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

This study examined the effects of electroconvulsive therapy (ECT) treatmen t conditions, patient individual difference factors, and clinical outcome o n global electroencephalogram (EEG) power during and immediately following ECT-induced seizures. Sixty-two patients were randomized to ECT conditions differing in electrode placement (right unilateral versus bilateral) and st imulus dosage (just above seizure threshold versus 2.5 times seizure thresh old). At the second and penultimate treatments, global total power (1.5-28. 5 Hz) and global power in specific frequency bands were quantified in 19-le ad EEG recordings of the generalized seizure and the immediate postictal pe riod. Seizures induced with high dosage, and to lesser extent, with bilater al electrode placement, resulted in greater global power. Patient age, init ial seizure threshold, and baseline depression severity were inversely rela ted to global power during seizures. While superior clinical outcome follow ing ECT was associated with greater global power during seizures, this effe ct was small. The factors associated with more robust seizure expression al so resulted in greater postictal bioelectric suppression. Associations with treatment parameters and patient variables were stronger at the second tha n penultimate treatment. We conclude that manipulations of ECT technique st rongly determine the magnitude of seizure expression, but relations with cl inical outcome are weak. The findings raise doubt about the clinical utilit y of algorithms based on analysis of EEG features to guide ECT parameter se lection.