Paraneoplastic and autoimmune encephalopathies

Immune-mediated encephalitis is an increasingly recognized cause of neurologic dysfunction including behavioral change, psychosis, movement disorders, seizures, autonomic instability, and coma. Associated antineuronal antibodies are of two main subtypes, those targeting neuronal cell surface antigens, which are pathogenic, and nonpathogenic antibodies targeting intracellular antigens. Antibody identification aids in screening for underlying cancers and prediction of outcome. Cancer is found most commonly with antibodies targeting intracellular neural components. Certain cancers, such as small-cell lung carcinoma, and breast and ovarian cancer are particularly immunogenic. When cancer is detected, oncologic treatment should be followed with immunotherapy. Nonpathogenic antibody disorders respond poorly to treatment, whereas pathogenic antibodies predict a favorable response to immune treatment. If no cancer is identified, then ongoing surveillance is recommended for 5 years after detection of most antineuronal antibodies.