Periodic EEG discharges are signs of severe CNS dysfunction. In psychiatry they usually indicate presenile dementia of the Jacob-Creutzfeldt type. Psychiatric patients are presented in whom the occurrence and EEG features of diffuse and lateralized periodic discharges are discussed. It appears that toxic conditions other than acute barbiturate intoxication, such as drug withdrawal states and psychotropic drug overdosage, represent important etiological factors for inducing periodic EEG discharges. Their relation to clinical signs such as epileptic symptoms, metabolic dysfunction, and disturbance of consciousness is particularly stressed and related to current literature data.

The prevalence of cerebral malignancy in psychiatric patients is investigated in our own clinical material and compared with literature data. The importance of cellular type and localization of the lesion is checked and related to clinical symptoms such as seizures and psychopathological symptoms. The recognition of cerebral malignancy in psychiatric patients, especially in the early stages when few or no neurological signs are present, is shown to be a complex clinical problem. The possibilities and restrictions of technical investigations in general and of the EEG in particular are stressed.