Phenotyping the late- and younger-onset neuronal surface antibody-mediated autoimmune encephalitis: a multicenter study.

Neuronal surface antibody-mediated autoimmune encephalitis (NSAE) occurs across a wide age range. However, few studies focused on the onset age and their related characteristics. We aimed to explore the age-dependent profile of NSAE. A total of 134 patients with a definite diagnosis of NSAE were retrospectively enrolled from 3 tertiary hospitals between July 2014 and August 2020. Demographic, clinical, therapeutic, and prognostic data were collected and compared between the late- (≥45) and younger-onset (<45) groups. The results showed that 56 (41.8%) patients were classified as late-onset NSAE, and 78 (58.2%) as younger-onset NSAE. There were more males, especially in the late-onset group (P = 0.036). Prodromal symptoms were more common in the younger-onset group (P = 0.004). Among the onset symptoms, more late-onset patients presented as seizures, while more younger-onset patients presented as psychiatric symptoms. Throughout the disease course, the late-onset patients were more likely to have memory dysfunction (P < 0.001), but less likely to have central hypoventilation (P = 0.045). The late-onset patients also had a significantly lower modified Rankin Scale score on admission (P = 0.042), required intensive care unit (ICU) admission less frequently during hospitalization (P = 0.042) and had a shorter hospital stay (P = 0.014). Our study revealed that the late- and younger-onset NSAE had a distinct spectrum of demographic features, presentations, and prognoses. More attention is needed for the younger-onset patients, given a higher disease severity on admission, more frequent requirement for ICU admission and longer length of stay.