Clinical manifestations and outcomes of the treatment of patients with GABAB encephalitis

Clinical characteristics of autoimmune encephalitis with co-existence of multiple anti-neuronal antibodies

BACKGROUND

An increasing number of cases of autoimmune encephalitis (AE) with co-existing multiple anti-neuronal antibodies have been reported in recent years. However, the clinical significance of the concurrent presence of multiple anti-neuronal antibodies in patients with AE remains unclear.

METHODS

We retrospectively enrolled AE patients with multiple anti-neuronal antibodies treated at our center between August 2019 and February 2022. We also reviewed cases reported in multiple literature databases. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline was followed on selection process. And then the clinical and laboratory data of these cases were collected for review and summary.

RESULTS

A total of 83 AE cases with multiple antibodies (9 cases from our center and 74 cases from the literatures reviewed) were identified. In our center, nine patients presented with encephalitis symptoms, clinically characterized as disturbed consciousness, seizures, cognitive impairment, and psychiatric disorders. Of the 83 cases, 73 cases had co-existence of 2 types of antibodies, 8 cases had 3 types, and 2 cases had 4 types. Thirty-nine cases (39/83, 46.9%) were confirmed or suspected of also having a tumor, of which the most common was lung cancer (28/83, 33.7%). Partial or complete recovery was achieved in 57 cases (57/83, 68.6%), while 26 cases (26/83, 31.3%) died during treatment or follow-up.

CONCLUSIONS

AE with co-existing multiple anti-neuronal antibodies is a specific subgroup, that is increasingly recognized in clinical practice. The co-existence of multiple anti-neuronal antibodies has a major impact on clinical features, disease progression, and prognosis.

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.

Discrimination between leucine-rich glioma-inactivated 1 antibody encephalitis and gamma-aminobutyric acid B receptor antibody encephalitis based on ResNet18

This study aims to discriminate between leucine-rich glioma-inactivated 1 (LGI1) antibody encephalitis and gamma-aminobutyric acid B (GABAB) receptor antibody encephalitis using a convolutional neural network (CNN) model. A total of 81 patients were recruited for this study. ResNet18, VGG16, and ResNet50 were trained and tested separately using 3828 positron emission tomography image slices that contained the medial temporal lobe (MTL) or basal ganglia (BG). Leave-one-out cross-validation at the patient level was used to evaluate the CNN models. The receiver operating characteristic (ROC) curve and the area under the ROC curve (AUC) were generated to evaluate the CNN models. Based on the prediction results at slice level, a decision strategy was employed to evaluate the CNN models' performance at patient level. The ResNet18 model achieved the best performance at the slice (AUC = 0.86, accuracy = 80.28%) and patient levels (AUC = 0.98, accuracy = 96.30%). Specifically, at the slice level, 73.28% (1445/1972) of image slices with GABAB receptor antibody encephalitis and 87.72% (1628/1856) of image slices with LGI1 antibody encephalitis were accurately detected. At the patient level, 94.12% (16/17) of patients with GABAB receptor antibody encephalitis and 96.88% (62/64) of patients with LGI1 antibody encephalitis were accurately detected. Heatmaps of the image slices extracted using gradient-weighted class activation mapping indicated that the model focused on the MTL and BG for classification. In general, the ResNet18 model is a potential approach for discriminating between LGI1 and GABAB receptor antibody encephalitis. Metabolism in the MTL and BG is important for discriminating between these two encephalitis subtypes.

Late-Onset Anti-GABAB Receptor Encephalitis: Clinical Characteristics and Outcomes Differing From Early-Onset Patients

BACKGROUND AND OBJECTIVES

Existing evidence indicates anti-GABA_B receptor encephalitis (GABA_BR-E) seems to occur more commonly later in life, yet the age-associated differences in clinical features and outcomes are not well determined. This study aims to explore the demographic, clinical characteristics, and prognostic differences between late-onset and early-onset GABA_BR-E and identify predictors of favorable long-term outcomes.

METHODS

This is an observational retrospective study conducted in 19 centers from China. Data from 62 patients with GABA_BR-E were compared between late-onset (aged 50 years or older) and early-onset (younger than 50 years) groups and between groups with favorable outcomes (modified Rankin scale (mRS) ≤ 2) and poor outcomes (mRS >2). Logistic regression analyses were applied to identify factors affecting long-term outcomes.

RESULTS

Forty-one (66.1%) patients experienced late-onset GABA_BR-E. A greater proportion of males, a higher mRS score at onset, higher frequencies of ICU admission and tumors, and a higher risk of death were demonstrated in the late-onset group than in the early-onset group. Compared with poor outcomes, patients with favorable outcomes had a younger onset age, a lower mRS score at onset, lower frequencies of ICU admission and tumors, and a greater proportion with immunotherapy maintenance for at least 6 months. On multivariate regression analysis, age at onset (OR, 0.849, 95% CI 0.739-0.974, p = 0.020) and the presence of underlying tumors (OR, 0.095, 95% CI 0.015-0.613, p = 0.013) were associated with poorer long-term outcomes, whereas immunotherapy maintenance for at least 6 months was associated with favorable outcomes (OR, 10.958, 95% CI 1.469-81.742, p = 0.020).

DISCUSSION

These results demonstrate the importance of risk stratification of GABA_BR-E according to age at onset. More attention should be paid to older patients especially with underlying tumors, and immunotherapy maintenance for at least 6 months is recommended to achieve a favorable outcome.

Autoimmune encephalitis : Part 1 (Epidemiology, Pathophysiology and Clinical spectrum)

Since the identification of anti-N-methyl-D-aspartate (NMDA) receptor antibodies about 15 years ago, many patients with rapidly progressing psychiatric symptoms, abnormal movements, seizures or unexplained coma, have been diagnosed with autoimmune encephalitis (AE). The symptom onset is often unspecific and might mimic psychiatric disease, but the later course is frequently characterized by severe disease, often requiring intensive care. Clinical and immunological criteria are helpful in identifying the patients, but no biomarkers exist to guide the clinician in therapy or predict outcome. While persons of all ages can be affected by AE, some types of AE affect more children and young adults and are more prevalent in women. This review will focus on encephalitides associated with neuronal cell-surface or synaptic antibodies, which can result in characteristic syndromes, and are often recognizable on clinical grounds. AE subtypes associated with antibodies against extracellular epitopes can occur with or without tumours. Because the antibodies bind and alter the function of the antigen, the effects are often reversible if immunotherapy is initiated, and the prognosis is favourable in most instances. The first part of this series will introduce the topic, provide an overview of current neuronal surface antibodies and how they present, describe the most common subtype, anti-NMDA receptor encephalitis, and discuss the difficulties in recognizing patients with underlying AE amongst patients with new onset psychiatric disorders.

Clinical characteristics and prognosis of anti-GABABR encephalitis: A single-center experience

The purpose of this study was to assess the demographic data, clinical manifestations, cerebrospinal fluid (CSF), hematology, brain magnetic resonance imaging, electroencephalograms, and therapy and prognosis related to anti-gamma-aminobutyric acid B (anti-GABABR) encephalitis. We retrospectively examined the demographic data, clinical manifestations, laboratory results, brain magnetic resonance imaging, electroencephalograms, and therapy and prognosis of 6 patients with anti-GABABR encephalitis. We used the clinical data of patients with anti-GABABR encephalitis admitted to the Department of Neurology of Mianyang Central Hospital obtained from January 2017 to September 2020. Six patients with anti-GABABR encephalitis were included. Generalized tonic-clonic seizure was the first clinical symptom in 5 patients, while 1 patient first showed behavior disorder. After the first clinical symptom attack, 2 patients developed a memory deficit, 4 cases showed cognitive decline, 3 cases showed behavior disorder, 1 patient developed status epilepticus and only 1 patient returned to normal. CSF testing indicated normal intracranial pressure in 5 patients and elevated pressure in only 1 patient. Additionally, the cerebrospinal fluid tests revealed slight leukocytosis in all patients and elevated protein levels in 5 patients. The anti-GABABR antibody was positive in both serum and CSF in all patients. Brain magnetic resonance imaging showed limbic system lesions in 4 patients. Long-term electroencephalograms revealed abnormal waves in half of the patients. All patients were treated with high dosages of methylprednisolone, which was combined with intravenous immunoglobulin in 2 patients; symptoms were improved in 4 patients, 1 patient showed no significant change and 1 patient with status epilepticus died of severe pneumonia during hospitalization. Epilepsy is the most common initial symptom in patients of anti-GABABR encephalitis. Many patients are also affected by tumors. Early immunotherapy can achieve excellent effects, the long-term prognosis is good for most patients.

Case report: Pediatric anti-gamma aminobutyric acid-B receptor encephalitis with benign prognosis

Objective

To explore the clinical characteristics of pediatric anti-gamma-aminobutyric acid-B receptor (GABA_BR) encephalitis to enhance the understanding and improve the diagnostic and therapeutic strategies for this disease.

Methods

We report a rare case of a female pediatric patient with anti-GABA_BR encephalitis who was treated at the Children's Hospital of Zhejiang University School of Medicine. Literature search was performed to explore the clinical characteristics of pediatric anti-GABA_BR encephalitis.

Results

The patient exhibited recurrent epileptic seizure, status epilepticus, and psychiatric symptoms at the age of 11 years and 10 months. Anti-GABA_BR antibodies were positive in cerebrospinal fluid and serum. Brain magnetic resonance imaging (MRI) exhibited abnormal signals in the left hippocampus. Symptoms and abnormality of brain MRI were improved after administration of immunosuppressants, anti-seizure and antipsychotic drugs. Two of pediatric anti-GABA_BR encephalitis with clinical data were identified through literature search. Analysis of these three cases suggested that the pediatric patients primarily experienced limbic encephalitis, with no tumor incidence. A favorable immunotherapy response was demonstrated with a superior prognosis in all the cases.

Conclusions

We reported a pediatric anti-GABA_BR encephalitis case with early age of onset. Promt autoimmune antibody testing and tumor screening, as well as immunomodulatory treatment immediately after a definitive diagnosis are warranted to improve prognosis.

Seronegative autoimmune encephalitis: clinical characteristics and factors associated with outcomes

Seronegative autoimmune encephalitis is autoimmune encephalitis without any identifiable pathogenic antibody. Although it is a major subtype of autoimmune encephalitis, many unmet clinical needs exist in terms of clinical characteristics, treatments and prognosis. In this institutional cohort study, patients diagnosed with seronegative autoimmune encephalitis with available 2-year outcomes were analysed for the disease course, 2-year outcome prediction system, effect of immunotherapy, necessity of further immunotherapy at 6 or 12 months and pattern of brain atrophy. Seronegative autoimmune encephalitis was subcategorized into antibody-negative probable autoimmune encephalitis, autoimmune limbic encephalitis and acute disseminated encephalomyelitis. Poor 2-year outcome was defined by modified Rankin scale scores 3-6, and the 2-year serial data of Clinical Assessment Scales in Autoimmune Encephalitis score was used for longitudinal data analyses. A total of 147 patients were included. The frequency of achieving a good 2-year outcome (modified Rankin scale 0-2) was 56.5%. The antibody-negative probable autoimmune encephalitis subtype exhibited the poorest outcomes, although the baseline severity was similar among the subtypes. The RAPID score, consisting of five early usable clinical factors, refractory status epilepticus, age of onset ≥60 years, probable autoimmune encephalitis (antibody-negative probable autoimmune encephalitis subtype), infratentorial involvement and delay of immunotherapy ≥1 month, was associated with poorer 2-year outcomes. Any immunotherapy was associated with clinical improvement in the patients with low risk for poor 2-year outcomes (RAPID scores 0-1), and the combination immunotherapy of steroid, immunoglobulin, rituximab and tocilizumab was associated with better outcomes in the patients with high risk for poor 2-year outcomes (RAPID scores 2-5). In patients with persistent disease at 6 months, continuing immunotherapy was associated with more improvement, while the effect of continuing immunotherapy for more than 12 months was unclear. In the longitudinal analysis of MRI, the development of cerebellar atrophy indicated poor outcomes, while the absence of diffuse cerebral atrophy or medial temporal atrophy indicated the possibility of a good outcome. This study provides information about the clinical characteristics and courses, the effect of immunotherapy and its duration, and prognostic factors in seronegative autoimmune encephalitis.

Positron emission tomography in autoimmune encephalitis: Clinical implications and future directions

¹⁸ F-fluoro-deoxyglucose position emission tomography (¹⁸ F-FDG-PET) has been proven as a sensitive and reliable tool for diagnosis of autoimmune encephalitis (AE). More attention was paid to this kind of imaging because of the shortage of MRI, EEG, and CSF findings. FDG-PET has been assessed in a few small studies and case reports showing apparent abnormalities in cases where MRI does not. Here, we summarized the patterns (specific or not) in AE with different antibodies detected and the clinical outlook for the wide application of FDG-PET considering some limitations. Specific patterns based on antibody subtypes and clinical symptoms were critical for identifying suspicious AE, the most common of which was the anteroposterior gradient in anti- N -methyl- d -aspartate receptor (NMDAR) encephalitis and the medial temporal lobe hypermetabolism in limbic encephalitis. And the dynamic changes of metabolic presentations in different phases provided us the potential to inspect the evolution of AE and predict the functional outcomes. Except for the visual assessment, quantitative analysis was recently reported in some voxel-based studies of regions of interest, which suggested some clues of the future evaluation of metabolic abnormalities. Large prospective studies need to be conducted controlling the time from symptom onset to examination with the same standard of FDG-PET scanning.

Postvaccinal GABA-B receptor antibody encephalitis after ChAdOx1 nCoV-19 vaccination

Several cases of autoimmune encephalitis have been reported after ChAdOx1 nCoV-19 (AZD1222) vaccination. We encountered a male patient who presented with generalized tonic-clonic seizures, cognitive decline, and gait disturbance that occurred suddenly after the second dose of the ChAdOx1 nCoV-19 vaccine. Clinical presentation and magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) test results were compatible with limbic encephalitis. Synaptic autoantibody tests confirmed serum and CSF GABA B receptor antibodies were present. The patient was treated with immunotherapy with intravenous immunoglobulin and rituximab. This GABA-B receptor antibody encephalitis case occurred presumably due to transient autoantibody production following vaccine administration.

Psychiatric manifestations of autoimmune encephalitis

Autoimmune encephalitis is increasingly recognized as a cause of psychiatric symptoms. A wide spectrum of psychiatric manifestations have been described which may precede, follow or occur independently of neurologic features. Patients typically respond to immunotherapy, however diagnosis is challenging due to phenotypic heterogeneity. The aim of this review is to provide an overview of the psychiatric features associated with encephalitis mediated by autoantibodies targeting neuronal cell-surface antigens and describe indicators of potential immunopathology underlying psychiatric manifestations.

Rare antibody-mediated and seronegative autoimmune encephalitis: An update

Paralleling advances with respect to more common antibody-mediated encephalitides, such as anti-N-methyl-D-aspartate receptor (NMDAR) and anti-leucine-rich glioma-inactivated 1 (LGI1) Ab-mediated encephalitis, the discovery and characterisation of novel antibody-mediated encephalitides accelerated over the past decade, adding further depth etiologically to the spectrum of antibody-mediated encephalitis. Herein, we review the major mechanistic, clinical features and management considerations with respect to anti-γ-aminobutyric acid B (GABA_B)-, anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropinoic receptor- (AMPAR), anti-GABA_A-, anti-dipeptidyl-peptidase-like protein-6 (DPPX) Ab-mediated encephalitides, delineate rarer subtypes and summarise findings to date regarding seronegative autoimmune encephalitis.

A scoping review on paraneoplastic autoimmune limbic encephalitis (PALE) psychiatric manifestations

The term limbic encephalitis has been used with an oncological precedent for over 50 years and, since then, has been applied in relation to multiple antibodies found in its etiological process. Over the last decade, the psychiatric community has brought paraneoplastic autoimmune limbic encephalitis (PALE) to a new light, scattering the once known relationships between said screened antibodies responsible for causing limbic encephalitis. Due to the fact that some individuals with this condition have a psychiatric syndrome as an initial manifestation, the aim of this updated scoping review is to reestablish a causal relationship between the onconeuronal autoantibodies, both intracellular and extracellular, possible underlying malignancies and subsequent neuropsychiatric syndrome. In pair with it, there is the idea of sketching a cleaner thorough picture of what poses as psychiatric symptoms as well as possible therapeutics. Even though the always evolving epistemology of the neurosciences achieved a significant unveiling of what includes PALE in its relevant pathological subgroups, the amount of gray literature still is much superior, appealing to a further research with more randomized controlled trials, with larger populations, so that the results corroborate the small amount of data that already exist and posteriorly be applied in the general population.

Research progress of anti-γ-aminobutyric acid B receptor encephalitis and a case report of paraneoplastic associated encephalitis and treatment analysis

Encephalitis is one of the common diseases in neurology. Early diagnosis and appropriate treatments are essential. Autoimmune encephalitis (AE) generally refers to a type of encephalitis mediated by autoimmune mechanisms. It is gradually considered to be an important cause of reversible encephalitis caused by noninfectious factors. It can occur in children, adolescents, and adults, and is clinically characterized by multifocal or diffuse brain damage such as personality changes, seizures, and cognitive impairment, with an overall good effect of immunotherapy. According to the clinical features of the patients, blood and cerebrospinal fluid tests, neuroelectrophysiology, cranial imaging, treatment and prognosis, AEs can be broadly divided into specific antigen (antibody)-related AEs and nonspecific antigen (or antibody) -related AEs. With the development of AEs research, more and more anti-neuron antibodies have been found, which provides an important reference for the diagnosis and treatment of AEs. Understanding the knowledge about AEs is important to discover new diseases and deepen the understanding of the immunopathological mechanisms of existing central nervous system diseases. Anti-γ-aminobutyric acid B (GABA-B) receptor encephalitis is a type of AE, but this disease is rare in AE, often develop to the clinical manifestations of marginal encephalitis, accompanied by obvious seizures or status epilepticus, Some patients had tumors, mainly small-cell carcinoma, prompt diagnosis, early immunotherapy and, if necessary, tumor treatment resulted in complete or partial neurological improvement in most patients.

SCLC and anti‐GABABR encephalitis: A retrospective analysis of 60 cases in China

Background

Methods

Results

Conclusions

Case Analysis and Literature Review of Thirteen Patients with Autoimmune Encephalitis

Objective. To investigate the clinical manifestations, laboratory and imaging examinations, and the treatment outcomes of autoimmune encephalitis (AE). Methods. The clinical data of 13 patients with autoimmune encephalitis who were hospitalized in the department of neurology, Liaocheng People’s Hospital from July 2016 to August 2018 were retrospectively analyzed. Results. The average age of onset of the 13 patients was 45 years, including 6 cases (46%) of anti-NMDAR encephalitis, 3 cases (23%) of anti-GABAB receptor encephalitis, and 4 cases (30%) of anti-LG11 encephalitis, and 4 of them showed abnormal signals of brain MRI (30%). 13 patients (100%) had cognitive impairment and psychiatric symptoms; seizures occurred in 12 patients (92%); lung cancer was found in 1 patient (7%). One case was given up because of the treatment of lung cancer, the other was controlled obviously in epilepsy, and cognitive impairment and abnormal mental behavior were also significantly improved. Conclusion. Patients with AE still need to be diagnosed early to avoid missed diagnosis and receive early immunosuppressive therapy, which could effectively reduce mortality and morbidity. A detailed history, clinical manifestations, and positive results for specific NSAbs tests can confirm the diagnosis, and the treatment is mainly done by immunosuppressive therapy.

Autoimmune Epilepsy - Novel Multidisciplinary Analysis, Discoveries and Insights

Epilepsy affects ~50 million people. In ~30% of patients the etiology is unknown, and ~30% are unresponsive to anti-epileptic drugs. Intractable epilepsy often leads to multiple seizures daily or weekly, lasting for years, and accompanied by cognitive, behavioral, and psychiatric problems. This multidisciplinary scientific (not clinical) 'Perspective' article discusses Autoimmune Epilepsy from immunological, neurological and basic-science angles. The article includes summaries and novel discoveries, ideas, insights and recommendations. We summarize the characteristic features of the respective antigens, and the pathological activity in vitro and in animal models of autoimmune antibodies to: Glutamate/AMPA-GluR3, Glutamate/NMDA-NR1, Glutamate/NMDA-NR2, GAD-65, GABA-R, GLY-R, VGKC, LGI1, CASPR2, and β2 GP1, found in subpopulations of epilepsy patients. Glutamate receptor antibodies: AMPA-GluR3B peptide antibodies, seem so far as the most exclusive and pathogenic autoimmune antibodies in Autoimmune Epilepsy. They kill neural cells by three mechanisms: excitotoxicity, Reactive-Oxygen-Species, and complement-fixation, and induce and/or facilitate brain damage, seizures, and behavioral impairments. In this article we raise and discuss many more topics and new insights related to Autoimmune Epilepsy. 1. Few autoimmune antibodies tilt the balance between excitatory Glutamate and inhibitory GABA, thereby promoting neuropathology and epilepsy; 2. Many autoantigens are synaptic, and have extracellular domains. These features increase the likelihood of autoimmunity against them, and the ease with which autoimmune antibodies can reach and harm these self-proteins. 3. Several autoantigens have 'frenetic character'- undergoing dynamic changes that can increase their antigenicity; 4. The mRNAs of the autoantigens are widely expressed in multiple organs outside the brain. If translated by default to proteins, broad spectrum detrimental autoimmunity is expected; 5. The autoimmunity can precede seizures, cause them, and be detrimental whether primary or epiphenomenon; 6. Some autoimmune antibodies induce, and associate with, cognitive, behavioral and psychiatric impairments; 7. There are evidences for epitope spreading in Autoimmune Epilepsy; 8. T cells have different 'faces' in the brain, and in Autoimmune Epilepsy: Normal T cells are needed for the healthy brain. Normal T cells are damaged by autoimmune antibodies to Glutamate/AMPA GluR3, which they express, and maybe by additional autoantibodies to: Dopamine-R, GABA-R, Ach-R, Serotonin-R, and Adrenergic-R, present in various neurological diseases (summarized herein), since T cells express all these Neurotransmitter receptors. However, autoimmune and/or cytotoxic T cells damage the brain; 9. The HLA molecules are important for normal brain function. The HLA haplotype can confer susceptibility or protection from Autoimmune Epilepsy; 10. There are several therapeutic strategies for Autoimmune Epilepsy.

Comparison of the clinical syndromes of anti-GABAa versus anti-GABAb associated autoimmune encephalitis: A systematic review

The main objective of this article is to improve our understanding of the differences and similarities of these two anti-gamma-aminobutyric acid receptor encephalitis, anti-GABAaR and anti-GABAbR. The data were systematically collected and we found 26 studies: seven studies and 37 patients corresponded to anti-GABAaR encephalitis, and 21 manuscripts and 116 patients were diagnosed with anti-GABAbR encephalitis. Both anti-GABAR encephalitis were marked by prominent seizures. Anti-GABAaR patients were younger and showed multifocal encephalitis. On the other hand, anti-GABAbR patients were older and showed temporal limbic encephalitis. Tumor occurred in a fifth of anti-GABAaR encephalitis and in half of anti-GABAbR encephalitis. The main tumor associated with anti-GABAbR encephalitis is SCLC, whereas the most common tumor associated with anti-GABAaR encephalitis was thymoma. Our data confirms the differences in clinical features between both encephalitis.

18 F-fluorodeoxy-glucose positron emission tomography pattern and prognostic predictors in patients with anti-GABAB receptor encephalitis

Aims

To identify the metabolic pattern and prognostic predictors in anti‐gamma‐aminobutyric‐acid B (GABAB) receptor encephalitis using ¹⁸F‐fluorodeoxy‐glucose positron emission tomography (¹⁸F‐FDG‐PET).

Methods

Twenty‐one patients diagnosed anti‐GABAB receptor encephalitis who underwent ¹⁸F‐FDG‐PET at first hospitalization were retrospectively reviewed. ¹⁸F‐FDG‐PET images were analyzed in comparison with controls. Further group comparisons of ¹⁸F‐FDG‐PET data were carried out between prognostic subgroups.

Results

¹⁸F‐FDG‐PET was abnormal in 81% patients with anti‐GABAB receptor encephalitis and was more sensitive than MRI (81% vs. 42.9%, p = 0.025). Alter limbic lobe glucose metabolism (mostly hypermetabolism) was observed in 14 patients (66.7%), of whom 10 (10/14, 71.4%) demonstrated hypermetabolism in the medial temporal lobe (MTL). Group analysis also confirmed MTL hypermetabolism in association with relative frontal and parietal hypometabolism was a general metabolic pattern. After a median follow‐up of 33 months, the group comparisons revealed that patients with poor outcome demonstrated increased metabolism in the MTL compared to those with good outcome.

Conclusion

¹⁸F‐FDG‐PET may be more sensitive than MRI in the early diagnosis of anti‐GABAB receptor encephalitis. MTL hypermetabolism was associated with relative frontal or parietal hypometabolism and may serve as a prognostic biomarker in anti‐GABAB receptor encephalitis.

Lung cancer masquerading as a paraneoplastic neurologic syndrome without a primary lung mass: Case report and review of literature

Paraneoplastic and autoimmune encephalitis (AIE) syndromes describe a range of inflammatory disorders of the brain. "Classic" paraneoplastic encephalitis syndromes occur due to a remote neoplasm and are associated with antibodies that target intracellular neuronal proteins while the more recently described AIE syndromes are not always paraneoplastic and occur in association with antibodies that target cell-surface neuronal receptors (e.g., anti-NMDA receptor, anti-LGI1, anti-GABA_B receptor).^[1] Diagnosis can be difficult and delayed due to nonspecific clinical, imaging, and laboratory findings, and in those syndromes associated with a neoplasm, the neurologic syndromes often precede the cancer diagnosis. We present a case of a 64-year-old patient diagnosed with anti-GABA_B receptor encephalitis that subsequently revealed an underlying small cell lung cancer without a primary lung tumor. This case highlights the clinical challenge in diagnosing immune-mediated encephalitis, its methodical work up, and subsequent management.

Subcortical Hypermetabolism Associated With Cortical Hypometabolism Is a Common Metabolic Pattern in Patients With Anti-Leucine-Rich Glioma-Inactivated 1 Antibody Encephalitis

Purpose

Brain 18F-fluorodeoxyglucose positron emission tomography (FDG PET) is a sensitive technique for assisting in the diagnosis of patients with anti-leucine-rich glioma-inactivated 1 (LGI1) antibody encephalitis. However, the common pattern of this disorder assessed by FDG PET remains unknown. The present study aimed to explore the glucose metabolic patterns of this disorder based on PET voxel analysis.

Methods

This retrospective study enrolled 25 patients with anti-LGI1 encephalitis, who were admitted in Beijing Tiantan Hospital between September 2014 and July 2019. The glucose metabolic pattern was compared between the included patients and 44 age- and gender-matched healthy controls using Statistical Parametric Mapping. Then, the correlation between the metabolic pattern and scaled activities of daily living (ADLs) of the patients was assessed.

Results

The median time from symptom onset to PET scans was 9 w (range:2-53w). The groupwise analysis revealed that patients with anti-LGI1 encephalitis had left hippocampal hypermetabolism and hypometabolism in almost all neocortical regions. The individual-level results showed most patients presented a decreased metabolism in neocortical regions, as well as an increase in metabolism in the hippocampus and basal ganglia. Furthermore, the metabolic gradient between hippocampus and neocortical regions was positively associated with the ADLs (frontal lobe, r=0.529, P=0.008; parietal lobe, r=0.474, P=0.019; occipital lobe, r=0.413, P=0.045; temporal lobe, r=0.490, P=0.015), respectively. In addition, the patients with facio-brachial dystonic seizures (FBDS) presented bilateral putamen hypermetabolism, when compared to patients without FBDS and healthy controls.

Conclusion

Subcortical hypermetabolism associated with cortical hypometabolism presented with a common metabolic pattern in patients with anti-LGI1 encephalitis in the present study. The resolution of the metabolic gradient of the hippocampal hypermetabolism and neocortical hypometabolism may bring about improved clinical neurologic disability.

Clinical characteristics and elevated ProGRP and positive oligoclonal bands of 13 Chinese cases with anti-GABABR encephalitis

OBJECTIVE

To improve the clinical understanding of anti-gamma-aminobutyric-acid B receptor encephalitis (anti-GABABR encephalitis) by analyzing 13 cases.

METHODS

We retrospectively studied demographic and clinical features including clinical symptoms, serum/cerebrospinal fluid (CSF) laboratory findings (including antibody test), brain magnetic resonance imaging (MRI), electroencephalogram (EEG), treatment plan, and treatment effect for 13 patients with a definitive diagnosis of anti-GABABR encephalitis.

RESULTS

Seven patients (53.8%, 7/13) were complicated with lung cancer. Epileptic seizures were the most common symptoms at onset in 11 patients (84.6%, 11/13). All patients had seizures in the course of the disease. Abnormalities in craniocerebral MRI examination, including hippocampus, occipital lobe, insular lobe, were found in six of nine tested patients, and EEG abnormalities were found in seven out of nine tested patients. Elevated pro-gastrin releasing peptide (ProGRP) levels were found in 70% of patients with a median value of 490.10 pg/ml; and CSF oligoclonal bands were positive for 4 of 10 tested cases. However, there were no significant differences in modified Rankin Scale (mRS) between the ProGRP or CSF oligoclonal band positive and negative groups at admission and follow-up (p > .05). The value between SCLC and non-SCLC subgroup was significantly different (p < .05). Ten patients received immunotherapy (three patients refused treatment). After immunotherapy, the frequency of seizures was significantly reduced. There was a significant difference in mRS between admission and after treatment (p < .05). The average survival time after onset was 27.7 months.

CONCLUSIONS

Epilepsy is the most common clinical manifestation of Anti-GABABR encephalitis. The prognosis of anti-GABABR encephalitis is poor. Section of anti-GABABR encephalitis patients have higher level of serum ProGRP and positive GSF oligoclonal bands. Elevated ProGRP or positive CSF oligoclonal bands with classic clinical features can potentially help to improve early recognition of anti-GABABR encephalitis.

The long-term outcome of neuropsychological function is favorable in patients with non-malignancy related anti-GABABR encephalitis: a case series

Background

Anti-GABA_BR encephalitis is a rare type of autoimmune encephalitis, which often presents with memory impairments, behavioral changes and seizures. This case series describes the neuropsychological function recovery pattern in five adult patients with anti-GABA_BR encephalitis.

Case presentation

We recruited five patients with clinically confirmed anti-GABA_BR encephalitis without any accompanying malignancy. Comprehensive neuropsychological evaluation was conducted on each patient. All the five patients were evaluated in the chronic phase. Five age and gender matched healthy adults were recruited as control group. Our study demonstrated that the neuropsychological function of the patients with anti-GABA_BR encephalitis was no different with respect to the control group during the chronic phase (more than 6 months after onset). Moreover, one patients with neuropsychological evaluation at acute (within 2 months after onset of symptoms), post-acute (2 to 6 months after onset) and chronic phases respectively, presented neuropsychological function recovered as early as in the post-acute phase and only showed cognition impairment in the acute phase.

Conclusions

The results of this retrospective study indicate a favorable long-term neuropsychological function outcome in adult patients with anti-GABA_BR encephalitis, despite severe memory deficits occurring during the acute phase. These findings improve our understanding related to the prognosis of neuropsychological function in anti-GABA_BR encephalitis.

Teratoma Removal, Steroid, IVIG, Rituximab and Tocilizumab (T-SIRT) in Anti-NMDAR Encephalitis

In anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, we analysed the efficacy of a combined immunotherapy protocol consisting of teratoma removal, steroid, intravenous immunoglobulin (IVIG), rituximab and tocilizumab (T-SIRT). This cohort study included seventy-eight consecutive patients treated for anti-NMDAR encephalitis between Jan 2014 and Oct 2019 in a national referral hospital. Detailed 2-year disease time course was analysed using Clinical Assessment Scale for Autoimmune Encephalitis (CASE) scores at every 2 weeks for 12 weeks from baseline, every month for the next 3 months and then every 3 months. Treatment regimens at each time point were categorized as SI, SIR, or SIRT with/without teratoma removal (T). Adverse events were classified according to the Common Terminology Criteria for Adverse-Events (CTCAE v5.0), where a severe adverse event was defined as an adverse event with CATAE grade 4. In a linear mixed model analysis, using the SIRT regimen was more effective than SIR or SI regimens in lowering CASE scores (P < 0.001 and P = 0.001, respectively). The presence of teratoma (P = 0.001), refractory status epilepticus (P < 0.001) and a higher CASE score at baseline (P < 0.001) predicted a higher CASE score at each time point. Completion of the (T)-SIRT regimen within 1 month of onset resulted in better 1-year improvements in CASE score (P < 0.001) and modified Rankin scale scores (P = 0.001), compared to those of using other regimens within 1 month or delaying teratoma removal for more than 1 month. Pneumonia was a frequent adverse event (52/78, 66.7%) in the whole study population and neutropenia was frequent during SIRT (11/52, 21.2%), but the regimen was well tolerated in most patients. We concluded that the early application of combined immunotherapy consisting of T-SIRT had better efficacy than was found for delayed or partial application of this combination in anti-NMDAR encephalitis.

A Retrospective Study of Patients with GABABR Encephalitis: Therapy, Disease Activity and Prognostic Factors

PURPOSE

To explore the effects of immunotherapy and tumour treatment on patients with GABA_BR encephalitis, evaluate the correlation between immune cell subsets and disease activity, and investigate effective prognostic factors.

PATIENTS AND METHODS

Twenty patients with γ-aminobutyric acid B receptor (GABA_BR) encephalitis were enrolled from December 2015 to April 2020. The clinical data, modified Rankin Scale (mRS) score, prognosis and percentage of serum lymphocytes were recorded.

RESULTS

All patients received first-line immunotherapy. The median mRS scores were 4 and 3 before and after first-line immunotherapy (P<0.01). Seven patients received second-line immunotherapy and had median mRS scores of 3 and 2 before and after second-line immunotherapy (P=0.015). Small-cell lung cancer was detected in twelve patients. Among the patients who died because of tumours, patients who received tumour treatment lived longer than patients who did not receive tumour treatment (P=0.025). All four surviving patients who received tumour treatment had good outcomes (mRS≤2). The median serum CD19⁺B cell percentage in sixteen patients were 20.00% and 13.42% prior first-line immunotherapy and at the last follow-up (P<0.01). After a maximum follow-up of 54 months (median: 12; range: 3-54), eleven patients (55%) had a poor prognosis (mRS>2). Predictors of a poor prognosis were older age (P=0.031), delayed initial improvement after immunotherapy (>4 weeks) (P=0.038) and respiratory failure (P=0.038).

CONCLUSION

Aggressive immunotherapy and tumour treatment contribute to improvements in neurological function and a better prognosis of patients with GABA_BR encephalitis. The serum CD19⁺B cell percentage may be an indicator of disease activity. Older age, delayed initial improvement after immunotherapy, and respiratory failure may be associated with poor outcomes.

Diagnostic Value of Structural and Functional Neuroimaging in Autoimmune Epilepsy

Epilepsy is a common nervous system disease, which affects about 70 million people all over the world. In 2017, the International League Against Epilepsy (ILAE) considered immune factors as its independent cause, and the concept of autoimmune epilepsy (AE) was widely accepted. Early diagnosis and timely treatment can effectively improve the prognosis of the disease. However, due to the diversity of clinical manifestations, the expensive cost of autoantibody detection, and the increased prevalence in Western China, the difficulty for clinicians in early diagnosis and treatment has increased. Fortunately, convenient and fast imaging examinations are expected to help even more. The imaging manifestations of AE patients were characteristic, especially the combined application of structural and functional neuroimaging, which improved the diagnostic value of imaging. In this paper, several common autoantibodies associated with AE and their structure and function changes in neuroimaging were reviewed to provide help for neurologists to achieve the goal of precision medicine.

Anti-LGI1, anti-GABABR, and Anti-CASPR2 encephalitides in Asia: A systematic review

AIM

We aim to review the literature to collate and describe features of encephalitides arising from autoantibodies against leucine-rich glioma-inactivated 1 (LGI1), gamma aminobutyric acid receptor (GABABR), and contactin-associated protein-like 2 (CASPR2) in Asian populations and compare them with findings of Western studies.

METHODS

Peer-reviewed articles published till 24 May 2020 were searched, and original, full-text studies from Asia with serum/CSF antibody-based diagnosis and at least 2 patients were selected. Twenty-four studies with 263 patients (139 anti-LGI1, 114 anti-GAGABR, and 10 anti-CASPR2) were included. Data were pooled to produce descriptive information on demographics, clinical characteristics, diagnostics, treatments, and outcome.

RESULTS

The mean age was 54.2 (anti-LGI1), 55.2 (anti-GABABR), and 47.7 years (anti-CASPR2), with an overall male predominance of 62.0%. Commonest clinical features across all types were seizures (87.5%), memory deficits (80.7%), psychiatric disturbances (75.9%), and altered consciousness (52.9%). Four anti-LGI1, 40 anti-GABABR, and 1 anti-CASPR2 patients had tumors. CSF, MRI, and EEG were abnormal in 33.3%, 54.1%, and 75% patients in anti-LGI1; 60.0%, 49.6%, and 85.7% in anti-GABABR; and 50%, 44.4%, and 100% in anti-CASPR2 patients, respectively. 95.6% patients received first-line therapy alone (steroids/IVIG/Plasma therapy), and 4.4% received second-line therapy (rituximab/cyclophosphamide). 91.7%, 63.6%, and 70% of patients had favorable outcomes (modified Rankin Score 0-2) with mortality rates at 2.5%, 23.2%, and 0% in the three types, respectively.

CONCLUSION

Our findings suggest that these disorders present in Asian patients at a relatively young age often with features of seizures, memory deficits, and psychiatric disturbances and usually demonstrate a favorable clinical outcome.

Neuroimmunological antibody-mediated encephalitis and implications for diagnosis and therapy in neuropsychiatry

The past decade has seen a surge of reports and investigations into cases of autoimmune-mediated encephalitis. The increasing recognition of these disorders is especially of relevance to the fields of neurology and psychiatry. Autoimmune encephalitis involves antibodies against synaptic receptors, neuronal cell surface proteins and intracellular targets. These disorders feature prominent symptoms of cognitive impairment and behavioural changes, often associated with the presence of seizures. Early in the clinical course, autoimmune encephalitis may manifest as psychiatric symptoms of psychosis and involve psychiatry as an initial point of contact. Although commonly associated with malignancy, these disorders can present in the absence of an inciting neoplasm. The identification of autoimmune encephalitis is of clinical importance as a large proportion of individuals experience a response to immunotherapy. This review focuses on the current state of knowledge on n-methyl-d-aspartate (NMDA) receptor-associated encephalitis and limbic encephalitis, the latter predominantly involving antibodies against the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, the γ-aminobutyric acid (GABA)B receptor and leucine-rich glioma-inactivated 1 (LGI1) protein. In addition, we briefly describe anti-dopamine D2 receptor encephalitis. A summary of the literature will focus on common clinical presentations and course, diagnostic approaches and response to treatment. Since a substantial proportion of patients with autoimmune encephalitis exhibit symptoms of psychosis, the relevance of this disorder to theories of psychosis and schizophrenia will also be discussed.

GABA-B Receptor Encephalitis Triggered by Enterovirus Encephalitis in a Patient With Small Cell Lung Cancer: A Case Report

INTRODUCTION

Encephalitis with gamma-aminobutyric acid (GABA)-B receptor antibodies (GABA-B receptor encephalitis) is known to have underlying neoplastic condition in half of the cases; however, there could be an additional event that could work as a trigger factor. Here, we report a patient with GABA-B receptor encephalitis associated with small cell lung cancer, which was probably triggered by enterovirus encephalitis.

CASE REPORT

A 53-year-old man was admitted for a seizure, following fever and headache for 3 days. Status epilepticus developed on the following day. Brain magnetic resonance imaging (MRI) was normal. Cerebrospinal fluid (CSF) study revealed lymphocyte-dominant pleocytosis, and enterovirus was detected by polymerase chain reaction test in CSF later. The patient recovered after 2 weeks of treatment. Another 2 weeks later, he showed confusion and seizure without fever. Follow-up CSF study revealed no abnormalities; however, MRI showed a lesion with vasogenic edema on the right posterior hippocampus. GABA-B receptor antibodies were found in the serum and CSF. The chest computed tomography revealed a mass on his right upper lung, which was confirmed as a small cell lung cancer. GABA-B receptor encephalitis associated with small cell lung cancer was diagnosed, and intravenous immunoglobulin and methylprednisolone were infused. Following treatment, seizures and delirium stopped, and the patient recovered to a near normal state. Follow-up MRI performed 2 months later showed that the hippocampal lesion had disappeared.

CONCLUSION

In cases of infectious encephalitis with an atypical recurrent course, the possibility of newly onset autoimmune encephalitis should be considered.

Clinical features and outcomes of Chinese patients with anti-γ-aminobutyric acid B receptor encephalitis

Antibodies against γ-aminobutyric acid B (GABAB) receptor are associated with limbic encephalitis (LE). It is estimated that ~1/2 of patients with LE have small-cell lung cancer. The present study analyzed the specific GABAB receptor antibodies in serum and cerebrospinal fluid (CSF) samples of 12 patients. The clinical manifestations, therapy and outcome were retrospectively compared. The median onset age was 65.1 years and all patients presented with new-onset seizures. In total, 11 (91.6%) patients had memory deficits, 7 (58.3%) patients had psychiatric problems and 4 (33.3%) patients had a disturbance of consciousness. Furthermore, lung cancer was detected in 7 patients (58.3%) by CT scan. Lymphocytic pleocytosis and protein concentration elevation in CSF were detected in 3 (25%) and 4 (33.3%) patients, respectively. Furthermore, MRI scan results identified 4 (33.3%) patients with abnormalities in the mesial temporal region. The lung cancer tissues of 3 patients were positively stained for anti-GABAB receptor on immunohistochemistry. All patients received antiepileptic drugs and immunotherapy. In total, 3 patients with lung cancer were subjected to tumor resection. Those patients without cancer exhibited neurological improvement at the follow-up. The present results suggested that seizures and memory deficits were the major manifestations in Chinese patients with anti-GABAB receptor antibodies who were responsive to immunotherapy. The lung cancer tissues from patients with anti-GABAB receptor antibodies were positively stained for anti-GABAB receptor. Collectively, the present results suggested that patients with underlying lung cancer have a relatively poor prognosis.

The Clinical Value of 18 F-FDG-PET in Autoimmune Encephalitis Associated With LGI1 Antibody

Purpose: The metabolic patterns of ¹⁸F-fluoro-2-deoxy-d-glucose positron emission tomography (¹⁸F-FDG-PET) in autoimmune encephalitis associated with leucine-rich glioma-inactivated 1 antibody (LGI1 AE) are still unclear. We performed a cohort study to investigate the clinical metabolic characteristics and diagnostic value based on ¹⁸F-FDG-PET in patients with LGI1 AE.

Materials and Methods: A total of 34 patients including 18 patients (53%) in the acute phase and 16 patients (47%) in the chronic phase who were diagnosed with LGI1 AE were retrospectively analyzed from October 2014 to June 2018 at the Department of Neurology in Beijing Tiantan Hospital, the Capital Medical University. The clinical data were collected by searching through electronic medical records.

Results: The initial ¹⁸F-FDG-PET scan indicated a significant abnormal metabolic pattern in 31 LGI1 AE patients (91%), whereas only 20 patients (59%) showed an abnormal MRI signal (P < 0.05). The ¹⁸F-FDG-PET metabolic pattern was reversible after treatment; most of the patients showed an almost normal uptake of ¹⁸F-FDG-PET after discharge. Regarding the spatial distribution, the abnormal metabolic pattern in LGI1 AE subjects exhibiting hypermetabolism was specifically located in the basal ganglia (BG) and medial temporal lobe (MTL). BG hypermetabolism was observed in 28 subjects (82%), and 68% of patients showed MTL hypermetabolism. A total of 17 patients (50%) exhibited faciobrachial dystonic seizures (FBDS), and the remaining subjects showed non-FBDS symptoms (50 and 50%). BG-only hypermetabolism was detected in seven subjects in the FBDS subgroup (7/16) but in only one subject in the non-FBDS subgroup (1/15) (44 vs. 7%, P < 0.05).

Conclusion:¹⁸F-FDG-PET imaging was more sensitive than MRI in the diagnosis of LGI1 AE. Isolated BG hypermetabolism was more frequently observed in subjects with FBDS, suggesting the potential involvement of the BG.

Autoimmune Encephalitis Associated with Anti-gamma-aminobutyric Acid B Receptor Antibodies Mimicking Syncope

Autoimmune encephalitis associated with autoantibodies to the gamma-aminobutyric acid B receptor (GABA_BR-AE) typically involves limbic symptoms with limbic abnormalities visible in brain magnetic resonance imaging (MRI). We herein report a case of a 48-year-old man with GABA_BR-AE whose initial presentation was limited to syncope without limbic symptoms or MRI abnormalities. Interestingly, serial MRI also revealed no abnormalities even after the appearance of limbic symptoms. Our findings suggest that GABA_BR-AE can initially mimic common syncope and that MRI findings may remain normal throughout the clinical course. Even if patients have normal MRI findings, GABA_BR-AE should be considered if limbic symptoms worsen.

Clinical characteristics and prognostic analysis of anti-gamma-aminobutyric acid-B (GABA-B) receptor encephalitis in Northeast China

Objective

To investigate the clinical characteristics and prognosis of anti-gamma-aminobutyric acid-B (GABA-B) receptor encephalitis.

Methods

This retrospective study enrolled nineteen patients with anti-GABA-B receptor encephalitis. Clinical manifestations, radiological and electroencephalogram features, treatment and outcomes were collected and analyzed. The neurological function was evaluated according to the modified Rankin Scale (mRS).

Results

There were eleven patients in the favorable-prognosis group (mRS ≤ 2) and eight patients in the poor-prognosis group (mRS > 2). In the favorable-prognosis group, clinical symptoms included memory deterioration (n = 10; 90.9%), epileptic seizures (n = 9; 81.8%), psychiatric disorders (n = 9; 81.8%), and conscious disturbance (n = 5; 45.5%); magnetic resonance imaging (MRI) indicated an involvement of the limbic system in three (27.3%) cases in this group. Lung cancer was detected in one patient (9.1%). After an average follow-up period of 11.7 months, four (36.4%) patients were cured, and seven (63.6%) patients showed significant improvements. In the poor-prognosis group, all patients presented with memory deterioration, epileptic seizures, psychiatric disorders, and conscious disturbance; five (62.5%) patients had convulsive status epilepticus, and five (62.5%) patients developed respiratory failure; MRI indicated an involvement of the limbic system in seven (87.5%) cases. Malignant tumors were detected in five (62.5%) patients. After an average follow-up period of 14.8 months, seven (87.5%) patients died and one (12.5%) patient remained dependent in daily life.

Conclusions

The clinical manifestations of anti-GABA-B receptor encephalitis include epileptic seizures, cognitive impairment and psychiatric disorders. Patients with convulsive status epilepticus or respiratory failure have poor outcomes. In anti-GABA-B receptor encephalitis, limbic system involvement is associated with a poor prognosis in and radiological examinations can reflect disease progression. Early diagnosis and appropriate treatment should be highlighted.

Neuronal Surface Antibody Syndrome: A Review of the Characteristics of the Disease and Its Association with Autoantibodies

Several studies have certified that autoantibodies play an important role in the manifestation of neuromuscular diseases. Scientists have discovered specific neuronal tumor antibodies in patients with typical paraneoplastic neurological disorders. But in some clinical cases, it is not useful to cure this disease with common treatments unless the autoantibodies are addressed. In addition, recent studies have shown a close relationship between certain antibodies and neuronal surface proteins in some special cases. These antibodies, which act on the surface of neurons, mainly include voltage-gated calcium channel (VGKC) antibodies. VGKC antibodies are further divided into several types including anti-leucine-rich glioma inactivated 1 (LGI1), anti-contactin-associated protein-like 2 (Caspr2), anti-N-methyl-D-aspartate receptor (NMDAR), anti-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), anti-γ-aminobutyric acid receptor (GABAR), and glycine receptor. For the purpose of this review, cases of clinical studies of autoantibody-associated encephalitis were collected, the key points regarding the pathogenesis were summarized, the clinical manifestation was discussed, and all this information was organized as this review in order to introduce the relationship between autoantibodies and autoimmune encephalitis. Furthermore, it is hoped that it can effectively direct the development of diagnostic and therapeutic approach in the future.

A paraneoplastic limbic encephalitis from an anorectal small cell neuroendocrine carcinoma: a case report

BACKGROUND

Paraneoplastic limbic encephalitis (PLE) is a rare autoimmune neurological syndrome observed in cancer patients. PLE is difficult to diagnose and presents a variable response to treatment, depending on the characteristics of the tumor and neuronal autoantibodies.

CASE PRESENTATION

A 64-year-old, Caucasian, non-smoker man presented with a rapidly developing cognitive impairment, personality change, spatial disorientation, and short-term memory loss associated with anorexia and cervical and inguinal lymph nodes. The ¹⁸F-FDG PET scan documented intensely hypermetabolic lymph nodes, which histologically corresponded to a metastasis from a small cell neuroendocrine carcinoma. The brain MRI revealed a high T2-weighted FLAIR signal of the hippocamps, consisted with a PLE. The presence of anti-neuronal Hu antibodies confirmed the diagnosis. The patient underwent plasmapheresis, associated to a systemic chemotherapy resulting in a partial and temporary improvement of the neurological symptoms. Four cycles of intravenous immunoglobulins were also necessary. After six cures of chemotherapy, the lymph node metastases regressed. However, a new anorectal lesion was detected and was histologically confirmed as a primary small cell neuroendocrine carcinoma, which was treated with concomitant chemoradiotherapy. At the end of this treatment, the patient showed a rapid tumor progression leading to his death.

CONCLUSIONS

This case highlights the rare entity, PLE, which is difficult to diagnose and manage. In addition, this is the first published case of PLE associated with an anorectal small cell neuroendocrine carcinoma, which appeared after completion of systemic chemotherapy.

Clinical characteristics and long-term follow-up of seven cases of anti-GABABR encephalitis in patients of Han Chinese descent

Objective

To improve the diagnosis and treatment of anti-GABAB receptor (anti-GABABR) encephalitis and prevent misdiagnosis or non-diagnosis.

Methods

We retrospectively examined the chief clinical manifestations, auxiliary examination results, treatment strategies, treatment efficacy, and long-term follow-up results of seven consecutive patients with anti-GABABR encephalitis.

Results

Epileptic seizures were the first symptom in 100% of the patients; 85.7% had memory deficit in the hospital, 42.8% had residual symptoms of cognitive impairment at discharge, and 28.6% had cognitive impairment at the end of follow-up; 71.4% of the patients had psychosis in the hospital, 57.1% had residual symptoms of psychosis at discharge, and 14.3% still had psychosis at the end of follow-up. However, the clinical symptoms (psychiatric disorders, cognitive decline) and signs (consciousness disturbance) at onset and after follow-up were not significantly different (P > 0.05). In 71.4% of the patients, anti-GABABR antibody serum levels were higher than those in the cerebrospinal fluid (especially in patients with lung cancer). Magnetic resonance imaging in 71.4% of patients indicated that the marginal lobe demonstrated encephalitis lesions. The average modified Rankin Scale score (2.0 ± 2.31) at follow-up was significantly better than that (3.86 ± 0.90) at the time of admission (P < 0.05).

Conclusion

The clinical characteristics of anti-GABABR encephalitis were refractory epilepsy, psychiatric disorders, and cognitive impairment. Multiple antiepileptic drugs are crucial for the treatment of intractable epilepsy. Clinicians should eliminate the possibility of small-cell lung cancer in patients with high anti-GABABR antibody levels. Early active immunotherapy is effective, and the long-term prognosis is good for patients without tumors.

Encephalitis With Antibodies Against the GABAB Receptor: High Mortality and Risk Factors

Objective: To measure mortality, identify predictors of death and investigate causes of death in patients with anti-gamma-aminobutyric-acid B receptor (anti-GABA_BR) encephalitis.

Methods: Prospective analysis of anti-GABA_BR encephalitis cases diagnosed between June 2013 and August 2018 in West China Hospital of Sichuan University, with assessment of factors associated with mortality.

Results: A total of 28 patients (11 females) with anti-GABA_BR encephalitis were included in this study. After a maximum time of 52 months (median 11 months, range 2–52) of follow-up, 9 (32.1%) patients died, with a median survival time of 6.5 months. Five patients died of tumor progression, one patient died of convulsive status epilepticus, one patient died of septic shock, and two patients died of severe pneumonia. Predictors of death were older age at onset (P = 0.025), presence of a tumor (66.7 vs. 15.8%, P = 0.013), the number of complications (2.6 vs. 1.0, P = 0.009) and deep venous thrombosis (33.3% vs. 0, P = 0.026).

Conclusion: Patients with GABA_BR encephalitis have a high mortality rate within 5 years. Older age at onset, presence a tumor, the number of complications, and deep venous thrombosis are associated with death.

Relevance of Surface Neuronal Protein Autoantibodies as Biomarkers in Seizure-Associated Disorders

The detection of neuronal surface protein autoantibody-related disorders has contributed to several changes in our understanding of central nervous system autoimmunity. The clinical presentation of these disorders may be associated (or not) with tumors, and often patients develop an inexplicable onset of epilepsy, catatonic or autistic features, or memory and cognitive dysfunctions. The autoantigens in such cases have critical roles in synaptic transmission and plasticity, memory function, and process learning. For months, patients with such antibodies may be comatose or encephalopathic and yet completely recover with palliative care and immunotherapies. This paper reviews several targets of neuronal antibodies as biomarkers in seizure disorders, focusing mainly on autoantibodies, which target the extracellular domains of membrane proteins, namely leucine-rich glioma-inactivated-1 (LGI1), contactin-associated protein-like 2 (CASPR2), the N-methyl-D-aspartate receptor (NMDAR), γ-aminobutyric acid receptor-B (GABA_BR), the glycine receptor (GlyR), and a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). In order to restore health status, limit hospitalization, and optimize results, testing these antibodies should be done locally, using internationally certified procedures for a precise and rapid diagnosis, with the possibility of initiating therapy as soon as possible.

Semi-quantitative FDG-PET Analysis Increases the Sensitivity Compared With Visual Analysis in the Diagnosis of Autoimmune Encephalitis

Objective: The purpose of this study is to evaluate the potential diagnostic benefit of SPM-based semi-quantitative FDG-PET analysis in autoimmune encephalitis (AE) compared with visual analysis by experienced neuroradiologists using a larger sample size.

Methods: This observational retrospective case series study was conducted from a tertiary epilepsy center between May 2014 and March 2017. Healthy individuals without any neurologic or psychiatric diseases were recruited as control. We determined brain FDG-PET abnormal glucose metabolism on medial temporal lobe and basal ganglia using semi-quantitative analysis and compared this method with visual analysis at the same time among patients with autoantibody positive AE.

Results: Twenty-eight patients with clinically diagnosed AE and 53 healthy individuals without any neurologic or psychiatric diseases were recruited. On the medial temporal lobe and the basal ganglia, semi-quantitative analysis showed consistency with the visual assessment for whom they had abnormal metabolism by visual assessment. More importantly, 56% patients on medial temporal lobe and 73% patients on the basal ganglia respectively who were not identified by visual inspection can be detected by semi-quantitative analysis, demonstrating the greater sensitivity of semi-quantitative analysis compared with visual assessment.

Significance: This study showed semi-quantitative brain FDG-PET analysis was better than visual analysis in view of observing the abnormal glucose metabolism of patients with autoantibody positive AE. Semi-quantitative FDG-PET analysis appears to be a helpful tool in early diagnosis of patients with AE.

Autoimmune encephalitis with anti-IgLON5 and anti-GABAB-receptor antibodies: A case report

RATIONALE

Anti-IgLON5 disease is a complex neurological illness which is characterized by progressive sleep and movement disorders and defined by specific autoantibodies to IgLON5. We here describe the first case of a patient with coexisting anti-IgLON5 as well as anti-γ-aminobutyric acid B (GABAB)-receptor antibodies and predominant clinical features of anti-IgLON5 disease.

PATIENT CONCERNS

The patient initially presented with subacute symptoms of severe sleep disorder, gait stability, dysarthria, cognitive impairment, depressive episode and hallucinations.

DIAGNOSES

The patient was diagnosed with autoimmune encephalitis, based on clinical features and positive anti-IgLON5 antibodies in serum as well as in cerebrospinal fluid and anti-GABAB-receptor antibodies in serum only.

INTERVENTIONS

Initially, the patient was treated with high dosages of methylprednisolone and subsequently with plasmapheresis. Due to the lack of clinical improvement immunosuppressive treatment with intravenous cyclophosphamide was initiated.

OUTCOMES

Following the first year of cyclophosphamide treatment, neurological examination revealed an improvement in gait instability, visual and acoustic hallucinations and sleep disorder.

LESSONS

The case report demonstrates that anti-IgLON5 and anti-GABAB-receptor antibodies can coexist in the same patient whereas clinical leading symptoms are determined by those antibodies that were tested positive in cerebrospinal fluid.

Clinical characteristics and factors associated with short-term prognosis in adult patients with autoimmune encephalitis of non-neoplastic etiology

BACKGROUND

Reports that autoimmune encephalitis (AE) is associated with antibodies have increased; however, little is known about the distribution of clinical symptoms, imaging changes, and prognostic factors in patients with AE of non-neoplastic etiology. Accordingly, we evaluated the clinical characteristics and factors associated with short-term prognosis.

METHODS

From January 2016 to June 2018, 31 adult patients were diagnosed with AE of non-neoplastic etiology at Shengjing Hospital of China Medical University and their demographic and clinical characteristics were abstracted. Factors affecting disease severity and predictors of prognosis were analyzed.

RESULTS

Among 31 patients, 19 had anti-NMDAR, 5 had anti-GABABR, and 7 had anti-LGI1 antibody encephalitis. Status epilepticus, ataxia, and cognitive dysfunction were the most common neurological symptoms. Deep white matter (DWM) abnormalities were the most common changes observed on MRI. Logistic regression analysis indicated that conscious disturbance (odds ratio = 11.67, 95%, confidence interval 2.13-64.04; p = 0.005) is an independent factor associated with poor prognosis in AE.

CONCLUSION

The clinical manifestations of AE are diverse; status epilepticus, ataxia, and cognitive dysfunction are most common. The DWM of the brain, rather than the limbic lobe system, was most prone to MR signal abnormalities. Conscious disturbance may be an important predictor of poor short-term prognosis in patients with AE of non-neoplastic etiology.

Autoantibodies and Psychosis

Research into antibody-mediated disease, in response to immune dysfunction or to tumour development, has rapidly expanded in recent years. Antibodies binding to neuroreceptors can cause psychiatric features, including psychosis, in a minority of patients as well as neurological features. The responsiveness of some of these cases to immunotherapy supports the hypothesis that antibody-associated mechanisms play a role in the pathogenesis of psychotic diseases. The purpose of this chapter is to review autoantibodies that are most likely to be relevant for patients with psychotic symptoms. Herein, we describe receptor structure and mechanism of action, clinical and psychiatric features for the growing number of neuronal surface antibodies, including those to the N-methyl-D-aspartate (NMDA) receptor. The identification of a subgroup of patients with psychiatric features having antibody-mediated disease highlights the importance of considering the diagnosis, particularly in those patients presenting with a first episode of psychosis.

Autoimmune epilepsy: findings on MRI and FDG-PET

Autoimmune epilepsy (AE) is becoming increasingly recognized as a potentially reversible cause of frequent or medically intractable seizures and cognitive deterioration. We describe various presentations of autoimmune encephalopathy which have specifically presented with seizure and describe reported imaging findings. This is organized as a review of the more common autoantibodies which can specifically precipitate seizure according to the intracellular or extracellular location of the targeted antigen. For each antibody, we illustrate their pathophysiology, characteristic clinical presentations with typical effective treatments and prognoses and imaging findings on MRI and PET/CT exams. Parenchymal involvement is variable with the limbic structures typically affected; however, non-limbic cortex, cerebellum, brainstem and basal ganglia can also be involved. In the acute setting, affected regions typically demonstrate T₂ hyperintensity with mild mass effect from edema and increased ¹⁸F-fludeoxyglucose uptake. Chronically involved parenchyma will often undergo atrophy and demonstrate decreased metabolism; mesial temporal sclerosis is often the end result when the limbic system is involved. Without treatment, long-term effects from AE range from ongoing cognitive dysfunction and refractory seizures to death. Familiarity with AE may prompt appropriate antibody screening, particularly in cases of refractory seizure disorders. Early investigation and proper management of AE cases may help to prevent parenchymal and neurologic deterioration in these patients.

Paraneoplastic limbic encephalitis associated with lung cancer

Paraneoplastic limbic encephalitis (PLE) is a rare autoimmune neurological syndrome observed in lung cancer patients. We retrospectively investigated the clinical characteristics, treatment responses, and prognoses in 16 PLE patients who were subsequently diagnosed with lung cancer. Fifteen patients initially presented with disturbance of consciousness, 13 with disorientation, and 12 with seizures. Thirteen patients had autoantibodies, including eight with gamma aminobutyric acid B receptor (GABABR) antibodies and eight with Hu antibodies. PET-CT revealed lung neoplasms in 13 patients, nine of whom exhibited abnormal metabolic activity in the temporal lobe and hippocampus. Fifteen cases were confirmed as limited-stage small cell lung cancer and one as stage IV large cell neuroendocrine carcinoma. Eleven patients received immunomodulatory therapy, and four showed neurological improvement, who all had antibodies against GABABR. Fifteen patients received chemotherapy, of which 14 maintained or improved their PLE status. The overall cancer response rate was 75%, and two-year overall survival was 74.7%. Our results suggest patients with GABAB encephalitis might respond better to immunotherapy than the classical PLE patients with anti-Hu antibodies. Anti-cancer treatment could further improve neurological symptoms. Lung cancer patients with PLE, especially those in limited stage, might have better outcome due to earlier diagnosis and prompt anti-cancer treatment.

Gamma-aminobutyric acid-B limbic encephalitis and asystolic cardiac arrest: a case report

Background

Gamma-aminobutyric acid-B receptor autoantibodies are becoming an increasingly recognized contributor to the spectrum of autoimmune limbic encephalitis. They are classically associated with seizures and behavioral disturbance, and may coexist with other autoantibodies. Many are paraneoplastic, most commonly associated with small cell lung cancer. Until now there have been no reports of cardiac dysrhythmias in these patients.

Case presentation

A 65-year-old Caucasian man presented with multiple seizures, dysarthria and behavioral disturbance of unclear etiology, with associated asystolic cardiac arrest. Antibody testing showed anti-Gamma-aminobutyric acid-B receptor and anti-Hu antibodies in serum and Gamma-aminobutyric acid-B receptor autoantibodies in cerebrospinal fluid. The diagnosis of small cell lung cancer was subsequently made after lung biopsy, and the patient showed improvement with chemotherapy and intravenous immunoglobulin.

Conclusions

We present the case of a patient with Gamma-aminobutyric acid-B receptor limbic encephalitis associated with asystolic cardiac arrest, an association not previously described. This case illustrates how difficult it is to make the diagnosis on clinical grounds alone. We therefore propose more routine antibody testing in patients with similar symptomatology who remain undifferentiated after initial workup. We also recommend that in the acute setting, patients with Gamma-aminobutyric acid-B receptor encephalitis should receive cardiac monitoring, as further research is required to clarify its possible link with cardiac dysrhythmias.

Encephalitis with antibodies against the GABAB receptor: seizures as the most common presentation at admission

OBJECTIVE

Autoimmune encephalitis associated with antibodies against gamma-aminobutyric-acid B receptor (GABA_BR) has not been described in detail in Chinese patients.

METHODS

Patients with anti-GABA_BR encephalitis treated between January 2013 and December 2015 were analyzed in terms of clinical characteristics, laboratory findings, tumor presence, autoantibody patterns, treatment response and outcomes.

RESULTS

Eleven patients were identified (male, N = 8; female, N = 3), with the median age of 51 years. All patients presented with seizures (N = 11; 100%), and they were given anti-epileptic drugs and first-line immunotherapy to address the disease. Seizures always accompanied by limbic manifestations (N = 10; 90.9%). Extralimbic manifestations were present in 4 patients (N = 4; 36.4%). MRI Brain abnormality with increased medio-temporal lobe T2/FLAIR signal were present in 2 patients (N = 2; 18.2%), and epileptiform epileptiform activity on electroencephalography were observed in 2 patients (N = 2; 18.2%). Small-cell lung cancer was histologically confirmed in 3 patients (N = 3; 27.3%). Seven patients showed good outcomes (mRS 1-2; N = 7; 63.6%), one patient showed poor neurological status with minimal changes (mRS 4; N = 1; 9.1%), and three patients died during follow-up (mRS = 6; N = 3; 27.3%). Outcomes were correlated with age-of-onset, and were worse among older patients (P = 0.0112).

CONCLUSION

Anti-GABA_BR encephalitis is a potentially treatable disorder involving seizures as the most predominant presentation at admission. It should be considered as a possible diagnosis in middle-aged and older patients with refractory new-onset epilepsy.