Encephalitis and AMPA receptor antibodies: Novel findings in a case series of 22 patients

MR Imaging Findings in Anti-Leucine-Rich Glioma Inactivated Protein 1 Encephalitis: A Systematic Review and Meta-analysis

BACKGROUND

Antibodies against leucine-rich glioma inactivated protein 1 (LGI1) constitute a common form of autoimmune encephalitis. On MR imaging, it may show T2 FLAIR hyperintensities of the medial temporal lobe (T2 FLAIR-MTL), involve the basal ganglia, or be unremarkable.

PURPOSE

We performed a systematic review and meta-analysis to obtain prevalence estimates of abnormal findings on MR imaging in anti-LGI1 encephalitis. A human brain map of the LGI1 microarray gene expression was derived from the Allen Human Brain Atlas.

DATA SOURCES

PubMed and Web of Science were searched with the terms "LGI1" and "encephalitis" from inception to April 7, 2022.

STUDY SELECTION

Thirty-one research publications, encompassing case series and retrospective cohort and case-control studies, with >10 patients with anti-LGI1 encephalitis and MR imaging data were included.

DATA ANALYSIS

Pooled prevalence estimates were calculated using Freeman-Tukey double-arcsine transformation. Meta-analysis used DerSimonian and Laird random effects models.

DATA SYNTHESIS

Of 1318 patients in 30 studies, T2 FLAIR-MTL hyperintensities were present in 54% (95% CI, 0.48-0.60; I2 = 76%). Of 394 patients in 13 studies, 27% showed bilateral (95% CI, 0.19-0.36; I2 = 71%) and 24% unilateral T2 FLAIR-MTL abnormalities (95% CI, 0.17-0.32; I2 = 61%). Of 612 patients in 15 studies, basal ganglia abnormalities were present in 10% (95% CI, 0.06-0.15; I2 = 67%). LGI1 expression was highest in the amygdala, hippocampus, and caudate nucleus.

LIMITATIONS

Only part of the spectrum of MR imaging abnormalities in anti-LGI1 encephalitis could be included in a meta-analysis. MR imaging findings were not the main outcomes in most studies, limiting available information. I2 values ranged from 62% to 76%, representing moderate-to-large heterogeneity.

CONCLUSIONS

T2 FLAIR-MTL hyperintensities were present in around one-half of patients with anti-LGI1. The prevalence of unilateral and bilateral presentations was similar, suggesting unilaterality should raise the suspicion of this disease in the appropriate clinical context. Around 10% of patients showed basal ganglia abnormalities, indicating that special attention should be given to this region. LGI1 regional expression coincided with the most frequently reported abnormal findings on MR imaging. Regional specificity might be partially determined by expression levels of the target protein.

Management of Autoimmune Encephalitis in a 7-Year-Old Child With CTLA-4 Haploinsufficiency and AMPA Receptor Antibodies: A Case Report

OBJECTIVES

We report on the therapeutic management of early-onset severe neurologic symptoms in cytotoxic T lymphocyte antigen-4 haploinsufficiency (CTLA-4h) and the presence of antibodies to the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) as an important finding.

METHODS

This is a case report from a Dutch academic hospital. Repeated clinical examinations, repeated brain MRI and extended diagnostics on serum and CSF were performed. We used the CARE checklist.

RESULTS

A 7-year-old boy was diagnosed with CTLA-4h based on family screening. On diagnosis, he had mild chronic diarrhea and autism spectrum disorder, but no abnormalities in extensive laboratory screening. Six months later, he presented with sudden-onset autoimmune encephalitis. Repeated brain MRI revealed no abnormalities, but immunohistochemistry analysis on serum and CSF showed the presence of AMPAR antibodies. Treatment was initially focused on immunomodulation and targeted CTLA-4 replacement therapy. Because of the persistent fluctuating cerebellar and neuropsychiatric symptoms and the potential clinical significance of the AMPAR antibodies, treatment was intensified with repetition of first-line immunomodulation and rituximab. This combined therapy resulted in sustained clinical improvement and served as a bridge to curative hematopoietic stem cell transplantation.

DISCUSSION

This case illustrates the rare early onset of autoimmune encephalitis and presence of AMPAR antibodies in CTLA-4h. Targeted CTLA-4 replacement therapy resulted in a partial response. However, awaiting its optimal therapeutic effect, refractory CNS symptoms required intensification of immunomodulation. The identification of AMPAR antibodies guided our treatment decisions.

CLASSIFICATION OF EVIDENCE

This provides Class IV evidence. It is a single observational study without controls.

Anti-α-Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic Acid (AMPA) Receptor Antibody Encephalitis in an Immunosuppressed Patient With Myasthenia Gravis Post-thymoma Treatment

Anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor encephalitis is a rare form of autoimmune encephalitis. We report a case of a patient with myasthenia gravis post-thymoma treatment who presented with deteriorating mental status. She was found to have positive AMPA receptor titers in her cerebrospinal fluid and subsequently attained full recovery. Of the limited number of cases that were documented, we report the only case of a patient who was previously immunocompromised to develop the condition. Even though autoimmune encephalitis is an emerging condition, its early differentiation from other causes of encephalitis is crucial in the prognosis of the patient.

Mechanisms of autoimmune encephalitis

PURPOSE OF REVIEW

To provide an overview of the pathogenic mechanisms involved in autoimmune encephalitides mediated by antibodies against neuronal surface antigens, with a focus on NMDAR and LGI1 encephalitis.

RECENT FINDINGS

In antibody-mediated encephalitides, binding of IgG antibodies to neuronal surface antigens results in different pathogenic effects depending on the type of antibody, IgG subclass and epitope specificity. NMDAR IgG1 antibodies cause crosslinking and internalization of the target, synaptic and brain circuitry alterations, as well as alterations of NMDAR expressing oligodendrocytes, suggesting a link with white matter lesions observed in MRI studies. LGI1 IgG4 antibodies, instead, induce neuronal dysfunction by disrupting the interaction with cognate proteins and altering AMPAR-mediated signaling. In-vitro findings have been corroborated by memory and behavioral changes in animal models obtained by passive transfer of patients' antibodies or active immunization. These models have been fundamental to identify targets for innovative therapeutic strategies, aimed at counteracting or preventing antibody effects, such as the use of soluble ephrin-B2, NMDAR modulators (e.g., pregnenolone, SGE-301) or chimeric autoantibody receptor T cells (CAART) in models of NMDAR encephalitis.

SUMMARY

A deep understanding of the pathogenic mechanisms underlying antibody-mediated encephalitides is crucial for the development of new therapeutic approaches targeting brain autoimmunity.

Autoimmune encephalitis: what the radiologist needs to know

Autoimmune encephalitis is a relatively novel nosological entity characterized by an immune-mediated damage of the central nervous system. While originally described as a paraneoplastic inflammatory phenomenon affecting limbic structures, numerous instances of non-paraneoplastic pathogenesis, as well as extra-limbic involvement, have been characterized. Given the wide spectrum of insidious clinical presentations ranging from cognitive impairment to psychiatric symptoms or seizures, it is crucial to raise awareness about this disease category. In fact, an early diagnosis can be dramatically beneficial for the prognosis both to achieve an early therapeutic intervention and to detect a potential underlying malignancy. In this scenario, the radiologist can be the first to pose the hypothesis of autoimmune encephalitis and refer the patient to a comprehensive diagnostic work-up - including clinical, serological, and neurophysiological assessments.In this article, we illustrate the main radiological characteristics of autoimmune encephalitis and its subtypes, including the typical limbic presentation, the features of extra-limbic involvement, and also peculiar imaging findings. In addition, we review the most relevant alternative diagnoses that should be considered, ranging from other encephalitides to neoplasms, vascular conditions, and post-seizure alterations. Finally, we discuss the most appropriate imaging diagnostic work-up, also proposing a suggested MRI protocol.

Paediatric antibody prevalence in seizure score to predict autoimmune aetiology in seizure disorders

AIM

To modify the antibody prevalence in epilepsy (APE) score of children with suspected autoimmune central nervous system disease with seizures.

METHODS

We retrospectively analysed the cerebrospinal fluid of 157 children (aged 0-18 years) with suspected autoimmune central nervous system disease for antineuronal antibodies in our laboratory from 2016 to 2023. Participants were randomly divided into the development cohort (n = 79, 35 females; median 7 years, SD 4 years 7 months, range 4-11 years) and validation cohort (n = 78, 28 females; median 7 years, SD 4 years 5 months, range 4-12 years). A paediatric antibody prevalence in seizure (PAPS) score was created for one cohort and evaluated in the other. Seven variables were selected through univariate and multivariate analysis to create a PAPS score.

RESULTS

One hundred and fifty-seven children who fulfilled the inclusion criteria were enrolled; 49 tested positive for antineuronal antibodies. The sensitivity and specificity of an APE score of 4 and greater were 92% and 22.2% respectively; the sensitivity and specificity of a PAPS score of 2.5 and greater were 83.3% and 77.8% respectively. The area under the curve was 0.832 (95% confidence interval = 0.743-0.921), which was significantly better than that for the APE score (p < 0.001).

INTERPRETATION

The APE score had high sensitivity but low specificity in children. The PAPS score may be useful for determining the need for antineuronal antibody testing.

Pediatric anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis: Exploring psychosis, related risk factors, and hospital outcomes in a nationwide inpatient sample: A cross-sectional study

OBJECTIVE

Our study aims to examine the risk factors for comorbid psychosis in pediatric patients hospitalized for anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis and its impact on hospital outcomes.

METHODS

We conducted a cross-sectional study using the nationwide inpatient sample (NIS 2018-2019). We included 3,405 pediatric inpatients (age 6-17 years) with a primary discharge diagnosis of anti-NMDAR encephalitis. We used binomial logistic regression model to evaluate the odds ratio (OR) of variables (demographic and comorbidities) associated with comorbid psychosis.

RESULTS

The prevalence of comorbid psychosis in anti-NMDAR encephalitis inpatients was 5.3%, and majorly constituted of adolescents (72.2%) and females (58.3%). In terms of race, Blacks (OR 2.41), and Hispanics (OR 1.80) had a higher risk of comorbid psychosis compared to Whites. Among comorbidities, encephalitis inpatients with depressive disorders (OR 4.60), sleep-wake disorders (OR 3.16), anxiety disorders (OR 2.11), neurodevelopmental disorders (OR 1.95), and disruptive behavior disorders (OR 2.15) had a higher risk of comorbid psychosis. Anti-NMDAR encephalitis inpatients with comorbid psychosis had a longer median length of stay at 24.6 days (vs. 9.8 days) and higher median charges at $262,796 (vs. $135,323) compared to those without psychotic presentation.

CONCLUSION

Adolescents, females, and Blacks with encephalitis have a higher risk of psychotic presentation leading to hospitalization for anti-NMDAR encephalitis. Identification of demographic predictors and comorbidities can aid in early recognition and intervention to optimize care and potentially reduce the healthcare burden.

Case report: Overlapping anti-AMPAR encephalitis with anti-IgLON5 disease post herpes simplex virus encephalitis

Autoimmune encephalitis (AE) is the result of an autoimmune process that occurs as a rapidly advancing encephalopathy. Autoimmune encephalitis was commonly linked to herpes simplex virus 1 (HSV-1) as the most frequently identified virus. The main areas affected by this invasion are the temporal lobe, frontal lobe, and limbic system. Limbic encephalitis is a highly uncommon occurrence involving anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis and anti-IgLON family member 5 (IgLON5) disease, both belonging to the rare category. As far as we know, this is the first report showing that a patient diagnosed with AMPAR encephalitis overlapped with anti-IgLON5 disease post herpes simplex virus encephalitis (HSE), which helps to broaden the range of this uncommon autoimmune disease. We recommend autoantibody testing in all patients with HSE, particularly those involving neurological relapses or progression.

The psychiatric symptoms in anti-IgLON5 disease: Case report and literature review

Immunotherapy may be ineffective in the advanced stages of anti-IgLON5 disease with psychiatric symptoms. The psychiatric symptoms in advanced stages of anti-IgLON5 disease may be associated with neurodegeneration.

Outcome and Sequelae of Autoimmune Encephalitis

Autoimmune etiologies are a common cause for encephalitis. The clinical syndromes consistent with autoimmune encephalitis are both distinct and increasingly recognized, but less is known about persisting sequelae or outcomes. We searched PubMed for reports on outcomes after autoimmune encephalitis. Studies assessing validated, quantitative outcomes were included. We performed a narrative review of the published literature of outcomes after autoimmune encephalitis. We found 146 studies that produced outcomes data. The mortality rates were 6%-19% and the relapse risks were 10%-62%. Most patients achieved a good outcome based on a score on the modified Rankin Scale (mRS) of ≤2. Forty-nine studies evaluated outcomes beyond mRS; these studies investigated cognitive outcome, psychiatric sequelae, neurological deficits, global function, and quality-of-life/patient-reported outcomes using various tools at varying time points after the index hospital discharge. These more-detailed assessments revealed that most patients had persistent impairments, with frequent deficits in cognitive function, especially memory and attention. Depression and anxiety were also common. Many of these sequelae continued to improve over months or even years after the acute illness. While we found that lasting impairments were common among survivors of autoimmune encephalitis, additional research is needed to better understand the nature and impact of these sequelae. Standardized evaluation protocols are needed to improve the ability to compare outcomes across studies, guide rehabilitation strategies, and inform outcomes of interest in treatment trials as the field advances.

Overview of Paraneoplastic Autoantibody-Mediated Cognitive Impairment and Behavioral Changes: A Narrative Review

Cognitive dysfunction and behavioral change can be some of the manifestations of cancer, occurring as a part of paraneoplastic neurological syndrome, most commonly in small cell lung cancer. Paraneoplastic limbic encephalitis is the leading cause of cognitive disturbance and abnormal behavior in paraneoplastic syndromes, which is usually autoantibody-mediated. Autoantibodies are the main contributors to the development of cognitive dysfunction and behavioral change in cancer patients, with studies suggesting a higher liability for antibody-positive cancer patients to be affected. Anti-NMDAR and anti-AMPAR are antibodies targeted against surface antigens, manifesting predominantly as memory disturbance, abnormal behavior, psychiatric symptoms, and seizures. Other surface antigen-targeted antibodies include anti-GABA, anti-CASPR2, and anti-LGI1, which were shown to have cognitive function impairment and abnormal behavior as some of the main presentations, predominantly affecting memory. Cognitive deterioration and changes in behavior were also relatively common with some of the intracellular antigen-targeted antibodies, including anti-Hu, anti-SOX1, anti-PCA2, and anti-Zic2. Affected behavior and cognition, however, were reported less commonly in other paraneoplastic antibodies against intracellular antigens (anti-Yo, anti-GAD, anti-Ma2, anti-Ri, anti-CV2, and anti-KLHL11). Our article will provide a comprehensive review of the clinical manifestations of cognitive impairment and behavioral changes among cancer patients who develop paraneoplastic syndrome. Additionally, this review will discuss the role of specific paraneoplastic autoantibodies and the clinical spectrum linked to each separately.

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.

Clinical approach to diagnosis of paraneoplastic neurologic syndromes

The correct diagnosis of a paraneoplastic neurologic syndrome (PNS) first requires the identification of the syndrome as one of those defined as high-risk (previously called classical) or intermediate-risk for cancer in the 2021 PNS diagnostic criteria. Testing for neuronal antibodies should be restricted to these syndromes as indiscriminate request decreases the diagnostic value of the antibodies. Identifying onconeural (high-risk for cancer) or intermediate-risk for cancer antibodies supports the paraneoplastic diagnosis and mandates the search for an underlying cancer. Tumor screening must follow the published guidelines. Repeated screening is indicated in neurologic syndromes with onconeural antibodies and patients with high-risk for cancer neurologic syndromes unless they present neuronal antibodies which are not associated with cancer. Neuronal antibodies should be screened by immunohistochemistry and confirmed by immunoblot (intracellular antigens) or cell-based assay (CBA) (surface antigens). Positive results only by immunoblot or CBA should be taken with caution. Although the 2021 diagnostic criteria for PNS do not capture all PNS, as they do not allow to diagnose definite PNS neurologic syndromes without neuronal antibodies, the updated criteria represent a step forward to differentiate true PNS from neurologic syndromes that coincide in time with cancer diagnosis without having a pathogenic link.

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.

Paraneoplastic autoimmune neurologic disorders associated with thymoma

Thymoma is often associated with paraneoplastic neurologic diseases. Neural autoantibody testing is an important tool aiding diagnosis of thymoma and its autoimmune neurologic complications. Autoantibodies specific for muscle striational antigens and ion channels of the ligand-gated nicotinic acetylcholine receptor superfamily are the most prevalent biomarkers. The autoimmune neurologic disorders associating most commonly with thymoma are myasthenia gravis (MG), peripheral nerve hyperexcitability (neuromyotonia and Morvan syndrome), dysautonomia, and encephalitis. Patients presenting with these neurologic disorders should be screened for thymoma at diagnosis. Although they can cause profound disability, they usually respond to immunotherapy and treatment of the thymoma. Worsening of the neurologic disorder following surgical removal of a thymoma may herald tumor recurrence. Prompt recognition of paraneoplastic neurologic disorders is critical for patient management. A multidisciplinary approach is required for optimal management of neurologic autoimmunity associated with thymoma.

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.

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.

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.

General features, pathogenesis, and laboratory diagnostics of autoimmune encephalitis

Autoimmune encephalitis (AE) is a group of inflammatory conditions that can associate with the presence of antibodies directed to neuronal intracellular, or cell surface antigens. These disorders are increasingly recognized as an important differential diagnosis of infectious encephalitis and of other common neuropsychiatric conditions. Autoantibody diagnostics plays a pivotal role for accurate diagnosis of AE, which is of utmost importance for the prompt recognition and early treatment. Several AE subgroups can be identified, either according to the prominent clinical phenotype, presence of a concomitant tumor, or type of neuronal autoantibody, and recent diagnostic criteria have provided important insights into AE classification. Antibodies to neuronal intracellular antigens typically associate with paraneoplastic neurological syndromes and poor prognosis, whereas antibodies to synaptic/neuronal cell surface antigens characterize many AE subtypes that associate with tumors less frequently, and that are often immunotherapy-responsive. In addition to the general features of AE, we review current knowledge on the pathogenic mechanisms underlying these disorders, focusing mainly on the potential role of neuronal antibodies in the most frequent conditions, and highlight current theories and controversies. Then, we dissect the crucial aspects of the laboratory diagnostics of neuronal antibodies, which represents an actual challenge for both pathologists and neurologists. Indeed, this diagnostics entails technical difficulties, along with particularly interesting novel features and pitfalls. The novelties especially apply to the wide range of assays used, including specific tissue-based and cell-based assays. These assays can be developed in-house, usually in specialized laboratories, or are commercially available. They are widely used in clinical immunology and in clinical chemistry laboratories, with relevant differences in analytic performance. Indeed, several data indicate that in-house assays could perform better than commercial kits, notwithstanding that the former are based on non-standardized protocols. Moreover, they need expertise and laboratory facilities usually unavailable in clinical chemistry laboratories. Together with the data of the literature, we critically evaluate the analytical performance of the in-house vs commercial kit-based approach. Finally, we propose an algorithm aimed at integrating the present strategies of the laboratory diagnostics in AE for the best clinical management of patients with these disorders.

Overview of treatment strategies in paraneoplastic neurological syndromes

Treatment strategies in paraneoplastic neurological syndromes rely on the three pillars of tumor treatment, immunotherapy, and symptomatic treatment, the first one being by far the most important in the majority of patients and syndromes. Classically, antibodies against extracellular antigens are directly pathogenic, and patients with these syndromes are more responsive to immunomodulatory or immunosuppressive treatments than the ones with antibodies against intracellular targets. This chapter first discusses some general principles of tumor treatment and immunotherapy, followed by a closer look at specific treatment options for different clinical syndromes, focusing on symptomatic treatments.

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.

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.

Clinical presentations and treatment outcomes of Hashimoto encephalopathy at Siriraj Hospital - Thailand's largest national tertiary referral center

BACKGROUND

Hashimoto encephalopathy has multiple clinical presentations, and other than the presence of thyroid antibody, laboratory and imaging investigations are all non-specific. Data specific to the clinical presentations and treatment outcomes of patients with Hashimoto encephalopathy in Thailand remain scarce.

OBJECTIVES

To retrospectively investigate the clinical presentations and treatment outcomes of patients with Hashimoto encephalopathy at Siriraj Hospital.

METHODS

Patients who presented with acute encephalopathy at our center during July 2012-March 2017 were evaluated for eligibility. The inclusion criteria were positive anti-thyroperoxidase (anti-TPO) or anti-thyroglobulin (anti-Tg) in serum with negative neuronal antibody in serum or cerebral spinal fluid (CSF). Clinical presentations, symptom duration, laboratory results of thyroid status and thyroid autoantibody, CSF study, and clinical outcomes were collected.

RESULTS

Of the 204 patients who presented with encephalopathy, 31 (15.2%) were positive for the anti-TPO or anti-Tg antibody. Of those, 13 patients met the diagnostic criteria for Hashimoto encephalopathy. Clinical presentations included cognitive impairment (76.9%), clouding of consciousness (46.2%), and behavior change (30.8%). The neuropsychiatric presentations were visual hallucination (30.8%), auditory hallucination (15.4%), delusion (7.7%), and mood disturbance (23.1%). Other clinical presentations included seizure (38.5%), abnormal movement (23.1%), sleep disturbance (38.5%), ataxia (46.2%), stroke-like episode (15.4%), and fever (15.4%). Most patients (76.9%) had onset within < 3 months. Regarding outcomes, 1 patient who did not receive corticosteroid died from status epilepticus and septic shock. Among the 12 patients who received corticosteroid, 9 (75%) had marked improvement, 1 (8.3%) had slight improvement, and 2 (16.6%) had no clinical improvement. Seven patients (53.9%) had normal thyroid function, 4 patients (30.8%) had subclinical hypothyroidism, and 2 patients (15.4%) had subclinical hyperthyroidism.

CONCLUSIONS

The results of this study revealed cognitive impairment, neuropsychiatric symptoms, seizure, ataxia, and sleep disturbance to be common manifestations of Hashimoto encephalopathy. This condition should always be considered in individuals with subacute onset of unexplained cognitive impairment or cerebellar ataxia. Laboratory and neuroimaging investigations were all found to be nonspecific in Hashimoto encephalopathy. Most patients responded well to treatment, so clinical suspicion and early diagnosis and treatment will lead to improved patient outcomes.

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.

A hospital-based retrospective study: early recognition of neuronal surface antibodies by clinical manifestations and CSF inflammation indicators in patients with unexplained epilepsy

BACKGROUND

There is a lack of actual and comprehensive data on the detection rate of neuronal surface antibodies in patients with unexplained epilepsy in China. Thus, we attempted to analyze the differences in clinical manifestations, cerebrospinal fluid (CSF) characteristics, seizure types and other aspects of antibody-positive and negative patients, to identify suspected antibody-positive epilepsy patients.

METHODS

In total, 137 inpatients with unexplained epilepsy were consecutively included, and neuronal surface antibodies (NSAbs) were detected by serological and/or CSF evaluations. The clinical features and seizure characteristics were analyzed between the NSAb-positive and negative patients. In addition, patients were divided into four groups based on CSF and blood antibody titers. CSF cell count and protein content were analyzed in relation to antibody titers.

RESULTS

There were 45 (32.8%) patients tested positive for antibodies. Multivariate analyses revealed that age, mental status changes or memory deterioration, CSF protein, CSF cell count, treatment, days of hospitalization, outcome, duration of symptoms before hospitalization, status epilepticus, and number of antiepileptic drugs were significantly associated with the NSAb-positive group and changes in inflammatory indicators in routine CSF analysis were associated with antibody titers.

CONCLUSIONS

A relatively high proportion of patients with unexplained epilepsy have positive NSAbs. Patients with the above clinical characteristics need to be highly suspected of NSAbs positivity and should be tested for antibodies in time to assist treatment. The decrease of CSF cell count and protein content has suggestive value for the decrease of antibody titer, which should be evaluated in the follow-up.

What is autoimmune encephalitis-associated epilepsy? Proposal of a practical definition

Seizures resulting from cerebral autoimmunity are either acutely symptomatic in the context of autoimmune encephalitis (AIE) with neural surface antibodies, or they are indicative of an enduring predisposition to seizures, that is, epilepsy. Here, we propose a practical definition for autoimmune encephalitis-associated epilepsy (AEAE): Seizures associated with antibodies against glutamic acid decarboxylase, paraneoplastic syndromes, or Rasmussen encephalitis are classified as AEAE. AEAE secondary to AIE with antibodies against the N-methyl-D-aspartate receptor, leucine-rich glioma inactivated protein 1, contactin-associated protein-2, or γ-aminobutyric acid-B receptor can be diagnosed if the following criteria are met: seizures persist for at least 2 years after immunotherapy initiation; no signs of encephalitis on magnetic resonance imaging and no fluorodeoxyglucose positron emission tomography hypermetabolism; normal cerebrospinal fluid cell count; and a substantial decrease in antibody titers. This classification corresponds to different disease mechanisms. While AIE results from the pathogenic effects of neural antibodies, AEAE is probably the consequence of encephalitis-related tissue damage and thereby mainly structurally mediated. The distinction between AIE and AEAE also has practical consequences: In AIE, immunotherapy is usually highly beneficial, whereas anti-seizure medication has little effect. In AEAE, immunotherapy is less promising and the usual anti-seizure interventions are preferable. In addition, the diagnosis of AEAE has social consequences in terms of driving and professional limitations.

Patient characteristics and outcome in patients with anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis

OBJECTIVE

Anti-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) encephalitis is a rare subtype of autoimmune encephalitis. We report patients diagnosed with anti-AMPAR encephalitis in western China, focusing on their clinical presentations, imaging results, treatment strategies, and prognosis.

METHODS

Data from patients diagnosed with anti-AMPAR encephalitis in the neurology center of West China Hospital from August 2018 to July 2021 were retrospectively collected and analyzed. Based on the diagnostic criteria of autoimmune encephalitis, nine cases were included.

RESULTS

Four patients (44%) were males, and the median age at presentation was 54 years (range, 25-85). Short-term memory loss was the most common initial symptom. Additional types of autoantibodies were identified in three patients. After presentation, four patients were found to have tumors: two with small cell lung cancer, one with ovarian teratoma, and one with thymoma. All patients accepted first-line immune therapy, and follow-up was available from 8 patients (median 20 weeks, range 4-78). At the last follow-up, three patients showed good outcomes (modified Rankin scale [mRS] 0-2; 37.5%). Five patients showed poor outcomes (mRS 3-6; 62.5%): two had minimal changes and remained hospitalized, two had residual severe cognitive impairments, and one patient died during follow-up. Outcomes were worse among patients with tumors. Finally, only one patient experienced relapse during follow-up.

CONCLUSION

Anti-AMPAR encephalitis should be considered in the differential diagnosis for middle- and senior-aged patients who present with predominantly acute or subacute short-term memory impairment. The long-term prognosis is correlated with the presence of a tumor.

Diagnostic criteria for autoimmune encephalitis: utility and pitfalls for antibody-negative disease

Increased awareness of autoimmune encephalitis has led to two unintended consequences: a high frequency of misdiagnoses and the inappropriate use of diagnostic criteria for antibody-negative disease. Misdiagnoses typically occur for three reasons: first, non-adherence to reported clinical requirements for considering a disorder as possible autoimmune encephalitis; second, inadequate assessment of inflammatory changes in brain MRI and CSF; and third, absent or limited use of brain tissue assays along with use of cell-based assays that include only a narrow range of antigens. For diagnosis of possible autoimmune encephalitis and probable antibody-negative autoimmune encephalitis, clinicians should adhere to published criteria for adults and children, focusing particularly on exclusion of alternative disorders. Moreover, for diagnosis of probable antibody-negative autoimmune encephalitis, the absence of neural antibodies in CSF and serum should be well substantiated. Neural antibody testing should use tissue assays along with cell-based assays that include a broad range of antigens. Live neuronal studies in specialised centres can assist in resolving inconsistencies with respect to syndrome-antibody associations. Accurate diagnosis of probable antibody-negative autoimmune encephalitis will identify patients with similar syndromes and biomarkers, which will provide homogeneous populations for future assessments of treatment response and outcome.

Paraneoplastic Neurological Syndromes of the Central Nervous System: Pathophysiology, Diagnosis, and Treatment

Paraneoplastic neurological syndromes (PNS) include any symptomatic and non-metastatic neurological manifestations associated with a neoplasm. PNS associated with antibodies against intracellular antigens, known as "high-risk" antibodies, show frequent association with underlying cancer. PNS associated with antibodies against neural surface antigens, known as "intermediate- or low-risk" antibodies, are less frequently associated with cancer. In this narrative review, we will focus on PNS of the central nervous system (CNS). Clinicians should have a high index of suspicion with acute/subacute encephalopathies to achieve a prompt diagnosis and treatment. PNS of the CNS exhibit a range of overlapping "high-risk" clinical syndromes, including but not limited to latent and overt rapidly progressive cerebellar syndrome, opsoclonus-myoclonus-ataxia syndrome, paraneoplastic (and limbic) encephalitis/encephalomyelitis, and stiff-person spectrum disorders. Some of these phenotypes may also arise from recent anti-cancer treatments, namely immune-checkpoint inhibitors and CAR T-cell therapies, as a consequence of boosting of the immune system against cancer cells. Here, we highlight the clinical features of PNS of the CNS, their associated tumors and antibodies, and the diagnostic and therapeutic strategies. The potential and the advance of this review consists on a broad description on how the field of PNS of the CNS is constantly expanding with newly discovered antibodies and syndromes. Standardized diagnostic criteria and disease biomarkers are fundamental to quickly recognize PNS to allow prompt treatment initiation, thus improving the long-term outcome of these conditions.

How autoimmunity changed our diagnostic practice in epileptology?

Since few years, a new etiology of epilepsy emerges with the labelling of new autoantibodies against the central nervous system. In 2017, the International League Against Epilepsy (ILAE) concluded that autoimmunity is one of six etiologies contributing to epilepsy and that autoimmune epilepsy is directly caused by immune disorders in which seizures constitute a core symptom. Epileptic disorders of immune origin are now distinguished in two different entities: acute symptomatic seizures secondary to autoimmune (ASS) and autoimmune-associated epilepsy (AAE) with different expected clinical outcome under immunotherapy. If acute encephalitis is usually related to ASS with a classic good control of the disease under immunotherapy, clinical phenotype characterized by isolated seizures (new onset seizures and chronic focal epilepsy patients) may be due to either ASS or to AAE. Decision of Abs testing and early immunotherapy initiation needs the development of clinical scores able to select patients with high risk of positive Abs testings. If this selection is now included in the usual medical care of encephalitic patients, specifically with NORSE, the actual bigger challenge is in patients with non or only mild encephalitic symptoms followed for new onset seizures or chronic focal epilepsy patients of unknown origin. The emergence of this new entity provides new therapeutic strategies with specific etiologic and probably anti epileptogenic medication rather than the usual and nonspecific ASM. In the world of the epileptology, this new autoimmune entity appears as a big challenge with an exciting chance to improve or even definitely cure patients of their epilepsy. However, the detection of these patients has to be done in the early phase of the disease to offer the best outcome.

The importance of ligand gated ion channels in sleep and sleep disorders

On average, humans spend about 26 years of their life sleeping. Increased sleep duration and quality has been linked to reduced disease risk; however, the cellular and molecular underpinnings of sleep remain open questions. It has been known for some time that pharmacological modulation of neurotransmission in the brain can promote either sleep or wakefulness thereby providing some clues about the molecular mechanisms at play. However, the field of sleep research has developed an increasingly detailed understanding of the requisite neuronal circuitry and key neurotransmitter receptor subtypes, suggesting that it may be possible to identify next generation pharmacological interventions to treat sleep disorders within this same space. The aim of this work is to examine the latest physiological and pharmacological findings highlighting the contribution of ligand gated ion channels including the inhibitory GABA_A and glycine receptors and excitatory nicotinic acetylcholine receptors and glutamate receptors in the sleep-wake cycle regulation. Overall, a better understanding of ligand gated ion channels in sleep will help determine if these highly druggable targets could facilitate a better night's sleep.

Thymoma-associated autoimmune encephalitis: Analysis of factors determining prognosis

INTRODUCTION

Autoimmune encephalitis (AE) is a heterogeneous group of inflammatory central nervous system disorders caused by a misdirected immune response against self-antigens expressed in the central nervous system. The thymus is a central organ in the immune system and thymic tumors are thought to be possible initiators of many neurological disorders. Recently, there is growing evidence that thymomas are associated with autoimmune encephalitis.

AIMS

Our study initially explored the characteristics of patients with autoimmune encephalitis combined with thymoma.

METHODS

We used patient data from January 1, 2011 to October 1, 2021 from the PubMed, Web of Science, Ovid, and CNKI platforms to analyze overall demographics, frequency of symptoms and associations, and treatment prognosis outcomes.

RESULTS

A total of 68 patients were included. There were 39 female cases (57.4%). The mean age was 50 years (IQR 40-66 years). All had acute and subacute onset. The clinical manifestations were mostly cognitive changes (70.6%), mental disorders (57.4%), and epilepsy (50.0%). The most common neuronal antibody was alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). Magnetic resonance imaging (MRI) abnormalities were present in 81.0% of patients, mostly in the hippocampus, temporal lobe, and some in cortical and subcortical areas. Abnormalities in the electroencephalogram (EEG) in 69.8% of patients. Treatment involved immunotherapy and thymoma treatment, with 79.7% of patients improving after treatment. While 20.3% of patients had a poor prognosis. Further, 14.8% of patients relapsed. Mental disorders, autonomic dysfunction, sleep disturbances, anti-Ma2, and thymoma untreated were more frequent in patients with poor prognosis.

CONCLUSION

Thymoma-associated autoimmune encephalitis is a unique disease entity. Long-term follow-up of chest CT findings is recommended for patients with autoimmune encephalitis.

AMPA and NMDA receptor antibody autoimmune encephalitis preceded by ocular myasthenia gravis: a case report

BACKGROUND

α-Amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors mediate excitatory neurotransmission in the brain and may be targeted by autoantibodies, leading to autoimmune synaptic encephalitis (AE). AE can be associated with other autoimmune diseases. However, the cooccurrence of anti-AMPA and NMDA receptor AE together with myasthenia gravis (MG) is unusual.

CASE PRESENTATION

A 24-year-old previously healthy male presented with seronegative ocular MG, the diagnosis of which was supported by single-fiber electrophysiology findings. Three months later, he developed AE, initially being positive for AMPA receptor antibodies and subsequently for NMDA receptor antibodies. No underlying malignancy was found. In response to aggressive immunosuppressive treatment, he recovered (modified Rankin Scale (mRS) score change from 5 to 1). Despite some cognitive problems at the 1-year follow-up, which were not revealed using the mRS, he was able to return to his studies.

CONCLUSIONS

AE may coexist with other autoimmune disorders. Patients with seronegative MG, including ocular MG, may develop autoimmune encephalitis with more than one cell-surface antibody.

From parasomnia to agrypnia excitata - An illustrative case on diagnostic approach

The diagnostic approach to sleep-related movements disorders is seldom discussed. We report a case of fatal familial insomnia who initially presented with persistent limb movements in sleep, which later progressed to a state of agrypnia excitata. Here, the evaluation of abnormal movements in sleep is discussed using a step-by-step diagnostic approach. Although no cure is available for fatal familial insomnia, prompt recognition of this condition is important to facilitate proper management, including the involvement of interdisciplinary neuropalliative care.

COVID-19-associated AMPA-R and CRMP-5 autoimmune encephalitis in a patient with thymoma and myasthenia gravis

Thymomas are associated with autoimmune disease, most commonly myasthenia gravis, and rarely with autoimmune encephalitis. More recently, viral triggers including COVID-19 have also been implicated in autoimmunity. We present a case of antibody-positive autoimmune encephalitis that developed in the setting of COVID-19 in a patient with thymomatous myasthenia gravis.

AMPAR autoimmunity: Neurological and oncological accompaniments and co-existing neural autoantibodies

α -amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) encephalitis is rare but treatable. We reviewed the clinical and autoantibody profiles of 52 AMPAR-IgG-positive patients (median age 48 years [range 12-81]; 38 female) identified at the Mayo Clinic neuroimmunology laboratory. Main presentation was encephalitis; symptoms other than encephalitis associated with co-existing antibodies (p = 0.004). A tumor was found in 33/44; mostly thymoma. Most patients had partial (14/29) or complete (11/29) immunotherapy response. Thirty-one patients had at least one co-existing antibody that predicted thymoma in paraneoplastic patients (p = 0.008). In conclusion, in AMPAR encephalitis co-existing antibodies predict clinical presentation other than encephalitis and thymoma.

Autoimmune-mediated encephalitis and mimics: A neuroimaging review

Autoimmune encephalitis is a category of autoantibody-mediated neurological disorders that often presents a diagnostic challenge due to its variable clinical and imaging findings. The purpose of this image-based review is to provide an overview of the major subtypes of autoimmune encephalitis and their associated autoantibodies, discuss their characteristic clinical and imaging features, and highlight several disease processes that may mimic imaging findings of autoimmune encephalitis. A literature search on autoimmune encephalitis was performed and publications from neuroradiology, neurology, and nuclear medicine literature were included. Cases from our institutional database that best exemplify major imaging features were presented.

Epilepsy, Immunity and Neuropsychiatric Disorders

Several studies have focused on the emerging role of immunity and inflammation in a wide range of neurological disorders. Autoimmune diseases involving central nervous system share well defined clinical features including epileptic seizures and additional neuropsychiatric symptoms, like cognitive and psychiatric disturbances. The growing evidence about the role of immunity in the pathophysiologic mechanisms underlying these conditions lead to the concept of autoimmune epilepsy. This relatively-new term has been introduced to highlight the etiological and prognostic implications of immunity in epileptogenesis. In this review, we aim to discuss the role of autoimmunity in epileptogenesis and its clinical, neurophysiological, neuroimaging and therapeutic implications. Moreover, we wish to address the close relationship between immunity and additional symptoms, particularly cognitive and psychiatric features, which deeply impact clinical outcomes in these patients. To assess these aspects, we first analyzed Rasmussen's encephalitis. Subsequently, we have covered autoimmune encephalitis, particularly those associated with autoantibodies against surface neuronal antigens, as these autoantibodies express a direct immune-mediated mechanism, different from those against intracellular antigens. Then, we discussed the connection between systemic immune disorders and neurological manifestations. This review aims to highlight the need to expand knowledge about the role of inflammation and autoimmunity in the pathophysiology of neurological disorders and the importance to early recognize these clinical entities. Indeed, early identification may result in faster recovery and a better prognosis.

Autoimmune encephalitis with mGluR5 antibodies: A case series from China and review of the literature

Background

Only 15 patients of autoimmune encephalitis with metabotropic glutamate receptor 5 (mGluR5) antibodies have been reported worldwide since 2011, mostly from western countries. Patients with different genetic backgrounds are necessary to further clarify the clinical phenotype and prognosis of this rare disease.

Objective

We initially describe a case series from China to confirm the previous findings, expand the clinical phenotype, and identify the prognostic factors of autoimmune encephalitis with mGluR5 antibodies.

Methods

Observational data with follow-up were prospectively collected from autoimmune encephalitis patients with mGluR5 antibodies. Clinical information and outcomes on current and previously reported cases were combined and analyzed.

Results

We identified five patients (median age 35 years); two were female. The main clinical manifestations were behavioral/personality changes (five of five, 100%) and cognitive disorders (four of five, 80%), accompanied with other neurologic symptoms. Hypoventilation occurred in two (40%) patients, which was life-threatening. One patient had meningoencephalitis, suggesting a new phenotype in anti-mGluR5 encephalitis. All patients received immunotherapy. At the last follow-up (median 18 months), two (40%) patients showed complete recovery, two (40%) patients showed partial recovery, and one (20%) patient died. One (20%) patient had multiple relapses. Together with the 15 previously reported cases, associated tumors occurred in seven of 12 (58%) Western patients vs. one of eight (13%) Chinese patients. Modified Rankin Scale (mRS) scores at the last follow-up (median 31 months) were available in 16 patients. Patients with bad outcomes (mRS > 2, n = 4) were more likely to have hypoventilation at onset and higher mRS scores at peak of the disease.

Conclusions

In patients with different genetic background, as Chinese, the clinical phenotype of anti-mGluR5 encephalitis is similar. Fewer paraneoplastic cases were observed in Chinese patients. Most patients showed good responses to immunotherapy and cancer treatment. The clinical outcomes were favorable in most patients.

[Autoimmune encephalitis-An update]

Detection of autoantibodies against neurons and glia cells has brought about the early and specific diagnosis of autoimmune encephalitis in patients with variable neurological and psychiatric symptoms. Growing knowledge not only resulted in profound changes in treatment algorithms including immunotherapy but also in the understanding of disease mechanisms and etiological factors. The still increasing numbers of new autoantibodies calls for continuous updates on the state of the art in antibody diagnostics, frequencies of associated tumors and the clinical spectrum linked to each antibody, which can range from mood changes, cognitive impairment and epileptic seizures to abnormal movements, autonomic dysfunction and impaired levels of consciousness. This article summarizes the recent developments in the predominant clinical presentations of autoimmune encephalitis patients in imaging and cerebrospinal fluid diagnostics and also in prognostic markers, in the establishment of innovative immunotherapies, in the use of diagnostic pathways even before the results of the antibody tests are available and the understanding of the autoimmune etiology.

Early-Stage Contactin-Associated Protein-like 2 Limbic Encephalitis: Clues for Diagnosis

Background and Objectives

Previous studies suggested that autoimmune limbic encephalitis with antibodies against contactin-associated protein-like 2 (CASPR2-encephalitis) is clinically heterogeneous and progresses slowly, preventing its early recognition. We aimed to describe the onset and progression of CASPR2-encephalitis and to assess long-term outcomes.

Methods

We retrospectively analyzed the medical records of all patients whose CSF tested positive for anti-CASPR2 antibodies in our center between 2006 and 2020. Standardized telephone interviews of all available patients and relatives were conducted, assessing long-term functional independence using the Functional Activity Questionnaire (FAQ) and quality of life using the 36-Item Short-Form Survey (SF36).

Results

Forty-eight patients were included (98% males; median age 64 years), and 35 participated in telephone interviews (73%). At onset, 81% had at least 1 neurologic symptom among the following: limbic (54%), peripheral nerve hyperexcitability (PNH; 21%), and/or cerebellar symptoms (17%). Most of the patients (75%) had initially symptoms of only one of these categories. Limbic symptoms at onset included mostly seizures (33%), while memory disturbances were less frequent (10%). PNH signs were mostly neuropathic pain (9/10 patients). Other symptoms seen at onset included asthenia (33%), mood disorders (25%), and insomnia (21%); 19% of patients did not show any limbic, peripheral, or cerebellar symptom at onset but only asthenia (15%), mood disorders (6%), weight loss (8%), dysautonomia (4%), and/or insomnia (2%). The peak of the disease was attained in median 16.7 months after onset. Over the study period (median follow-up, 58.8 months, range 10.6–189.1), 77% of patients developed ≥3 core CASPR2 symptoms and 42% fulfilled the diagnostic criteria for autoimmune limbic encephalitis, although all patients ultimately developed limbic symptoms. At the last visit, most interviewed patients (28/35 patients, 80%; median, 5 years after onset) had recovered functional independence (FAQ <9) while only the vitality subscore of the SF36 was lower than normative data (mean 49.9 vs 58.0, p = 0.0369).

Discussion

CASPR2-encephalitis has a progressive course and is highly heterogeneous at the early stage. In men older than 50 years, otherwise unexplained seizures, cerebellar ataxia, and/or neuropathic pain are suggestive of early-stage CASPR2-encephalitis, especially if they coincide with recent asthenia, mood disorders, or insomnia.

Targeting NMDA Receptor Complex in Management of Epilepsy

N-methyl-D-aspartate receptors (NMDARs) are widely distributed in the central nervous system (CNS) and play critical roles in neuronal excitability in the CNS. Both clinical and preclinical studies have revealed that the abnormal expression or function of these receptors can underlie the pathophysiology of seizure disorders and epilepsy. Accordingly, NMDAR modulators have been shown to exert anticonvulsive effects in various preclinical models of seizures, as well as in patients with epilepsy. In this review, we provide an update on the pathologic role of NMDARs in epilepsy and an overview of the NMDAR antagonists that have been evaluated as anticonvulsive agents in clinical studies, as well as in preclinical seizure models.

The Role of Autoantibody Testing in Modern Personalized Medicine

Personalized medicine (PM) aims individualized approach to prevention, diagnosis, and treatment. Precision Medicine applies the paradigm of PM by defining groups of individuals with akin characteristics. Often the two terms have been used interchangeably. The quest for PM has been advancing for centuries as traditional nosology classification defines groups of clinical conditions with relatively similar prognoses and treatment options. However, any individual is characterized by a unique set of multiple characteristics and therefore the achievement of PM implies the determination of myriad demographic, epidemiological, clinical, laboratory, and imaging parameters. The accelerated identification of numerous biological variables associated with diverse health conditions contributes to the fulfillment of one of the pre-requisites for PM. The advent of multiplex analytical platforms contributes to the determination of thousands of biological parameters using minute amounts of serum or other biological matrixes. Finally, big data analysis and machine learning contribute to the processing and integration of the multiplexed data at the individual level, allowing for the personalized definition of susceptibility, diagnosis, prognosis, prevention, and treatment. Autoantibodies are traditional biomarkers for autoimmune diseases and can contribute to PM in many aspects, including identification of individuals at risk, early diagnosis, disease sub-phenotyping, definition of prognosis, and treatment, as well as monitoring disease activity. Herein we address how autoantibodies can promote PM in autoimmune diseases using the examples of systemic lupus erythematosus, antiphospholipid syndrome, rheumatoid arthritis, Sjögren syndrome, systemic sclerosis, idiopathic inflammatory myopathies, autoimmune hepatitis, primary biliary cholangitis, and autoimmune neurologic diseases.