How I Do It: An Imaging Approach and Review of Autoimmune Encephalitis

Encephalitis is a medical emergency characterized by inflammation of the brain parenchyma due to an infective cause or an immune-mediated process. Autoimmune encephalitis (AE) is characterized by a misdirected immune attack against neuronal structures, resulting in an inflammatory response. Triggers for the development of antibodies are often paraneoplastic or parainfectious. AE may occur in children or adults with symptoms including subacute onset of altered mentation, cognitive issues, drug-resistant epilepsy, movement disorders, and/or autonomic dysfunction. Limbic encephalitis is a common imaging feature of many forms of AE; however, cortical, basal ganglia, diencephalon, brainstem, and cerebellar involvement have been described. This article provides an overview of the general imaging appearances of AE, with a detailed discussion of key patterns encountered with common causes of AE, as well as a review of the relevant differential diagnoses, thus serving as a practical reference for radiologists.