Seizure duration decreases over a course of bifrontal and not bitemporal electroconvulsive therapy

Mechanism of action of electroconvulsive therapy (ECT) is unclear. Anticonvulsant action of ECT has also been one among the hypothesized mechanisms. Anticonvulsant effect may manifest during ECT in at least two ways (a) increased seizure threshold (b) decrease in seizure duration. In depression, increased seizure threshold has been shown to be associated with better antidepressant response. However, relationship between seizure duration and antidepressant activity has been inconsistent. These issues are not investigated in conditions other than depression.

We examined seizure duration over the course of ECT in schizophrenia patients.

Material for this analysis was obtained from a clinical trial examining the differential efficacy of bifrontal ECT (BFECT) versus bitemporal ECT (BTECT) in schizophrenia patients. As a part of study 122 schizophrenia patients who were prescribed ECT were randomized to receive either BFECT or BTECT.

Final analysis was conducted on data from 70 patients, as the rest of the data either had artifact or there was a significant change in medication status. Electroencephalogram seizure duration was noted in each session for these patients.

Seizure duration declined significantly from second ECT to 6(th) ECT (repeated measures analysis of variance F = 4.255; P = 0.006). When separate analysis was conducted for BTECT and BFECT patients the decline in seizure duration from 2(nd) to 6(th) ECT was significant only with BFECT (F = 3.94; P = 0.014) and not with BTECT (F = 0.966; P = 0.424).

Better anticonvulsant effects with BFECT may explain the better therapeutic observed with BFECT in schizophrenia as well as mania in our earlier studies.