A case of anti-leucine-rich glioma inactivated protein 1 (LGI1) antibody-positive autoimmune encephalitis with electrographic seizures without epileptic seizure symptoms

A 59-year-old woman had abnormal behavior, anorexia and drowsiness from three weeks ago. She had disorientation, recent memory impairment, elevated blood pressure, and hyponatremia. Brain MRI showed a FLAIR high signal intensity lesion in the left medial temporal lobe. The cerebrospinal fluid was normal. Autoimmune encephalitis was suspected, and steroid pulse therapy and plasma exchange were performed. Electroencephalogram showed repeated electrographic seizure waveforms, and lacosamide was administered. Serum anti-leucine-rich glioma inactivated protein 1 (LGI1) antibody was found to be positive. The lesion had disappeared by the 90th days after onset. In autoimmune encephalitis, the possibility of epilepsy should be suspected and electroencephalogram (EEG) recording should be actively performed. Electrographic seizure pattern on EEG may be useful for early diagnosis of LGI1 antibody-associated encephalitis.