Quantitative EEG during seizures induced by electroconvulsive therapy: Relations to treatment modality and clinical features. II. Topographic analyses

This study tested three alternative theories of the mechanisms of therapeut ic action of electroconvulsive therapy (ECT). The theories differed in pred ictions about the global and topographic effects of effective and ineffecti ve forms of ECT on electroencephalogram (EEG) seizure expression. At the se cond treatment, 19-lead EEG recordings were obtained in 57 depressed patien ts randomized to conditions that differed in ECT electrode placement and st imulus dosage. Power in the delta frequency band was quantified during the seizure and analyzed with traditional multivariate methods and the Scaled S ubprofile Model. Electrical dosage of the ECT stimulus had a powerful effec t on ictal global delta power and, more so, than electrode placement. Great er ictal global delta power was associated with superior therapeutic outcom e, but the magnitude of this effect was small. Effective forms of ECT resul ted in a topography where delta power was accentuated in prefrontal EEG sit es. High dosage right unilateral ECT also resulted in stronger asymmetry in prefrontal regions than the ineffective, low dosage right unilateral ECT. Greater bilateral generalization of seizure expression does not appear to b e a prerequisite for therapeutic effects. Instead, more intense seizure exp ression in prefrontal regions may be critical for efficacy.