Accumulating data on patients with autoimmune encephalitis have shed light on specificities concerning clinical presentation and outcomes, which are dependent on the antigen targeted by the autoantibodies found in the patients' cerebrospinal fluid or sera. Such specificities include seizure-related clinical manifestations as well as the responsiveness to antiepileptic drugs. Although increased enthusiasm accompanies the discovery of novel antibodies and their associated clinical syndromes, several issues remain unsettled. First, it appears that therapy needs to be personalized in the view of the severity of each antibody-mediated syndrome, patient-related characteristics, and timing of treatment. Second, the lack of randomized controlled trials is a major drawback in the formulation of an appropriate immunotherapeutic strategy. In this review, we discuss the novel developments and challenges for the diagnosis and treatment of epilepsy in patients with well-characterized autoimmune encephalitis, and delineate the principles for a rational approach toward precision medicine in this emerging field.

Seizure specificities in patients with antibody-mediated autoimmune encephalitis.

Seizure characteristics, treatment, and outcome in autoimmune synaptic encephalitis: A long-term study.

This study was undertaken to develop consensus‐based recommendations for the management of adult and pediatric patients with new onset refractory status epilepticus (NORSE)/febrile infection‐related epilepsy syndrome (FIRES) based on best evidence and experience.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/epi.17397

International consensus recommendations for management of new onset refractory status epilepticus including febrile infection‐related epilepsy syndrome: Statements and supporting evidence

Purpose of review Autoimmune encephalitides are established diagnoses in contemporary neurology. Their management poses a regular challenge for almost all neurologists. One may ask if the concept of 1st line and 2nd line treatment is still up to date, which new data on the antibody-defined encephalitis types exist, and how to organize long-term management. Recent findings The 1st line/2nd line concept of initial immunological intervention is accepted worldwide. A randomized controlled trial confirmed that one 1st line compound (intravenous immunoglobulins) is superior to a placebo in patients with antibodies against leucine-rich glioma inactivated protein 1. Rituximab, a 2nd line compound, is increasingly and apparently successfully used in treating different types of autoimmune encephalitis. It may find its place even earlier in the treatment cascade. Long-term management needs to be improved and is under development. Summary There have been no groundbreaking new developments in the field. The published experience confirms existing suggestions. Aspects of long-term management including rehabilitation measures and counseling about driving eligibility require further research.

Management of autoimmune encephalitis.

Epilepsy is a common neurological disorder that increases the risk of morbidity and mortality. Autoimmune epilepsy is a subset of epilepsy that occurs in the setting of autoimmunity, such as in autoimmune encephalitis (AIE). AIE is an autoimmune disorder characterized by immune-mediated neuroinflammation resulting in a variety of neurological symptoms, including psychiatric disturbance, cognitive dysfunction, and seizures. Seizures in AIE are thought to be a result of antibodies directed against neuronal cell-surface proteins involved in synaptic transmission. The role of blood-brain barrier dysfunction, myeloid cell infiltration, and the initiation of proinflammatory cascades in epileptogenesis has been shown to be important in animal models and human patients with epilepsy. Epileptogenesis in AIE is likely to arise from the synergistic effect of both innately driven neuroinflammation and antibody-induced hyperexcitability. Together, these processes produce persistent drug-resistant seizures that contribute to the morbidity seen in AIE. Understanding the proinflammatory pathways involved in this process may improve diagnostics and provide alternative treatment targets in AIE.

/pdf/seizures-in-autoimmune-encephalitis-kindling-the-fire-2zy36ovyrr.pdf

Seizures in autoimmune encephalitis: Kindling the fire

Objective Review the evidence of the efficacy of AEDs (antiepileptic drugs) in autoimmune epilepsy. Material and methods Literature research on Medline and Embase was carried out through January 2018. We included MeSH terms, free text and terms related to "autoimmune epilepsy", "autoimmune encephalitis", "limbic encephalitis", "autoimmune seizures", "antiepileptic drug", "seizure treatment", and "epilepsy treatment". The research was carried out by two reviewers who independently examined titles, abstracts and selection criteria. The main outcome was AED efficacy. Results regarding types of AEDs and autoantibody presence and type in responding patients were considered secondary endpoints. Quality of evidence was analysed by reading the whole text and following Scottish Intercollegiate Guidelines Network (SIGN) guidelines. Results After an initial selection of 1656 articles, only six retrospective observational studies with a level of evidence between 2+ and 3 and a SIGN B recommendation degree remained. The total number of patients examined was 139. The estimated efficacy of AEDs with AE was 10.7%. There was response to AEDs in 18% of seronegative patients, 11% in VGKC positives and in 8% with GAD65. Seventy-three percent of responders to AEDs were in treatment with Na+ channel blockers in monotherapy or in combination. Conclusions The efficacy of AEDs in AE was low, although this may be in part due to a selection bias. Nevertheless, patients could benefit from these drugs even after immunotherapy failure. Seronegative patients seemed to have a better response to AEDs.

Efficacy of antiepileptic drugs in autoimmune epilepsy: A systematic review

Neurotoxicity and safety of the rechallenge of immune checkpoint inhibitors: a growing issue in neuro-oncology practice

Novelties in Autoimmune and Paraneoplastic Cerebellar Ataxias: Twenty Years of Progresses

Background and Objectives To clinically characterize post–immune checkpoint inhibitor (ICI) Hu antibody (Ab) neurologic disorders, we analyzed Hu-Ab–positive patients with neurologic immune-related adverse events (n-irAEs) and compared them with patients with other n-irAEs, ICI-naive patients with Hu-Ab paraneoplastic neurologic syndromes (PNSs) identified in the same study center, and those with Hu-Ab n-irAEs reported elsewhere. Methods Patients whose samples were sent to the French reference center for a suspicion of n-irAE (2015–2021) were identified; those with a final diagnosis of n-irAE and Hu-Ab were included. Control groups included patients with a final diagnosis of n-irAE occurring during the same period as the patients included (2018–2021) but without Hu-Ab, and ICI-naive patients with Hu-Ab PNS diagnosed during the same period; a systematic review was performed to identify previous reports. Results Eleven patients with Hu-Ab and n-irAEs were included (median age, 66 years, range 44–76 years; 73% men). Ten patients had small cell lung cancer, and 1 had lung adenocarcinoma. The median follow-up from onset was 3 months (range 0.5–18 months). Compared with those with other n-irAEs (n = 63), Hu-Ab–positive patients had more frequently co-occurring involvement of both central and peripheral nervous systems (36% vs 8%, p = 0.02) and limbic (54% vs 14%, p < 0.01), brainstem (27% vs 5%, p = 0.02), and dorsal root ganglia (45% vs 5%, p < 0.01) involvement. The proportion of patients with severe disability (modified Rankin Scale score >3) at diagnosis was higher among Hu-Ab n-irAEs (91% vs 52%, p = 0.02). Patients with Hu-Ab had also poorer outcome (100% vs 28%, p < 0.01) and higher mortality (91% vs 46%, p < 0.01). There was no significant difference in terms of clinical features between Hu-Ab n-irAEs and ICI-naive Hu-Ab PNS (n = 92), but there was a poorer outcome (56/78, 71%, p < 0.01) and higher mortality (26%, p < 0.01) among the former. No significant difference was found between the patients reported herein and those in the literature. Discussion The presence of Hu-Ab identifies a subgroup of n-irAEs that consistently reproduce the phenotypes of Hu-Ab-related PNS, supporting the hypothesis of ICI triggering or unmasking PNS. As these patients show high disability and mortality, further studies are required to investigate the underlying immunopathogenic mechanisms and to improve the outcome of Hu-Ab n-irAEs.

https://nn.neurology.org/content/nnn/10/1/e200058.full.pdf

Anti-Hu Antibodies in Patients With Neurologic Side Effects of Immune Checkpoint Inhibitors

Abstract Autoimmune encephalitides constitute a diverse group of immune-mediated central nervous system disorders mainly characterized by the presence of antibodies targeting neuronal or glial antigens. Despite the notable contribution of antibody discovery to the understanding of their physiopathology, the specific immune cells and inflammatory mediators involved in autoimmune encephalitis are still poorly defined. However, cytokines have recently emerged as crucial signalling molecules in the pathogenesis of autoimmune encephalitis. Cytokines are biologically active, soluble, low-molecular-weight proteins or glycoproteins involved in a wide variety of physiological functions, including central nervous system development and homeostasis, immune surveillance, as well as proliferation and maturation of immune cells. Since unbalanced cytokine expression is considered a hallmark of many autoimmune central nervous system disorders, their identification and quantification has become an essential element in personalized medicine applied to the field of neuroimmunology. Several studies have explored the cytokine profile of autoimmune encephalitis, but their interpretation and comparison is challenging due to their small sample sizes and extremely high heterogeneity, especially regarding the cytokines analysed, type of sample used, and associated neural antibody. Only the cytokine profile of anti-N-methyl-D-aspartate receptor encephalitis has extensively been investigated, with findings suggesting that, although humoral immunity is the main effector, T cells may also be relevant for the development of this disorder. A better understanding of cytokine dynamics governing neuroinflammation might offer the opportunity of developing new therapeutic strategies against specific immune cells, cytokines, antibodies, or intracellular signalling cascades, therefore leading to better outcomes and preventing undesired side effects of the presently used strategies. In this review, we first summarize the current knowledge about the role of cytokines in the pathogenesis of autoimmune encephalitis, combining theoretical analysis with experimental validations, to assess their suitability as clinical biomarkers. Second, we discuss the potential applicability of the novel targeted immunotherapies in autoimmune encephalitis depending on the immunobiology of the associated antibody, their limitations, as well as the main limitations that should be addressed in future studies.

Macarena Villagrán-García

Papers

Efficacy of antiepileptic drugs in autoimmune epilepsy: A systematic review

Neurotoxicity and safety of the rechallenge of immune checkpoint inhibitors: a growing issue in neuro-oncology practice

Novelties in Autoimmune and Paraneoplastic Cerebellar Ataxias: Twenty Years of Progresses

Anti-Hu Antibodies in Patients With Neurologic Side Effects of Immune Checkpoint Inhibitors

Cytokine dynamics and targeted immunotherapies in autoimmune encephalitis