Diagnostic tools for immune causes of encephalitis

BackgroundAutoimmune encephalitis (AE) refers to a central nervous system (CNS) antibody-mediated entity characterized by a rapid onset behavioural and cognitive decline that can be associated with movement disorders, epileptic and dysautonomic features. Interestingly, it is thought to be as common as its infectious disease counterpart and can share some clinical, radiological, and laboratory findings.ObjectivesThe aim is to describe the main clinical features of AE caused by antibodies targeting cell-surface neuronal agents and the diagnostic means to identify them. Paraneoplastic syndromes, associated with intracellular antibodies, will not be tackled in this review.SourcesPubMed/MEDLINE were the sources.ContentAccording to a recent population-based study, autoimmunity is one of the most frequent cause of encephalitis after infectious agents. Its diagnosis lies upon ‘classic’ clinical features, which are dominated by neuropsychiatric symptoms and epileptic seizures. Cerebral spinal fluid (CSF) and serum autoantibody testing can confirm AE. Complementary examination with magnetic resonance imaging (MRI) and electroencephalogram (EEG) may be helpful for excluding other causes and managing seizures. In addition, exclusion of infectious and other origins must be considered.ImplicationsAE misdiagnosis can lead to a delay in treatment onset and, thus, clinical worsening. In this sense, identifying the causative agent is of utmost importance. However, the absence of CSF or serum antibody detection does not exclude the diagnosis of AE. Despite extensive testing, many encephalitis cases remain of unknown origin. It is obvious that some autoantibodies have not yet been identified in AE. Since radiological and biological examinations are not always contributive, early symptom recognition might help to hasten the diagnostic process.