Autoimmune Epilepsy

Abstract

Purpose of review: This review presents recent developments in the clinical features, immunologic basis, and treatment options for autoimmune encephalitis, seizures, and epilepsy.

Recent findings: In addition to the expansion of our knowledge on classic paraneoplastic limbic encephalitis with onconeural antibodies, recent years have witnessed the development of the category of encephalitis associated with antibodies directed toward neuronal surface antigens. Antibodies against the voltage-gated potassium channel are, in fact, directed toward an array of targets within a large molecular complex. The most common target, leucine-rich, glioma inactivated 1 (LGI1), is associated with a syndrome of limbic encephalitis, sometimes preceded by disease-specific faciobrachial dystonic seizures, which could allow early diagnosis and treatment. Encephalitis with N-methyl-D-aspartate (NMDA) receptor antibodies, only discovered a few years ago, has emerged as the leading syndrome of this new category. Its clinical features and EEG signature are well defined, which should allow prompt recognition and treatment. The list of antibodies is still growing as new antibodies are identified that recognize other synaptic proteins, such as the γ-aminobutyric acid (GABA), α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), and glycine receptors. The role of glutamic acid decarboxylase 65 (GAD65) antibodies is still a controversy, as is the cause of Rasmussen encephalitis and syndromes of cryptogenic refractory status epilepticus and the mechanisms of seizures in systemic autoimmune diseases. A link between autoimmunity and epilepsy has been substantiated by large epidemiologic studies, but the nature of the causality requires more research.

Summary: Autoimmune encephalitis is an important cause of seizures to recognize as it entails a specific therapeutic approach. Paraneoplastic limbic encephalitis and NMDA receptor and LGI1 encephalitis are well-characterized immunoclinical associations. Other syndromes and antibodies are being actively identified and described. A concept of autoimmune epilepsy is emerging and, if confirmed, is likely to alter the therapeutic approach and improve the outcome of some patients with pharmacoresistant epilepsy.