Pitfalls in ictal EEG interpretation: critical care and intracranial recordings

EEG is the cornerstone examination for seizure diagnosis, especially nonconvulsive seizures in the critically ill, but is still subject to many errors that can lead to a wrong diagnosis and unnecessary or inadequate treatment. Many of these pitfalls to EEG interpretation are avoidable. This article reviews common errors in EEG interpretation, focusing on ictal or potentially ictal recordings obtained in critically ill patients. Issues discussed include artifacts, nonepileptic events, equivocal EEG patterns seen in comatose patients, and quantitative EEG artifacts. This review also covers some difficulties encountered with intracranial EEG recordings in patients undergoing epilepsy surgery, including issues related to display resolution.