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

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.

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.

Performance of assessment tools in predicting neural autoantibody positivity in patients with seizures

BACKGROUND

The identification of patients with seizures of unknown etiology who would benefit from neural antibody testing necessitates effective assessment tools. The study aimed to compare the performance of the Antibody Prevalence in Epilepsy and Encephalopathy (APE2) score and the "Obvious" Indications for Neural Antibody Testing in Epilepsy or Seizures (ONES) checklist. We also intended to evaluate whether the performance of the tools varied by types of antibody.

METHODS

Patients diagnosed with epilepsy, seizures, or status epilepticus of unknown etiology at West China Hospital from January 2019 to December 2021 were included. Paired serum/cerebrospinal fluid samples were analyzed for antineuronal and antiglial antibodies. The APE2 score and ONES checklist were applied, and their outcomes were compared to laboratory antibody test results. Possible false positive neuronal antibody results were excluded in sensitivity/specificity analysis reasonably.

RESULTS

A total of 113 antibody-positive and 159 antibody-negative patients were enrolled in sensitivity/specificity analysis. The ONES checklist showed superior sensitivity than APE2 score (95.6 % vs.79.6 %, P < 0.001). Specificity was not statistically different (60.4 % vs. 57.9 %, P = 0.557). The negative predictive value (NPV) of ONES checklist was higher than that of APE2 score (94.8 % vs 80.7 %, P < 0.001). The positive predictive value of them was not statistically different (61.7 % vs 58.8 %, P = 0.557). APE2 score exhibited lower sensitivity for predicting LGI-Abs (52.9 % vs. 80.3 %, P = 0.022) compared to NMDAR-Abs. Similarly, ONES checklist showed lower sensitivity for LGI1-Abs than NMDAR-Abs (82.4 % vs. 100.0 %, P = 0.009).

CONCLUSIONS

The ONES checklist demonstrates superior sensitivity for neural antibody positivity than APE2 score. Specificity of the two assessment tools was similar. ONES checklist performed better NPV than the APE2 score. Both assessment tools performed less well in predicting the presence of LGI1- Abs when compared to NMDAR-Abs.

Autoimmune and paraneoplastic seizures

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

The three pillars in treating antibody-mediated encephalitis

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

Mechanisms and Emerging Therapies for Treatment of Seizures in Pediatric Autoimmune Encephalitis and Autoinflammatory/Autoimmune-Associated Epilepsy

There has been increasing understanding of the role of inflammation in seizures and epilepsy, as well as targeted immunomodulatory treatments. In children, immune-mediated seizures often present acutely in the setting of autoimmune encephalitis and are very responsive to immunotherapy with low rates of subsequent epilepsy. Conversely, seizures in autoimmune-associated epilepsies, such as Rasmussen syndrome, can remain refractory to multimodal therapy, including immunomodulation. In this review, the authors discuss the presentations of immune-mediated seizures in children, underlying mechanisms, and emerging therapies.

Metabolic phenotyping of pilomotor seizures in autoimmune encephalitis

OBJECTIVES

Ictal piloerection (IP) is an uncommon symptom in focal epilepsy and is associated with autoimmune encephalitis (AE). However, the networks involved in AE-associated IP are still unclear. To have a better understanding of IP underlying mechanisms, the current study investigated whole-brain metabolic networks for the analysis of AE-associated IP.

METHODS

Patients with AE and IP diagnosed at our Institute between 2018 and 2022 were selected. We then investigated the brain regions associated with AE-associated IP using positron emission tomography (PET). Anatomometabolic changes (interictal 18 F fluorodeoxyglucose PET) in AE patients with IP were compared with those of AE patients of similar age without IP (p-voxel <0.001, uncorrected).

RESULTS

Sixteen patients showed significant IP. The overall IP prevalence was 4.09% of patients with AE and 12.9% of patients with limbic encephalitis. The most common autoantibodies were against LGI1 (68.8%) followed by GAD65 (6.3%), NMDA (6.3%), GABAb (6.3%), CASPR2 (6.3%), and antibodies recognizing both GAD65 and mGLUR5 (6.3%). Most patients responded well to immunotherapy. Analysis of the imaging results at the voxel level showed that patients with IP had hypermetabolic changes in the right inferior temporal gyrus, suggesting involvement of this brain region in IP.

CONCLUSIONS

Our findings indicate that IP as an uncommon AE-associated manifestations should be recognized. We observed that the metabolic pattern of IP was conspicuous in the right inferior temporal gyrus.

Clinical features of 28 cases of antileucinerich gliomainactivated protein 1 encephalitis and anticontactinassociated proteinlike 2 encephalitis

OBJECTIVES

Autoimmune encephalitis arising from autoantibodies against leucine-rich glioma-inactivated protein 1 (LGI1) and contactin-associated protein-like 2 (CASPR2) are rare and with high clinical heterogeneity. They are easily misdiagnosed and missing diagnosed. This study aims to explore the clinical characteristics, auxiliary examinations, therapies and prognosis of anti-LGI1 and anti-CASPR2 encephalitis.

METHODS

Seventeen anti-LGI1 and 11 anti-CASPR2 encephalitis patients who were admitted to the Department of Neurology, Xiangya Hospital, Central South University between January 2018 and January 2021 were collected and retrospectively analyzed. Autoimmune encephalitis related antibodies and paraneoplastic antibodies were screened in all patients. The clinical manifestations, results of laboratory tests, imaging features, treatments and outcomes of 2 encephalitis groups were analyzed and compared.

RESULTS

In the anti-LGI1 encephalitis group, the age of 17 patients was 28-83 (53.18±19.08) years old, and the ratio of male to female was 9꞉8. There were 10 patients with cognitive impairment, 7 seizures, 4 faciobrachial dystonic seizures, and 1 psychiatric disturbance. Hyponatremia was observed in 7 patients. Eight patients had increased slow waves and 5 had epileptic discharge in electroencephalogram (EEG). Brain magnetic resonance (MRI) showed T2-weighted imaging (T2WI) and fluid attenuated inversion recovery (FLAIR) hyperintense signal in the temporal lobe, hippocampus and basal ganglia in 13 patients. In the anti-CASPR2 group, the age of 11 patients was 17-68 (47.18±16.20) years old, and the ratio of male to female was 5꞉6, with 7 limbic encephalitis, 1 Morvan syndrome, and 3 acquired neuromyotonia (NMT). Three patients had increased slow waves and 2 had epileptic discharge in EEG. Brain MRI showed T2WI and FLAIR hyperintense signal in the temporal lobe, hippocampus in 2 patients. Steroids, intravenous immunoglobin, and plasma exchange were administrated in 16 anti-LGI1 encephalitis and 8 anti-CASPR2 encephalitis patients with good therapeutic responses. Among them, 1 patient with anti-LGI1 encephalitis and 3 with anti-CASPR2 encephalitis were administrated with mycophenolate mofetil for immune maintenance therapy. No recurrences were observed in all patients with immunotherapy except for 2 patients who lost of follow-up. There were significant differences in cognitive impairment, hyponatremia, and brain MRI abnormalities between anti-LGI1 and anti-CASPR2 encephalitis patients (all P<0.05).

CONCLUSIONS

Limbic encephalitis is a common syndrome in both anti-LGI1 and anti-CASPR2 encephalitis patients. Anti-CASPR2 encephalitis has a wider clinical spectrum than anti-LGI1 encephalitis, presenting as NMT and Morvan syndrome, which has a closer relationship with tumors. Both of these 2 antibodies associated disorders are sensitive to immunotherapy and have a good prognosis.

Early predictors of new-onset immune-related seizures: a preliminary study

BACKGROUND

Approximately 60% of patients with autoimmune encephalitis (AE) exhibit secondary acute symptomatic seizures and showed highly sensitive to immunotherapy. However, it is difficult for many patients to receive early immunotherapy since the early identification of the cause in AE is more complex. This study aimed to investigate the early predictors of initial immune-related seizures and to guide the evaluation of treatment and prognosis.

METHODS

One hundred and fifty-four patients with new-onset "unknown etiology" seizures with a course of disease less than 6 months were included. Serum and/or cerebrospinal fluid neuron-specific autoantibodies (NSAbs), including N-methyl-D-aspartate receptor (NMDAR), α-amino-3-hydroxy-5- Methyl-4-isoxazole propionic acid receptor 1 (AMPAR1), AMPAR2, anti-leucine rich glioma inactivated 1 antibody (LGI1), anti-gamma-aminobutyric acid type B receptor (GABABR), anti-contact protein-related protein-2 (CASPR2) were used to screen for immune etiology of the seizures. In addition, patients with epilepsy and encephalopathy were also examined via brain MRI, long-term video EEG, antibody prevalence in epilepsy and encephalopathy (APE2) score, and modified Rankin Scale (mRS). A logistic regression model was used to analyze the early predictors of immune etiology.

RESULTS

Thirty-four cases (22.1%) were positive for NSAbs. Among all 154 patients, 23 cases of autoimmune encephalitis (AE) (21 cases of NSAbs positive), 1 case of ganglionic glioma (NSAbs positive), 130 cases of epilepsy or seizures (12 cases of NSAbs positive) were recorded. Also, there were 17 patients (11.0%) with APE2 ≥ 4 points, and all of them met the clinical diagnosis of AE. The sensitivity and specificity of APE2 ≥ 4 points for predicting AE were 73.9% and 100%. The results of multivariate analysis showed that the NSAbs and APE2 scores independently influenced the early prediction of initial immune-related seizures (P < 0.05).

CONCLUSION

NSAbs and APE2 scores could act as early predictors of initial immune-related seizures.

Parallel roles of neuroinflammation in feline and human epilepsies

Autoimmune encephalitis refers to a group of disorders characterised by a non-infectious encephalitis, often with prominent seizures and surface neuronal autoantibodies. AE is an important cause of new-onset refractory status epilepticus in humans and is frequently responsive to immunotherapies including corticosteroids, plasma exchange, intravenous immunoglobulin G and rituximab. Recent research suggests that parallel autoantibodies can be detected in non-human mammalian species. The best documented example is leucine-rich glioma-inactivated 1 (LGI1)-antibodies in domestic cats with limbic encephalitis (LE). In this review, we discuss the role of neuroinflammation and autoantibodies in human and feline epilepsy and LE.

Detection and significance of neuronal autoantibodies in patients with meningoencephalitis in Vientiane, Lao PDR

BACKGROUND

The importance of autoimmune encephalitis and its overlap with infectious encephalitides are not well investigated in South-East Asia.

METHODS

We report autoantibody testing, using antigen-specific live cell-based assays, in a series of 134 patients (cerebrospinal fluid and sera) and 55 blood donor controls (sera), undergoing lumbar puncture for suspected meningoencephalitis admitted in Vientiane, Lao People's Democratic Republic (PDR).

RESULTS

Eight of 134 (6%) patients showed detectable serum neuronal autoantibodies, against the N-methyl-D-aspartate and gamma-aminobutyric acid A receptors (NMDAR and GABAAR), and contactin-associated protein-like 2 (CASPR2). Three of eight patients had accompanying autoantibodies in cerebrospinal fluid (two with NMDAR and one with GABAAR antibodies), and in two of these the clinical syndromes were typical of autoimmune encephalitis. Three of the other five patients had proven central nervous system infections, highlighting a complex overlap between diverse infectious and autoimmune causes of encephalitis. No patients in this cohort were treated with immunotherapy, and the outcomes were poor, with improvement observed in a single patient.

CONCLUSIONS

In Lao PDR, autoimmune encephalitis is underdiagnosed and has a poor prognosis. Empiric immunotherapy should be considered after treatable infectious aetiologies are considered unlikely. Awareness and diagnostic testing resources for autoimmune encephalitis should be enhanced in South-East Asia.

Diagnostic value of an algorithm for autoimmune epilepsy in a retrospective cohort

Purpose

This study aims to propose a diagnostic algorithm for autoimmune epilepsy in a retrospective cohort and investigate its clinical utility.

Methods

We reviewed 60 patients with focal epilepsy with a suspected autoimmune etiology according to board-certified neurologists and epileptologists. To assess the involvement of the autoimmune etiology, we used the patients' sera or cerebrospinal fluid (CSF) samples to screen for antineuronal antibodies using rat brain immunohistochemistry. Positive samples were analyzed for known antineuronal antibodies. The algorithm applied to assess the data of all patients consisted of two steps: evaluation of clinical features suggesting autoimmune epilepsy and evaluation using laboratory and imaging findings (abnormal CSF findings, hypermetabolism on fluorodeoxyglucose-positron emission tomography, magnetic resonance imaging abnormalities, and bilateral epileptiform discharges on electroencephalography). Patients were screened during the first step and classified into five groups according to the number of abnormal laboratory findings. The significant cutoff point of the algorithm was assessed using a receiver-operating characteristic curve analysis.

Results

Fourteen of the 60 patients (23.3%) were seropositive for antineuronal antibodies using rat brain immunohistochemistry. Ten patients had antibodies related to autoimmune epilepsy/encephalitis. The cutoff analysis of the number of abnormal laboratory and imaging findings showed that the best cutoff point was two abnormal findings, which yielded a sensitivity of 78.6%, a specificity of 76.1%, and an area under the curve of 0.81.

Conclusion

The proposed algorithm could help predict the underlying autoimmune etiology of epilepsy before antineuronal antibody test results are available.

Drug-resistant epilepsy at the age extremes: Disentangling the underlying etiology

The incidence of epilepsy is highest at the extreme age ranges: childhood and elderly age. The most common syndromes in these demographics - self-limited epilepsies of childhood and idiopathic generalized epilepsies in pediatric age, focal epilepsy with structural etiology in older people - are expected to be drug responsive. In this work, we focus on such epilepsy types, overviewing the complex clinical background of unexpected drug-resistance. For self-limited epilepsies of childhood and idiopathic generalized epilepsies, we illustrate drug-resistance resulting from syndrome misinterpretation, reason on possible unexpected courses of epilepsy, and explicate the influence of inappropriate treatments. For elderly-onset epilepsy, we show the challenges in differential diagnosis possibly leading to pseudoresistance and analyze how drug-resistant epilepsy can arise in stroke, neurocognitive disorders, brain tumors, and autoimmune encephalitis. In children and senior people, drug-resistance can be regarded as a hint to review the diagnosis or explore alternative therapeutic strategies. Refractory seizures are not only a therapeutic challenge, but also a cardinal sign not to be overlooked in syndromes commonly deemed to be drug-responsive.

Immunity, Ion Channels and Epilepsy

Epilepsy is a common chronic neurological disorder in modern society. One of the major unmet challenges is that current antiseizure medications are basically not disease-modifying. Among the multifaceted etiologies of epilepsy, the role of the immune system has attracted considerable attention in recent years. It is known that both innate and adaptive immunity can be activated in response to insults to the central nervous system, leading to seizures. Moreover, the interaction between ion channels, which have a well-established role in epileptogenesis and epilepsy, and the immune system is complex and is being actively investigated. Some examples, including the interaction between ion channels and mTOR pathways, will be discussed in this paper. Furthermore, there has been substantial progress in our understanding of the pathophysiology of epilepsy associated with autoimmune encephalitis, and numerous neural-specific autoantibodies have been found and documented. Early recognition of immune-mediated epilepsy is important, especially in cases of pharmacoresistant epilepsy and in the presence of signs of autoimmune encephalitis, as early intervention with immunotherapy shows promise.

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.

Autoimmune-Associated Seizures

PURPOSE OF REVIEW

This article focuses on the seizure manifestations and presentations of autoimmune-associated epilepsy and acute symptomatic seizures in autoimmune encephalitis. It discusses the specificity of the various central nervous system autoantibodies and clarifies when their presence can be considered indicative of an immune etiology. Finally, current recommendations regarding patient selection for autoimmune antibody evaluation are reviewed, and an approach to immunotherapy is provided.

RECENT FINDINGS

Although autoimmune seizures are caused by a heterogeneous group of autoantibodies, key features reported in the literature should alert clinicians to the possible diagnosis. In particular, seizure characteristics including frequency, timing, duration, and symptomatology can provide vital clues to help differentiate autoimmune-associated seizures from other causes of epilepsy. Diagnostic certainty also requires an understanding and integration of the spectrum of clinical and paraclinical presentations, and several scoring systems have been developed that may be useful to aid the identification of autoimmune seizures.

SUMMARY

Seizures due to autoimmune etiology are increasingly encountered in clinical practice. It is critical that clinicians recognize immune seizure etiologies early in their course given they are often responsive to immunotherapy but are usually resistant to antiseizure medications. Currently, however, it is unfortunately not uncommon for autoimmune-associated seizure disorders to remain undiagnosed, resulting in missed opportunities to administer effective therapies. Efforts to better understand autoimmune seizure manifestations and treatment strategies are ongoing.

Kv5.1 antibody in epilepsy patients with unknown etiology

BACKGROUND

Neuronal autoantibodies and favorable response to immunosuppressive treatment have been described in patients with chronic epilepsy of unknown cause, suggesting autoimmune etiology. Our aim was to identify novel epilepsy-specific autoantibodies reactive with neuronal surface antigens.

METHODS

Sera of 172 epilepsy patients with unknown cause and 30 healthy controls were screened with indirect immunofluorescence to identify IgG reacting with primary rat neuronal cultures. Putative target autoantigens were investigated with immunoprecipitation (IP) and liquid chromatography-mass/mass spectrometry (LC-MS/MS) studies using SH-SY5Y cells. Validation of LC-MS/MS results was carried out by IP and immunocytochemistry assays.

RESULTS

Antibodies to neuronal cell surface antigens were detected in 18 epilepsy patients. LC-MS/MS analysis identified voltage-gated potassium channel modifier subfamily F member 1 (KCNF1, Kv5.1) as the single common cell surface antigen in 4 patients with Lennox-Gastaut syndrome (n = 2), focal epilepsy of unknown cause (n = 1) and mesial temporal lobe epilepsy with hippocampal sclerosis (n = 1). These patients had the common features of early seizure onset and treatment-resistance. IP assays and co-localization (serum IgG and commercial Kv5.1-antibody) studies done with non-fixed Kv5.1-transfected HEK293 cells and primary neuronal cultures confirmed the presence of Kv5.1-antibody in 4 epilepsy patients identified by LC-MS/MS. Similar findings were not obtained by sera of other patients with epilepsy, patients with autoimmune encephalitis and healthy controls.

CONCLUSION

The herein described novel neuronal surface antibody to Kv5.1 appears to be associated with treatment-resistant epilepsy of unknown cause. Exact clinical and pathogenic significance of this antibody remains to be elucidated.

Autoimmune Encephalitis and Autoantibodies: A Review of Clinical Implications

BACKGROUND

Autoimmune encephalitis (AE) is a common cause of encephalitis. We review the most recent evidence on this neuroimmune condition and autoantibody testing currently available.

CONTENT

Clinical criteria, neuroimaging and electroencephalography can facilitate the diagnosis of AE prior to obtaining autoantibody testing results, and lead to a diagnosis of AE even in the absence of a recognized antibody. Early treatment of AE has been found to correlate with improved long-term functional and cognitive outcomes. We suggest a clinical approach to diagnosis based on the predominant area of nervous system involvement and the results of ancillary testing that are widely available. We also propose a 2-tiered approach to the acute management of probable or definite AE. We, finally, provide guidance on the long-term management of AE-a challenging and understudied area.

SUMMARY

Much work remains to be done to improve the care of patients with AE. As understanding of the pathophysiology and predisposing factors underlying this condition steadily increases, a more evidence-based, targeted approach to the treatment of AE is still desired. Nonetheless, looking at the progress made over the past 2 decades, since the discovery of the first autoantibodies associated with AE, one cannot help but feel optimistic about the road ahead.

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.

The Search for Autoimmune-Associated Epilepsy Continues-Are We Getting Closer to Our Target?

Clinical Features Which Predict Neuronal Surface Autoantibodies in New-Onset Focal Epilepsy: Implications for Immunotherapies

McGinty RN, Handel A, Moloney T, et al. J Neurol Neurosurg Psychiatry. 2020;92(3):291-294. doi:10.1136/jnnp-2020-325011

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:

A total of 10.5% (23/219) of people with new-onset focal epilepsy had detectable serum autoantibodies to known or novel cell surface antigenic targets. Nine of 23 with autoantibodies were diagnosed with encephalitis, by contrast to 0/196 without autoantibodies (P < .0001). Multivariate analysis identified 6 features which predicted autoantibody positivity (area under the curve = 0.83): age ≥54 years, ictal piloerection, lowered self-reported mood, reduced attention, magnetic resonance imaging limbic system changes, and the absence of conventional epilepsy risk factors. Eleven (79%) of 14 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 < .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 suggest 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.