A Neurophysiological Study of Untilateral ECT

Abstract

The studies in this thesis were carried out in order to investigate electrophysiological and neurological differences in hemisphere function following administration of unilateral ECT. Three separate studies were performed in which the electroencephalogram (EEG), visual evoked potential (VEP), and somatosensory evoked potential (SEP) were recorded continuously for a period extending from just before to half an hour after ECT. In a further study, patients were neurologically examined before and after ECT. Quantitative analysis of the EEG showed that during the induced seizure, epileptic slow wave activity was of larger amplitude on the treated side. Immediately after the seizure, there was more delta and less alpha and beta activity on the treated side. This asymmetry, though becoming less marked, was usually still present at the end of the recording. The evoked potential studies revealed different results for the VEP and SEP. There was a clear asymmetry of the VEP after ECT with the P140 component being smaller and later on the treated side. Both amplitude and latency asymmetry resolved within fifteen minutes after the shock, but a significant latency increase, common to both hemispheres, persisted. In contrast, the SEP did not show any consistent hemisphere differences in either amplitude or latency, but a bilateral persistent latency increase was found for the P49 component. Neurological assessment of patients after ECT showed that most had signs of transient neurological dysfunction referable to the treated hemisphere. These signs included reflex asymmetry, hemiparesis, sensory and visual inattention, and homonymous hemianopia. All tested neurological abnormalities resolved within seventeen minutes of treatment. The seizures induced by unilateral ECT were compared with spontaneous unilateral seizures. Specific and non-specific mechanisms were invoked in order to explain the dissimilar behaviour of the VEP and SEP.