AbstractBackgroundWe investigate the frequency and diagnostic yield of cerebrospinal fluid (CSF) analysis in adult patients with status epilepticus (SE) and its impact on the outcome.MethodsFrom 2011 to 2018, adult patients treated at the University Hospital Basel were included. Primary outcomes were defined as the frequency of lumbar puncture and results from chemical, cellular, and microbiologic CSF analyses. Secondary outcomes were differences between patients receiving and not receiving lumbar puncture in the context of SE.ResultsIn 18% of 408 patients, a lumbar puncture was performed. Of those, infectious pathogens were identified in 21% with 15% detected ± 24 h around SE diagnosis. 74% of CSF analyses revealed abnormal chemical or cellular components without infectious pathogens. Screening for autoimmune diseases was only performed in 22%. In 8%, no or late (i.e., > 24 after SE diagnosis) lumbar puncture was performed despite persistent unknown SE etiology in all, transformation into refractory SE in 78%, and no recovery to premorbid neurologic function in 66%. Withholding lumbar puncture was associated with no return to premorbid neurologic function during hospital stay independent of potential confounders. Not receiving a lumbar puncture was associated with presumed known etiology and signs of systemic infectious complications.ConclusionsWithholding lumbar puncture in SE patients is associated with increased odds for no return to premorbid neurologic function, and CSF analyses in SE detect infectious pathogens frequently. These results and pathologic chemical and cellular CSF findings in the absence of infections call for rigorous screening to confirm or exclude infectious or autoimmune encephalitis in this context which should not be withheld.