Current Status of Diagnosis and Treatment in Cryptogenic New-onset Refractory Status Epilepticus (C-NORSE) in Japan
Takahiro Iizuka1, Tomomi Iwami1, Shintaro Saegusa1, Masaki Iizuka1, Naomi Kanazawa1, Hitomi Nakagawa1, Masaaki Nakamura1, Juntaro Kaneko1, Eiji Kitamura1, Kazutoshi Nishiyama1
1Department of Neurology, Kitasato University School of Medicine
Objective:
To report current status of diagnosis and treatment in patients with cryptogenic new-onset refractory status epileptics (C-NORSE) in Japan.
Background:

Approximately half of the patients with NORSE is cryptogenic, but it is often difficult to differentiate C-NORSE from secondary NORSE in an emergency situation because it is not easy to get antibody test results quickly. We therefore developed C-NORSE score to identify C-NORSE patients quickly in 2017.

Design/Methods:

Among 721 patients with suspected autoimmune encephalitis (AE) tested for neuronal surface antibodies between Jan. 2007 and Dec. 2025, 63 (admitted to 34 hospitals) were diagnosed with C-NORSE.

Results:

Among the 721 patients, C-NORSE was the second most common disorder (n=63, 9%) after anti-NMDAR encephalitis (n=107, 15%). High C-NORSE score (≥5/6) was seen in 58/61 (95%) and exclusively in C-NORSE patients. 34 (54%) were female. Median age at onset was 29 years (range, 5-74 years). CSF analysis revealed pleocytosis in 67%, but not oligoclonal bands. Brain MRI was initially normal in 31/61 (51%) but abnormal at follow-up in 55/60 (92%); autoimmune-limbic encephalitis (ALE) MRI pattern was less frequently seen than ALE-Plus pattern (8% vs. 42%). First-line immunotherapy was used in 62 (98%) a median of 2 days, while second/third-line immunotherapy in 29 (46%) a median of 20 days. Tocilizumab has increasingly been used since 2022. The last follow-up outcome at median 16.8 months (IQR 6-45) was poor (mRS ≥3) in 40/63 (63%), with a mortality rate of 11% (n=7). Poor outcome was associated with initial brain MRI abnormalities, but not with ALE or ALE-Plus pattern, or the use of second/third-line immunotherapy. 59 (94%) developed drug-resistant post-NORSE epilepsy.

Conclusions:

C-NORSE is the second most common disorder in patients with suspected AE. C-NORSE score is useful for identification of C-NORSE patients. Second/third-line immunotherapy didn't improve functional outcome or prevent development of post-NORSE epilepsy, but further study is needed. 

 

 

10.1212/WNL.0000000000212927
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