BACKGROUND AND PURPOSE:The amygdala plays a key role in the pathophysiology of autoimmune limbic encephalitis (ALE), contributing to epileptic seizures and neuropsychiatric symptoms. While no study has examined microstructural changes in individual amygdala nuclei in ALE, we used the T1-weighted/T2-weighted (T1w/T2w) ratio to explore amygdalar pathology and its associations with clinical manifestations, including epilepsy and neuropsychiatric symptoms. METHODS:This single-center study examined 57 patients diagnosed with ALE and 16 healthy controls (HC). Patients underwent a comprehensive assessment that included clinical, electroencephalogram (EEG), magnetic resonance imaging (MRI), and neuropsychological assessments. Patients were stratified by epileptic focus based on long-term EEG. T1w/T2w ratio and volumetric measures of the amygdala and its nuclei were analyzed and correlated with epileptic focus and neuropsychiatric outcomes. RESULTS:EEG revealed 26 left temporal, 26 bitemporal, and five right temporal epileptic foci. The T1w/T2w ratio in the left amygdala was markedly reduced in patients with left temporal (p = 0.013) and bitemporal (p = 0.018) epileptic foci compared to HC. This reduction was most pronounced in the left basolateral complex (p = 0.011). Whereas amygdalar volumes were similar between patients and HC, exploratory analyses showed an increased volume of the left lateral nucleus in left temporal ALE (p = 0.036). Furthermore, we found no correlations between MRI measures and neuropsychiatric scores. CONCLUSION:Our findings indicate that the basolateral complex of the amygdala is preferentially affected in ALE, suggesting a region-specific vulnerability to autoimmune-mediated inflammation. T1w/T2w ratio alterations reflect the epileptogenic focus and may serve as a clinically accessible, noninvasive biomarker for early diagnosis and treatment monitoring in ALE.

Seizure freedom represents a clinically meaningful outcome in autoimmune limbic encephalitis (ALE). Rituximab (RTX) is commonly used, but the factors associated with seizure outcomes remain unclear. We conducted a retrospective single-center cohort study including 107 adults with ALE and seizures treated between 2005 and 2024. Patients were stratified by RTX treatment, treatment timing, cerebrospinal fluid (CSF) findings, and seizure outcome. The primary endpoint was seizure freedom for ≥12 months. Overall, 72/107 patients (70.6%) achieved seizure freedom, including 18 RTX-treated patients. Earlier RTX initiation (< 12 months) was numerically associated with higher seizure freedom rates than later treatment (77.8% vs. 37.5%). In RTX-treated patients, positive CSF immune findings were associated with seizure freedom (100% vs. 62.5%). Combining early RTX initiation and positive CSF findings was associated with increased odds of seizure freedom. In multivariable analysis, RTX treatment was not independently associated with seizure freedom. These exploratory findings require prospective validation.

BACKGROUND:Autoimmune encephalitis (AIE) is a disabling inflammatory condition of the brain deemed to be due to a dysregulated immune response. Viral infections and malignancies together with certain genetic polymorphisms are thought to contribute to the pathogenesis of AIE, yet the exact mechanisms remain insufficiently understood. Diagnosis of AIE currently relies on clinical consensus criteria. However, diagnostic workup can be challenging in some cases, potentially delaying treatment initiation associated with poor clinical outcomes. This study aims to investigate the systemic and intrathecal immune cell profiles of AIE in comparison to viral meningoencephalitis (VME) as a clinically relevant differential diagnosis and evaluate its diagnostic and therapeutic potential. METHODS:97 mainly treatment-naïve AIE patients, 47 patients with VME, and 109 somatic symptom disorder (SD) controls were included. Analysis of peripheral blood (PB) and cerebrospinal fluid (CSF) immune cell profiles was performed using multidimensional flow cytometry (mFC) in combination with novel computational approaches. RESULTS:We were able to identify alterations in the adaptive B and T cell-mediated immune response in AIE compared to SD controls which correspond to respective changes in the brain parenchyma. AIE and VME exhibit similar patterns of adaptive B and T cell responses and differ in pattern of innate immunity especially NK cells. MFC together with routine CSF parameters can differentiate AIE from VME and SD controls implying diagnostic potential. CONCLUSION:AIE is characterized by a B and T cell-mediated systemic and intrathecal immune-cell signature which corresponds to changes reported in the brain parenchyma providing insights into immunopathogenesis. Differences between AIE and VME were most prominent for the innate immune response indicating a potential role of NK cells in the pathogenesis of autoimmunity. Our data provides evidence that mFC could be a novel complementary approach to the diagnosis of AIE with diagnostic, therapeutic, and prognostic implications.

Autoimmune limbic encephalitis is an inflammatory condition confined to the limbic system of the brain that is deemed to be due to a dysregulated immune response. However, the exact pathophysiological mechanisms remain elusive. Diagnosis of autoimmune limbic encephalitis currently relies on clinical consensus criteria. However, diagnostic workup can be challenging, potentially delaying treatment initiation associated with poor clinical outcomes. We retrospectively identified 640 patients (81 autoimmune limbic encephalitis, 148 relapsing-remitting multiple sclerosis, 197 Alzheimer's disease, 67 frontotemporal dementia, 37 temporal lobe epilepsy with hippocampal sclerosis and 110 somatic symptom disorder patients). Applying multidimensional flow-cytometry together with novel computational approaches, we analysed the peripheral blood and cerebrospinal fluid immune cell profiles at different disease stages and performed correlations with clinical parameters (i.e. neuropsychological performance, EEG and MRI). We were able to identify a shared immune signature of autoimmune limbic encephalitis showing similarities in adaptive B and T cell response with other inflammatory central nervous system diseases and in T cell patterns with neurodegenerative disorders. Antibody-negative autoimmune limbic encephalitis showed a pronounced T cell response in peripheral blood similar to temporal lobe epilepsy and hippocampal sclerosis and neurodegenerative disorders differentiating from antibody-positive autoimmune limbic encephalitis and classical inflammatory central nervous system diseases with regard to B and plasma cell response. Longitudinal immune cell phenotyping in autoimmune limbic encephalitis revealed dynamic changes over time mainly affecting the innate, B and plasma cell compartment. Correlation analysis indicated associations between the baseline immune cell profile, especially lymphocytes, and neuropsychological performance, as well as EEG and MRI abnormalities. Applying novel computational approaches, we found that multidimensional flow cytometry together with routine CSF parameters could reliably distinguish autoimmune limbic encephalitis from controls and clinical differential diagnoses. Incorporation of multidimensional flow cytometry parameters showed superior discriminatory ability compared with CSF routine parameters alone. Taken together, autoimmune limbic encephalitis is characterized by a B and T cell dominated intrathecal immune-cell signature corresponding to changes reported in the brain parenchyma and showing similarities with classical inflammatory central nervous system diseases and neurodegenerative disorders. Incorporating clinical parameters and applying novel computational approaches, we could show that multidimensional flow cytometry might be a beneficial complement to the established diagnostic workup of autoimmune limbic encephalitis promoting early diagnosis and facilitating outcome prediction to enhance individualized treatment regimes.

BACKGROUND:Tuberous sclerosis (TSC) is characterised by the formation of benign tumours across various organs, particularly in the central nervous system (CNS), where they can lead to epilepsy and neurodevelopmental disorders. TSC results from variants in either TSC1 or TSC2 genes, leading to hyperactivation of the mTORC1 pathway, which plays a pivotal role in regulating cell growth and survival. While the influence of mTOR on immune function has been extensively investigated, our understanding of the composition of immune cells in TSC patients remains limited. OBJECTIVE:Blood immune cell profiles from healthy controls, epilepsy patients, and TSC patients (with or without mTOR inhibitor therapy) were collected and analyzed via flow cytometry in a multicenter study. RESULTS:Between 12/2020 and 12/2023, 47 blood samples (mean age: 21 years, range 1-52, 72.3 % female) were analyzed via flow cytometry. Overall, we could not observe a unique immune cell profile between the subgroups as a potential distinguishing feature. However, a few cell populations (T cells, CD8+ T cells) seem to shift in patients with epilepsy (independent of TSC diagnosis) or those receiving mTOR inhibitor therapy (B cells, plasma cells) compared with healthy controls. CONCLUSION:The overall blood immune cell profile is not changed in patients with epilepsy or TSC. However, analysis of subpopulations (T cells and B cells) has revealed changes in immune cell constitution in patients with epilepsy and those receiving mTOR inhibitor therapy.

Importance Anti-IgLON5 disease is an autoimmune encephalopathy that often leads to severe disability or death. The efficacy of immunotherapy remains unknown. Objective To investigate whether early immunotherapy is associated with disability and death in anti-IgLON5 disease. Design, Setting, and Participants This retrospective, multicenter cohort study of patients with anti-IgLON5 disease was conducted from 2014 to 2024, with a median (IQR) follow-up of 66 (33-97) months after disease onset. Data from the German Network for Research on Autoimmune Encephalitis Registry, University Hospital Clinic of Barcelona (Spain), and Erasmus University Medical Center (the Netherlands) were analyzed. Eligibility criteria were clinical features consistent with anti-IgLON5 disease and the presence of IgLON5 antibodies in serum or cerebrospinal fluid. Data were collected by treating physicians using a structured questionnaire. Of 121 patients systematically selected from participating centers and registries, 14 patients were excluded due to insufficient clinical information or withdrawal of consent. Intervention Initiation of immunotherapy based on the treating physician’s decision. Main Outcomes and Measures Clinical disability was assessed using the modified Rankin Scale (mRS) at the most recent follow-up visit and the proportion of patients who died. Results Among 107 patients with anti-IgLON5 disease (46 female [43.0%] and 61 male [57.0%]; median [IQR] age at the time of disease onset, 64 [57-70] years), 25 patients (23.4%) received immunotherapy during the first year of disease onset and 57 patients (53.3%) received it later. Among early treated patients, 9 individuals (36.0%) received intravenous immunoglobulins and 13 individuals (52.0%) received rituximab. A total of 44 patients (41.1%) died, and at least two-thirds of these deaths were related to anti-IgLON5 disease (28 patients [63.6%]). Early immunotherapy was the only modifiable independent factor associated with a lower long-term disability (odds ratio, 0.32; 95% CI, 0.13-0.83; P = .02) and survival (odds ratio, 2.70; 95% CI, 0.99-7.69; P = .047). Only intravenous immunoglobulin started within the first year of disease onset was associated with a lower median (IQR) mRS score at the most recent follow-up (2 [1-2.5] vs 3 [2-6]; P = .005; r = 0.55) and a lower proportion of deaths (0 of 9 patients vs 6 of 16 patients [37.5%]; P = .04) compared with other early immunotherapies despite a similar baseline mRS score. Conclusions and Relevance In this study, early initiation of intravenous immunoglobulins (within the first year of onset) was associated with favorable long-term outcomes and improved survival in anti-IgLON5 disease. Larger prospective studies are needed to validate this finding.

Autoimmune limbic encephalitis (ALE) represents a heterogeneous disease associated with antibodies targeting extracellular (ALEextra) epitopes, intracellular (ALEintra) epitopes, anti-glutamic acid decarboxylase65 ALE (ALEGAD65), and ALE without detectable antibodies (ALEabneg). Combining analysis of cellular parameters, investigated by flow cytometry, and soluble parameters in the blood and cerebrospinal fluid (CSF) from a large cohort of 148 ALE patients (33 ALEextra, 12 ALEintra, 28 ALE-GAD65, 37 ALEabneg) in comparison to paradigmatic examples for neuro-inflammatory (51 relapsing remitting MS patients (RRMS)), and neuro-degenerative (34 Alzheimer’s disease patients (AD)) diseases revealed discrete immune signatures in ALE subgroups. Identification of ALE-subtype specific markers facilitated classification of rare ALE-associated tumors, which may prompt further diagnostic efforts in clinical practice. While ALEintra exhibited features of neuro-inflammation, ALEextra displayed features of neuro-inflammation as well as neuro-degeneration. Moreover, ALEGAD65 and ALEabneg lacked hallmarks of inflammation. This may explain the low efficacy of anti-inflammatory treatment regimens in ALEGAD65 and presumably also ALEabneg.

BACKGROUND:Immune dysregulation is a hallmark of autoimmune diseases of the central nervous system (CNS), characterized by an excessive immune response, and primary CNS tumors (pCNS-tumors) showing a highly immunosuppressive parenchymal microenvironment. METHODS:Aiming to provide novel insights into the pathogenesis of CNS autoimmunity and cerebral tumor immunity, we analyzed the peripheral blood (PB) and cerebrospinal fluid (CSF) of 81 autoimmune limbic encephalitis (ALE), 148 relapsing-remitting multiple sclerosis (RRMS), 33 IDH-wildtype glioma, 9 primary diffuse large B cell lymphoma of the CNS (CNS-DLBCL), and 110 controls by flow cytometry (FC). Additionally, an in-depth immunophenotyping of the PB from an independent cohort of 20 RRMS and 18 IDH-wildtype glioblastoma patients compared to 19 controls was performed by FC combined with unsupervised computational approaches. RESULTS:We identified alterations in peripheral and intrathecal adaptive immunity, mainly affecting the T cell (Tc) but also the B cell (Bc) compartment in ALE, RRMS, and pCNS-tumors compared to controls. ALE, RRMS, and pCNS-tumors featured higher expression of the T cell activation marker HLA-DR, which was even more pronounced in pCNS-tumors than in ALE or RRMS. Glioblastoma patients showed signs of T cell exhaustion that were not visible in RRMS patients. In-depth characterization of the PB revealed differences mainly in the T effector and memory compartment between RRMS and glioblastoma patients and similar alterations in the Bc compartment, including atypical Bc, CD19+CD20- double negative Bc, and plasma cells. PB and CSF mFC together with CSF routine parameters could reliably differentiate ALE and RRMS from pCNS-tumors facilitating early diagnosis and treatment. CONCLUSIONS:ALE, RRMS, and pCNS-tumors show distinct but partially overlapping changes mainly in HLA-DR+ Tc, memory Tc, exhausted Tc, and Bc subsets providing insights into disease pathogenesis. Moreover, mFC shows diagnostic potential facilitating early diagnosis and treatment.

Background Immunoglobulin (Ig) G4 auto-antibodies (Abs) against contactin-associated protein-like 2 (Caspr2), a transmembrane cell adhesion protein expressed in the central and peripheral nervous system, are found in patients with a broad spectrum of neurological symptoms. While the adoptive transfer of Caspr2-specific IgG induces brain pathology in susceptible rodents, the mechanisms by which Caspr2-Abs mediate neuronal dysfunction and translate into clinical syndromes are incompletely understood. Methods We use a systems-level approach combined with high-dimensional characterization of Ab-associated immune features to deeply profile humoral biosignatures in patients with Caspr2-Ab-associated neurological syndromes. Findings We identify two signatures strongly associated with two major clinical phenotypes, limbic encephalitis (LE) and predominant peripheral nerve hyperexcitability without LE (non-LE). Caspr2-IgG Fc-driven pro-inflammatory features, characterized by increased binding affinities for activating Fcγ receptors (FcγRs) and C1q, along with a higher prevalence of IgG1-class Abs, in addition to IgG4, are strongly associated with LE. Both the occurrence of Caspr2-specific IgG1 and higher serum levels of interleukin (IL)-6 and IL-15, along with increased concentrations of biomarkers reflecting neuronal damage and glial cell activation, are associated with poorer clinical outcomes at 1-year follow-up. Conclusions The presence of IgG1 isotypes and Fc-mediated effector functions control the pathogenicity of Caspr2-specific Abs to induce LE. Biologics targeting FcR function might potentially restrain Caspr2-Ab-induced pathology and improve clinical outcomes. Funding This study was funded by a German-French joint research program supported by the German Research Foundation (DFG) and the Agence Nationale de la Recherche (ANR) and by the Interdisciplinary Centre for Clinical Research (IZKF) Münster.

Epilepsy is one of the most common neurological disorders in the world. Common epileptic drugs generally affect ion channels or neurotransmitters and prevent the emergence of seizures. However, up to a third of the patients suffer from drug-resistant epilepsy, and there is an urgent need to develop new therapeutic strategies that go beyond acute antiepileptic (antiseizure) therapies towards therapeutics that also might have effects on chronic epilepsy comorbidities such as cognitive decline and depression. The mitochondrial calcium uniporter (MCU) mediates rapid mitochondrial Ca2+ transport through the inner mitochondrial membrane. Ca2+ influx is essential for mitochondrial functions, but longer elevations of intracellular Ca2+ levels are closely associated with seizure-induced neuronal damage, which are underlying mechanisms of cognitive decline and depression. Using neuronal-specific MCU knockout mice (MCU−/−ΔN), we demonstrate that neuronal MCU deficiency reduced hippocampal excitability in vivo. Furthermore, in vitro analyses of hippocampal glioneuronal cells reveal no change in total Ca2+ levels but differences in intracellular Ca2+ handling. MCU−/−ΔN reduces ROS production, declines metabolic fluxes, and consequently prevents glioneuronal cell death. This effect was also observed under pathological conditions, such as the low magnesium culture model of seizure-like activity or excitotoxic glutamate stimulation, whereby MCU−/−ΔN reduces ROS levels and suppresses Ca2+ overload seen in WT cells. This study highlights the importance of MCU at the interface of Ca2+ handling and metabolism as a mediator of stress-related mitochondrial dysfunction, which indicates the modulation of MCU as a potential target for future antiepileptogenic therapy.

Autoimmune limbic encephalitis (ALE) presents with new-onset mesial temporal lobe seizures, progressive memory disturbance, and other behavioral and cognitive changes. CD8 T cells are considered to play a key role in those cases where autoantibodies (ABs) target intracellular antigens or no ABs were found. Assessment of such patients presents a clinical challenge, and novel noninvasive imaging biomarkers are urgently needed. Here, we demonstrate that visualization of the translocator protein (TSPO) with [18F]DPA-714-PET-MRI reveals pronounced microglia activation and reactive gliosis in the hippocampus and amygdala of patients suspected with CD8 T cell ALE, which correlates with FLAIR-MRI and EEG alterations. Back-translation into a preclinical mouse model of neuronal antigen-specific CD8 T cell-mediated ALE allowed us to corroborate our preliminary clinical findings. These translational data underline the potential of [18F]DPA-714-PET-MRI as a clinical molecular imaging method for the direct assessment of innate immunity in CD8 T cell-mediated ALE.

Abstract Autoimmune neurological syndromes (AINS) with autoantibodies against the 65 kDa isoform of the glutamic acid decarboxylase (GAD65) present with limbic encephalitis, including temporal lobe seizures or epilepsy, cerebellitis with ataxia, and stiff-person-syndrome or overlap forms. Anti-GAD65 autoantibodies are also detected in autoimmune diabetes mellitus, which has a strong genetic susceptibility conferred by human leukocyte antigen (HLA) and non-HLA genomic regions. We investigated the genetic predisposition in patients with anti-GAD65 AINS. We performed a genome-wide association study (GWAS) and an association analysis of the HLA region in a large German cohort of 1214 individuals. These included 167 patients with anti-GAD65 AINS, recruited by the German Network for Research on Autoimmune Encephalitis (GENERATE), and 1047 individuals without neurological or endocrine disease as population-based controls. Predictions of protein expression changes based on GWAS findings were further explored and validated in the CSF proteome of a virtually independent cohort of 10 patients with GAD65-AINS and 10 controls. Our GWAS identified 16 genome-wide significant (P < 5 × 10−8) loci for the susceptibility to anti-GAD65 AINS. The top variant, rs2535288 [P = 4.42 × 10−16, odds ratio (OR) = 0.26, 95% confidence interval (CI) = 0.187–0.358], localized to an intergenic segment in the middle of the HLA class I region. The great majority of variants in these loci (>90%) mapped to non-coding regions of the genome. Over 40% of the variants have known regulatory functions on the expression of 48 genes in disease relevant cells and tissues, mainly CD4+ T cells and the cerebral cortex. The annotation of epigenomic marks suggested specificity for neural and immune cells. A network analysis of the implicated protein-coding genes highlighted the role of protein kinase C beta (PRKCB) and identified an enrichment of numerous biological pathways participating in immunity and neural function. Analysis of the classical HLA alleles and haplotypes showed no genome-wide significant associations. The strongest associations were found for the DQA1*03:01-DQB1*03:02-DRB1*04:01HLA haplotype (P = 4.39 × 10−4, OR = 2.5, 95%CI = 1.499–4.157) and DRB1*04:01 allele (P = 8.3 × 10−5, OR = 2.4, 95%CI = 1.548–3.682) identified in our cohort. As predicted, the CSF proteome showed differential levels of five proteins (HLA-A/B, C4A, ATG4D and NEO1) of expression quantitative trait loci genes from our GWAS in the CSF proteome of anti-GAD65 AINS. These findings suggest a strong genetic predisposition with direct functional implications for immunity and neural function in anti-GAD65 AINS, mainly conferred by genomic regions outside the classical HLA alleles.

Abstract Objective Autoimmune limbic encephalitis (ALE) is characterized by memory impairment, psychiatric symptoms, and epileptic seizures. Though, the neuropsychological profile of ALE is not yet well defined. However, there is some evidence that neuropsychological impairments might exceed those related to the limbic system and that different autoantibodies (AABs) are associated with distinguishable pattern of neuropsychological impairments. We provide a comprehensive presentation of neuropsychological performance of ALE in an immune therapy-naïve sample. Methods We retrospectively analyzed 69 immunotherapy-naïve ALE-patients (26 seropositive—[8 LGI1-, 4 CASPR2-, 2 GABAB-R-, 3 Hu-, 4 GAD65-, 2 Ma2-, 2 unknown antigen, and 1 Yo-AABs] and 43 seronegative patients, mean age 56.0 years [21.9–78.2], mean disease duration 88 weeks [0–572]). Neuropsychological evaluations comprised of the domains memory, attention, praxis, executive functions, language, social cognition, and psychological symptoms. We compared these functions between seronegative −, seropositive patients with AABs against intracellular neural antigens and seropositive patients with AABs against surface membrane neural antigens. Results No effect of AAB group on neuropsychological performance could be detected. Overall, ALE predominantly presents with deficits in long-term memory and memory recognition, autobiographical-episodic memory loss, impairment of emotion recognition, and depressed mood. Furthermore, deficits in praxis of pantomimes and imitations, visuo-construction, and flexibility may occur. Conclusion ALE shows a wide spectrum of neuropsychological impairments, which might exceed the limbic system, with no evidence of differences between AAB groups. Neuropsychological assessment for diagnosing ALE should include long-term memory, memory recognition, autobiographical-episodic memory, emotion recognition, and a detailed investigation of depression.

Background: Temporal lobe seizures are typical symptoms in patients with Autoimmune Limbic Encephalitis (ALE), but also occur in the context of Multiple Sclerosis (MS). We here report a series of four patients with Temporal Lobe Epilepsy (TLE) and MS with features of ALE, focusing on clinical, MRI, EEG and serological findings. Arch Clin Med Case Rep 2021; 5 (6): 941-949 DOI: 10.26502/acmcr.96550438 Archives of Clinical and Medical Case Reports 942 Case series: Four patients diagnosed with relapsingremitting (RR) or primary progressive (PP) forms of MS according to the amended McDonald criteria from 2017 and TLE with additional features of ALE (according the Graus criteria from 2016) were retrospectively identified based on medical records from five German tertiary epilepsy centers. All patients (female) suffered from additional limbic symptoms including memory disturbances and depression. All patients had additional signs of bilateral temporomesial affection on MRI and bilateral temporal slowing and epileptiform activity on EEG. Three patients had CSFspecific oligoclonal bands. In two patients TLE with additional limbic symptoms preceded MS, in one patient MS preceded TLE, and in one patient TLE and MS occurred simultaneously. In all cases, serum and CSF samples were negative for well-characterized neuronal antibodies. Conclusions: Our case series showed that TLE and MS symptoms may resemble the symptoms of ALE. Diagnosing of overlapping MS and ALE could not be made definitively because neither clinical symptoms nor temporomesial MRI findings could help clearly to distinguish between MS and antibody-negative ALE.

Background and Objectives To determine the real-world use of rituximab in autoimmune encephalitis (AE) and to correlate rituximab treatment with the long-term outcome. Methods Patients with NMDA receptor (NMDAR)-AE, leucine-rich glioma-inactivated-1 (LGI1)- AE, contactin-associated protein-like-2 (CASPR2)-AE, or glutamic acid decarboxylase 65 (GAD65) disease from the GErman Network for Research on AuToimmune Encephalitis who had received at least 1 rituximab dose and a control cohort of non–rituximab-treated patients were analyzed retrospectively. Results Of the 358 patients, 163 (46%) received rituximab (NMDAR-AE: 57%, CASPR2-AE: 44%, LGI1-AE: 43%, and GAD65 disease: 37%). Rituximab treatment was initiated significantly earlier in NMDAR- and LGI1-AE (median: 54 and 155 days from disease onset) compared with CASPR2-AE or GAD65 disease (median: 632 and 1,209 days). Modified Rankin Scale (mRS) scores improved significantly in patients with NMDAR-AE, both with and without rituximab treatment. Although being more severely affected at baseline, rituximab-treated patients with NMDAR-AE more frequently reached independent living (mRS score ≤2) (94% vs 88%). In LGI1-AE, rituximab-treated and nontreated patients improved, whereas in CASPR2-AE, only rituximab-treated patients improved significantly. No improvement was observed in patients with GAD65 disease. A significant reduction of the relapse rate was observed in rituximab-treated patients (5% vs 13%). Detection of NMDAR antibodies was significantly associated with mRS score improvement. A favorable outcome was also observed with early treatment initiation. Discussion We provide real-world data on immunosuppressive treatments with a focus on rituximab treatment for patients with AE in Germany. We suggest that early and short-term rituximab therapy might be an effective and safe treatment option in most patients with NMDAR-, LGI1-, and CASPR2-AE. Class of Evidence This study provides Class IV evidence that rituximab is an effective treatment for some types of AE.

Autoimmune limbic encephalitis (ALE) is the most common type of autoimmune encephalitis (AIE). Subacute memory disturbance, temporal lobe seizures, and psychiatric symptoms are clinical hallmarks of the disease. However, little is known on the factors contributing to cognitive functioning in ALE. Hence, we here investigate major determinants of cognitive functioning in ALE. In a retrospective analysis of 102 patients with ALE, we first compared verbal learning capacity, nonverbal learning capacity, and attentional and executive functioning by absence or presence of different types of neural autoantibodies (AABs). Subsequently we established three linear regression models including 63, 38, and 61 patients, respectively to investigate how cognitive functioning in these domains may depend on common markers of ALE such as intrathecal inflammation, blood-cerebrospinal fluid (CSF)-barrier function, mesiotemporal epileptiform discharges and slowing, determined by electroencephalography (EEG) and structural mesiotemporal changes, measured with magnetic resonance imaging (MRI). We also accounted for possible effects of cancer- and immunotherapy and other centrally effective medication. There was no effect of AAB status on cognitive functioning. Although the regression models could not predict verbal and nonverbal learning capacity, structural mesiotemporal neural network alterations on T2-/fluid attenuated inversion recovery (FLAIR)-signal-weighted MRI and mesiotemporal epileptiform discharges or slowing on EEG exerted a significant impact on memory functions. In contrast, the regression model significantly predicted attentional and executive functioning with CSF white blood cell count and centrally effective medication being significant determinants. In this cohort, cognitive functioning in ALE does not depend on the AAB status. Common markers of ALE cannot predict memory functioning that only partially depends on structural and functional alterations of mesiotemporal neural networks. Common markers of ALE significantly predict attentional and executive functioning that is significantly related to centrally effective medication and CSF white blood cell count, which may point toward inflammation affecting brain regions beyond the limbic system.

AbstractObjectiveDirect pathogenic effects of autoantibodies to the 65 kDa isoform of glutamic acid decarboxylase (GAD65) in autoimmune limbic encephalitis (LE) have been questioned due to its intracellular localization. We therefore hypothesized a pathogenic role for T cells.MethodsWe assessed magnet resonance imaging, neuropsychological and peripheral blood, and CSF flow cytometry data of 10 patients with long‐standing GAD65‐LE compared to controls in a cross‐sectional manner. These data were related to each other within the GAD65‐LE group and linked to neuropathological findings in selective hippocampectomy specimen from another two patients. In addition, full‐resolution human leukocyte antigen (HLA) genotyping of all patients was performed.ResultsCompared to controls, no alteration in hippocampal volume but impaired memory function and elevated fractions of activated HLADR+ CD4+ and CD8+ T cells in peripheral blood and cerebrospinal fluid were found. Intrathecal fractions of CD8+ T cells negatively correlated with hippocampal volume and memory function, whereas the opposite was true for CD4+ T cells. Consistently, antigen‐experienced CD8+ T cells expressed increased levels of the cytotoxic effector molecule perforin in peripheral blood, and perforin‐expressing CD8+ T cells were found attached mainly to small interneurons but also to large principal neurons together with wide‐spread hippocampal neurodegeneration. 6/10 LE patients harbored the HLA‐A*02:01 allele known to present the immunodominant GAD65114–123 peptide in humans.InterpretationOur data suggest a pathogenic effect of CD8+ T cells and a regulatory effect of CD4+ T cells in patients with long‐standing GAD65‐LE.

ObjectiveLimbic encephalitis (LE) comprises a spectrum of inflammatory changes in affected brain structures including the presence of autoantibodies and lymphoid cells. However, the potential of distinct lymphocyte subsets alone to elicit key clinicopathological sequelae of LE potentially inducing temporal lobe epilepsy (TLE) with chronic spontaneous seizures and hippocampal sclerosis (HS) is unresolved.MethodsHere, we scrutinized pathogenic consequences emerging from CD8+ T cells targeting hippocampal neurons by recombinant adeno‐associated virus‐mediated expression of the model‐autoantigen ovalbumin (OVA) in CA1 neurons of OT‐I/RAG1−/− mice (termed "OVA‐CD8+ LE model").ResultsViral‐mediated antigen transfer caused dense CD8+ T cell infiltrates confined to the hippocampal formation starting on day 5 after virus transduction. Flow cytometry indicated priming of CD8+ T cells in brain‐draining lymph nodes preceding hippocampal invasion. At the acute model stage, the inflammatory process was accompanied by frequent seizure activity and impairment of hippocampal memory skills. Magnetic resonance imaging scans at day 7 of the OVA‐CD8+ LE model revealed hippocampal edema and blood–brain barrier disruption that converted into atrophy until day 40. CD8+ T cells specifically targeted OVA‐expressing, SIINFEKL‐H‐2Kb–positive CA1 neurons and caused segmental apoptotic neurodegeneration, astrogliosis, and microglial activation. At the chronic model stage, mice exhibited spontaneous recurrent seizures and persisting memory deficits, and the sclerotic hippocampus was populated with CD8+ T cells escorted by NK cells.InterpretationThese data indicate that a CD8+ T‐cell–initiated attack of distinct hippocampal neurons is sufficient to induce LE converting into TLE‐HS. Intriguingly, the role of CD8+ T cells exceeds neurotoxic effects and points to their major pathogenic role in TLE following LE. ANN NEUROL 2021;89:666–685