Clinical Features, CSF Antibody Titer, and Outcome of Anti-NMDA Receptor Encephalitis in Japan
Shintaro Saegusa1, Masaki Iizuka1, Tomomi Iwami1, Kensuke Ogata1, Emi Furusawa1, Hitomi Nakagawa1, Masaaki Nakamura1, Juntaro Kaneko1, Taira Toki2, Yutaka Nonoda2, Eiji Kitamura1, Naomi Kanazawa1, Kazutoshi Nishiyama1, Takahiro Iizuka1
1Deaprtment of Neurology, 2Department of Pediatrics, Kitasato University School of Medicine
Objective:

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

Background:
A few studies have addressed CSF-titers at diagnosis. Second/third-line immunotherapy has increasingly been used but it remains unclear when or to whom it should be administered.
Design/Methods:

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. 

Results:

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.

Conclusions:

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. 

10.1212/WNL.0000000000213027
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