Ketamine-induced electroconvulsive phenomena in the human limbic and thalamic regions.

In nine patients with cortical, limbic and thalamic electrode implants, correlative electrical activity and gross behavior were observed following administration of ketamine, 70 per cent N2O, and thiopental. Ketamine was administered in four dosages: 0.5, 1, 2, and 4 mg/kg. One patient who received 0.5 mg/kg iv manifested depth-clectrode seizure activity without loss of consciousness. Two patients, receiving 1 mg/kg iv, developed increased frequency in their depth-clectrode EEC's with transient unconsciousness. All six patients receiving 2 or 4 mg/kg iv developed electrical seizure activity in the limbic and thalamic areas, with uncorrected behavioral manifestations ranging from apparent “unconsciousness” and immobility to actual tonic and clonic motor activity. The surface EEG did not manifest the intense electrical activity in the limbic region at all times. In contrast, administration of 70 per cent N:O and 400 mg thiopental did not induce electrical seizure phenomena. It is suggested that ketamine be used cautiously in patients with seizure disorders.