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.
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