New-onset refractory status epilepticus (NORSE) and febrile infection-related epilepsy syndrome (FIRES) of unknown aetiology: A comparison of the incomparable?

Purpose: The discussion is ongoing whether new-onset refractory status epilepticus (NORSE) in adults and febrile infection-related epilepsy syndrome (FIRES) in children are one syndrome if the aetiology is unknown. In this study we will compare an adult cohort with NORSE and a paediatric cohort with FIRES in order to determine if they are similar or different.

Methods: We retrospectively compared 18 adults with NORSE versus 48 children with FIRES, both cohorts without identifiable cause despite extensive investigations. We analyzed demographic and clinical data using Mann-Whitney-U and χ- tests.

Results: NORSE affected more women (78% vs. 42%; P = 0.009) than in FIRES. Median acute hospital stay was longer in FIRES (35 days [interquartile range, IQR=36] vs. 20 days [IQR=19]; P<0.001). FIRES was treated more frequently with coma therapy (82% vs. 28%; P<0.001) and with a higher median number of antiseizure medicines (7 [IQR=5] vs. 4 [IQR=2]; P<0.001). Children with FIRES showed a higher cerebrospinal fluid (CSF) cell count (10 cells/μl; P = 0.002) but a lower CSF protein level than adults with NORSE (48 mg/dl; P = 0.028). Immunotherapy was administered more frequently in FIRES (73% vs. 22%; P<0.001) than in NORSE. Group differences in number of antiseizure medicines after hospital stay (P = 0.229) and in overall mortality (P = 0.327) were not significant.

Conclusion: In our explorative comparison, differences prevailed. NORSE and FIRES should be compared prospectively in age-matched cohorts.