A Case of Anti-LGI1 Limbic Encephalitis Presenting With Non-convulsive Status Epilepticus and Requiring a Long Period of Hospitalization.

An 81-year-old man was brought to our hospital with tonic-clonic seizures and a gradual progression of cognitive dysfunction. Four months prior, he experienced transient episodes of stiffness and unresponsiveness. One month later, the patient began to exhibit disorientation to time and place. Upon admission, fluid-attenuated inversion recovery (FLAIR) brain magnetic resonance imaging (MRI) revealed hyperintense lesions in the right limbic cortex. Electroencephalography (EEG) revealed lateralized periodic discharges in the right temporal lobe. Serum anti-LGI1 antibody was detected. Based on these findings, anti-LGI1 limbic encephalitis (LE) was diagnosed. His symptoms improved with corticosteroid treatment; however, six months of hospitalization were necessary for him to regain independence in daily living. Although the prognosis of anti-LGI1 LE is generally favorable, older age at onset, non-convulsive status epilepticus, diffuse limbic lesions, and delayed treatment may have influenced the clinical course in this case.