Seizure identification in the ICU using quantitative EEG displays

Abstract

Objective: To evaluate the diagnostic accuracy of 2 quantitative EEG display tools, color density spectral array (CDSA) and amplitude-integrated EEG (aEEG), for seizure identification in the intensive care unit (ICU).

Methods: A set of 27 continuous EEG recordings performed in pediatric ICU patients was transformed into 8-channel CDSA and aEEG displays. Three neurophysiologists underwent 2 hours of training to identify seizures using these techniques. They were then individually presented with a series of CDSA and aEEG displays, blinded to the raw EEG, and asked to mark any events suspected to be seizures. Their performance was compared to seizures identified on the underlying conventional EEG.

Results: The 27 EEG recordings contained 553 discrete seizures over 487 hours. The median sensitivity for seizure identification across all recordings was 83.3% using CDSA and 81.5% using aEEG. However, among individual recordings, the sensitivity ranged from 0% to 100%. Factors reducing the sensitivity included low-amplitude, short, and focal seizures. False-positive rates were generally very low, with misidentified seizures occurring once every 17-20 hours.

Conclusions: Both CDSA and aEEG demonstrate acceptable sensitivity and false-positive rates for seizure identification among critically ill children. Accuracy of these tools would likely improve during clinical use, when findings can be correlated in real-time with the underlying raw EEG. In the hands of neurophysiologists, CDSA and aEEG displays represent useful screening tools for seizures during continuous EEG monitoring in the ICU. The suitability of these tools for bedside use by ICU nurses and physicians requires further study.

Figure 1 EEG recordings studied and overall performance using CDSA and aEEG displays Ability of reviewers to discriminate between the presence or absence of seizures in a given EEG recording using color density spectral array (CDSA) and amplitude-integrated EEG (aEEG) (based on median values).

Figure 2 Color density spectral array (CDSA) and amplitude-integrated EEG (aEEG) testing displays With the raw EEG tracing concealed, neurophysiologists were individually presented with either an 8-channel CDSA display (A) or an 8-channel aEEG display (B). Participants were instructed to “mark any epochs that they suspected to be seizures.” Their performance was compared to seizures identified by analysis of the raw EEG, as indicated in the top channel (concealed during testing).

Figure 3 Sensitivity and false-positive rates of color density spectral array (CDSA) and amplitude-integrated EEG (aEEG) for seizure identification among individual EEG recordings Bars represent median values for all 3 neurophysiologists, with error bars indicating the range of values obtained by individual reviewers.