Autoimmune encephalitis: Epidemiology, pathophysiology and clinical spectrum (part 1)

Abstract

Since the identification of anti-N-methyl-D-aspartate (NMDA) receptor antibodies about 15 years ago, many patients with rapidly progressing psychiatric symptoms, abnormal movements, seizures or unexplained coma have been diagnosed with autoimmune encephalitis (AE). The symptom onset is often unspecific, and might mimic psychiatric disease, but the later course is frequently characterised by severe disease, often requiring intensive care. Clinical and immunological criteria are helpful in identifying the patients, but no biomarkers exist to guide the clinician in therapy or predict outcome. While persons of all ages can be affected by AE, some types of AE affect more children and young adults and are more prevalent in women. This review focuses on encephalitides associated with neuronal cell-surface or synaptic antibodies, which can result in characteristic syndromes, and are often recognisable on clinical grounds. AE subtypes associated with antibodies against extracellular epitopes can occur with or without tumours. Because the antibodies bind and alter the function of the antigen, the effects are often reversible if immunotherapy is initiated, and the prognosis is favourable in most instances. The first part of this series introduces the topic, provides an overview of currently known neuronal surface antibodies and how they present, describes the most common subtype anti-NMDA receptor encephalitis, and discusses the difficulties in recognising patients with underlying AE among patients with new-onset psychiatric disorders.