Evoked potentials following unilateral ECT. I. The somatosensory evoked potential

The somatosensory evoked potential (SEP) was recorded in 14 patients undergoing unilateral ECT for the treatment of depression. All patients received right-sided ECT. One patient was studied on a second occasion during leftsided ECT. The index and middle fingers of each hand were electrically stimulated 1/sec throughout anaesthesia, the fit and the 0.5 h period following the fit. During barbiturate anaesthesia the SEP showed the characteristic change of the P49 component and enhancement of P32, while during the seizure induced by right ECT, the SEP was seen more clearly on the left side of the head, despite the high voltage epileptic activity. No significant asymmetries of any of the SEP components were seen post-ictally, the response returning rapidly on both sides. The subjective threshold to electrical stimulation of the fingers of each hand was significantly raised following ECT.