Scott M. Zoldi

EEG effects of ECT: Implications for rTMS

Electroconvulsive therapy (ECT) involves the use of electrical stimulation to elicit a series of generalized tonic–clonic seizures for therapeutic purposes and is the most effective treatment known for major depression. These treatments have significant neurophysiologic effects, many of which are manifest in the electroencephalogram (EEG). The relationship between EEG data and the response to ECT has been studied since the 1940s, but for many years no consistent correlates were found. Recent studies indicate that a number of specific EEG features recorded during the induced seizures (ictal EEG) as well as before and after a course of treatment (interictal EEG) are related to both the therapeutic efficacy and cognitive side effects. Similar to ECT, repetitive transcranial magnetic stimulation (rTMS), which involves focal electromagnetic stimulation of cortical neurons, has also been studied as an antidepressant therapy and also appears to have neurophysiologic effects, although these have not been as fully investigated as is the case with ECT. Given the similarity of these treatments, it is natural to consider whether advances in understanding the electrophysiologic correlates of the ECT response might have implications for rTMS. The present article reviews the literature on the EEG effects of ECT and discusses the implications in terms of the likely efficacy and side effects associated with rTMS in specific anatomic locations, the potential for producing an antidepressant response with rTMS without eliciting seizure activity, eliciting focal seizures with rTMS, and the possibility of using rTMS to focally modulate seizure induction and spread with ECT to optimize treatment. Depression and Anxiety 12:157–165, 2000.

Stationarity and redundancy of multichannel EEG data recorded during generalized tonic-clonic seizures.

To improve our understanding of the physiology of generalized tonic-clonic (GTC) seizures, we have investigated the stationarity and redundancy of 21-electrode EEG data recorded from ten patients during GTC seizures elicited by electroconvulsive therapy (ECT). Stationarity was examined by calculating probability density functions (pdfs) and power spectra over small equal-length non-overlapping time windows and then by studying, visually and quantitatively, the evolution of these quantities over the duration of the seizures. Our analysis shows that some seizures had no demonstrable stationarity, that most seizures had time intervals of at least a few seconds that were statistically stationary by several criteria, and that, in some seizures, there were leads which were delayed in manifesting the statistical changes associated with seizure onset evident in other leads. The redundancy analysis demonstrated for the first time posterior-to-anterior time delays in the mid-ictal region of GTC seizures. The implications of these findings are discussed for the analysis of GTC seizure EEG data, for the physiology of GTC seizures, and for ECT research.