Quantitative EEG for predicting outcome in postanoxic status epilepticus


Introduction: Electrographic status epilepticus is observed in 10-35% of patients with postanoxic encephalopathy after cardiac arrest, and is associated with poor neurological outcome. We aim to identify quantitative electrographic features that indicate either a good or poor outcome, with respect to seizure patterns and their temporal evolution.

Methods: For 46 patients with electrographic status epilepticus, we assessed continuous EEG recordings during the first 72 hours after cardiopulmonary resuscitation. For every hour, we selected five minute epochs that were assessed visually and categorized into one of seven categories. Temporal evolution of the signal was further assessed using a quantitative continuity parameter. From epochs that were classified as epileptiform, additional quantitative EEG features were extracted. These features were selected for best mimicking a human observer reading EEG. The administration of all sedative medication and antiepileptic drugs was recorded. Outcomes after three months were categorized according to the Cerebral Performance Category, dichotomized into ‘good’ (CPC 1 to 2 = no or moderate neurological disability) and ‘poor’ (CPC 3 to 5 = severe disability, coma, or death).

Results: A poor neurological outcome was observed in 36 patients. All 18 patients who developed status epilepticus from a non-continuous background pattern or during sedative treatment had a poor outcome. Patients with poor outcome had been treated more often with antiepileptic drugs, while their seizures were less likely to disappear within the first 72 hours. In terms of quantitative features, their EEGs showed epileptic discharges with a higher spatial generalization, a more regular inter-discharge interval, a higher morphologic correlation of subsequent discharges, a more suppressed background and their discharges made a higher contribution to the total signal power.

Discussion: We demonstrate that quantitative EEG features can be used to predict poor outcome in patients with postanoxic status epilepticus. Our findings suggest that EEG patterns leading to poor outcome merely reflect severe ischemic brain damage rather than a purely epileptic phenomenon.

Wednesday 10 December 2014, 16:30 – 17:30 h

Building Carré- room 3718