Anti-NMDA-receptor encephalitis: case series and analysis of the effects of antibodies

Autoimmune encephalitis in a resource-limited public health setting: a case series analysis

BACKGROUND

 Autoimmune encephalitis (AE) consists of a group of acquired diseases that affect the central nervous system. A myriad of phenotypes may be present at the onset. Due to the heterogeneity of clinical presentations, it is difficult to achieve uniformity for the diagnostic and therapeutic processes and follow-up strategies.

OBJECTIVE

 To describe a series of patients diagnosed with AE in a resource-limited public hospital in southern Brazil and to analyze therapeutics and outcomes.

METHODS

 We retrospectively reviewed the electronic medical records of patients diagnosed with AE at the Hospital de Clínicas de Porto Alegre from 2014 to 2022. Data collected included clinical presentation, neuroimaging, cerebrospinal fluid testings, electroencephalogram, autoantibodies, treatments, outcomes, follow-up time, degree of neurological impairment, and mortality.

RESULTS

 Data from 17 patients were retrieved. Eleven cases were classified as definite AE and 6 as possible AE. Autoantibodies were identified in 9 patients. Timing for diagnosis was impacted by the high costs associated with autoantibody testing. Most patients became functionally dependent (82.4%) and most survivors remained with autoimmune-associated epilepsy (75%). Five patients died during hospitalization, and one after a 26-month of follow-up.

CONCLUSION

 In this resource-limited hospital, patients with AE had a worse clinical outcome than that previously described in the literature. Development of epilepsy during follow-up and mortality were greater, whilst functional outcome was inferior. Autoantibody testing was initially denied in most patients, which impacted the definitive diagnosis and the use of second-line therapies.

Brain magnetic resonance imaging as predictors in pediatric anti-N-methyl-D-aspartate receptor encephalitis

OBJECTIVE

To investigate the associations between brain magnetic resonance imaging (MRI) changes and clinical profiles in children with anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis.

METHODS

Clinical data and brain MRI results of children diagnosed with anti-NMDAR encephalitis in Guangzhou Women and Children's Medical Center from October 2014 to June 2022 were retrospectively studied.

RESULTS

A total of 143 children (Male: female 54:89) were enrolled, with a mean onset age of 6.8 years (6.8 ± 3.1). 40.6 % (58/143) of patients had abnormal initial brain MRI. Lesions in temporal lobe (34.5 %, 20/58) and frontal lobe (25.9 %, 15/58) were relatively common. Children with abnormal initial brain MRI were prone to have fever (P = 0.023), dystonia (P = 0.037), positive MOG antibodies (P = 0.015), higher cerebrospinal fluid (CSF) white blood cell count (WBC) (P = 0.019) and to receive rituximab treatment (P = 0.037). There were no significant differences in modified Rankin Scale (mRS) scores before immunotherapy, after immunotherapy and at last follow-up between the normal initial brain MRI group and abnormal group. No initial brain MRI changes were found to be associated with relapses. Brain MRI was reviewed in 72 patients at last follow-up with a median follow-up time of 25.5 months and 48.6 % (35/72) of patients had abnormal brain MRI. The mRS score of the group with normal brain MRI at last follow-up was significantly lower than that of the abnormal group.

CONCLUSIONS

About 40.0 % of children with anti-NMDAR encephalitis had abnormal initial brain MRI. Initial brain MRI was associated with certain clinical profiles, but not with relapse and prognosis. Around half of patients had abnormal brain MRI at last follow-up and were prone to have higher mRS score.

Cortical atrophy in early-stage patients with anti-NMDA receptor encephalitis: a machine-learning MRI study with various feature extraction

Conventional brain magnetic resonance imaging (MRI) of anti-N-methyl-D-aspartate-receptor encephalitis (NMDARE) is non-specific, thus showing little differential diagnostic value, especially for MRI-negative patients. To characterize patterns of structural alterations and facilitate the diagnosis of MRI-negative NMDARE patients, we build two support vector machine models (NMDARE versus healthy controls [HC] model and NMDARE versus viral encephalitis [VE] model) based on radiomics features extracted from brain MRI. A total of 109 MRI-negative NMDARE patients in the acute phase, 108 HCs and 84 acute MRI-negative VE cases were included for training. Another 29 NMDARE patients, 28 HCs and 26 VE cases were included for validation. Eighty features discriminated NMDARE patients from HCs, with area under the receiver operating characteristic curve (AUC) of 0.963 in validation set. NMDARE patients presented with significantly lower thickness, area, and volume and higher mean curvature than HCs. Potential atrophy predominately presented in the frontal lobe (cumulative weight = 4.3725, contribution rate of 29.86%), and temporal lobe (cumulative weight = 2.573, contribution rate of 17.57%). The NMDARE versus VE model achieved certain diagnostic power, with AUC of 0.879 in validation set. Our research shows potential atrophy across the entire cerebral cortex in acute NMDARE patients, and MRI machine learning model has a potential to facilitate the diagnosis MRI-negative NMDARE.

Anti-N-methyl-D-aspartate receptor-associated encephalitis: A review of clinicopathologic hallmarks and multimodal imaging manifestations

Anti-N-methyl-D-aspartate receptor-associated encephalitis (NMDARE) is a rare immune-mediated neuroinflammatory condition characterized by the rapid onset of neuropsychiatric symptoms and autonomic dysfunction. The mechanism of pathogenesis remains incompletely understood, but is thought to be related to antibodies targeting the GluN1 subunit of the NMDA receptor with resultant downstream dysregulation of dopaminergic pathways. Young adults are most frequently affected; the median age at diagnosis is 21 years. There is a strong female predilection with a female sex predominance of 4:1. NMDARE often develops as a paraneoplastic process and is most commonly associated with ovarian teratoma. However, NMDARE has also been described in patients with small cell lung cancer, clear cell renal carcinoma, and other benign and malignant neoplasms. Diagnosis is based on correlation of the clinical presentation, electroencephalography, laboratory studies, and imaging. Computed tomography, positron emission tomography, and magnetic resonance imaging are essential to identify an underlying tumor, exclude clinicopathologic mimics, and predict the likelihood of long-term functional impairment. Nuclear imaging may be of value for prognostication and to assess the response to therapy. Treatment may involve high-dose corticosteroids, intravenous immunoglobulin, and plasma exchange. Herein, we review the hallmark clinicopathologic features and imaging findings of this rare but potentially devastating condition and summarize diagnostic criteria, treatment regimens, and proposed pathogenetic mechanisms.

Clinical characteristics of Chinese pediatric patients positive for anti-NMDAR and MOG antibodies: a case series

Introduction

The cases of MOG-AD (MOG antibody-associated disorder) and anti-NMDAR encephalitis overlapping syndrome (MNOS) are rare, especially among pediatric patients, and their clinical understanding is limited. This study aimed to investigate the clinical manifestations, imaging findings, treatments, and prognosis of Chinese pediatric patients who tested positive for anti-NMDAR and MOG antibodies.

Methods

This retrospective study enrolled 10 MNOS pediatric patients, 50 MOG-AD (anti-NMDAR antibody-negative), and 81 anti-NMDAR encephalitis (MOG antibody-negative) pediatric patients who were admitted from July 2016 to June 2022 and used their clinical data for comparison.

Results

The MNOS patients had a significantly lower incidence of psycho-behavioral abnormalities and involuntary movements than anti-NMDAR antibody (+)/MOG antibody (-) patients and had a significantly higher incidence of sleep disorders, seizures, and psycho-behavioral abnormalities than MOG antibody (+)/anti-NMDAR antibody (-) patients. The MNOS patients had a significantly higher incidence of MRI abnormalities than the anti-NMDAR antibody (+)/MOG antibody (-) patients, while there was no significant difference in the incidence between the MNOS patients and the MOG antibody (+)/anti-NMDAR antibody (-) patients. No significant difference was seen in the initial mRS score between the three groups of patients. The anti-NMDAR antibody (+)/MOG antibody (-) patients had a higher rate of admission to the ICU, a longer length of in-hospital stay, and a higher rate of introduction to second-line treatment than the other two groups of patients. No significant difference was seen in the mRS score at the last follow-up and in the disease recurrence rate between the three groups. All these patients respond well to immunosuppressive therapy.

Discussion

In the presence of psycho-behavioral abnormalities, sleep disorders, and frequent seizures in MOG-AD patients or demyelinating symptoms of the central nervous system or demyelinating lesions on head MRI in anti-NMDAR encephalitis patients, the coexistence of MOG and anti-NMDAR antibodies should be considered and would suggest a diagnosis of MNOS for these patients. Immunotherapy is effective among these patients and should be given possibly earlier.

Comparing clinical features, severity and prognosis of autoimmune encephalitis and with and without oligoclonal bands

Objective

This study aimed to examine the clinical distinctions among patients diagnosed with autoimmune encephalitis (AE) based on the presence or absence of cerebrospinal fluid (CSF) oligoclonal bands (OCBs). Additionally, it sought to explore the relationship between OCBs and the severity and prognosis of autoimmune encephalitis.

Methods

A retrospective analysis was conducted on 94 patients diagnosed with AE at the People's Hospital of Zhengzhou University between October 2016 and June 2022. The patients were divided into OCB-positive and OCB-negative groups based on CSF-OCBs. Patient severity at admission was assessed utilizing the Clinical Assessment Scale for Autoimmune Encephalitis (CASE) and the modified Rankin scale (mRS). Additionally, some oligoclonal-positive patients underwent dynamic longitudinal analysis of cerebrospinal fluid test indices. The mRS score was ultimately employed to evaluate patients' short-term prognosis (6 months) and long-term prognosis (at least 12 months) following immunotherapy.

Results

Of the 94 patients, 34 (36.2%) belonged to the OCB-positive group, while 60 (63.8%) belonged to the OCB-negative group. The group with anti-n-methyl-d-aspartate receptor (anti-NMDAR) encephalitis exhibited the highest rate of oligoclonal positivity at 27 (49.1%), followed by anti-aminobutyric acid B receptor (GABABR) encephalitis with 4 cases (30.8%), anti-contactin-associated protein-like 2 (CASPR2) encephalitis with 2 cases (20%), and anti-leucine-rich glioma inactivating protein 1 (LGI1) encephalitis with 1 case (6.25%). No statistically significant differences were found between the two groups regarding gender, age, prodromal symptoms, psychiatric disorders, seizures, language disorders, motor dysfunction, cognitive dysfunction, tumor incidence, and magnetic resonance imaging (MRI) abnormalities (p > 0.05). The OCB-positive group exhibited higher rates of autonomic dysfunction, intensive care unit (ICU) admission, CSF leukocytes, and IgG index compared to the OCB-negative group (p < 0.05). Additionally, the OCB-positive group had significantly higher median CASE and mRS scores prior to immunotherapy than the OCB-negative group (p < 0.001 and p < 0.001). Furthermore, in both short-term follow-up and long-term follow-up, the OCB-positive group had a significantly lower proportion of patients with a favorable prognosis compared to the OCB-negative group (50% vs. 71.7, 61.8% vs. 83.3%; p = 0.036, p = 0.002).

Conclusion

Autonomic dysfunction, ICU admission, leukocytes in the cerebrospinal fluid, and elevated IgG index are more commonly observed in OCB-positive patients. OCB-positivity has also been linked to the severity and prognosis of AE, making it a potential biomarker. Initial OCB testing aids clinicians in identifying potentially critically ill patients early and monitoring disease progression, thereby optimizing clinical treatment decisions.

Mature cystic teratoma overlapping with giant serous cystadenoma of the ovary: A case report

Ovarian lesions represent a diagnostic challenge for the radiologist and should be approached according to the patient's age, menstrual cycle, and imaging characteristics. These lesions can be cystic, mixed, or solid-predominant structures. Generally, the occurrence of benign lesions surpasses that of malignant ones at a ratio of 3:1. However, within infantile and juvenile age groups, this becomes an infrequent occurrence, making up only about 5% of ovarian tumor cases. This case report sheds light on a unique scenario involving a pediatric patient who harbored 2 benign tumors simultaneously: a mature cystic teratoma and a serous cystadenoma.

Paraneoplastic movement disorders

Paraneoplastic movement disorders are diverse autoimmune neurological illnesses occurring in the context of systemic cancer, either in isolation or as part of a multifocal neurological disease. Movement phenomena may be ataxic, hypokinetic (parkinsonian), or hyperkinetic (myoclonus, chorea, or other dyskinetic disorders). Some disorders mimic neurodegenerative or hereditary illnesses. The subacute onset and coexisting nonclassic features of paraneoplastic disorders aid distinction. Paraneoplastic autoantibodies provide further information regarding differentiating cancer association, disease course, and treatment responses. A woman with cerebellar ataxia could have metabotropic glutamate receptor 1 autoimmunity, in the setting of Hodgkin lymphoma, a mild neurological phenotype and response to immunotherapy. A different woman, also with cerebellar ataxia, could have Purkinje cytoplasmic antibody type 1 (anti-Yo), accompanying ovarian adenocarcinoma, a rapidly progressive phenotype and persistent disabling deficits despite immune therapy. The list of antibody biomarkers is growing year-on-year, each with its own ideal specimen type for detection (serum or CSF), accompanying neurological manifestations, cancer association, treatment response, and prognosis. Therefore, a profile-based approach to screening both serum and CSF is recommended. Immune therapy trials are generally undertaken, and include one or more of corticosteroids, IVIg, plasma exchange, rituximab, or cyclophosphamide. Symptomatic therapies can also be employed for hyperkinetic disorders.

Autoimmune and paraneoplastic seizures

Seizures are a common feature of autoimmune encephalitis and are especially prevalent in patients with the commonest autoantibodies, against LGI1, CASPR2 and the NMDA, GABAB, and GABAA receptors. In this chapter, we discuss the classification, clinical, investigation, and treatment aspects of patients with these, and other autoantibody-mediated and -associated, illnesses. We highlight distinctive and common seizure semiologies which, often alongside other features we outline, can help the clinical diagnosis of an autoantibody-associated syndrome. Next, we classify these syndromes by either focusing on whether they represent underlying causative autoantibodies or T-cell-mediated syndromes and on the distinction between acute symptomatic seizures and a more enduring tendency to autoimmune-associated epilepsy, a practical and valuable distinction for both patients and clinicians which relates to the pathogenesis. We emphasize the more effective immunotherapy response in patients with causative autoantibodies, and discuss the emerging evidence for various first-, second-, and third-line immunotherapies. Finally, we highlight available clinical rating scales which can guide autoantibody testing and immunotherapy in patients with seizures of unknown etiology. Throughout, we relate the clinical and therapeutic observations to the immunobiology and neuroscience which drive these seizures.

The three pillars in treating antibody-mediated encephalitis

The rapid initiation of immunotherapy has a decisive impact on the course of the disease in patients with antibody-mediated encephalitis (AE). The importance of treating AE with antiseizure medication and antipsychotics is discussed controversially; however, standardized procedures should be ensured, especially for the initiation of treatment in severe disease. Recommendations and guidelines for further interventions in refractory courses are needed. In this review, we contrast the three mainstays of treatment options in patients with AE and attempt to highlight the importance of 1) antiseizure therapy, 2) antipsychotic therapy, and 3) immunotherapy/tumor resection from today's perspective.

Hematologic malignancies and hematopoietic stem cell transplantation

Paraneoplastic neurologic syndromes are rarely associated with hematologic malignancies. In their rarity, lymphomas are the diseases with more frequent paraneoplastic neurologic syndrome. High-risk antibodies are absent in most lymphoma-associated paraneoplastic neurologic syndromes, with the exception of antibodies to Tr/DNER in paraneoplastic cerebellar degeneration, mGluR5 in limbic encephalitis, and mGluR1 in some cerebellar ataxias. Peripheral nervous system paraneoplastic neurologic syndromes are rare and heterogeneous, with a prevalence of demyelinating polyradiculoneuropathy in non-Hodgkin lymphoma. Polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, skin changes (POEMS) is a rare, paraneoplastic syndrome due to an underlying plasma cell disorder. The diagnosis is based on defined criteria, and vascular endothelial growth factor (VEGF), not an antibody, is considered a reliable diagnostic marker that also mirrors therapy response. As with the paraneoplastic neurologic syndromes in solid tumors, therapies rely on cancer treatment associated with immunomodulatory treatment with better response in PNS with antibodies to surface antigens. The best outcome is generally present in Ophelia syndrome/limbic encephalitis with anti-mGluR5 antibodies, with frequent complete recovery. Besides patients with isolated osteosclerotic lesions (where radiotherapy is indicated), hematopoietic stem-cell transplantation is the therapy of choice in patients with POEMS syndrome. In the paraneoplastic neurologic syndromes secondary to immune checkpoint inhibitors, discontinuation of the drug together with immunomodulatory treatment is recommended.

Autonomic nervous system involvement in autoimmune encephalitis and paraneoplastic neurological syndromes

In autoimmune neurological diseases, the autonomic nervous system can be the primary target of autoimmunity (e.g. autoimmune autonomic ganglionopathy), or, more frequently, be damaged together with other areas of the nervous system (e.g. Guillain-Barré syndrome). Patients with autoimmune encephalitis and paraneoplastic neurological syndromes (PNS) often develop dysautonomia; however, the frequency and spectrum of autonomic signs and symptoms remain ill defined except for those scenarios in which dysautonomia is a core feature of the disease. Such is the case of Lambert-Eaton myasthenic syndrome, Morvan syndrome or anti-NMDAR encephalitis; in the latter, patients with dysautonomia have been reported to carry a more severe disease and to retain higher disability than those without autonomic dysfunction. Likewise, the presence of autonomic involvement indicates a higher risk of death due to neurological cause in patients with anti-Hu PNS. However, in anti-Hu and other PNS, as well as in the context of immune checkpoint inhibitors' toxicities, the characterization of autonomic involvement is frequently overshadowed by the severity of other neurological symptoms and signs. When evaluated with tests specific for autonomic function, patients with autoimmune encephalitis or PNS usually show a more widespread autonomic involvement than clinically suggested, which may reflect a potential gap of care when it comes to diagnosing dysautonomia. This review aims to revise the autonomic involvement in patients with autoimmune encephalitis and PNS, using for that purpose an antibody-based approach. We also discuss and provide general recommendations for the evaluation and management of dysautonomia in these patients.

Optimizing the diagnostic performance of neural antibody testing for paraneoplastic and autoimmune encephalitis in clinical practice

The detection of neural antibodies in patients with paraneoplastic and autoimmune encephalitis has majorly advanced the diagnosis and management of neural antibody-associated diseases. Although testing for these antibodies has historically been restricted to specialized centers, assay commercialization has made this testing available to clinical chemistry laboratories worldwide. This improved test accessibility has led to reduced turnaround time and expedited diagnosis, which are beneficial to patient care. However, as the utilization of these assays has increased, so too has the need to evaluate how they perform in the clinical setting. In this chapter, we discuss assays for neural antibody detection that are in routine use, draw attention to their limitations and provide strategies to help clinicians and laboratorians overcome them, all with the aim of optimizing neural antibody testing for paraneoplastic and autoimmune encephalitis in clinical practice.

Epidemiology of paraneoplastic neurologic syndromes

Paraneoplastic neurologic syndromes (PNS), initially depicted as seemingly cryptic remote manifestations of malignancy, were first described clinically in the early 20th century, with pathophysiologic correlates becoming better elucidated in the latter half of the century. There remain many questions not only about the pathophysiology but also regarding the epidemiology of these conditions. The continuous discovery of novel autoantigens and related neurologic disease has broadened the association in classical PNS to include conditions such as paraneoplastic cerebellar degeneration. It has also brought into focus several other neurologic syndromes with a putative neoplastic association. These conditions are overall rare, making it difficult to capture large numbers of patients to study, and raising the question of whether incidence is increasing over time or improved identification is driving the increased numbers of cases. With the rise and increasing use of immunotherapy for cancer treatment, the incidence of these conditions is additionally expected to rise and may present with various clinical symptoms. As we enter an era of clinical trial intervention in these conditions, much work is needed to capture more granular data on population groups defined by socioeconomic characteristics such as age, ethnicity, economic resources, and gender to optimize care and clinical trial planning.

Changing landscape in the field of paraneoplastic neurology: Personal perspectives over a 35-year career

Paraneoplastic neurologic syndromes are a group of rare disorders that have fascinated neurologists for more than a century. The discovery in the 1980s that many of these disorders occurred in association with antibodies against neuronal proteins revived the interest for these diseases. This chapter first traces the history of the paraneoplastic neurologic syndromes during the era that preceded the discovery of immune mechanisms and then reviews the immunologic period during which many of these syndromes were found to be associated with antibodies against intracellular onconeuronal proteins and pathogenic cytotoxic T-cell mechanisms. Alongside these developments, investigations on the antibody-mediated disorders of the peripheral nervous system, such as the myasthenic syndromes or neuromyotonia, provided suggestions for the study of the central nervous system (CNS) syndromes. These converging areas of research culminated with the groundbreaking discovery of a new category of CNS disorders mediated by antibodies against neuronal surface proteins or receptors. These disorders are not always paraneoplastic, and the understanding of these syndromes and mechanisms has changed the landscape of neurology and neurosciences.

Management of Paraneoplastic Syndromes in the Era of Immune Checkpoint Inhibitors

OPINION STATEMENT

Our understanding of paraneoplastic neurologic syndromes (PNS) has blossomed over the past few decades. Clinicians have access to more robust diagnostic criteria and have a heightened index of suspicion for these disorders. Nonetheless, treatment, which typically includes immunosuppression, and response to treatment, varies. Due to persistent difficulty in making a definitive diagnosis, we favor empiric treatment when a possible diagnosis of PNS is suspected, and other alternative causes have substantially been excluded (e.g., infections, toxic-metabolic derangements, metastasis, or leptomeningeal disease). Treatment of the underlying cancer, if identified, is the first therapeutic step and can prevent disease worsening and in rare cases, can reverse neurologic symptoms. In addition to anti-cancer treatment, first line immunotherapies, which include corticosteroids, intravenous immunoglobulins (IVIG), or plasma exchange (PLEX) are typically used. If partial or no benefit is seen, second line immunotherapeutic agents such as rituximab are considered. Additionally, the severity of the initial presentation and possible risk for relapse influences the use of the latter agents. Symptomatic management is also an important component in our practice and will depend on the syndrome being treated. One of the more novel entities we are facing currently is the management of immune checkpoint (ICI)-induced PNS. In those cases, current American Society of Clinical Oncology (ASCO) guidelines are followed.

[Autoimmune encephalitis: psychiatric aspects]

Autoimmune encephalitis is a group of diseases researched by both neurologists and psychiatrists. Despite a large number of studies and practical recommendations, the differential diagnosis and early diagnostics still remains an important issue. The most difficult to diagnose are cases that debut as mental disorders and/or occur without neurological symptoms. The literature review presents the current state of the problem with an emphasis on the practice of a psychiatrist.

Antibodies to neural cell surface and synaptic proteins in paraneoplastic neurologic syndromes

Among patients with paraneoplastic neurologic syndromes (PNS), emphasis has historically been placed on neural antibodies against intracellular proteins that have a strong association with malignancy. Because of the intracellular location of their antigenic targets, these antibodies are typically considered to be non-pathogenic surrogate markers of immune cell-mediated neural injury. Unfortunately, patients with these antibodies often have suboptimal response to immunotherapy and poor prognosis. Over the last two decades, however, dramatic advancements have been made in the discovery and clinical characterization of neural antibodies against extracellular targets. These antibodies are generally considered to be pathogenic, given their potential to directly alter antigen structure or function, and patients with these antibodies often respond favorably to prompt immunotherapy. These antibodies also associate with tumors and may thus occur as PNS, albeit more variably than neural antibodies against intracellular targets. The updated 2021 PNS diagnostic criteria, which classifies antibodies as high-risk, intermediate-risk, or lower-risk for an associated cancer, better clarifies how neural antibodies against extracellular targets relate to PNS. Using this recently created framework, the clinical presentations, ancillary test findings, oncologic associations, and treatment responses of syndromes associated with these antibodies are discussed.

Paraneoplastic encephalitis

The first reports of encephalitis associated with cancer date to the 1960s and were characterized by clinical and pathologic involvement of limbic areas. This specific association was called limbic encephalitis (LE). The subsequent discovery of several "onconeural" antibodies (Abs), i.e., Abs targeting an antigen shared by neurons and tumor cells, supported the hypothesis of an autoimmune paraneoplastic etiology of LE and other forms of rapidly progressive encephalopathy. Over the past 20 years, similar clinical pictures with different clinical courses have been described in association with novel Abs-binding neuronal membrane proteins and proved to be pathogenic. The most well-known encephalitis in this group was described in 2007 as an association of a complex neuro-psychiatric syndrome, N-methyl-d-aspartate (NMDA) receptor-Abs, and ovarian teratoma in young women. Later on, nonparaneoplastic cases of NMDA receptor encephalitis were also described. Since then, the historical concept of LE and Ab associated encephalitis has changed. Some of these occur in fact more commonly in the absence of a malignancy (e.g., anti-LG1 Abs). Lastly, seronegative cases were also described. The term paraneoplastic encephalitis nowadays encompasses different syndromes that may be triggered by occult tumors.

Paraneoplastic neurologic syndrome and autoantibody accompaniments of germ cell tumors

Paraneoplastic neurologic syndromes (PNSs) are a group of diseases affecting the central and/or peripheral nervous system caused by immune-mediated processes directed toward antigens with shared expression in tumor and neural tissue. Germ cell tumors (GCTs) are associated with PNSs with varied clinical phenotypes. Early diagnosis of PNS is vital to potentially uncover and treat underlying tumors, improving the chances of recovery, and preventing permanent neurologic complications. In this chapter, we outline the pathophysiology and epidemiology of PNS. We briefly provide a summary of GCTs in males and females. We review the neural-specific autoantibodies and PNSs associated with GCTs and their clinical and radiologic accompaniments. We also provide an overview of the treatment and prognosis of these disorders.

Pathogenesis and immunopathology of paraneoplastic disorders

Paraneoplastic neurologic syndromes (PNS) represent a rare group of immune-mediated complications associated with an underlying tumor. Ectopic protein expression in neoplastic cells or an aberrant immune regulation in the course of hematooncologic diseases or thymomas trigger an autoimmune response that may affect any part of the central and/or peripheral nervous system. Recent advances in drug therapies as well as novel animal models and neuropathologic studies have led to further insights on the immune pathomechanisms of PNS. Although the syndromes share common paths in pathogenesis, they may differ in the disease course, prognosis, and therapy targets, depending on the localization and type of antibody epitope. Neuropathologic hallmarks of PNS associated with antibodies directed against intracellular epitopes are characterized by T cell-dominated inflammation, reactive gliosis including microglial nodules, and neuronal degeneration. By contrast, the neuropathology of cell surface antibody-mediated PNS strongly depends on the targeted antigen and varies from B cell/plasma cell-dominated inflammation and well-preserved neurons together with a reduced expression of the target antigen in anti-NMDAR encephalitis to irreversible Purkinje cell loss in anti-P/Q-type VGCC antibody-associated paraneoplastic cerebellar degeneration. The understanding of different pathomechanisms in PNS is important because they strongly correspond with therapy response and prognosis, and should guide treatment decisions.

Evolution of methods to detect paraneoplastic antibodies

An adaptive immune response in less than 1% of people who develop cancer produces antibodies against neuronal proteins. These antibodies can be associated with paraneoplastic syndromes, and their accurate detection should instigate a search for a specific cancer. Over the years, multiple systems, from indirect immunofluorescence to live cell-based assays, have been developed to identify these antibodies. As the specific antigens were identified, high throughput, multi-antigen substrates such as line blots and ELISAs were developed for clinical laboratories. However, the evolution of assays required to identify antibodies to membrane targets has shone a light on the importance of antigen conformation for antibody detection. This chapter discusses the early antibody assays used to detect antibodies to nuclear and cytosolic targets and how new approaches are required to detect antibodies to membrane targets. The chapter presents recent data that support international recommendations against the sole use of line blots for antibody detection and highlights a new antigen-specific approach that appears promising for the detection of submembrane targets.

Movement disorders associated with pediatric encephalitis

New onset movement disorders are a common clinical problem in pediatric neurology and can be infectious, inflammatory, metabolic, or functional in origin. Encephalitis is one of the more important causes of new onset movement disorders, and movement disorders are a common feature (~25%) of all encephalitis. However, all encephalitides are not the same, and movement disorders are a key diagnostic feature that can help the clinician identify the etiology of the encephalitis, and therefore appropriate treatment is required. Movement disorders are a characteristic feature of autoimmune encephalitis such as anti-NMDAR encephalitis, herpes simplex virus encephalitis-induced autoimmune encephalitis, and basal ganglia encephalitis. Other rarer autoantibody-associated encephalitis syndromes with movement disorder associations include encephalitis associated with glycine receptor, DPPX, and neurexin-3 alpha autoantibodies. In addition, movement disorders can accompany acute disseminated encephalomyelitis with and without myelin oligodendrocyte glycoprotein antibodies. Extremely important infectious encephalitides that have characteristic movement disorder associations include Japanese encephalitis, dengue fever, West Nile virus, subacute sclerosing panencephalitis (SSPE), and SARS-CoV-2 (COVID-19). This chapter discusses how specific movement disorder phenomenology can aid clinician diagnostic suspicion, such as stereotypy, perseveration, and catatonia in anti-NMDAR encephalitis, dystonia-Parkinsonism in basal ganglia encephalitis, and myoclonus in SSPE. In addition, the chapter discusses how the age of the patients can influence the movement disorder phenomenology, such as in anti-NMDAR encephalitis where chorea is typical in young children, even though catatonia and akinesia is more common in adolescents and adults.

Pathophysiological Effects of Autoantibodies in Autoimmune Encephalitides

The heterogeneity of autoantibody targets in autoimmune encephalitides presents a challenge for understanding cellular and humoral pathophysiology, and the development of new treatment strategies. Thus, current treatment aims at autoantibody removal and immunosuppression, and is primarily based on data generated from other autoimmune neurological diseases and expert consensus. There are many subtypes of autoimmune encephalitides, which now entails both diseases with autoantibodies targeting extracellular antigens and classical paraneoplastic syndromes with autoantibodies targeting intracellular antigens. Here, we review the current knowledge of molecular and cellular effects of autoantibodies associated with autoimmune encephalitis, and evaluate the evidence behind the proposed pathophysiological mechanisms of autoantibodies in autoimmune encephalitis.

Surgical procedures and plasma exchange for ovarian teratoma-associated anti-N-methyl D-aspartate receptor encephalitis: a case report and review of literature

We reported a case of ovarian teratoma-associated Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis with recurrent epileptic seizures and disturbance of consciousness. Although surgical excision of the tumor remains the established standard of care, unlike other reported cases, the patient exhibited limited response to early oophorocystectomy, as well as IVIG and steroid therapy; however, a favorable response was observed with Plasma exchange (PE) initiated on postoperative day 12. Literature review revealed no definite recommended surgical extent for ovarian teratomas, and outstanding improvement in patients with anti-NMDAR encephalitis following PE. Our case raises the question regarding the optimal surgical extent for tumor resection, necessitating careful consideration when deciding between oophorectomy and adnexectomy as the preferred surgical procedure for anti-NMDAR encephalitis in female teens and adults. Furthermore, for refractory patients who fail to respond following tumor resection, PE can be performed early instead of immediately initiating second-line therapy.

Clinical characteristics and prognosis in patients with neuronal surface antibody-mediated autoimmune encephalitis: a single-center cohort study in China

Objective

This retrospective observational study primarily aimed to analyse the clinical characteristics of patients with neuronal surface antibody-mediated autoimmune encephalitis (AE) in China and report their prognosis after immunotherapy.

Methods

Clinical characteristics, laboratory or imaging examinations, and treatment outcomes of 103 patients diagnosed with AE between 1 September 2014 and 31 December 2020 were collected. Univariate and multivariate logistic regression analyses were performed to determine the predictors of poor prognosis.

Results

Overall, 103 patients were enrolled in the study. The main clinical symptoms included seizures (74.8%), psychiatric and behavior disorders (66.0%), cognitive deficits (51.5%), disturbances of consciousness (45.6%), and movement disorders/involuntary movements (26.2%). The distribution of clinical syndromes also differed for different AE subtypes. The efficacy rates of first-line immunotherapy for anti-NMDAR, anti-LGI1, anti-GABABR, and anti-CASPR2 encephalitis were 70.2%, 92.3%, 70%, and 83.3%, respectively, and rituximab was administered to 21 patients as second-line immunotherapy, including 14 patients with anti-NMDAR encephalitis, 4 with anti-LGI1 encephalitis, 2 with anti-GABABR encephalitis, and 1 with anti-CASPR2 encephalitis. Five patients with poor effect of the second-line treatment received bortezomib. According to the results of the last follow-up, 78 patients had a good prognosis (mRS 0-2), and 21 patients had a poor prognosis (mRS 3-6). The proportion of patients with a poor prognosis was significantly higher in anti-GABABR encephalitis compared to the other AE subtypes (p<0.001). Multivariate analysis indicated that elevated neutrophil-to-lymphocyte ratio (NLR) and tumour presence were independent risk factors for poor prognosis. The regression equation of the model was logit(P)=-3.480 + 0.318 NLR+2.434 with or without tumour (with assignment =1, without assignment =0). The prediction probability generated by the regression model equation was used as the independent variable for receiver operating curve (ROC) analysis. The results showed that the area under the curve (AUC) of the prediction probability was 0.847 (95% CI, 0.733-0.961; p < 0.001).

Conclusions

Different AE subtypes demonstrated different clinical symptom spectra throughout the disease stage. Anti-LGI1 encephalitis and anti-CASPR2 encephalitis were more sensitive to first-line and second-line treatments. Anti-GABABR encephalitis had the worst prognosis among the abovementioned subtypes. The regression equation constructed using NLR and tumour presence effectively predicted the poor prognosis.

Anti-NMDAR antibodies, the blood-brain barrier, and anti-NMDAR encephalitis

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an antibody-related autoimmune encephalitis. It is characterized by the existence of antibodies against NMDAR, mainly against the GluN1 subunit, in cerebrospinal fluid (CSF). Recent research suggests that anti-NMDAR antibodies may reduce NMDAR levels in this disorder, compromising synaptic activity in the hippocampus. Although anti-NMDAR antibodies are used as diagnostic indicators, the origin of antibodies in the central nervous system (CNS) is unclear. The blood-brain barrier (BBB), which separates the brain from the peripheral circulatory system, is crucial for antibodies and immune cells to enter or exit the CNS. The findings of cytokines in this disorder support the involvement of the BBB. Here, we aim to review the function of NMDARs and the relationship between anti-NMDAR antibodies and anti-NMDAR encephalitis. We summarize the present knowledge of the composition of the BBB, especially by emphasizing the role of BBB components. Finally, we further provide a discussion on the impact of BBB dysfunction in anti-NMDAR encephalitis.

Controversies in immunotherapy for anti-NMDA receptor encephalitis: a scoping review with a proposal of operational definitions

Anti-NMDA receptor encephalitis (NMDARE), an autoimmune encephalitis associated with autoantibodies against the N-methyl-D-aspartate (NMDA) receptor, affects predominantly young women and is associated with psychiatric symptoms, seizures, movement disorders, and autonomic instability. Traditional treatments of anti-NMDA receptor encephalitis involve corticosteroids, intravenous immunoglobulin, plasmapheresis, cyclophosphamide, and rituximab. However, many controversies remain in the treatment for NMDA receptor encephalitis, such as optimal timing and combination of different immunotherapies, the role of newer strategies (e.g., bortezomib or tocilizumab) for severe and refractory patients, and the need or not for long-term immunosuppression. Our goal was to perform a scoping review to discuss the controversial topics of immunotherapy for NMDA receptor encephalitis and propose operational definitions to guide clinical practice and future research in the field.

The Management and Diagnosis of Anti-NMDA Receptor Autoimmune Encephalitis in Pregnant Women: A Case Report and Literature Review

Rationale: Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is a form of autoimmune synaptic encephalitis, often mediated by neuronal surface antibodies. Clinically, it manifests through a diverse range of neurological and psychiatric symptoms, primarily affecting young women with ovarian teratoma, which is rare in pregnant women. Patient concerns: We report a case of a 35-year-old multiparous pregnant patient at 38 weeks of gestation presented to the emergency room with seizure, psychiatric symptoms like delirious speech with mystical visual and auditory hallucinations, bradylalia, and retrograde amnesia. Diagnosis: The diagnosis of autoimmune encephalitis with anti-NMDA antibodies was concluded by considering the lumbar puncture results, brain imaging, and the patient's persistent symptoms. Outcomes: This case is noteworthy for its rarity and the symptoms' breadth. At 38 weeks of gestation, the patient underwent a cesarean section, resulting in excellent maternal recovery observed during the 6-month follow-up and good neonatal adaptation. Lessons: Our goals include raising awareness about this condition and emphasizing the significance of early diagnosis. This encephalitis is treatable and potentially reversible, underscoring the importance of prompt identification.

Dynamic and static changes of amplitude of low-frequency fluctuations in anti‑N‑methyl‑D‑aspartate receptor encephalitis

BACKGROUND

Previous neuroimaging research has examined static local brain activity changes in patients with anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis. However, the dynamic properties of local brain activity in anti-NMDAR encephalitis remain unknown.

METHODS

This study used a combination of the amplitude of low-frequency fluctuation (ALFF) method and a sliding-window dynamic analysis approach to examine the time-varying local brain activity changes in anti-NMDAR encephalitis.

RESULTS

Results showed that patients with anti-NMDAR encephalitis exhibited increased dynamic ALFF (dALFF) variability in the left inferior occipital gyrus compared to healthy controls (HCs), while the patients exhibited decreased sALFF in widespread regions, including the left inferior frontal gyrus, left medial frontal gyrus, bilateral putamen, left medial superior frontal gyrus. dALFF had superior classification performance in distinguishing anti-NMDAR encephalitis patients from HCs over sALFF, but sALFF was correlated with multiple clinical and neuropsychological measures.

CONCLUSIONS

These findings may shed light on anti-NMDAR encephalitis brain dysfunction from the perspective of dynamic local brain activity. sALFF and dALFF analyses provide complementary information, emphasizing the potential usefulness of combining sALFF and dALFF in elucidating the neuropathological mechanisms of autoimmune encephalitis and may ultimately inform future disease diagnosis.

Autoimmune receptor encephalitis in ApoE‑/‑ mice induced by active immunization with NMDA1

Subacute progressive neuropsychiatric symptoms with cognitive and motor impairment and autoimmune seizures are some of the typical symptoms of anti‑N‑methyl‑D‑aspartate receptor (anti‑NMDAR) encephalitis. The mechanisms underlying this disease are yet to be elucidated, which could be partly attributed to the lack of appropriate animal models. The present study aimed to establish an active immune mouse model of anti‑NMDAR encephalitis. Mice were immunized with the extracellular segment of the NMDA1 protein, then subjected to open‑field and novel object recognition experiments. Plasma was collected after euthanasia on day 30 after immunization and anti‑NMDA1 antibodies were detected using ELISA. Furthermore, brain slices were analyzed to measure postsynaptic density protein 95 (PSD‑95) and NMDA1 expression. Western blot analysis of NMDA1 and PSD‑95 protein expression levels in the hippocampus was also performed. In addition, protein expression levels of PSD‑95 and NMDA1 in mouse neuronal HT‑22 cells were evaluated. Compared with controls, mice immunized with NMDA1 exhibited anxiety, depression and memory impairment. Moreover, high anti‑NMDA1 antibody titers were detected with ELISA and the levels of anti‑NMDA1 antibody reduced postsynaptic NMDA1 protein density in the mouse hippocampus. These findings demonstrated the successful construction of a novel mouse model of anti‑NMDAR encephalitis by actively immunizing the mice with the extracellular segment of the NMDA1 protein. This model may be useful for studying the pathogenesis and drug treatment of anti‑NMDAR encephalitis in the future.

Systematic review: clinical characteristics of anti-N-methyl-D-aspartate receptor encephalitis

Background

The number of reported cases of anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis has gradually increased since its discovery in 2007, while there are no uniform treatment guidelines.

Objective

To summarize the clinical characteristics of patients with anti-NMDAR encephalitis and to analyze the factors affecting the disease prognosis.

Methods

A systematic analysis of medical records was conducted, and PubMed, Embase, and Cochrane Library were searched from January 1, 2011, to December 31, 2021. Data were extracted, analyzed, and recorded in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines.

Results

This study included 472 case reports. Most patients had prodromal symptoms of about 2 weeks, including psychiatric symptoms (53.2%), flu-like symptoms (51.5%), and seizures (23.9%), among others. Poor prognoses were associated with patients who had autonomic instability (p = 0.010), central hypoventilation (p = 0.014), and ICU support (p = 0.002). Patients with a higher age of onset were more likely to develop central hypoventilation (OR 1.024, CI 1.006-1.042, p = 0.009), cognitive impairment (OR 1.023, CI 1.009-1.037, p = 0.001), and memory impairment (OR 1.034, CI 1.017-1.050, p < 0.001), whereas patients with a lower age were more likely to have seizures (OR 0.979, CI 0.965-0.993, p = 0.003). In this study, 97.0% of patients received immunotherapy, with the most commonly used treatment regimen being intravenous methylprednisolone (IVGC) and intravenous immunoglobulin (IVIG). When compared with other treatment regimens, the IVGC+IVIG regimen (p < 0.001) resulted in better prognoses.

Conclusion

When encountering patients with fever, headache, and initial psychiatric symptoms of unknown etiology, clinicians should test their CSF for antibodies to distinguish autoimmune encephalitis. Patients with autonomic instability, central hypoventilation, and ICU support had poorer prognoses. Clinicians should be aware that older patients are more likely to develop central hypoventilation, cognitive impairment, and memory impairment, while younger patients are more likely to develop seizures. The IVGC+IVIG treatment regimen has better prognoses than others. This study includes case reports, which have obvious selection bias, and there are no unified standards to measure the severity of the disease. Therefore, in the future, larger samples and randomized controlled trials are needed to evaluate the efficacy of different treatment regimens.

Autoimmune and paraneoplastic neurological disorders: A review of relevant neuroimaging findings

INTRODUCTION

Paraneoplastic neurologic syndromes (PNS) and autoimmune encephalitis (AIE) are immune-mediated disorders. PNS is linked to cancer, while AIE may not Their clinical manifestations and imaging patterns need further elucidation.

OBJECTIVE/AIMS

To investigate the clinical profiles, antibody associations, neuroimaging patterns, treatments, and outcomes of PNS and AIE.

METHODS

A systematic review of 379 articles published between 2014 and 2023 was conducted. Of the 55 studies screened, 333 patients were diagnosed with either PNS or AIE and tested positive for novel antibodies. Data on demographics, symptoms, imaging, antibodies, cancer associations, treatment, and outcomes were extracted.

RESULTS

The study included 333 patients (mean age 54 years, 67% males) with PNS and AIE positive for various novel antibodies. 84% had central nervous system issues like cognitive impairment (53%), rhombencephalitis (17%), and cerebellar disorders (24%). Neuroimaging revealed distinct patterns with high-risk antibodies associated with brainstem lesions in 98%, cerebellar in 91%, hippocampal in 98%, basal ganglia in 75%, and spinal cord in 91%, while low/intermediate-risk antibodies were associated with medial temporal lobe lesions in 71% and other cortical/subcortical lesions in 55%. High-risk antibodies were associated with younger males, deep brain lesions, and increased mortality of 61%, while low/intermediate-risk antibodies were associated with females, cortical/subcortical lesions, and better outcomes with 39% mortality. Associated cancers included seminomas (23%), lung (19%), ovarian (2%), and breast (2%). Treatments included IVIG, chemotherapy, and plasmapheresis. Overall mortality was 25% in this cohort.

CONCLUSION

PNS and AIE have distinct clinical and radiological patterns based on antibody profiles. High-risk antibodies are associated with increased mortality while low/intermediate-risk antibodies are associated with improved outcomes. Appropriate imaging and antibody testing are critical for accurate diagnosis.

Analysis of the relation between cerebrospinal fluid antibody titers and clinical characteristics in pediatric patients with anti-N-methyl-D-aspartate receptor encephalitis

OBJECTIVE

This retrospective study aimed to investigate the relationship between cerebrospinal fluid (CSF) antibody titers of N-methyl-d-aspartate receptor (NMDAR), and clinical characteristics in pediatric patients with anti-NMDAR encephalitis.

METHODS

The clinical and laboratory characteristics of hospitalized patients with anti-NMDAR encephalitis, stratified by antibody titers in CSF and disease severity, were retrospectively studied. The demographics, clinical characteristics, main accessory examinations, immunotherapy, and prognosis of patients were recorded, and each observed indicator was statistically analyzed.

RESULTS

A total of 103 pediatric anti-NMDAR encephalitis patients were enrolled in the study, including 41 males (39.8%) and 62 females (60.2%) with a mean age of 8.0 ± 4.0 years. The proportion of patients with cognitive dysfunction and the positive pathogen was higher in the high-titer group than in the low-titer group (p = 0.023, p = 0.042). Consciousness disturbance that occurred as an initial symptom or during the course in the severe group was higher than in the non-severe group (p = 0.002, p < 0.001). More patients in the high-titer group received plasma exchange (PE) than in the low-titer group (p = 0.022). The cure rate of patients was higher with PE (65.2%) than with Corticosteroids and (or) intravenous immunoglobulin (58.1%).

CONCLUSIONS

Patients with symptoms of disturbance of consciousness may be severer. The severity in pediatric anti-NMDAR encephalitis patients was not correlated with anti-NMDAR antibody titers. Patients with high CSF antibody titers had a better prognosis after early PE therapy.

Mimics of Autoimmune Encephalitis: Validation of the 2016 Clinical Autoimmune Encephalitis Criteria

BACKGROUND AND OBJECTIVES

The clinical criteria for autoimmune encephalitis (AE) were proposed by Graus et al. in 2016. In this study, the AE criteria were validated in the real world, and common AE mimics were described. In addition, criteria for probable anti-LGI1 encephalitis were proposed and validated.

METHODS

In this retrospective cohort study, patients referred to our national referral center with suspicion of AE and specific neuroinflammatory disorders with similar clinical presentations were included from July 2016 to December 2019. Exclusion criteria were pure cerebellar or peripheral nerve system disorders. All patients were evaluated according to the AE criteria.

RESULTS

In total, 239 patients were included (56% female; median age 42 years, range 1-85). AE was diagnosed in 104 patients (44%) and AE mimics in 109 patients (46%). The most common AE mimics and misdiagnoses were neuroinflammatory CNS disorders (26%), psychiatric disorders (19%), epilepsy with a noninflammatory cause (13%), CNS infections (7%), neurodegenerative diseases (7%), and CNS neoplasms (6%). Common confounding factors were mesiotemporal lesions on brain MRI (17%) and false-positive antibodies in serum (12%). Additional mesiotemporal features (involvement extralimbic structures, enhancement, diffusion restriction) were observed more frequently in AE mimics compared with AE (61% vs 24%; p = 0.005). AE criteria showed the following sensitivity and specificity: possible AE, 83% (95% CI 74-89) and 27% (95% CI 20-36); definite autoimmune limbic encephalitis (LE), 10% (95% CI 5-17) and 98% (95% CI 94-100); and probable anti-NMDAR encephalitis, 50% (95% CI 26-74) and 96% (95% CI 92-98), respectively. Specificity of the criteria for probable seronegative AE was 99% (95% CI 96-100). The newly proposed criteria for probable anti-LGI1 encephalitis showed a sensitivity of 66% (95% CI 47-81) and specificity of 96% (95% CI 93-98).

DISCUSSION

AE mimics occur frequently. Common pitfalls in AE misdiagnosis are mesiotemporal lesions (predominantly with atypical features) and false-positive serum antibodies. As expected, the specificity of the criteria for possible AE is low because these criteria represent the minimal requirements for entry in the diagnostic algorithm for AE. Criteria for probable AE (-LGI1, -NMDAR, seronegative) and definite autoimmune LE are applicable for decisions on immunotherapy in early disease stage, as specificity is high.

Movement disorders in autoimmune encephalitis: an update

Autoimmune encephalitis (AE) is a form of encephalitis resulting from an immune response targeting central nervous system antigens, which is characterized by cognitive impairment, neuropsychiatric symptoms, seizures, movement disorders (MDs), and other encephalopathy symptoms. MDs frequently manifest throughout the progression of the disease, with recurrent involuntary movements leading to discomfort and, in some cases, necessitating admission to the intensive care unit. Prompt identification and management of MDs can aid in the diagnosis and prognosis of AE. This review synthesizes current knowledge on the characteristics, underlying mechanisms, and treatment options for MDs in the context of AE.

Anti-NMDA and Anti-AMPA Receptor Antibodies in Central Disorders: Preclinical Approaches to Assess Their Pathological Role and Translatability to Clinic

Autoantibodies against NMDA and AMPA receptors have been identified in the central nervous system of patients suffering from brain disorders characterized by neurological and psychiatric symptoms. It has been demonstrated that these autoantibodies can affect the functions and/or the expression of the targeted receptors, altering synaptic communication. The importance to clarify, in preclinical models, the molecular mechanisms involved in the autoantibody-mediated effects has emerged in order to understand their pathogenic role in central disorders, but also to propose new therapeutic approaches for preventing the deleterious central consequences. In this review, we describe some of the available preclinical literature concerning the impact of antibodies recognizing NMDA and AMPA receptors in neurons. This review discusses the cellular events that would support the detrimental roles of the autoantibodies, also illustrating some contrasting findings that in our opinion deserve attention and further investigations before translating the preclinical observations to clinic.

Neurologic complications in herpes simplex encephalitis: clinical, immunological and genetic studies

Patients with herpes simplex virus (HSV) encephalitis (HSE) often develop neuronal autoantibody-associated encephalitis (AE) post-infection. Risk factors of AE are unknown. We tested the hypotheses that predisposition for AE post-HSE may be involved, including genetic variants at specific loci, human leucocyte (HLA) haplotypes, or the blood innate immune response against HSV, including type I interferon (IFN) immunity. Patients of all ages with HSE diagnosed between 1 January 2014 and 31 December 2021 were included in one of two cohorts depending on whether the recruitment was at HSE onset (Spanish Cohort A) or by the time of new neurological manifestations (international Cohort B). Patients were assessed for the type of neurological syndromes; HLA haplotypes; blood type I-IFN signature [RNA quantification of 6 or 28 IFN-response genes (IRG)] and toll-like receptor (TLR3)-type I IFN-related gene mutations. Overall, 190 patients (52% male) were recruited, 93 in Cohort A and 97 in Cohort B. Thirty-nine (42%) patients from Cohort A developed neuronal autoantibodies, and 21 (54%) of them developed AE. Three syndromes (choreoathetosis, anti-NMDAR-like encephalitis and behavioural-psychiatric) showed a high (≥95% cases) association with neuronal autoantibodies. Patients who developed AE post-HSE were less likely to carry the allele HLA-A*02 (4/21, 19%) than those who did not develop AE (42/65, 65%, P = 0.0003) or the Spanish general population (2005/4335, 46%, P = 0.0145). Blood IFN signatures using 6 or 28 IRG were positive in 19/21 (91%) and 18/21 (86%) patients at HSE onset, and rapidly decreased during follow-up. At Day 21 after HSE onset, patients who later developed AE had higher median IFN signature compared with those who did not develop AE [median Zs-6-IRG 1.4 (0.6; 2.0) versus 0.2 (-0.4; 0.8), P = 0.03]. However, a very high median Zs-6-IRG (>4) or persistently increased IFN signature associated with uncontrolled viral infection. Whole exome sequencing showed that the percentage of TLR3-IFN-related mutations in patients who developed AE was not different from those who did not develop AE [3/37 (8%) versus 2/57 (4%), P = 0.379]. Multivariate logistic regression showed that a moderate increase of the blood IFN signature at Day 21 (median Zs-6-IRG >1.5 but <4) was the most important predictor of AE post-HSE [odds ratio 34.8, interquartile ratio (1.7-691.9)]. Altogether, these findings show that most AE post-HSE manifest with three distinct syndromes, and HLA-A*02, but not TLR3-IFN-related mutations, confer protection from developing AE. In addition to neuronal autoantibodies, the blood IFN signature in the context of HSE may be potentially useful for the diagnosis and monitoring of HSE complications.

Neuroendocrine carcinoma of the small intestine diagnosed as a result of paraneoplastic neurological syndrome

Paraneoplastic neurological syndromes, a diverse group of neurological syndromes, are associated with small cell lung, testicular, ovarian, and breast cancers; however, their association with neuroendocrine carcinoma of the small intestine remains unreported. In this report, we present the case of a 78-year-old man diagnosed with neuroendocrine carcinoma of the small intestine and experienced symptoms such as subacute progressive numbness of the extremities and impaired gait. These symptoms were diagnosed as tumor-associated neurological syndrome. The patient had also undergone pyloric gastrectomy for early-stage gastric cancer several years prior to the appearance of the neurological symptoms. Therefore, we could not determine whether the tumor-related neurologic syndrome was owing to gastric cancer or neuroendocrine carcinoma of the small intestine; however, one of these conditions was the cause of the neuropathy. The gait disturbance and numbness relatively improved after surgery for the neuroendocrine carcinoma of the small intestine, suggesting that the neuroendocrine carcinoma of the small intestine likely caused the paraneoplastic neurological syndrome. Collectively, we present a unique report highlighting the putative relationship between small bowel neuroendocrine carcinoma and tumor-associated neurologic syndromes.

Inhibiting PI3K/Akt-Signaling Pathway Improves Neurobehavior Changes in Anti-NMDAR Encephalitis Mice by Ameliorating Blood-Brain Barrier Disruption and Neuronal Damage

The disruption of the blood-brain barrier (BBB) is hypothesized to be involved in the progression of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, but its mechanism is still unclear. Recently, the phosphatidylinositol 3-kinase (PI3K)/threonine kinase (Akt) pathway is involved in the regulation of the BBB in various diseases. This study is aimed to investigate the mechanism of BBB damage and neurobehavior changes in anti-NMDAR encephalitis mice. Female C57BL/6J mice were actively immunized to establish an anti-NMDAR encephalitis mouse model and evaluate the neurobehavior changes of mice. To study its potential mechanism, LY294002 (PI3K inhibitor, 8 mg/kg) and Recilisib (PI3K agonist, 10 mg/kg) were treated by intraperitoneal injection, respectively. Anti-NMDAR encephalitis mice showed neurological deficits, increased BBB permeability, open endothelial tight junctions (TJs), and decreased expression of TJ-related proteins zonula occludens (ZO)-1 and Claudin-5. However, administration of PI3K inhibitor significantly reduced the expression of p-PI3K and p-Akt, improved neurobehavior function, decreased BBB permeability, and upregulated the expressions of ZO-1 and Claudin-5. Furthermore, PI3K inhibition reversed the decline of NMDAR NR1 in the membranes of hippocampal neurons, which reduced the loss of neuron-specific nucleoprotein (NeuN) and microtubule-associated protein 2 (MAP2). In contrast, administration of the PI3K agonist Recilisib showed a tendency to exacerbate BBB breakdown and neurological deficits. Our results showed that the activation of PI3K/Akt, along with the changes in TJ-related proteins ZO-1 and Claudin-5, may be closely related to BBB damage and neurobehavior changes in anti-NMDAR encephalitis mice. PI3K inhibition attenuates BBB disruption and neuronal damage in mice, thereby improving neurobehavior.

Autoimmune encephalitis and paraneoplastic encephalitis: difficulties in diagnosis and management in the ICU

Autoimmune encephalitis (AIE) represents a category of relatively newly described neurological disorders associated with an increasing prevalence, a significant impact on the healthcare system, and a high rate of intensive care unit (ICU) admission. This category of diseases often requires prompt treatment, even before a definitive diagnosis is established. In the ICU, patients present with nonspecific signs and symptoms for AIE, which pose challenges in both management and diagnosis. Patients frequently exhibit dysautonomia, severe physical and psychic agitation, as well as tremors and dyskinesia, all of which complicate the diagnosis. They are prone to developing infections, including ventilator-associated pneumonia, and issues related to difficult venous access and pressure ulcers. Early initiation of immunosuppressive treatment is necessary to improve patients' outcome. Through this article, we aimed to summarize current knowledge in terms of the difficulties in diagnosing and management of this pathology in the ICU, as well as the implications for the healthcare system in terms of human and financial resources.

A juvenile mouse model of anti-N-methyl-D-aspartate receptor encephalitis by active immunization

Introduction

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a common autoimmune encephalitis, and it is associated with psychosis, dyskinesia, and seizures. Anti-NMDAR encephalitis (NMDARE) in juveniles and adults presents different clinical charactreistics. However, the pathogenesis of juvenile anti-NMDAR encephalitis remains unclear, partly because of a lack of suitable animal models.

Methods

We developed a model of juvenile anti-NMDAR encephalitis using active immunization with an amino terminal domain peptide from the GluN1 subunit (GluN1356 - 385) against NMDARs in 3-week-old female C57BL/6J mice.

Results

Immunofluorescence staining suggested that autoantibody levels in the hippocampus increased, and HEK-293T cells staining identified the target of the autoantibodies as GluN1, suggesting that GluN1-specific immunoglobulin G was successfully induced. Behavior assessment showed that the mice suffered significant cognition impairment and sociability reduction, which is similar to what is observed in patients affected by anti-NMDAR encephalitis. The mice also exhibited impaired long-term potentiation in hippocampal CA1. Pilocarpine-induced epilepsy was more severe and had a longer duration, while no spontaneous seizures were observed.

Conclusion

The juvenile mouse model for anti-NMDAR encephalitis is of great importance to investigate the pathological mechanism and therapeutic strategies for the disease, and could accelerate the study of autoimmune encephalitis.

Anti-N-methyl-d-aspartate receptor encephalitis preceded by meningitis lasting up to 60 days

Long-lasting meningitis complicated by N-methyl-d-aspartate receptor (NMDAR) encephalitis has not been discussed widely in the literature. Herein, we present two cases of anti-NMDAR encephalitis preceded by meningitis. The patients had 60- and 22-day periods of preceding meningitis, which improved with intravenous methylprednisolone and plasmapheresis. No tumors were detected in either of the patients. Although meningitis preceding anti-NMDAR encephalitis is not rare, our patients, especially those who had it for a duration of 60 days, had longer durations of meningitis. This manuscript foregrounds that anti-NMDAR encephalitis might be included in the differential diagnosis of long-lasting meningitis.

Effect and timing of operative treatment for teratoma associated N-Methyl-d-Aspartate receptor-antibody encephalitis: A systematic review with meta-analysis

Resection of an underlying ovarian teratoma in patients with N-Methyl-d-Aspartate receptor (NMDAR)-antibody encephalitis is supported by pathophysiological studies demonstrating the production of NMDAR antibodies within the teratoma. This systematic review assesses the clinical effect of teratoma resection and compares early versus late resection. Literature search was performed on the first of October 2022 (MEDLINE, Embase, CENTRAL, Web of Science). Original studies including more than three patients with NDMAR encephalitis and associated ovarian teratoma were included and evaluated with the Study Quality Assessment Tool for risk of bias. Fourteen studies referring to 1499 patients were included and analyzed in four syntheses using the fixed Mantel-Haenszel method. The rate of relapse in patients with ovarian teratoma resection was lower than in patients without resection (risk ratio for relapse 0.30, 95% CI 0.17-0.51), however the certainty level of evidence is very low. Despite some evidence pointing to a beneficial effect of early teratoma resection in patients with NMDAR-antibody encephalitis, systematically accessible data are insufficient to provide recommendations for or against resection, as well as for timing of surgery. The authors received no financial support for the research, authorship, or publication of this article. For the systematic review no clinical-trial database registration had been done.

Clinical study of autonomic dysfunction in patients with autoimmune encephalitis

BACKGROUND

Autoimmune encephalitis (AE) is a collective name, covering an emerging spectrum of autoimmune-mediated neurological diseases related to antibodies and synaptic or intracellular proteins. Anti-NMDAR, anti-LGI1, and anti-GABABR are three types of neuronal cell surface antibodies. Autonomic dysfunction represents a frequently occurring clinical manifestation. This observational study purposes to investigate comparisons between two groups with or without autonomic dysfunction and detect the autonomic dysfunction and other indexes in anti-NMDAR, anti-LGI1, and anti-GABABR cohorts.

METHODS

Patients with anti-NMDAR, anti-LGI1 and anti-GABABR encephalitis were recruited from the May 2017 to the April 2022. The following information was recorded: age, age at onset, tumor presence, gender, prodromal symptoms, clinical manifestations, cranial magnetic resonance imaging, cerebrospinal fluid and blood examinations, and immunotherapy.

RESULTS

There were totally 161 patients enrolled in this study. Among these participants, 104 individuals (64.6%) presented autonomic dysfunction and the remaining 57 (35.4%) were free of autonomic dysfunction. Sinus tachycardia was the most common autonomic dysfunction, followed by pollakiuria/uroclepsia, feverscence, central hypoventilation, sinus bradycardia, constipation, uroschesis, hyperhidrosis, hypersalivation, hypotension, and early satiety/emesis. Compared to patients without autonomic dysfunction, those with autonomic dysfunction had a higher incidence of central hypoventilation and ICU admissions. Meanwhile, in both groups with or without autonomic dysfunction, meatal behavior disorder, cognitive impairment, and epileptic seizure were three most common clinical manifestations. There were no significant differences in cranial magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) examination, antibody titers and number of immunotherapy types. Further analysis of AE mediated by distinct neuronal surface antibodies demonstrated that there were 85 anti-NMDAR, 56 anti-LGI1, and 20 anti-GABABR encephalitis patients. The significant differences between these three cohorts appeared in age, tumor presence, fervescence presence and antibody titers.

CONCLUSION

This study demonstrated the comparisons between autonomic dysfunction group and autonomic dysfunction-free group and provided insights into better diagnosis and treatment.

A small mature cystic ovarian teratoma associated with anti-NMDA receptor encephalitis and acute respiratory failure: A case report

OBJECTIVE

To report a rare case of anti-N-Methyl-d-aspartate receptor encephalitis (anti-NMDARE) presented by mental and behavioral changes and seizures accompanied with respiratory failure.

CASE REPORT

A 37-year-old multiparous woman was initially presented with abnormal mental behavior and the diagnosis of schizophrenia was made, but the disease progressed rapidly to general convulsion and acute respiratory failure. Although active treatment, including steroids, intravenous immunoglobulins (IVIGs) and plasma exchange was applied, no significant improvement was obtained. Transvaginal ultrasound and pelvic magnetic resonance image (MRI) were arranged and the results showed a suspicious cystic lesion (3 × 2.3 cm) at the right ovary. Laparoscopic unilateral salpingo-oophorectomy was performed and final pathology reported a matured cystic teratoma, suggesting that this patient had anti-NMDARE secondary to ovarian mature teratoma. After surgery, the clinical condition was dramatically improved and she recovered completely without sequelae.

CONCLUSION

Although it is well-known about the relation between anti-NMDARE and ovarian mature teratoma, this small tumor may result in the missing diagnosis. Remind us to consider the possibility of any small ovarian cystic lesion-related anti-NMDARE in women with autoimmune encephalitis.

Efficacy of immunotherapy and prognosis in anti-LGI1 encephalitis patients: A meta-analysis

OBJECTIVE

To assess the efficacy and safety of immunotherapy for LGI1 antibody encephalitis, and consider the predictors of poor outcomes following immunotherapy.

METHODS

We searched PubMed and Embase for articles reporting the immunotherapy data of anti-LGI1 encephalitis patients. The proportions of patients with poor outcomes (modified Rankin Scale [mRS] score > 2) at 3 months, 12 months, and the last follow-up, as well as the odds ratio [OR] of predictors were pooled.

RESULTS

The review included 162 articles with 1066 patients. The proportion of patients with poor functional outcomes was 21% at 3 months, 14% at 12 months, and 14% at the last follow-up after receiving immunotherapy. The proportion of patients with reported relapse was 16.6%. The mean duration from onset to the first relapse was 15.6 months. Predictors significantly associated with poor outcomes were age (increase of 1 year), the presence of cognitive impairment, and CSF LGI1 antibody positive. We did not find a statistically significant association between the worst mRS score in the acute phase, the presence of faciobrachial dystonic seizures (FBDS), days from symptom onset to immunotherapy, second-line treatment, maintenance immunotherapy, or follow-up time and outcomes.

INTERPRETATION

Although most patients respond to immunotherapy, a minority of patients still have poor outcomes. Advanced age, cognitive impairment, and CSF LGI1 antibody positive are associated with an increased risk of poor outcomes. However, due to the insufficiency of the data, these conclusions need to be interpreted with caution.

Olfactory dysfunction after autoimmune encephalitis depending on the antibody type and limbic MRI pathologies

Objective

Patients' olfactory function after autoimmune encephalitis (AE) involving limbic structures may be impaired. This study aimed to characterize olfactory function in patients after autoimmune encephalitides.

Methods

A case-control study was performed including 11 AE patients with antibodies against NMDAR (n = 4), GAD (n = 3), VGKC (n = 3) and antibody-negative AE (n = 1) and a control group of 12 patients with pneumococcal meningo-encephalitis (PC). In subgroup analyses, AE patients with and without NMDAR-antibodies were compared. Olfactory function was assessed using the Sniffin Sticks test and the resulting TDI-score (threshold, discrimination, identification). Involvement of limbic structures was evaluated on imaging data (MRI). Statistical analyses were performed to test for correlations of TDI-score and MRI results.

Results

The overall olfactory function of the AE-group and the PC-group was comparable (mean TDI 32.0 [CI 27.3-36.7], 32.3 [CI 28.5-36.0)]. The proportions of hyposmic patients were similar compared to the general population. However, AE patients of the non-NMDAR group had significantly lower TDI-scores (28.9 ± 6,8) than NMDAR patients (37.4 ± 3.5) (p = 0.046) and a significantly lower discrimination capability than the NMDAR patients (9.9 ± 2.0 vs. 14.5 ± 0.6) (p = 0.002). The non-NMDAR patients had significantly more limbic MRI pathologies (6/7) compared to the NMDAR patients (0/4) (p = 0.015). Furthermore, a correlation between limbic MRI pathologies and worse capability of smelling discrimination was found (p = 0.016, r = -0.704, n = 11).

Conclusion

Our results indicate that patients with NMDAR autoimmune encephalitis have normal long term olfactory function. However, patients with non-NMDAR autoimmune encephalitis appear to have a persistently impaired olfactory function, probably mediated by encephalitic damage to limbic structures.

The Dysfunctional Mechanisms Throwing Tics: Structural and Functional Changes in Tourette Syndrome

Tourette Syndrome (TS) is a high-incidence multifactorial neuropsychiatric disorder characterized by motor and vocal tics co-occurring with several diverse comorbidities, including obsessive-compulsive disorder and attention-deficit hyperactivity disorder. The origin of TS is multifactorial, with strong genetic, perinatal, and immunological influences. Although almost all neurotransmettitorial systems have been implicated in TS pathophysiology, a comprehensive neurophysiological model explaining the dynamics of expression and inhibition of tics is still lacking. The genesis and maintenance of motor and non-motor aspects of TS are thought to arise from functional and/or structural modifications of the basal ganglia and related circuitry. This complex wiring involves several cortical and subcortical structures whose concerted activity controls the selection of the most appropriate reflexive and habitual motor, cognitive and emotional actions. Importantly, striatal circuits exhibit bidirectional forms of synaptic plasticity that differ in many respects from hippocampal and neocortical plasticity, including sensitivity to metaplastic molecules such as dopamine. Here, we review the available evidence about structural and functional anomalies in neural circuits which have been found in TS patients. Finally, considering what is known in the field of striatal plasticity, we discuss the role of exuberant plasticity in TS, including the prospect of future pharmacological and neuromodulation avenues.

Autoimmune Encephalitis with Antibodies: Anti-NMDAR, Anti-AMPAR, Anti-GQ1b, Anti-DPPX, Anti-CASPR2, Anti-LGI1, Anti-RI, Anti-Yo, Anti-Hu, Anti-CV2 and Anti-GABAAR, in the Course of Psychoses, Neoplastic Diseases, and Paraneoplastic Syndromes

Encephalitis is a condition with a variety of etiologies, clinical presentations, and degrees of severity. The causes of these disorders include both neuroinfections and autoimmune diseases in which host antibodies are pathologically directed against self-antigens. In autoimmune encephalitis, autoantibodies are expressed in the central nervous system. The incidence of this disease is approximately 4% of all reported cases of encephalitis. Autoimmune encephalitis can be induced by antibodies against neuronal surface antigens such as N-methyl-D-aspartate-activated glutamate receptors (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors (AMPAR) or gangliosides GQ1b, DPPX, CASPR2, LGI1, as well as by antibodies against neuronal intracellular antigens. The paper presents a number of both mental and neurological symptoms of autoimmune encephalitis. Moreover, the coexistence of psychoses, neoplastic diseases, and the methods of diagnosing autoimmune encephalitis are discussed. Attention was also drawn to the fact that early diagnosis, as well as early initiation of targeted treatment, increases the chance of a successful course of the therapeutic process. Strategy and Methodology: The articles on which the following paper was based were searched using search engines such as PubMed and Medline. Considering that anti-NMDAR antibodies were first described in 2007, the articles were from 2007 to 2023. The selection of papers was made by entering the phrases "autoimmune encephalitis and psychosis/paraneplastic syndromes or cancer". The total number of articles that could be searched was 747, of which 100 items were selected, the most recent reports illustrating the presented topic. Thirty-four of them were rejected in connection with case reports or papers that could not be accessed.