Missed and brief seizures during ECT: differential response between unilateral and bilateral electrode placement

The number of electroconvulsive therapy (ECT) stimulations over a course of treatment that resulted in brief or no seizure activity was evaluated for depressed patients (N = 58, treated for DSM-III diagnosed major depressive disorder) who had been randomly assigned to either bilateral or unilateral nondominant ECT in a double-blind study. Comparable treatment efficacy between both groups was found. Although there were no group differences in brief seizures, unilateral nondominant ECT resulted in more missed seizures (p less than 0.01) and required more restimulations than bilateral ECT. Of 27 unilateral ECT patients, 63% had at least one missed seizure over the course of treatment, compared to 29% of 31 bilateral ECT patients (p less than 0.02). Although more missed seizures occurred early in treatment, brief seizures occurred later in treatment. As missed seizures are not always detected clinically, it is possible that without seizure monitoring, patients with unilateral nondominant ECT will not improve at the same rate as patients with bilateral ECT. Lack of seizure monitoring in the clinic is one likely explanation for the discrepancy between a number of research studies reporting equivalent efficacy for bilateral and unilateral ECT and the clinical impression that bilateral ECT is more effective.