The ictal EEG in ECT: A systematic review of the relationships between ictal features, ECT technique, seizure threshold and outcomes.

OBJECTIVE:To provide guidance for ECT practitioners in utilising the ictal EEG to inform treatment decisions. METHODS:A systematic review of studies examining the ictal EEG, treatment technique, seizure threshold and treatment outcomes was conducted. MEDLINE, EMBASE and PsycINFO databases were searched up to July 31, 2019. Studies were included if they examined the use of ECT in human subjects and compared an ictal EEG analysis (either quantitative or manually rated) with either: a) clinical outcomes, b) seizure threshold/threshold change, c) ECT dosing decisions, or d) different aspects of ECT technique (comparison of different electrode placements, pulse widths, waveforms, or dose/dose relative to seizure threshold). RESULTS:A total of 853 studies were identified, with 44 meeting inclusion criteria. A qualitative review revealed ictal EEG indices have been linked to therapeutic outcome, though the strength of this relationship appears modest. Ictal EEG features are influenced by variations in ECT treatment technique. Serial ictal EEG monitoring can detect changes in seizure threshold across an ECT course for right unilateral brief and ultrabrief pulse ECT. CONCLUSION:While there is some relationship between ictal EEG manifestation and treatment outcomes, the primary utility of ictal EEG monitoring during an ECT course may lie in the capacity to detect changes in seizure threshold and adjust dosing accordingly. Prospective validation of a dosing regime informed by serial ictal EEG monitoring is warranted.