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Autoantibody encephalitis causes distinct clinical syndromes involving alterations in mentation, abnormal movements, seizures, psychiatric symptoms, sleep disruption, spasms, and neuromyotonia. The diagnoses can be confirmed by specific antibody tests, although some antibodies may be better detected in spinal fluid and others in serum. Each disorder conveys a risk of certain tumors which may inform diagnosis and be important for treatment. Autoantibodies to receptors and other neuronal membrane proteins are generally thought to be pathogenic and result in loss of function of the targets, so understanding the pharmacology of the receptors may inform our understanding of the syndromes. Patients may be profoundly ill but the syndromes usually respond to immune therapy, although there are differences in the types of immune therapy that are thought to be most effective for the various disorders.

Autoimmune encephalitis causes subacute deficits of memory and cognition, often followed by suppressed level of consciousness or coma. A careful history and examination may show early clues to particular autoimmune causes, such as neuromyotonia, hyperekplexia, psychosis, dystonia, or the presence of particular tumors. Ancillary testing with MRI and EEG may be helpful for excluding other causes, managing seizures, and, rarely, for identifying characteristic findings. Appropriate autoantibody testing can confirm specific diagnoses, although this is often done in parallel with exclusion of infectious and other causes. Autoimmune encephalitis may be divided into several groups of diseases: those with pathogenic antibodies to cell surface proteins, those with antibodies to intracellular synaptic proteins, T-cell diseases associated with antibodies to intracellular antigens, and those associated with other autoimmune disorders. Many forms of autoimmune encephalitis are paraneoplastic, and each of these conveys a distinct risk profile for various tumors. Tumor screening and, if necessary, treatment is essential to proper management. Most forms of autoimmune encephalitis respond to immune therapies, although powerful immune suppression for weeks or months may be needed in difficult cases. Autoimmune encephalitis may relapse, so follow-up care is important.