The ictal EEG as a marker of adequate stimulus intensity with unilateral ECT.

Relative stimulus intensity above seizure threshold has been shown to affect therapeutic outcome with unilateral ECT. The authors sought to explore whether a multivariate ictal EEG model would permit ongoing clinical assessment of this parameter. Twenty-five depressed subjects were randomized to either barely (T) or moderately (2.5T) suprathreshold ECT treatments. Seizures in 2.5T subjects had significantly greater ictal spectral amplitude and coherence, greater postictal suppression, and shorter latency until ictal slow-wave onset. A multivariate logistic regression ictal EEG model distinguished between stimulus intensity groups with 90% accuracy. Preliminary evidence suggests a relationship between several ictal EEG indices and therapeutic outcome. A multivariate ictal EEG algorithm holds promise as a tool for clinical determination of adequate stimulus intensity with unilateral ECT.