The diagnosis of autoimmune encephalitis should be considered in patients with rapid progression (<3 months) of short-term memory loss, decreased or altered level of consciousness, lethargy, personality change, or psychiatric manifestations in association with at least one of the following criteria: new-onset seizures or focal CNS symptoms, CSF pleocytosis, or MRI features suggestive of brain inflammation. Many alternative causes of encephalitis can be excluded after a careful clinical history and evaluation of the CSF, brain MRI, and routine blood tests. Some types of encephalitis can be suspected before receiving the results of neural antibodies, according to the clinical presentation (for instance, faciobrachial dystonic seizures in anti-LGI encephalitis, or psychotic manifestation in anti-NMDAR encephalitis) or brain MRI features (temporal lobe involvement in limbic encephalitis). Antibody testing may show false positive and negative results, particularly when only serum is examined, results are not confirmed with additional laboratory studies, or the test is used indiscriminately without selection of patients.