Postictal Encephalopathy After Status Epilepticus: Outcome and Risk Factors

BACKGROUND: Postictal encephalopathy is well known after status epilepticus (SE), but its prognostic impact and triggers are unknown. Here, we aimed to establish risk factors for the development of postictal encephalopathy and to study its impact on survival after discharge.

METHODS: This retrospective cohort study comprised adult patients diagnosed with first nonanoxic SE at Odense University Hospital between January 2008 and December 2017. Patients with ongoing SE at discharge or unknown treatment success were excluded. Postictal symptoms of encephalopathy were estimated retrospectively using the West Haven Criteria (WHC). WHC grade was determined for postictal day 1 to 14 or until the patient died or was discharged from the hospital. Cumulative postictal WHC during 14 days after SE-cessation was used to quantify postictal encephalopathy. Clinical characteristics, patient demographics, electroencephalographic and imaging features, and details on intensive care treatment were assessed from medical records.

RESULTS: Of all eligible patients (n = 232), 198 (85.3%) had at least WHC grade 2 postictal encephalopathy that lasted for > 14 days in 24.5% of the surviving patients. WHC grade at discharge was strongly associated with poor long-term survival (p < 0.001). Postictal encephalopathy was not associated with nonconvulsive SE, postictal changes on magnetic resonance imaging, or distinct ictal patterns on electroencephalography. Although duration of SE and treatment in the intensive care unit showed an association with cumulative postictal WHC grade, they were not independently associated with the degree of encephalopathy when controlling for confounders. In a linear regression model, etiology, duration of sedation, age, and premorbid modified Rankin Scale were significant and consistent predictors for higher cumulative postictal WHC grade. Exploratory analyses showed an association of a cumulative midazolam dosage (mg/kg/h) with higher cumulative postictal WHC grade.

DISCUSSION: In this cohort, postictal encephalopathy after SE was common and associated with poor long-term survival. Seizure characteristics were not independently associated with postictal encephalopathy; the underlying etiology, long (high-dose midazolam) sedation, high age, and poor premorbid condition were the major risk factors for its development.