<scp>Acute and Long‐Term EEG</scp> and seizure characteristics in new onset refractory status epilepticus (NORSE)

OBJECTIVE: This study was undertaken to examine acute and chronic electroencephalographic (EEG) and seizure characteristics in new onset refractory status epilepticus (NORSE). METHODS: Multicenter inpatient and follow-up clinical and EEG data were analyzed using International League Against Epilepsy definitions and American Clinical Neurophysiology Society (ACNS) EEG terminology. RESULTS: Forty-four patients were included from the Yale NORSE/FIRES Biorepository (median age = 29 years, 33 female, 38 cryptogenic). Nine hundred twenty inpatient EEG days were reviewed (median = 13.5 days/patient). Presenting status epilepticus (SE) types included 24 convulsive SE (CSE), five focal-motor (FMSE), and 15 nonconvulsive (NCSE). Of 39 patients with post discharge follow-up (median = 14.7 months), 61.5% (n = 24) had seizures and required more antiseizure medications than seizure-free patients (median = 4 vs. 1, p < .001). Inpatient EEG captured epileptiform discharges in all and periodic discharges in 38 patients. Seizures were captured in 38 patients: 33 electrographic (11 only electrographic) and 27 electroclinical. Total seizure burden ranged 6.5-29 615.0 min (median = 50.7). Seizures fulfilling ACNS EEG criteria for SE were captured in 20 patients; two had CSE and the remainder NCSE with coma, nine of whom also had FMSE. Inpatient seizure days (median = 50.0 vs. 15.5%, p = .004) and seizure burden (median = 42.9 vs. 0 min, p = .009) were higher in the first half of monitored days. Interictal findings were equally present and did not predict postdischarge seizures, whereas electroclinical seizures (90.9% vs. 45.5%, p = .037), seizure burden (median = 116.8 vs. 32.5 min, p = .045), and proportion of seizure days (36.3% vs. 20.0%, p = .037) did. Among 12 patients with follow-up EEGs (median = 19.6 months post onset), posterior-dominant rhythm (PDR) returned in nine; five had periodic discharges, and three had seizure captured. SIGNIFICANCE: Seizures are most commonly convulsive upon presentation and nonconvulsive or clinically subtle throughout the inpatient course in NORSE. Inpatient seizures, but not interictal abnormalities, occur earlier in the inpatient course and presence of electroclinical seizures, seizure burden, and proportion of seizure days but not interictal findings are associated with postdischarge seizures. Although return of PDR reflects neurological recovery, seizure persistence and EEG abnormalities post-NORSE are common.

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Journal
Epilepsia
Published
2026-06-26
DOI
https://doi.org/10.1002/epi.70349
Primary Topic
Epilepsy research and treatment
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article
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article

Acute and Long‐Term EEG and seizure characteristics in new onset refractory status epilepticus (NORSE)

Nicolas Gaspard, Ayush Batra, Aurélie Hanin, Kia Gilani et al.
Epilepsia
Epilepsy research and treatment
article

Acute and Long‐Term EEG and seizure characteristics in new onset refractory status epilepticus (NORSE)

Nicolas Gaspard, Ayush Batra, Aurélie Hanin, Kia Gilani, Olga D. Taraschenko, Stephen Hantus, Teneille Gofton, Aaron F. Struck, Karnig Kazazian, Sophie Demeret, Minjee Kim, Elizabeth E. Gerard, Ji Yeoun Yoo, Gregory Scott Day, Krista Eschbach, Alexandra Ramírez, Brandon Foreman, Raquel Farias‐Moeller, Vincent Navarro, Claude Steriade, Padmaja Kandula, Lawrence J. Hirsch, Hiba A. Haider, Mark S. Wainwright, Laken Behrndt, Anthony D. Jimenez, M. Morales, Cederic M. Pimentel, Carla Cobos‐Hernandez, Margaret T. Gopaul, Peter Kang, Marissa Kellogg, Amy Jongeling, Daniel J. Zhou
article en

Abstract

OBJECTIVE: This study was undertaken to examine acute and chronic electroencephalographic (EEG) and seizure characteristics in new onset refractory status epilepticus (NORSE). METHODS: Multicenter inpatient and follow-up clinical and EEG data were analyzed using International League Against Epilepsy definitions and American Clinical Neurophysiology Society (ACNS) EEG terminology. RESULTS: Forty-four patients were included from the Yale NORSE/FIRES Biorepository (median age = 29 years, 33 female, 38 cryptogenic). Nine hundred twenty inpatient EEG days were reviewed (median = 13.5 days/patient). Presenting status epilepticus (SE) types included 24 convulsive SE (CSE), five focal-motor (FMSE), and 15 nonconvulsive (NCSE). Of 39 patients with post discharge follow-up (median = 14.7 months), 61.5% (n = 24) had seizures and required more antiseizure medications than seizure-free patients (median = 4 vs. 1, p < .001). Inpatient EEG captured epileptiform discharges in all and periodic discharges in 38 patients. Seizures were captured in 38 patients: 33 electrographic (11 only electrographic) and 27 electroclinical. Total seizure burden ranged 6.5-29 615.0 min (median = 50.7). Seizures fulfilling ACNS EEG criteria for SE were captured in 20 patients; two had CSE and the remainder NCSE with coma, nine of whom also had FMSE. Inpatient seizure days (median = 50.0 vs. 15.5%, p = .004) and seizure burden (median = 42.9 vs. 0 min, p = .009) were higher in the first half of monitored days. Interictal findings were equally present and did not predict postdischarge seizures, whereas electroclinical seizures (90.9% vs. 45.5%, p = .037), seizure burden (median = 116.8 vs. 32.5 min, p = .045), and proportion of seizure days (36.3% vs. 20.0%, p = .037) did. Among 12 patients with follow-up EEGs (median = 19.6 months post onset), posterior-dominant rhythm (PDR) returned in nine; five had periodic discharges, and three had seizure captured. SIGNIFICANCE: Seizures are most commonly convulsive upon presentation and nonconvulsive or clinically subtle throughout the inpatient course in NORSE. Inpatient seizures, but not interictal abnormalities, occur earlier in the inpatient course and presence of electroclinical seizures, seizure burden, and proportion of seizure days but not interictal findings are associated with postdischarge seizures. Although return of PDR reflects neurological recovery, seizure persistence and EEG abnormalities post-NORSE are common.

Epilepsia
Northwestern University (US), Western University (CA), Centre National de la Recherche Scientifique (FR), University of Wisconsin System (US), Nebraska Medical Center (US), CARE USA (US), Brooklyn Hospital Center (US), Cleveland Clinic (US), Université Libre de Bruxelles (BE), Inserm (FR), Oregon Health & Science University (US), Neurosciences Institute (US), Medical College of Wisconsin (US), Washington University in St. Louis (US), Cornell University (US), London Health Sciences Centre (CA), Jacksonville College (US), Yale University (US), Sorbonne Université (FR), University of Chicago (US), University Hospital (CA), Children's Hospital Colorado (US), Assistance Publique – Hôpitaux de Paris (FR), Seattle Children's Hospital (US), Pitié-Salpêtrière Hospital (FR), Mayo Clinic in Florida (US), Institut du Cerveau (FR), The Neurological Institute (US), New York University (US), University of Nebraska Medical Center (US), University of Cincinnati (US), University of Pennsylvania (US), University of Colorado Denver (US), Icahn School of Medicine at Mount Sinai (US)
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Epilepsy research and treatment
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