Magnetic and seizure thresholds before and after six electroconvulsive treatments

Objectives: Electroconvulsive therapy (ECT) is a well-established treatment in psychiatry. It has been reported that in patients with nondelusional major depression, transcranial magnetic stimulation (TMS) may substitute for ECT. To explore whether ECT and TMS share mechanisms of action, we studied the effects of ECT on both seizure threshold (ST) and magnetic motor threshold (MT). Methods: We measured ST and MT in 10 patients referred for ECT. MT was defined as the minimal power of the TMS equipment at which a motor evoked potential (MEP) response could be detected 50% of the time. ST was defined as the minimal intensity of electrical stimulation needed to elicit an adequate seizure. ECT was performed following the methods recommended by the American Psychiatric Association. All subjects signed an informed consent for participation in the research. Results: We measured MT and ST in 10 patients before and after 6 ECT treatments. No changes in MT were detected from the treatment (paired t-test: t = 1.05, SD = 4.78, p = 0.25). ST, on the other hand, increased significantly with treatment (paired t-test: t = 2.99, SD = 190.20, p < 0.001). Conclusions: ECT and TMS do not share a common mechanism at least with regard to MT and ST.