EEG in unilateral and bilateral electroconvulsive therapy.

The investigation concerned 100 patients with endogenous depression treated with ECT, 52 unilaterally on the non-dominant hemisphere, and 48 bilaterally. A double-blind investigation of the therapeutic effect and the effect on memory and on EEG was carried out. With unilateral treatment, mainly diffuse and same-sided EEG changes appeared, while with bilateral treatment mainly diffuse and left-sided changes occurred. Bilateral treatment led to significantly more EEG changes than did unilateral treatment. For both groups there was a tendency to greater changes after the last than after the sixth treatment. At termination of treatment, a significantly better therapeutic effect was found in cases where EEG changes appeared, especially severe EEG changes. This applied to the total material but not to the groups of unilaterals and bilaterals taken separately. In the entire material after the first six treatments, the greatest representation of patients with unchanged and impaired memory was found in cases with deteriorated EEG compared to cases with no EEG deterioration. After the entire series of ECT, this correlation no longer was present. After separation of the patients into unilaterals and bilaterals it was not present at any of the stages. In the bilateral group ECT treatment gave more frequent and stronger EEG changes, among the older than among the younger patients. For the unilateral group, there was no comparable difference. The number of weak seizures was significantly greater among the unilaterals than among the bilaterals. The therapeutic effect was not correlated to the number of weak seizures, but the number of weak seizures was positively correlated to the number of treatments applied.