Abstract: Abstract: Objective To explore the clinical characteristics of leucine-rich glioma inactivated protein 1 (LGI1) antibody encephalitis. Methods The clinical data of three cases of LGI1 antibody encephalitis were retrospectively collected in the department of neurology of Tianjin Huanhu Hospital from 2014 to 2016, and the clinical characteristics were summarized. Results All the three patients were middle-aged males, and their clinical manifestations were cognitive dysfunction, involuntary movement and sleep dysfunction. Among the patients, two experienced mental symptoms, one showed preceding infection and facial dystonic seizures (FBDS), two experienced seizures and hyponatremia. MRI showed abnormalities in all the patients, mainly involving the unilateral or bilateral medial temporal lobe and the hippocampus. LGI1 antibody detection in blood and cerebrospinal fluid was positive. Tumors were not found by all examinations. Symptoms improved or alleviated after immunotherapy (steroids and intravenous immunoglobulin). Conclusion For the middle-aged and old male encephalitis patients with cognitive dysfunction, involuntary movement, psychiatric symptoms, sleep dysfunction and hyponatremia as the main manifestations, it should be alert to the possibility of LGI1 antibody encephalitis. Cerebrospinal fluid antibody detection is required for definite diagnosis. Early immunotherapy can significantly improve the clinical prognosis.

Key words: leucine-rich glioma inactivated protein 1, encephalitis, faciobrachial dystonic seizures, hippocampus, hyponatremia