Management of suspected infectious and autoimmune encephalitis in adults - National Guidelines from the United Kingdom Joint Societies.

Encephalitis, characterised by inflammation of the brain parenchyma, is a neurological emergency with diverse infectious, autoimmune and inflammatory causes. Delays in recognition and treatment carry significant risks of morbidity and mortality. Since the first UK guideline for management of suspected viral encephalitis in adults was published in 2012, there have been substantial developments in this field. Advances in molecular diagnostics, antibody testing, alongside improved access to neuroimaging and electrophysiology have broadened the capacity to identify underlying aetiologies. The recognised spectrum of infectious and immune-mediated causes has expanded, and clinical experience with immunomodulatory therapies has grown considerably. A multidisciplinary national working group, representing neurology, infectious diseases, microbiology, virology, neuroimmunology and acute medicine, alongside national professional and third-sector organisations, was convened in Liverpool in 2023 to develop updated UK Joint Societies guidelines for the management of suspected infectious and autoimmune encephalitis in adults. This guideline provides pragmatic, evidence-informed recommendations on clinical recognition, investigation, diagnosis, acute management and rehabilitation. It emphasises early identification and parallel consideration of infectious and immune-mediated causes, with particular attention to decision-making during the critical first 24-72hours of presentation. Standardised diagnostic and therapeutic pathways are presented to support consistent care across healthcare settings. Where the evidence base remains limited, the need for multidisciplinary input is highlighted. These recommendations aim to reduce mortality, limit long-term neurological morbidity and improve outcomes for adults with encephalitis across the UK.