Abstracts

Rationale: Continuous electroencephalography (EEG) is emerging as a valuable tool for the monitoring of brain function among the critically ill. Several quantitative EEG tools have been developed to facilitate the interpretation of these prolonged EEG recordings. The aim of this study was to evaluate the utility of two quantitative EEG tools, Color Density Spectral Array (CDSA) and amplitude-integrated EEG (aEEG) for seizure identification among critically ill children undergoing continuous EEG monitoring. Methods: We searched a database for continuous EEG recordings of at least 12 hours duration that had been performed in the pediatric intensive care unit at The Hospital for Sick Children, Toronto. A board-certified electroencephalographer reviewed the raw EEG recordings and marked all seizures. The raw 13- or 21-channel EEGs were then transformed into separate 8-channel CDSA and aEEG displays employing a double-distance anterior-posterior biopolar montage (see figure). Three neurophysiologists and three EEG technologists underwent training on the use of CDSA and aEEG for seizure identification. These experts were then asked to separately review the CDSA and aEEG displays of all recordings (blinded to the raw EEG) and mark epochs that they suspected to be seizures. Their CDSA and aEEG interpretation was then compared to the seizures identified by the ‘gold-standard’ raw EEG interpretation in order to calculate sensitivity of CDSA and aEEG for seizure identification, and the false-positive rates per hour. Recordings with and without seizures were included for review. Results: We identified 28 continuous EEGs totaling 509 hours of recording and containing 553 discrete seizures. The overall median sensitivity of CDSA for seizure identification was 83%, with a range of 73% to 89% for individual testers. The overall median sensitivity of aEEG for seizure identification was 74%, with a range of 60% to 84%. The overall average false-positive rate of CDSA was 0.24/hour, with a range of 0.04/hour to 0.61/hour. The overall average false-positive rate of aEEG was 0.12/hour, with a range of 0.02/hour to 0.30/hour. However, among individual recordings, the sensitivity of CDSA and aEEG for seizure identification varied from 0% to 99%. Factors reducing the sensitivity included seizures that were focal and of low amplitude. Among individual recordings, the false-positive rate of CDSA and aEEG varied from 0/hour to 2.22/hour. Factors increasing the false-positive rate included movement and electrode artifacts, and non-ictal EEG waveforms such as periodic epileptiform discharges and a burst-suppression background pattern. Conclusions: Both CDSA and aEEG appear to be promising tools for seizure identification in critically ill children, with similar sensitivity and false-positive rates when used by experts trained in electroencephalography. Future directions include evaluation of CDSA and aEEG for seizure identification by those without formal EEG training, such as intensive care physicians and bedside nurses.