[Clinical features and long-term prognosis of probable antibody-negative autoimmune encephalitis in children]

Objective: To investigate the clinical features and long-term prognosis of children with probable antibody-negative autoimmune encephalitis. Methods: A retrospective cohort study included 35 children who diagnosed with probable antibody-negative autoimmune encephalitis. They were admitted to the Department of Neurology, Capital Center for Children's Health, Capital Medical University, from September 2016 to December 2024. Demographic data (age at onset, sex), clinical manifestations (seizures, psychiatric symptoms, and altered consciousness), ancillary investigations (cerebrospinal fluid analysis, brain MRI, and electroencephalography), treatment strategies (immunotherapy and antiseizure medications), and long-term outcomes with a follow-up of ≥12 months were collected and analyzed. Results: Among the 35 children, 21 children (60%) were male and 14 children (40%) were female, with the age at onset of (8±4) years. The predominant neurological manifestations were seizures in 27 children (77%) and psychiatric symptoms in 21 children (60%). Status epilepticus occurred in 18 children (51%) during the acute phase. In terms of ancillary findings, 25 children (71%) showed inflammatory changes in cerebrospinal fluid. Brain MRI abnormalities were observed in 24 children (69%). Among this 24 children there were 13 cases (54%) in the basal ganglia involvement group, 6 cases (25%) in the limbic lobe involvement group, and 5 children (21%) in the other brain regions involvement group. The duration to appearance of abnormal MRI signals was 7 (3, 15), 22 (12, 28) and 7 (5, 76) d respectively. Abnormal background activity on electroencephalography was detected in 29 children (83%). All children received first-line immunotherapy, and 13 children (37%) required second-line immunotherapy. The follow-up duration was 41 (22, 60) months. At the last follow-up, 32 children (91%) had a favorable outcome. A total of 5 children (14%) experienced relapse, occurring 10 (5, 16) months after initial onset; all showed clinical improvement after re-initiation of immunotherapy. Conclusions: Probable antibody-negative autoimmune encephalitis in children predominantly affects school-age individuals and is characterized by seizures as the main clinical presentation. Immunotherapy is effective in most cases, with generally favorable long-term outcomes and a low relapse rate. Re-treatment with immunotherapy remains beneficial in relapsing patients.