Continuous EEG Monitoring and Quantitative EEG Techniques

Continuous EEG (cEEG) monitoring in critically ill patients is a noninvasive way to assess brain function and help identify clinically silent neurological events. Quantitative EEG (qEEG) is a method for analyzing and compressing vast amounts of cEEG-generated data and includes the visual representation of mathematically or statistically compressed raw EEG waveforms. Quantitative EEG techniques have allowed neurophysiologists to more efficiently review recordings reducing the time burden of analyzing complete raw EEG data sets. Furthermore, quantitative EEG trends are able to recognize subtle changes in the EEG earlier than other monitoring techniques and more easily display this information so that nonexpert staff can potentially recognize clinically important EEG patterns in a timely fashion. In this chapter, we will review the indications and potential uses for cEEG monitoring in critically ill patients including detection of nonconvulsive seizures or nonconvulsive status epilepticus, characterization of spells in comatose or stuporous patients as epileptic or non-epileptic, assessment of level of sedation, and the detection of early ischemia (using qEEG with trending of alpha/delta ratios).