A rise in seizure threshold during a course of electroconvulsive therapy (ECT) has been demonstrated in patients with depression and mania, but no information has been available as to whether the same result occurs in schizophrenia. Ninety-three patients with schizophrenia underwent estimation of the seizure threshold by the dose-titration method, at the first and second, seventh, fourteenth, and twentieth treatments over an index ECT course. The 3-week stabilization period was used as a response criterion. Eighty-six patients (92%) showed a rise in threshold. The magnitude of increment was 269±244%. The rise in seizure threshold could be predicted by the number of treatments, initial seizure threshold and EEG seizure duration, and these factors explained 42% of the variance.
A substantial number of studies suggest that electroconvulsive therapy (ECT) possesses anticonvulsant properties. In animals, electroconvulsive shock has powerful anticonvulsant effects in blocking the development or aborting the expression of amygdala-kindled seizures (Post et al., 1986). In humans, an ECT-induced generalized seizure is immediately followed by a relative refractory period during which the threshold may be so elevated that restimulation often fails to elicit a seizure. It is also known that there is usually a progressive increase in seizure threshold over the treatment course (Sackeim et al., 1987a, Sackeim et al., 1987b, Coffey et al., 1995a and Coffey et al., 1995b). Moreover, ECT has previously been used to treat seizure disorders and their associated behavioral problems (Kalinowsky and Kennedy, 1943, Caplan, 1946, Taylor, 1946 and Sackeim et al., 1983).
Prior ECT studies in depressed patients report 30–100% increases in seizure threshold over a treatment course, in which the threshold values were reported only at the sixth or eighth session (Malitz et al., 1986, Sackeim et al., 1987a, Sackeim et al., 1987b, Sackeim et al., 1991, Sackeim et al., 1993, Coffey et al., 1995b and Shapira et al., 1996). A similar finding has been reported in manic patients (Mukherjee, 1989). The present study was conducted in patients with schizophrenia, and seizure threshold was quantified over a longer ECT course to evaluate changes in threshold and their relationship to the therapeutic outcome and clinical variables.
