Abstracts

Rationale: Among the potential long-term consequences of New Onset Refractory Status Epilepticus (NORSE), the development of epilepsy poses a significant risk, often proving resistant to medications. Currently, little is known about the determinants of post-NORSE epilepsy, and comprehensive studies detailing continuous EEG (cEEG) findings in both acute and chronic phases of NORSE are limited.

Methods: We conducted a retrospective study of NORSE patients from 2018-2024 within the Mount Sinai Health System (MSHS) which is a large, tertiary hospital system in the New York City region. Data were collected using the NORSE registry at the MSHS and included demographics, time from first seizure to cEEG connection, seizure types and locations, changes in seizure burden in the initial 3 days of cEEG, total duration of cEEG, total days with seizures on cEEG, treatment modalities, and functional outcomes. For patients with available follow-up information, seizure control and functional outcome using the modified Rankin Scale (mRS) were also documented.

Results: We identified a total of 9 patients (8 females, median age 40 years, range 15-77). Four (44%) were cryptogenic, three exhibited mildly elevated serum GAD65 antibodies, one had a POLG mutation, and another was diagnosed with West Nile Virus (WNV) encephalitis. Prior fever was reported in 7/9. The average time from the first seizure to cEEG connection was 3 days (range 0-7) except for the two who were transferred (30 and 43 days, respectively). Tonic-clonic seizures were the predominant presenting seizure type, with only two presenting with focal motor seizures. The mean duration of cEEG was 24 days, during which seizures were identified for a mean of 10 days. The mean number of IV anesthetic drugs administered was 2.3, with a mean duration of 8.3 days. Bilateral temporal and posterior regions were the most common seizure onset areas (7/9). Most patients (7/9) experienced an increase in seizure burden during the initial 3 days of monitoring despite escalating medications. Except for one patient with WNV encephalitis, all received both first and second-line immunotherapy, 5 were on the ketogenic diet, and 7 underwent vagus nerve stimulation. One died during the acute admission. Longer-term follow-up was available for 5/8; all but one with WNV encephalitis developed epilepsy and remained on 3 Anti-Seizure Medications. Two had long-term EEG monitoring, revealing frontocentral epileptiform discharges. Notably, all 5 exhibited improved functional outcomes since discharge (mean mRS from 3.4 at discharge to 2.2 at 15 months).


Conclusions: In this case-series of NORSE patients in an urban tertiary hospital system, cEEG monitoring frequently showed increasing seizure burden in the first days despite escalating anti-seizure medications. Consistent with other series, most surviving patients later developed drug-resistant epilepsy. Further multi-center studies are imperative to elucidate the clinical variables determining the development of post-NORSE epilepsy and to identify strategies for its prevention and/or reduction of seizure burden. Continuous EEG findings may provide additional insight into this disorder.

Funding: None