To report the clinical features, outcome, and clinical significance of CSF antibody titers (CSF-titers) at diagnosis in anti-NMDAR encephalitis (anti-NMDARE). 

Of 106 patients diagnosed with anti-NMDARE between January 2007 and September 2025, 100 patients (median age at onset 28.5 years [IQR 21-37], 74 female) were included to assess whether second/third-line immunotherapy improves one-year outcome. We measured CSF-titers at diagnosis in 57 patients to investigate the clinical significance of measuring CSF-titers. 

95 received first-line immunotherapy median 9 days after symptom onset, 49/96 (51%) received second/third-line immunotherapy median 48 days. 5 died, but 60/89 (67%) achieved good outcome (mRS 0-2) at one year and 78% (78/100) at last follow-up (median 22 months [IQR 12-51 months]). 9 relapsed. Responders to first-line immunotherapy more frequently achieved good outcome at one year than non-responders. Among non-responders, those with second/third-line immunotherapy < 8 weeks of onset more frequently achieved good outcome than those without. Median CSF-titers at diagnosis were 1:128 (IQR 1:64-1:512). It was higher in patients with typical spectrum, ICU admission, ventilation support, the lack of improvement < 4 weeks of immunotherapy, and tumor compared with those without. CSF-titers at diagnosis had a significant effect on one-year outcome. CSF-titers at last follow-up declined in all 23 examined patients, but one had moderate CSF-titers (range 1:64-1:128) despite complete recovery 55 months after onset.

This study suggests 1) 67% achieved good outcome at one year, 78% at the last follow-up of median 22 months, 2) in non-responder, patients treated with second/third-line immunotherapy within 8 weeks of symptom onset more frequently achieved good outcome at one year than those without, 3) CSF-titers at diagnosis were associated with clinical features and one-year outcome.