability. In addition to delay in institution of appropriate antiviral or immune therapy, several potentially reversible factors associated with poor prognosis have been identified, including cerebral edema, status epilepticus, and thrombocytopenia.

SUMMARY

Encephalitis imposes a significant worldwide health burden and is associated with poor outcomes. Supportive treatment and early institution of therapy may improve outcomes. Careful neurocognitive assessment of survivors of encephalitis is needed to better define long-term outcomes.

Pediatric Opsoclonus-Myoclonus-Ataxia Syndrome Associated With Anti-N-methyl-D-aspartate Receptor Encephalitis

BACKGROUND

The full clinical spectrum of anti-N-methyl-D-aspartate receptor encephalitis is unknown in the pediatric population.

PATIENT

We describe a previously healthy 4-year-old girl presenting with opsoclonus-myoclonus together with ataxia who had NR1-specific, anti-N-methyl-D-aspartate receptor antibodies in the cerebral spinal fluid.

CONCLUSION

The presence of NR1-specific, anti-N-methyl-D-aspartate receptor antibodies in the setting of opsoclonus-myoclonus and ataxia syndrome may represent an expansion of the clinical presentations of anti-N-methyl-D-aspartate receptor encephalitis.

Clinical manifestations of patients with CASPR2 antibodies

Contactin-associated protein-like 2 (CASPR2) is one of the target antigens of voltage-gated potassium channels (VGKC) complex antibodies. There has been relatively little information in the literature regarding CASPR2 autoimmunity, especially in Asian population. We investigated the presence of CASPR2 antibodies in patients with presumed autoimmune neurological disorders and described the clinical features, laboratory findings, and responses to immunotherapy. Five patients were identified to be positive for CASPR2 antibodies. The results obtained here suggested that CASPR2 antibodies might be the possible cause of epilepsy even in the absence of typical features of limbic encephalitis and that immunotherapy could provide a favorable outcome.