Thymoma‐associated autoimmune encephalitis: Analysis of factors determining prognosis

INTRODUCTION: Autoimmune encephalitis (AE) is a heterogeneous group of inflammatory central nervous system disorders caused by a misdirected immune response against self‐antigens expressed in the central nervous system. The thymus is a central organ in the immune system and thymic tumors are thought to be possible initiators of many neurological disorders. Recently, there is growing evidence that thymomas are associated with autoimmune encephalitis. AIMS: Our study initially explored the characteristics of patients with autoimmune encephalitis combined with thymoma. METHODS: We used patient data from January 1, 2011 to October 1, 2021 from the PubMed, Web of Science, Ovid, and CNKI platforms to analyze overall demographics, frequency of symptoms and associations, and treatment prognosis outcomes. RESULTS: A total of 68 patients were included. There were 39 female cases (57.4%). The mean age was 50 years (IQR 40–66 years). All had acute and subacute onset. The clinical manifestations were mostly cognitive changes (70.6%), mental disorders (57.4%), and epilepsy (50.0%). The most common neuronal antibody was alpha‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA). Magnetic resonance imaging (MRI) abnormalities were present in 81.0% of patients, mostly in the hippocampus, temporal lobe, and some in cortical and subcortical areas. Abnormalities in the electroencephalogram (EEG) in 69.8% of patients. Treatment involved immunotherapy and thymoma treatment, with 79.7% of patients improving after treatment. While 20.3% of patients had a poor prognosis. Further, 14.8% of patients relapsed. Mental disorders, autonomic dysfunction, sleep disturbances, anti‐Ma2, and thymoma untreated were more frequent in patients with poor prognosis. CONCLUSION: Thymoma‐associated autoimmune encephalitis is a unique disease entity. Long‐term follow‐up of chest CT findings is recommended for patients with autoimmune encephalitis.