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

Overview and Diagnostic Approach in Autoimmune Neurology

OBJECTIVE

The field of autoimmune neurology is rapidly evolving. This article reviews the epidemiology and pathophysiology as well as current approaches to clinical and paraclinical assessment, testing paradigms, and general principles of treatment.

LATEST DEVELOPMENTS

Improved recognition of autoimmune diagnoses among patients who have phenotypically diverse, subacute onset neurologic presentations is facilitated by disease-specific antibody biomarker discovery. These antibodies have varying associations with paraneoplastic causation (from no association to greater than 70% positive predictive value), immunotherapy responses, and outcomes. To simplify assessment in an increasingly complex discipline, neurologic phenotype-specific serum and CSF antibody evaluations are recommended. Clinical trials have led to the approval of monoclonal therapies for neuromyelitis optica spectrum disorder (NMOSD) and are underway for N-methyl-d-aspartate (NMDA) receptor and leucine-rich glioma inactivated protein 1 (LGI1) encephalitides.

ESSENTIAL POINTS

Autoimmune neurology is now a mainstream subspecialty, consisting of disorders with diverse presentations detectable using antibody testing of serum and CSF. Early and sustained immunotherapy (eg, corticosteroids, intravenous immunoglobulin [IVIg], plasma exchange) is recommended and may be supplemented by immune suppressants (eg, rituximab or cyclophosphamide) to sustain responses and optimize outcomes.

Psychiatric features in NMDAR and LGI1 antibody-associated autoimmune encephalitis

Patients with autoimmune encephalitis (AE) often developed psychiatric features during the disease course. Many studies focused on the psychiatric characteristic in anti-NMDAR encephalitis (NMDAR-E), but anti-LGI1 encephalitis (LGI1-E) had received less attention regarding the analysis of psychiatric features, and no study compared psychiatric characteristic between these two groups. The clinical data of AE patients (62 NMDAR-E and 20 LGI1-E) who developed psychiatric symptoms were analyzed in this study. In NMDAR-E, the most common higher-level feature was "behavior changes" (60/62, 96.8%) and the lower-level feature "incoherent speech" was observed in 33 patients (33/62, 53.2%), followed by "agitation" (29/62, 46.8%) and "incongruent laughter/crying" (20/62, 32.3%). Similar to NMDAR-E, "behavior changes" was most common in LGI1-E (17/20, 85.0%), but the features of suicidality, eating, and obsessive-compulsive were not reported. The top three lower-level features were visual hallucinations (9/20, 45.0%), incoherent speech (8/20, 40.0%), and mood instability (7/20, 35.0%). The comparative study found that "incongruent laughter/crying", in lower-level features, was more frequently observed in NMDAR-E (32.3% vs. 0%, p = 0.002). Moreover, the Bush Francis Catatonia Rating Scale (BFCRS) assessing the catatonic symptoms in NMDAR-E were higher than LGI1-E, but the 18 item-Brief Psychiatric Rating Scale (BPRS-18) showed no difference in the two groups. In summary, both NMDAR-E and LGI1-E often developed psychiatric symptoms. In contrast with LGI1-E, the psychiatric feature "incongruent laughter/crying" was more frequently associated with NMDAR-E, and catatonic symptoms were more severe in NMDAR-E.

Autoimmune-associated seizure disorders

With the discovery of an expanding number of neural autoantibodies, autoimmune etiologies of seizures have been increasingly recognized. Clinical phenotypes have been identified in association with specific underlying antibodies, allowing an earlier diagnosis. These phenotypes include faciobrachial dystonic seizures with LGI1 encephalitis, neuropsychiatric presentations associated with movement disorders and seizures in NMDA-receptor encephalitis, and chronic temporal lobe epilepsy in GAD65 neurologic autoimmunity. Prompt recognition of these disorders is important, as some of them are highly responsive to immunotherapy. The response to immunotherapy is highest in patients with encephalitis secondary to antibodies targeting cell surface synaptic antigens. However, the response is less effective in conditions involving antibodies binding intracellular antigens or in Rasmussen syndrome, which are predominantly mediated by cytotoxic T-cell processes that are associated with irreversible cellular destruction. Autoimmune encephalitides also may have a paraneoplastic etiology, further emphasizing the importance of recognizing these disorders. Finally, autoimmune processes and responses to novel immunotherapies have been reported in new-onset refractory status epilepticus (NORSE) and febrile infection-related epilepsy syndrome (FIRES), warranting their inclusion in any current review of autoimmune-associated seizure disorders.

NMDAR autoimmune encephalitis and fulminant relapse of multiple sclerosis: a rare overlap syndrome

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune disease that has been rarely associated with AQP4-IgG and MOG-IgG demyelinating diseases, and even more rarely with multiple sclerosis. We present the case of a woman in her 40s with confirmed NMDAR encephalitis and coexistent fulminant relapse of multiple sclerosis treated with alemtuzumab 6 years prior, who had a favourable outcome following treatment with ocrelizumab. We proceed to systematic review of similar reported cases, finding a lower than anticipated prevalence of underlying malignancy compared with isolated NMDAR encephalitis, in this rare overlap syndrome.

Immune-related encephalitis after immune checkpoint inhibitor therapy

BACKGROUND

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment but can trigger immune-related encephalitis. We report one of the largest case series of patients with immune-related encephalitis and review of the literature.

METHODS

Retrospective series of patients with immune-related encephalitis and literature review.

RESULTS

Fourteen patients with cancer treated with ICI (50% combination therapy) developed immune-related encephalitis. Diagnostic testing revealed cerebral spinal fluid (CSF) lymphocytic pleocytosis (85%) and elevated protein (69%), abnormal brain magnetic resonance imaging(MRI) (33%) or brain FDG-PET (25%), electroencephalogram (EEG) abnormalities (30%), and autoantibodies (31%). Encephalitis treatment included: corticosteroids (86%), intravenous immunoglobulin (IVIg) (36%), plasmapheresis (7%), and rituximab (29%). There were no deaths and 12 patients had significant recovery, although long-term complications were observed. All patients discontinued ICI. Longitudinal follow-up demonstrated anti-cancer response to ICI at 3 months (85%) and 6 months post-ICI initiation (77%). A literature review identified 132 patients with immune-related encephalitis. Most were treated with PD-1 inhibitors (18% combination). Common abnormalities included elevated CSF protein (84%) or pleocytosis (77%), abnormal brain MRI (65%), or autoantibodies (47%). Nearly all were treated with corticosteroids, many required additional therapy with IVIg (26%) or rituximab (12%). Most patients had clinical improvement (81%) but a minority (10%) had a clinical relapse after completing corticosteroid taper. ICIs were resumed in 7 patients (5%), with relapse in 3.

CONCLUSIONS AND RELEVANCE

Immune-related encephalitis is treatable and improves with corticosteroids in most cases but may require additional immunosuppression. Re-emergence of encephalitis is rare and does not typically result in adverse outcomes, and this should be considered in neurological immune-related adverse event management guidelines.

NORSE seasonality may vary geographically in adults

The mechanisms causing new onset refractory status epilepticus (NORSE) are often unknown. Recently, a seasonal variation with NORSE peaking during the summer was described in a mixed cohort of adults and children why we here studied the seasonal variation in a Danish status epilepticus (SE) cohort. This retrospective cohort study comprised SE patients aged ≥18 diagnosed and treated 2008-2017 at the Odense University Hospital. Clinical characteristics and seasonality of patients fulfilling the diagnostic criteria for NORSE were compared with patients with refractory SE (RSE) due to other reasons and with the seasonal variation of autoantibodies associated with autoimmune encephalitis in the Danish autoimmune encephalitis register. In this cohort, 26 patients met NORSE criteria. As compared to RSE patients not fulfilling NORSE criteria (n = 152), NORSE patients were more likely to have symptoms of systemic inflammation (C-reactive protein concentrations ≥10 mg/L or fever ≥38°C) at admission; nine fulfilled the criteria for febrile infection related epilepsy syndrome (FIRES). In contrast to the even seasonal distribution of patients with RSE not fulfilling the NORSE criteria, admissions due to NORSE peaked during the winter (46.1%, p = 0.04 as compared to non-NORSE RSE); six out of nine FIRES episodes occurred in the winter season. The seasonal variation was not explained by a seasonal variation of the detection rates of autoantibodies associated with autoimmune encephalitis (incl. NMDAR, LGI1, CASPR2, GABAR, GFAP) in a Danish nationwide register (n = 259). In conclusion, we confirm the seasonality of NORSE in a Danish cohort, however, with a peak during winter suggesting a geographical variation not solely explained by autoimmune encephalitis associated with known autoantibodies. PLAIN LANGUAGE SUMMARY: The study investigated the seasonal patterns of new-onset refractory status epilepticus (NORSE), i.e. severe seizures that occur without an obvious cause and require very intensive treatment. In contrast to the previously observed peak frequency in summer, this Danish study found that NORSE cases peak in winter. Furthermore, the seasonal variation in NORSE cases was not found to be associated with autoimmune encephalitis caused by known autoantibodies. Together with the high rate of patients showing symptoms of systemic inflammation compared to other status epilepticus patients, the data suggest a link between misdirected immune system responses and NORSE. The study can therefore help in the further search for the currently unknown causes of NORSE.

Autoimmune encephalitis in glial fibrillary acidic protein astrocytopathy

Autoimmune encephalitis due to glial fibrillar acidic protein (GFAP) astrocytopathy is a rare cause of subacute neuropsychiatric changes. In this case, a young patient presented with a viral prodrome and meningismus, followed by progressive encephalopathy and movement disorders over the span of 2 weeks. Due to his clinical trajectory, inflammatory cerebrospinal fluid (CSF) analysis, initial normal brain imaging and negative serum autoimmune encephalopathy panel, his initial diagnosis was presumed viral meningoencephalitis. The recurrence and progression of neuropsychiatric symptoms and myoclonus despite antiviral treatment prompted further investigation, inclusive of testing for CSF autoimmune encephalopathy autoantibodies, yielding a clinically meaningful, positive GFAP autoantibody. This case highlights the importance of appropriately testing both serum and CSF autoantibodies when an autoimmune encephalitic process is considered. Through this case, we review the clinical and radiographic manifestations of GFAP astrocytopathy, alongside notable pearls pertaining to this autoantibody syndrome and its management.

Utilization of APE2 and RITE2 scores in autoimmune encephalitis patients with seizures

PURPOSE

Immune-mediated seizures are rare but are increasingly recognized as an etiology of seizures resistant to anti-seizure medications (ASMs). Antibody Prevalence in Epilepsy 2 (APE2) and Response to Immunotherapy in Epilepsy 2 (RITE2) scores were developed recently to identify patients who may be seropositive for serum central nervous system (CNS) specific antibodies (Ab) and may benefit from immunotherapy (Dubey et al. 2018). The goal of this study was to apply APE2 and RITE2 scores to an independent cohort of patients with seizures secondary to autoimmune encephalitis (AE) and to further verify the sensitivity and specificity of the scores.

PRINCIPAL RESULTS

We conducted a retrospective study at Stanford University Hospital between 2008 and 2021 and included patients who had acute seizures and AE using diagnostic criteria from Graus (n = 34 definite AE, 10 probable AE, and 12 possible AE) (Graus et al. 2016). Patients were excluded if they did not have a serum Ab panel investigated or had alternate diagnoses (n = 55). APE2 and RITE2 scores were calculated based on clinical and diagnostic data (n = 56). Serum Ab were positive in 73 % of patients, in which 63 % cases carried CNS specific Ab. An APE2 score ≥ 4 had a sensitivity of 97 % and specificity of 14 % to predict a positive serum CNS specific Ab. A RITE2 score ≥ 7 had a sensitivity of 93 % and specificity of 60 % to predict seizure responsiveness to immunotherapy.

CONCLUSION

APE2 and RITE2 scores had high sensitivities but low specificities to predict seropositivity and seizure responsiveness to immunotherapy in patients with autoimmune encephalitis with seizures.

[Clinical characteristics of seizure-predominant autoimmune encephalitis and utility of anti-neuronal antibody scores for early treatment]

We analyzed 20 patients diagnosed with autoimmune neurological diseases with seizure predominance. In these patients, we examined the usefulness of Antibody Prevalence in Epilepsy and Encephalopathy (APE2) score and Antibodies Contributing to Focal Epilepsy Signs and Symptoms (ACES) score in autoimmune encephalitis (AE) for facilitating early treatment. APE2 score was positive in 19 of 20 patients. ACES score was positive in 15 of 20 patients, and 4 of 5 of the patients with negative ACES score did not have AE. Comprehensive assessment including the use of the above scores is desirable in the early stage of AE.

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

AIM

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

METHODS

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

RESULTS

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

INTERPRETATION

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

Improving Early Recognition of Treatment-Responsive Causes of Rapidly Progressive Dementia: The STAM3 P Score

OBJECTIVE

To improve the timely recognition of patients with treatment-responsive causes of rapidly progressive dementia (RPD).

METHODS

A total of 226 adult patients with suspected RPD were enrolled in a prospective observational study and followed for up to 2 years. Diseases associated with RPD were characterized as potentially treatment-responsive or non-responsive, referencing clinical literature. Disease progression was measured using Clinical Dementia Rating® Sum-of-Box scores. Clinical and paraclinical features associated with treatment responsiveness were assessed using multivariable logistic regression. Findings informed the development of a clinical criterion optimized to recognize patients with potentially treatment-responsive causes of RPD early in the diagnostic evaluation.

RESULTS

A total of 155 patients met defined RPD criteria, of whom 86 patients (55.5%) had potentially treatment-responsive causes. The median (range) age-at-symptom onset in patients with RPD was 68.9 years (range 22.0-90.7 years), with a similar number of men and women. Seizures, tumor (disease-associated), magnetic resonance imaging suggestive of autoimmune encephalitis, mania, movement abnormalities, and pleocytosis (≥10 cells/mm3 ) in cerebrospinal fluid at presentation were independently associated with treatment-responsive causes of RPD after controlling for age and sex. Those features at presentation, as well as age-at-symptom onset <50 years (ie, STAM3 P), captured 82 of 86 (95.3%) cases of treatment-responsive RPD. The presence of ≥3 STAM3 P features had a positive predictive value of 100%.

INTERPRETATION

Selected features at presentation reliably identified patients with potentially treatment-responsive causes of RPD. Adaptation of the STAM3 P screening score in clinical practice may minimize diagnostic delays and missed opportunities for treatment in patients with suspected RPD. ANN NEUROL 2024;95:237-248.

Autoimmune and paraneoplastic seizures

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

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

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

Anti-NMDA receptor encephalitis presenting as a progression of disease in a patient with underlying congenital leukodystrophy: Case report

Anti-NMDA Receptor (NMDAR) Encephalitis (NMDARE) is an autoimmune disorder that is often debilitating and difficult to diagnose. Patients, especially those with underlying neuropsychiatric disorders, may experience delayed or misdiagnosis of NMDARE. Here, we report on a patient with known congenital leukodystrophy (CLD) and epilepsy with a challenging diagnosis of NMDARE. The patient first presented with progressive behavior changes and seizure-like episodes. Initial workup, including video EEG and brain MRI, were mostly unremarkable, and the patient's symptoms were resistant to treatment with multiple anti-epileptic drugs. Given the patient's complicated clinical history, his presentation was initially thought of as progression or exacerbation of his chronic disease. With continued lack of improvement, autoimmune encephalitis was considered. The patient was started on immunotherapy and autoimmune encephalitis panels were sent, which came back positive. He continued to improve over the next weeks and months. Despite a growing body of literature, our knowledge on confirmed risk factors for NMDAR remains limited outside of young age, ovarian teratomas, and herpes encephalitis. We know that maintenance of the blood brain barrier is key to preventing autoimmune disorders of the central nervous system (CNS), and multiple congenital leukodystrophies exhibit pathology in the neurovascular unit. This is the first described case of anti-NMDA receptor encephalitis in a patient with an underlying congenital leukodystrophy, which may reflect an underreported NMDAR encephalitis risk factor. With limited known risk factors and time to diagnosis and treatment so important, this case may reflect an important and underreported risk factor for NMDAR.

[Autoimmune encephalitis: psychiatric aspects]

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

Validation of different predictive scoring scales in patients with new-onset epileptic seizures or epilepsy related to neuronal surface antibody-mediated autoimmune encephalitis

OBJECTIVE

To validate the different predictive scoring scales in the Chinese population with new-onset epileptic seizures or epilepsy of unknown etiology related to neuronal surface antibody (Ab)-mediated autoimmune encephalitis (AE).

METHODS

We retrospectively reviewed the charts of 174 consecutive patients from October 2018 to December 2022, whose serum and cerebrospinal fluid samples were tested for neuronal surface Abs. The antibody prevalence in epilepsy and encephalopathy (APE2), antibodies contributing to focal epilepsy signs and symptoms (ACES), "obvious" indications for neural antibody testing in epilepsy or seizures (ONES) checklist, and the combinations were used to validate the predictive models of neuronal surface Ab-mediated AE.

RESULTS

A total of 139 patients with new-onset epileptic seizures or epilepsy of unknown etiology were enrolled. Abs were detected in 37 patients (26.6%). The APE2/ONES reflex score had the highest sensitivity (89.2%) and lowest specificity (41.7%). The ACES score had the lowest sensitivity (67.5%) and highest specificity (64.7%). Variations in the performance were observed in the different types of AE. 100% of patients with anti-γ-aminobutyric acid B-B receptor encephalitis were predicted by ONES, APE2/ONES reflex, and ACES/ONES reflex scores. Only 75% of patients with anti-N-methyl-D-aspartate receptor encephalitis were predicted by the APE2/ONES and ACES/ONES reflex scores.

CONCLUSION

Our study was the first to validate various predictive scoring scales in the Chinese cohort of patients with new-onset epileptic seizures or epilepsy of unknown etiology related to neuronal surface Ab-mediated AE. Based upon clinical suspicion, more than one scoring scale should be performed to predict the chance of AE in those patients.

Investigation of the presence of specific neural antibodies in dogs with epilepsy or dyskinesia using murine and human assays

BACKGROUND

Autoimmune mechanisms represent a novel category for causes of seizures and epilepsies in humans, and LGI1-antibody associated limbic encephalitis occurs in cats.

HYPOTHESIS/OBJECTIVES

To investigate the presence of neural antibodies in dogs with epilepsy or dyskinesia of unknown cause using human and murine assays modified for use in dogs.

ANIMALS

Fifty-eight dogs with epilepsy of unknown cause or suspected dyskinesia and 57 control dogs.

METHODS

Serum and CSF samples were collected prospectively as part of the diagnostic work-up. Clinical data including onset and seizure/episode type were retrieved from the medical records. Screening for neural antibodies was done with cell-based assays transfected with human genes for typical autoimmune encephalitis antigens and tissue-based immunofluorescence assays on mouse hippocampus slices in serum and CSF samples from affected dogs and controls. The commercial human und murine assays were modified with canine-specific secondary antibody. Positive controls were from human samples.

RESULTS

The commercial assays used in this study did not provide unequivocal evidence for presence of neural antibodies in dogs including one dog with histopathologically proven limbic encephalitis. Low titer IgLON5 antibodies were present in serum from one dog from the epilepsy/dyskinesia group and in one dog from the control group.

CONCLUSION AND CLINICAL IMPORTANCE

Specific neural antibodies were not detected using mouse and human target antigens in dogs with epilepsy and dyskinesia of unknown origin. These findings emphasize the need for canine-specific assays and the importance of control groups.

GAD65 Antibody-Associated Epilepsy

Autoimmune processes are an increasingly recognized cause of seizures. Antibodies against neuronal surface antigens are implicated in the development of acute symptomatic seizures secondary to autoimmune encephalitis, whereas antibodies against intracellular antigens (anti-glutamic acid decarboxylase (GAD) and onconeural antibodies) are found in cases of autoimmune-associated epilepsy (AAE). AAE is described as isolated drug-resistant epilepsy without any specific magnetic resonance imaging (MRI) or cerebrospinal fluid changes and with a very limited response to immunotherapy. We present a clinical case and a literature review on autoimmune-associated epilepsy to increase awareness of this disease and illustrate its complexity. This is a clinical case of a female with a history of refractory focal epilepsy. The patient had been given several trials of multiple antiepileptic drugs and their combinations without any clear effect. Multiple evaluations including brain MRI, PET, and interictal and ictal electroencephalograms were performed. An APE2 score was calculated with a result of 4 and, in the presence of anti-GAD65 antibodies in the serum, the diagnosis of AAE was confirmed. There was no effect after five sessions of plasma exchange; however, after a course of intravenous immunoglobulin, a positive but temporary clinical effect was noticed: anti-GAD65 levels initially decreased but rebounded to previous levels 6 months later.

Immune Mechanisms in Epileptogenesis: Update on Diagnosis and Treatment of Autoimmune Epilepsy Syndromes

Seizures and epilepsy can result from various aetiologies, yet the underlying cause of several epileptic syndromes remains unclear. In that regard, autoimmune-mediated pathophysiological mechanisms have been gaining attention in the past years and were included as one of the six aetiologies of seizures in the most recent classification of the International League Against Epilepsy. The increasing number of anti-neuronal antibodies identified in patients with encephalitic disorders has contributed to the establishment of an immune-mediated pathophysiology in many cases of unclear aetiology of epileptic syndromes. Yet only a small number of patients with autoimmune encephalitis develop epilepsy in the proper sense where the brain transforms into a state where it will acquire the enduring propensity to produce seizures if it is not hindered by interventions. Hence, the term autoimmune epilepsy is often wrongfully used in the context of autoimmune encephalitis since most of the seizures are acute encephalitis-associated and will abate as soon as the encephalitis is in remission. Given the overlapping clinical presentation of immune-mediated seizures originating from different aetiologies, a clear distinction among the aetiological entities is crucial when it comes to discussing pathophysiological mechanisms, therapeutic options, and long-term prognosis of patients. Moreover, a rapid and accurate identification of patients with immune-mediated epilepsy syndromes is required to ensure an early targeted treatment and, thereby, improve clinical outcome. In this article, we review our current understanding of pathogenesis and critically discuss current and potential novel treatment options for seizures and epilepsy syndromes of underlying or suspected immune-mediated origin. We further outline the challenges in proper terminology.

Status Epilepticus in Older Adults: Diagnostic and Treatment Considerations

Status epilepticus (SE) is one of the leading life-threatening neurological emergencies in the elderly population, with significant morbidity and mortality. SE presents unique diagnostic and therapeutic challenges in the older population given overlap with other causes of encephalopathy, complicating diagnosis, and the common occurrence of multiple comorbid diseases complicates treatment. First-line therapy involves the use of rescue benzodiazepine in the form of intravenous lorazepam or diazepam, intramuscular or intranasal midazolam and rectal diazepam. Second-line therapies include parenteral levetiracetam, fosphenytoin, valproate and lacosamide, and underlying comorbidities guide the choice of appropriate medication, while third-line therapies may be influenced by the patient's code status as well as the cause and type of SE. The standard of care for convulsive SE is treatment with an intravenous anesthetic, including midazolam, propofol, ketamine and pentobarbital. There is currently limited evidence guiding appropriate therapy in patients failing third-line therapies. Adjunctive strategies may include immunomodulatory treatments, non-pharmacological strategies such as ketogenic diet, neuromodulation therapies and surgery in select cases. Surrogate decision makers should be updated early and often in refractory episodes of SE and informed of the high morbidity and mortality associated with the disease as well as the high probability of subsequent epilepsy among survivors.

Seizures, Epilepsy, and NORSE Secondary to Autoimmune Encephalitis: A Practical Guide for Clinicians

The most recent International League Against Epilepsy (ILAE) classification has included "immune etiology" along with other well-known causes of epilepsy. This was possible thanks to the progress in detection of pathogenic neural antibodies (Abs) in a subset of patients, and resulted in an increased interest in identifying potentially treatable causes of otherwise refractory seizures. Most autoimmune encephalitides (AE) present with seizures, but only a minority of cases evolve to long-term epilepsy. The risk of epilepsy is higher for patients harboring Abs targeting intracellular antigens (T cell-mediated and mostly paraneoplastic, such as Hu, CV2/CRMP5, Ma2, GAD65 Abs), compared with patients with neuronal surface Abs (antibody-mediated and less frequently paraneoplastic, such as NMDAR, GABAbR, LGI1, CASPR2 Abs). To consider these aspects, conceptual definitions for two entities were provided: acute symptomatic seizures secondary to AE, and autoimmune-associated epilepsy, which reflect the different pathophysiology and prognoses. Through this manuscript, we provide an up-to-date review on the current state of knowledge concerning diagnosis and management of patients with Ab-mediated encephalitis and associated epilepsy. Special emphasis is placed on clinical aspects, such as brain magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) specificities, electroencephalographic (EEG) findings, cancer screening and suggestions for a rational therapeutic approach.

Circulating plasmablasts and follicular helper T-cell subsets are associated with antibody-positive autoimmune epilepsy

Autoimmune epilepsy (AE) is an inflammatory disease of the central nervous system with symptoms that have seizures that are refractory to antiepileptic drugs. Since the diagnosis of AE tends to rely on a limited number of anti-neuronal antibody tests, a more comprehensive analysis of the immune background could achieve better diagnostic accuracy. This study aimed to compare the characteristics of anti-neuronal antibody-positive autoimmune epilepsy (AE/Ab(+)) and antibody-negative suspected autoimmune epilepsy (AE/Ab(-)) groups. A total of 23 patients who met the diagnostic criteria for autoimmune encephalitis with seizures and 11 healthy controls (HC) were enrolled. All patients were comprehensively analyzed for anti-neuronal antibodies; 13 patients were identified in the AE/Ab(+) group and 10 in the AE/Ab(-) group. Differences in clinical characteristics, including laboratory and imaging findings, were evaluated between the groups. In addition, the immunophenotype of peripheral blood mononuclear cells (PBMCs) and CSF mononuclear cells, particularly B cells and circulating Tfh (cTfh) subsets, and multiplex assays of serum and CSF were analyzed using flow cytometry. Patients with AE/Ab(+) did not show any differences in clinical parameters compared to patients with AE/Ab(-). However, the frequency of plasmablasts within PBMCs and CSF in patients with AE/Ab(+) was higher than that in patients with AE/Ab(-) and HC, and the frequency of cTfh17 cells and inducible T-cell co-stimulator (ICOS) expressing cTfh17 cells within cTfh subsets was higher than that in patients with AE/Ab(-). Furthermore, the frequency of ICOS^highcTfh17 cells was positively correlated with that of the unswitched memory B cells. We also found that IL-12, IL-23, IL-6, IL-17A, and IFN-γ levels were elevated in the serum and IL-17A and IL-6 levels were elevated in the CSF of patients with AE/Ab(+). Our findings indicate that patients with AE/Ab(+) showed increased differentiation of B cells and cTfh subsets associated with antibody production. The elevated frequency of plasmablasts and ICOS expressing cTfh17 shift in PBMCs may be indicative of the presence of antibodies in patients with AE.

Evaluation of multiple consensus criteria for autoimmune encephalitis and temporal analysis of symptoms in a pediatric encephalitis cohort

Objective

To evaluate the sensitivity and specificity of current criteria for the diagnosis of autoimmune encephalitis (AE) and the temporal onset of neuropsychiatric symptoms (NP) in a pediatric encephalitis cohort.

Background

Multiple criteria for AE have been developed, including the Graus and pediatric-focused Cellucci consensus criteria, and the Determining Etiology in Encephalitis (DEE) score for patients with encephalitis. Early identification and treatment of AE is crucial to improve outcomes, but this can be difficult given the frequent overlap of clinical presentation between AE and infectious encephalitis (IE).

Design/methods

A retrospective review was conducted of patients seen at our institution from 2000 to 2021 with a final diagnosis of AE or IE. These were narrowed through multiple exclusions to etiology-confirmed IE or antibody-positive/negative AE. Time of onset or results of all symptoms and diagnostics were recorded. Sensitivity and specificity of each criterion under various clinical scenarios were calculated over the first month after initial NP symptom onset.

Results

A total of 23 antibody-positive AE, 9 antibody-negative AE and 23 IE patients were included in final analysis. Under an idealized scenario with rapid initial diagnostic evaluations, the sensitivity for pediatric AE by day 28 after onset of NP symptoms approached 90% for both Cellucci and Graus criteria. Specificity within these 28 days was low without infectious testing results, increasing the greatest with rapid PCR testing and second with infectious antibody testing-reaching ~90% with both. A DEE score of 3 provided a specificity of 100% in identifying IE, but low sensitivity (29%). Symptoms were noted to cluster within several days of onset in IE, but in AE were spread out. Personality/behavioral change, speech change, affective disorder, and sleep disturbance were noted more often in AE, while fever, elevated C-reactive protein or CSF protein, and abnormal MRI-Brain occurred more often in IE.

Conclusion

In this study, we provide the first evaluation of the Cellucci criteria and the first validation of the DEE score in the differentiation of pediatric AE and IE. Further refinement of AE criteria is needed to improve early detection and treatment of pediatric AE.

Late-onset seizures and epilepsy: Electroclinical features suggestive of autoimmune etiology

Introduction

Late-onset epilepsy (LOE) has recently become a topic of intense research. Besides stroke, tumors, and dementia, autoimmune encephalitis (AE) has emerged as another possible cause of recurrent seizures in the elderly, and may account for a proportion of cases of LOE of unknown origin (LOEUO). This 24-h ambulatory electroencephalography (AEEG)-based study compared patients with LOEUO and AE to identify features suggestive of immune-mediated seizures in the elderly.

Materials and methods

We retrospectively reviewed 232 AEEG examinations performed in patients over 55 years with ≥6-month follow-up, and selected 21 subjects with AE and 25 subjects with LOEUO. Clinical charts and AEEG recordings were carefully analyzed.

Results

Twenty-five patients with LOEUO (12 women, mean age at onset 67.9 years) and 21 AE subjects (8 women, mean age at onset 65.7 years) were enrolled. High-frequency seizures were reported in 20/21 AE and 7/25 LOEUO cases (p < 0.00001). Focal aware seizures were more common in AE (14/21 vs. 6/25, p = 0.00058), whereas “isolated” focal-to-bilateral tonic-clonic seizures occurred in 5/25 patients with LOEUO only (p = 0.053). AE subjects reported ictal autonomic manifestations more frequently (p = 0.0033). Three-hundred-seventy and 24 seizures were recorded in 13/21 patients with AE and 3/25 patients with LOEUO, respectively (p = 0.0006). Interictal epileptiform discharges were observed in 70% of both groups, but their sleep activation was more common in AE (p = 0.06).

Conclusion

Our study shows that high-frequency focal seizures with autonomic manifestations should raise the suspicion of AE in the elderly with new-onset seizures. It also highlights the relevant contribution of AEEG, which might reduce the diagnostic delay and provide useful clues to recognize AE.

Factors predicting neuronal surface antibodies in the elderly with new-onset and unknown seizures

Objective

To investigate risk factors of neuronal surface antibodies (NSAbs) and develop a nomogram that could identify patients at the odds of NSAbs among the elderly (aged 60 years or older) with new‐onset seizures of unknown etiology.

Methods

Clinical data for aged ≥60 years diagnosed with new‐onset seizures of unknown etiology were retrospectively reviewed. A nomogram based on multivariable logistic regression was constructed. Model performance of nomogram was evaluated using area under the curve (AUC), calibration curve, decision curve analysis (DCA), and clinical impact curve (CIC). Meanwhile, it was internally validated by bootstrap validation in current cohort.

Results

Of 147 patients included in final analysis, 68 (46.3%) had NSAbs‐mediated encephalitis. Six factors were identified: duration of seizures less than 3 months (OR:14.259; 95% CI: 4.480–45.386), focal‐onset seizures (OR:12.457; 95% CI: 2.710–57.261), psychiatric deficits (OR:10.063; 95% CI: 3.231–31.343), sleep disorders (OR:3.091; 95% CI: 1.011–9.454), hyponatremia (OR:6.252; 95% CI: 1.445–27.043), and medial temporal lobe (MTL) lesions on MRI (OR:4.102; 95% CI: 1.382–12.169). The nomogram had a good discrimination with an AUC of 0.916 and with a corrected AUC of 0.881 after the bootstrapping validation, our model also exhibited a better predictive performance than scoring systems commonly used clinically. Additionally, the calibration curve showed that predicted NSAbs‐positive rates of nomogram were closely aligned with actual observed results. Moreover, the nomogram achieved well on clinical utility by using the DCA and CIC.

Interpretation

Our nomogram may provide a convenient and useful tool for identifying the elderly with new‐onset seizures of unknown etiology who are at risk of NSAbs‐mediated encephalitis, which would allow these patients receive earlier immunotherapy.

"Obvious" indications for Neural antibody testing in Epilepsy or Seizures: The ONES checklist

OBJECTIVE

Numerous predictive scores have been developed to help determine which patients with epilepsy or seizures of unknown etiology should undergo neural antibody testing. However, their diagnostic advantage compared to only performing testing in patients with "obvious" indications (e.g. broader features of autoimmune encephalitis, characteristic seizure semiologies) requires further study. We aimed to develop a checklist that identifies patients who have "obvious" indications for neural antibody testing, and compare its diagnostic performance to predictive scores.

METHODS

We developed the "Obvious" indications for Neural antibody testing in Epilepsy or Seizures (ONES) checklist through literature review. We then retrospectively reviewed patients who underwent neural antibody testing for epilepsy or seizures at our center between March 2019 and January 2021, to determine and compare the sensitivity and specificity of the ONES checklist to the recently-proposed Antibody Prevalence in Epilepsy and Encephalopathy (APE2)/Antibodies Contributing to Focal Epilepsy Signs and Symptoms (ACES) reflex score.

RESULTS

One-hundred-seventy patients who underwent neural antibody testing for epilepsy or seizures were identified. Seventy-four of 170 (43.5%) with a known etiology were excluded from sensitivity/specificity analyses; none had a true-positive neural antibody. Of the 96 patients with an unknown etiology, fourteen (15%) had a true-positive neural antibody. The proportion of false-positives was significantly higher among patients with a known etiology (3/3, 100%) compared to an unknown etiology (2/16, 13%) (P = .01). There was no significant difference of the APE2/ACES reflex score compared to the ONES checklist with regard to sensitivity (93% for both, P > .99) or specificity (71% versus 78%, P = .18) for true-positive neural antibodies.

SIGNIFICANCE

Compared to only performing neural antibody testing in patients with epilepsy or seizures of unknown etiology who have "obvious" indications, predictive scores confer no clear diagnostic advantage. Pre-specified definitions of what constitutes a true-positive neural antibody is required in future studies to avoid false-positives that can confound results.

Immunopsychiatry: An Update on Autoimmune Encephalitis for Neuropsychiatrists

INTRODUCTION

Autoimmune encephalitis (AIE) is a group of immune-mediated inflammatory processes of the brain with marked psychiatric features. Although relatively rare, they might offer difficult differential diagnosis with psychiatric conditions, especially catatonia and psychotic syndromes. Anti-N-methyl-d-aspartate receptor (NMDAR) encephalitis is the most common AIE, presenting with psychiatric syndromes in 90% of cases. The associated psychopathology is complex, pleomorphic and best characterized when there is involvement of a psychiatrist in the assessment.

AREAS COVERED

This text will review the main aspects of AIE to psychiatrists and/or neuropsychiatrists.

EXPERT OPINION

Immune system dysfunction has been implicated in the pathophysiology of psychiatric symptoms and disorders. The use of diagnostic criteria of possible AIE, especially when specific antibodies of AIE are not available, allows early diagnosis and prompt treatment which are associated with better clinical outcomes. The study of the psychiatric aspects of AIE can broaden our knowledge of the underlying mechanisms of various psychiatric manifestations.

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.

Retrospective Evaluation of the Antibody Prevalence in Epilepsy and Encephalopathy (APE2) Score

BACKGROUND

Autoimmune encephalitis (AE) is a rare collection of disorders that present with a diverse and often nebulous set of clinical symptoms. Indiscriminate use of multi-antibody panels decreases their overall utility and predictive value. Application of a standardized scoring system may help reduce the number of specimens that generate misleading or uninformative results.

METHODS

The results of autoimmune encephalopathy, epilepsy, or dementia autoantibody panels performed on serum (n = 251) or cerebrospinal fluid (CSF) (n = 235) specimens from October 9th, 2016 to October 11th, 2019 were collected. Retrospective chart review was performed to calculate the Antibody Prevalence in Epilepsy and Encephalopathy (APE2) score for patients with an antibody above the assay-specific reference interval and to classify results as true or false positive.

RESULTS

Of the 486 specimens, 60 (12.3%) generated positive results for any AE antibody (6 CSF and 54 serum). After removing 2 duplicate specimens collected from a single patient, 10 of the remaining 58 were determined to be true positives and 8 contained neural-specific antibodies. Application of the APE2 score revealed that 89% of all true positives and 86% of specimens with neural-specific antibodies had a score ≥4. In contrast, 76% of false positives, 74% of clinically nonspecific antibodies, and 85% of the negative specimens had an APE2 score <4.

CONCLUSION

The APE2 score can improve the diagnostic utility of autoimmune encephalopathy evaluation panels.

Residual symptoms and long-term outcomes after all-cause autoimmune encephalitis in adults

BACKGROUND AND OBJECTIVES

To evaluate residual symptoms after all-cause autoimmune encephalitis in a real-life outpatient setting and compare long-term outcome measures. A secondary objective was to identify correlates of poor outcomes.

METHODS

We analyzed patients referred to the Neuroimmunology clinic for evaluation of autoimmune encephalitis for whom standardized data were collected. We compared the prevalence of symptoms at the latest follow-up to presentation and calculated symptom improvement rates. We compared the Modified Rankin Scale (mRS) to the Clinical Assessment Scale for Autoimmune Encephalitis (CASE). Non-parametric Wilcoxon rank sum tests and Fisher's exact tests were used to compare clinical attributes between patients with and without poor outcomes.

RESULTS

We evaluated 54 patients from 2017 to 2021 of whom 33 met inclusion criteria (average age 47±20 years, 57% females, 55% seropositive). By latest follow-up, 94% improved compared to presentation but six patients (18%) had poor outcomes as defined by an mRS ≥3. The most common residual symptoms were cognitive and mood dysfunction. The highest improvement rates were in alertness and psychosis while the lowest were in motor function and ataxia. CASE had moderate correlation with mRS (r2 = 0.53 [95%CI:0.23,0.74, p = 0.0015) but it captured more nuances than mRS at both presentation and follow-up. Older age and higher post-treatment CASE score correlated with poor outcomes.

DISCUSSION

Most autoimmune encephalitis patients experience symptom improvement post-treatment. The CASE score was more representative of the wide symptomatic spectrum of autoimmune encephalitis and correlated with poor outcomes. However, CASE did not capture patients with dysautonomia, sleep dysfunction, or death.

Antibody prevalence and immunotherapy response in Chinese patients with epilepsy and encephalopathy scores for patients with different neuronal surface antibodies

Background:

The scale assessment was helpful in predicting the presence of antibodies to autoimmune encephalitis. This study aimed to evaluate the application of antibody prevalence in Chinese patients with epilepsy and encephalopathy (APE2-CHN) and response to immunotherapy in Chinese patients with epilepsy and encephalopathy (RITE2-CHN) for patients with different neuronal surface antibodies.

Methods:

A total of 1365 patients with epileptic seizures as the prominent feature in Xuanwu Hospital, Capital Medical University, from June 2016 to June 2020 were enrolled in our study. Of these, 915 patients with epilepsy of unknown etiology whose serum and/or cerebrospinal fluid samples were examined for autoimmune antibodies were selected. All patients were scored with antibody prevalence in patients with epilepsy and encephalopathy (APE2), response to immunotherapy with epilepsy and encephalopathy (RITE2), APE2-CHN, and RITE2-CHN scores.

Results:

Of the 915 patients, 191 patients were positive for neural-surface specific antibodies (115 N-methyl-D-aspartate receptor (NMDAR) Ab, 47 leucine-rich glioma-inactivated protein 1 (LGI1) Ab, 8 contactin-associated protein 2 (CASPR2) Ab, 4 AMPA2R-Ab, and 11 GABAR-B-Ab; 3 CASPR2-Ab and LGI1-Ab, 2 NMDAR-Ab and CASPR2-Ab, and 1 NMDAR-Ab and myelin-oligodendrocyte glycoprotein [MOG] Ab). The sensitivity and specificity of APE2 ≥4 in predicting the presence of neural-surface specific antibodies in our study were 74.35% and 81.77%, respectively, and the sensitivity and specificity of APE2-CHN ≥4 were 75.92% and 84.53%, respectively. Eight cases had an APE2 score <4 and APE2-CHN score ≥5; all these patients had memory decline as the prominent manifestation. We divided the patients into six groups according to the different antibodies. APE2-CHN scores showed higher sensitivity for the prediction of NMDAR-Ab, but lower sensitivity for LGI1-Ab. A total of 187/191 (97.91%) patients received immunotherapy and 142/191 (74.35%) patients benefited from the treatments. The patients who were positive for LGI1-Ab with RITE2-CHN ≥8 responded well to immunotherapy.

Conclusions:

APE2-CHN had the highest value for predicting the positivity of NMDAR-Ab and RITE2-CHN evaluated the response of immunotherapy for anti-LGI1 encephalitis appropriately. However, RITE2 and RITE2-CHN do not appear to be good predictors of immunotherapy outcomes for patients with specific neuronal-surface antibodies and high APE2-CHN scores are often indicative of a poor response to immunotherapy.

Discerning the Role of Autoimmunity and Autoantibodies in Epilepsy: A Review

Importance

The literature on neural autoantibody positivity in epilepsy has expanded over the last decade, with an increased interest among clinicians in identifying potentially treatable causes of otherwise refractory seizures.

Observations

Prior studies have reported a wide range of neural autoantibody positivity rates among various epilepsy populations, with the highest frequency reported in individuals with focal epilepsy of unknown cause and new-onset seizures. The antibodies in some cases are of uncertain significance, and their presence can cause conundrums regarding therapy.

Conclusions and Relevance

There is likely some role for neural autoantibody assessment in patients with unexplained epilepsy who lack clear evidence of autoimmune encephalitis, but the clinical implications of such testing remain unclear owing to limitations in previous published studies. A framework for study design to bridge the current gaps in knowledge on autoimmune-associated epilepsy is proposed.

Validation of Predictive Models for Autoimmune Encephalitis-Related Antibodies to Cell-Surface Proteins Expressed in Neurons: A Retrospective Study Based in a Hospital

Objective: Autoimmune encephalitis (AE) is a severe but treatable autoimmune disorder that is diagnosed by antibody (Ab) testing. However, it is unrealistic to obtain an early diagnosis in some areas since the Ab status cannot be immediately determined due to time and technology restrictions. In our study, we aimed to validate the Antibody Prevalence in Epilepsy and Encephalopathy (APE²) score among patients diagnosed with possible AE as a predictive model to screen AE patients with antibodies to cell-surface proteins expressed in neurons.

Methods: A total of 180 inpatients were recruited, and antibodies were detected through serological and/or cerebrospinal fluid (CSF) evaluations. The APE² score was used to validate the predictive models of AE with autoantibodies.

Results: The mean APE² score in the Ab-positive cases was 7.25, whereas the mean APE² score in the Ab-negative cases was 3.18 (P < 0.001). The APE² score had a receiver operating characteristic (ROC) area under the curve of 0.924 [P < 0.0001, 95% confidence interval (CI) = 0.875–0.973]. With a cutoff score of 5, the APE² score had the best psychometric properties, with a sensitivity of 0.875 and a specificity of 0.791.

Conclusion: The APE² score is a predictive model for AE with autoantibodies to cell-surface proteins expressed in neurons and was validated and shown to have high sensitivity and specificity in our study. We suggest that such a model should be used in patients with a suspected diagnosis of AE, which could increase the detection rate of Abs, reduce testing costs, and help patients to benefit from treatment quickly.

A Validated Nomogram That Predicts Prognosis of Autoimmune Encephalitis: A Multicenter Study in China

The aim of this retrospective study was to derive and validate a reliable nomogram for predicting prognosis of autoimmune encephalitis (AE). A multi-center retrospective study was conducted in four hospitals in China, using a random split-sample method to allocate 173 patients into either a training (n = 126) or validation (n = 47) dataset. Demographic, radiographic and therapeutic presentation, combined with clinical features were collected. A modified Rankin Scale (mRS) at discharge was the principal outcome variable. A backward-stepwise approach based on the Akaike information criterion was used to test predictors and construct the final, parsimonious model. Multivariable analysis was conducted using logistic regression to develop a prognosis model and validate a nomogram using an independent dataset. The performance of the model was assessed using receiver operating characteristic curves and a Hosmer-Lemeshow test. The final nomogram model considered age, viral prodrome, consciousness impairment, memory dysfunction and autonomic dysfunction as predictors. Model validations displayed a good level of discrimination in the validation set: area under the Receiver operator characteristic curve = 0.72 (95% Confidence Interval: 0.56–0.88), Hosmer–Lemeshow analysis suggesting good calibration (chi-square: 10.33; p = 0.41). The proposed nomogram demonstrated considerable potential for clinical utility in prediction of prognosis in autoimmune encephalitis.

Autoimmune encephalopathies presenting as dementia of subacute onset and rapid progression

The terms autoimmune dementia and autoimmune encephalopathy may be used interchangeably; autoimmune dementia is used here to emphasize its consideration in young-onset dementia, dementia with a subacute onset, and rapidly progressive dementia. Given their potential for reversibility, it is important to distinguish the rare autoimmune dementias from the much more common neurodegenerative dementias. The presence of certain clinical features [e.g. facio-brachial dystonic seizures that accompany anti-leucine-rich-glioma-inactivated-1 (LGI1) encephalitis that can mimic myoclonus] can be a major clue to the diagnosis. When possible, objective assessment of cognition with bedside testing or neuropsychological testing is useful to determine the degree of abnormality and serve as a baseline from which immunotherapy response can be judged. Magnetic resonance imaging (MRI) head and cerebrospinal fluid (CSF) analysis are useful to assess for inflammation that can support an autoimmune etiology. Assessing for neural autoantibody diagnostic biomarkers in serum and CSF in those with suggestive features can help confirm the diagnosis and guide cancer search in paraneoplastic autoimmune dementia. However, broad screening for neural antibodies in elderly patients with an insidious dementia is not recommended. Moreover, there are pitfalls to antibody testing that should be recognized and the high frequency of some antibodies in the general population limit their diagnostic utility [e.g., anti-thyroid peroxidase (TPO) antibodies]. Once the diagnosis is confirmed, both acute and maintenance immunotherapy can be utilized and treatment choice varies depending on the accompanying neural antibody present and the presence or absence of cancer. The target of the neural antibody biomarker may help predict treatment response and prognosis, with antibodies to cell-surface or synaptic antigens more responsive to immunotherapy and yielding a better overall prognosis than those with antibodies to intracellular targets. Neurologists should be aware that autoimmune dementias and encephalopathies are increasingly recognized in novel settings, including post herpes virus encephalitis and following immune-checkpoint inhibitor use.

Clinical features which predict neuronal surface autoantibodies in new-onset focal epilepsy: implications for immunotherapies

OBJECTIVE

To generate a score which clinically identifies surface-directed autoantibodies in adults with new-onset focal epilepsy, and evaluate the value of immunotherapy in this clinical setting.

METHODS

Prospective clinical and autoantibody evaluations in a cohort of 219 consecutive patients with new-onset focal epilepsy.

RESULTS

10.5% (23/219) of people with new-onset focal epilepsy had detectable serum autoantibodies to known or novel cell surface antigenic targets. 9/23 with autoantibodies were diagnosed with encephalitis, by contrast to 0/196 without autoantibodies (p<0.0001). Multivariate analysis identified six features which predicted autoantibody positivity (area under the curve=0.83): age ≥54 years, ictal piloerection, lowered self-reported mood, reduced attention, MRI limbic system changes and the absence of conventional epilepsy risk factors. 11/14 (79%) patients with detectable autoantibodies, but without encephalitis, showed excellent long-term outcomes (modified Rankin Score=0) despite no immunotherapy. These outcomes were superior to those of immunotherapy-treated patients with confirmed autoantibody-mediated encephalitis (p<0.05).

CONCLUSIONS

Seizure semiology, cognitive and mood phenotypes, alongside inflammatory investigation findings, aid the identification of surface autoantibodies among unselected people with new-onset focal epilepsy. The excellent immunotherapy-independent outcomes of autoantibody-positive patients without encephalitis suggests immunotherapy administration should be guided by clinical features of encephalitis, rather than autoantibody positivity. Our findings suggest that, in this cohort, immunotherapy-responsive seizure syndromes with autoantibodies largely fall under the umbrella of autoimmune encephalitis.

Autoimmune encephalitis: proposed recommendations for symptomatic and long-term management

The objective of this paper is to evaluate available evidence for each step in autoimmune encephalitis management and provide expert opinion when evidence is lacking. The paper approaches autoimmune encephalitis as a broad category rather than focusing on individual antibody syndromes. Core authors from the Autoimmune Encephalitis Alliance Clinicians Network reviewed literature and developed the first draft. Where evidence was lacking or controversial, an electronic survey was distributed to all members to solicit individual responses. Sixty-eight members from 17 countries answered the survey. The most popular bridging therapy was oral prednisone taper chosen by 38% of responders while rituximab was the most popular maintenance therapy chosen by 46%. Most responders considered maintenance immunosuppression after a second relapse in patients with neuronal surface antibodies (70%) or seronegative autoimmune encephalitis (61%) as opposed to those with onconeuronal antibodies (29%). Most responders opted to cancer screening for 4 years in patients with neuronal surface antibodies (49%) or limbic encephalitis (46%) as opposed to non-limbic seronegative autoimmune encephalitis (36%). Detailed survey results are presented in the manuscript and a summary of the diagnostic and therapeutic recommendations is presented at the conclusion.

Antibody Prevalence in Epilepsy before Surgery (APES) in drug-resistant focal epilepsy

OBJECTIVE

There is a growing recognition of immune-mediated causes in patients with focal drug-resistant epilepsy (DRE); however, they are not systematically assessed in the pre-surgical diagnostic workup. Early diagnosis and initiation of immunotherapy is associated with a favorable outcome in immune-mediated seizures. Patients with refractory focal epilepsy with neuronal antibodies (Abs) tend to have a worse surgical prognosis when compared to other etiologies.

METHODS

We studied the prevalence of serum Abs in patients ≥18 years of age with DRE of unknown cause before surgery. We proposed and calculated a clinical APES (Antibody Prevalence in Epilepsy before Surgery) score for each subject, which was modified based on Dubey's previously published APE² score. RESULTS`: A total of 335 patients were screened and 86 subjects were included in final analysis. The mean age at the time of recruitment was 44.84 ± 14.86 years, with age at seizure onset 30.89 ± 19.88 years. There were no significant differences among baseline clinical features between retrospective and prospective sub-cohorts. The prevalence of at least one positive Ab was 33.72%, and central nervous system (CNS)-specific Abs was 8.14%. APES score ≥4 showed slightly better overall prediction (area under the curve [AUC]: 0.84 vs 0.74) and higher sensitivity (100% vs 71.4%), with slightly lower but similar specificity (44.3% vs 49.4%), when compared to APE² score ≥4. For subjects who had available positron emission tomography (PET) results and all components of APES score (n = 60), the sensitivity of APES score ≥4 yielded a similar prediction potential with an AUC of 0.80.

SIGNIFICANCE

Our findings provide persuasive evidence that a subset of patients with focal DRE have potentially immune-mediated causes. We propose an APES score to help identify patients who may benefit from a workup for immune etiologies during the pre-surgical evaluation for focal refractory epilepsy with unknown cause.

Brain dysfunction and thyroid antibodies: autoimmune diagnosis and misdiagnosis

Hashimoto encephalopathy, also known as steroid-responsive encephalopathy associated with autoimmune thyroiditis, has been defined by sub-acute onset encephalopathy, with elevated thyroid antibodies, and immunotherapy responsiveness, in the absence of specific neural autoantibodies. We aimed to retrospectively review 144 cases referred with suspected Hashimoto encephalopathy over a 13-year period, and to determine the clinical utility of thyroid antibodies in the course of evaluation of those patients. One hundred and forty-four patients (all thyroid antibody positive) were included; 72% were women. Median age of symptom onset was 44.5 years (range, 10-87). After evaluation of Mayo Clinic, 39 patients (27%) were diagnosed with an autoimmune CNS disorder [autoimmune encephalopathy (36), dementia (2) or epilepsy (1)]. Three of those 39 patients had neural-IgGs detected (high glutamic acid decarboxylase-65, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor-receptor and neural-restricted unclassified antibody), and 36 were seronegative. Diagnoses among the remaining 105 patients (73%) were functional neurological disorder (n = 20), neurodegenerative disorder (n = 18), subjective cognitive complaints (n = 14), chronic pain syndrome (n = 12), primary psychiatric (n = 11), sleep disorder (n = 10), genetic/developmental (n = 8), non-autoimmune seizure disorders (n = 2) and other (n = 10). More patients with autoimmune CNS disorders presented with sub-acute symptom onset (P < 0.001), seizures (P = 0.008), stroke-like episodes (P = 0.007), aphasia (P = 0.04) and ataxia (P = 0.02), and had a prior autoimmune history (P = 0.04). Abnormal brain MRI (P = 0.003), abnormal EEG (P = 0.007) and CSF inflammatory findings (P = 0.002) were also more frequent in the autoimmune CNS patients. Patients with an alternative diagnosis had more depressive symptoms (P = 0.008), anxiety (P = 0.003) and chronic pain (P = 0.002). Thyoperoxidase antibody titre was not different between the groups (median, 312.7 versus 259.4 IU/ml; P = 0.44; normal range, <9 IU/ml). None of the non-autoimmune group and all but three of the CNS autoimmune group (two with insidious dementia presentation, one with seizures only) fulfilled the autoimmune encephalopathy criteria proposed by Graus et al. (A clinical approach to diagnosis of autoimmune encephalitis. Lancet Neurol 2016; 15: 391-404.) (sensitivity, 92%; specificity, 100%). Among patients who received an immunotherapy trial at our institution and had objective post-treatment evaluations, the 16 responders with autoimmune CNS disorders more frequently had inflammatory CSF, compared to 12 non-responders, all eventually given an alternative diagnosis (P = 0.02). In total, 73% of the patients referred with suspected Hashimoto encephalopathy had an alternative non-immune-mediated diagnosis, and more than half had no evidence of a primary neurological disorder. Thyroid antibody prevalence is high in the general population, and does not support a diagnosis of autoimmune encephalopathy in the absence of objective neurological and CNS-specific immunological abnormalities. Thyroid antibody testing is of little value in the contemporary evaluation and diagnosis of autoimmune encephalopathies.

Sleep Disturbances Associated with Neurological Autoimmunity

Associations between sleep disorders and neurological autoimmunity have been notably expanding recently. Potential immune-mediated etiopathogenesis has been proposed for various sleep disorders including narcolepsy, Kleine-Levin syndrome, and Morvan syndrome. Sleep manifestations are also common in various autoimmune neurological syndromes, but may be underestimated as overriding presenting (and potentially dangerous) neurological symptoms often require more urgent attention. Even so, sleep dysfunction has been described with various neural-specific antibody biomarkers, including IgLON5; leucine-rich, glioma-inactivated protein 1 (LGI1); contactin-associated protein 2 (CASPR2); N-methyl-D-aspartate (NMDA)-receptor; Ma2; dipeptidyl-peptidase-like protein-6 (DPPX); alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA-R); anti-neuronal nuclear antibody type-1 (ANNA-1, i.e., Hu); anti-neuronal nuclear antibody type-2 (ANNA-2, i.e., Ri); gamma-aminobutyric acid (GABA)-B-receptor (GABA-B-R); metabotropic glutamate receptor 5 (mGluR5); and aquaporin-4 (AQP-4). Given potentially distinctive findings, it is possible that sleep testing could potentially provide objective biomarkers (polysomnography, quantitative muscle activity during REM sleep, cerebrospinal fluid hypocretin-1) to support an autoimmune diagnosis, monitor therapeutic response, or disease progression/relapse. However, more comprehensive characterization of sleep manifestations is needed to better understand the underlying sleep disruption with neurological autoimmunity.

Metabolic scoring in autoimmune epilepsy-Should APE scores be modified?

OBJECTIVE

We evaluate the potential utility of F-18 FDG-PET in addition to MRI in the diagnostic work-up of patients with autoimmune epilepsy (AE) and propose the inclusion of functional imaging in the antibody prevalence in epilepsy (APE) scoring system.

METHODS

This was a retrospective analysis in 60 patients, diagnosed and treated for AE, of whom 40 were antibody negative (presumed AE) and 20 were antibody positive (definitive AE). All patients had undergone a dedicated brain and whole body FDG-PET in the department of Nuclear Medicine.

RESULTS

In the antibody negative group, MRI supported a diagnosis of AE in 23 patients. Both MRI and PET were indicative in 12 cases, and standalone PET was positive in 8. While MRI alone was diagnostic in 57% (23/40), the combined yield of both modalities was 77% (31/40). When PET scores were added to assign the APE score in MRI negative cases, average APE score was 5.4. In the antibody positive group, MRI supported the diagnosis of AE in 7 patients. Both MRI and PET were positive in 4 patients and standalone PET was positive in 5 patients. While MRI alone was diagnostic in 35% (7/20), the combined yield of both modalities was 60% (12/20). When PET scores were added to assign the APE score in MRI negative cases, average APE score was 6.1.

CONCLUSION

The inclusion of metabolic information from PET distinctly improved (the sensitivity of) APE scores to predict autoimmune origin even in antibody negative cases. A larger prospective study of similar type could justify adoption of FDG-PET into the standard diagnostic procedure.

Neural Antibody Testing in Patients with Suspected Autoimmune Encephalitis

Background

Autoimmunity is an increasingly recognized cause of encephalitis with a similar prevalence to that of infectious etiologies. Over the past decade there has been a rapidly expanding list of antibody biomarker discoveries that have aided in the identification and characterization of autoimmune encephalitis. As the number of antibody biomarkers transitioning from the research setting into clinical laboratories has accelerated, so has the demand and complexity of panel-based testing. Clinical laboratories are increasingly involved in discussions related to test utilization and providing guidance on which testing methodologies provide the best clinical performance.

Content

To ensure optimal clinical sensitivity and specificity, comprehensive panel-based reflexive testing based on the predominant neurological phenotypic presentation (e.g., encephalopathy) is ideal in the workup of cases of suspected autoimmune neurological disease. Predictive scores based on the clinical workup can aid in deciding when to order a test. Testing of both CSF and serum is recommended with few exceptions. Appropriate test ordering and interpretation requires an understanding of both testing methodologies and performance of antibody testing in different specimen types.

Summary

This review discusses important considerations in the design and selection of neural antibody testing methodologies and panels. Increased collaboration between pathologists, laboratorians, and neurologists will lead to improved utilization of complex autoimmune neurology antibody testing panels.

Immunologic Treatments of Seizures and Status Epilepticus

An autoimmune etiology for seizures, epilepsy, and status epilepticus is becoming increasingly recognized. The role of autoimmunity in epilepsy has been highlighted in the literature and the International League Against Epilepsy now recognizes autoimmune epilepsy as a distinct entity. An appropriate and thorough work-up of all new-onset seizures and status epilepticus is paramount in determining the likely efficacy of immunotherapeutic agents in treating seizures and status epilepticus. Criteria for the clinical diagnosis of autoimmune mediated epilepsy and encephalitis have been published by expert consensus and validated models to predict response to immunotherapy exist. These guidelines should guide clinicians about when to promptly start immunotherapy. Immunotherapy has been shown to improve outcomes and may reduce relapse rates in autoimmune encephalitis. Treatment algorithms with immunotherapeutic agents have been established by expert opinion and multiple observational retrospective trials in the past 10 years. However, future prospective randomized controlled trials are still needed to better understand the optimal regimen, dosing schedule, and duration of treatment with immunotherapeutic agents.

Seizures in autoimmune encephalitis: Findings from an EEG pooled analysis

PURPOSE

Seizures are common in autoimmune encephalitis (AE), and an extensive work-up is required to exclude alternative etiologies. The aim of our study was to identify possible clinical/EEG peculiarities suggesting the immune-mediated origin of late-onset seizures.

METHODS

Thirty patients diagnosed with AE (19 men, median age 68 years, 18 seronegative) were included. Overall 212 video-electroencephalographic (EEG) and 31 24-h ambulatory EEG (AEEG) recordings were retrospectively reviewed. Posterior dominant rhythm, interictal epileptiform discharges (IEDs), clinical (CSs) and subclinical seizures (SCSs) were analyzed.

RESULTS

Six-hundred-nineteen ictal events were recorded in 19/30 subjects, mostly (568/619) during AE acute stage. Among ten patients with CSs other than faciobrachial dystonic seizures, 7 showed prominent autonomic and emotional manifestations. SCSs were detected in 11 subjects, mainly via AEEG (260/287 SCSs vs 150/332 CSs, p < 0.001). Eight patients presented seizures during hyperventilation. IEDs, documented in 21 cases, were bilateral in 14 and focal temporal in 13. Multiple ictal EEG patterns were detected in 9/19 patients, 6 of whom had both CSs and SCSs, bilateral asynchronous seizures and ictal activities arising from temporal and extra-temporal regions. No correlation was found between the lateralization of MRI alterations and that of EEG findings.

CONCLUSION

Our study confirms that adult-onset, high frequency focal seizures with prominent autonomic and emotional manifestations should be investigated for AE. Multiple ictal EEG patterns could represent a 'red flag', reflecting a widespread neuronal excitability related to the underlying immune-mediated process. Finally, our work enhances the crucial role of long-lasting EEG monitoring in revealing subclinical and relapsing seizures.