Epileptiform EEG activity of the centromedian thalamic nuclei in children with intractable generalized seizures of the Lennox-Gastaut syndrome.

Centromedian thalamic nuclei (CM) epileptiform EEG activities were recorded in children with intractable generalized seizures of Lennox-Gastaut syndrome (LGS) through implanted recording-stimulating electrodes used for seizure control. Ictal CM epileptiform activities were consistently correlated to widespread surface cortical EEG activities and symptoms in all patients and all types of generalized seizures; i.e., fast spike discharges at CM correlated at onset of tonic and tonic-clonic generalized seizures; slow (1-2 Hz) spike-wave complex discharges at CM correlated for atypical absence seizures; slow polyspike-wave complex discharges correlated for myoclonic seizures; and spike bursts and suppression patterns correlated for combined tonic-atonic-myoclonic seizures. Ictal EEG activities occurred simultaneously at right and left CM and surface at onset of all seizure types, with the exception of myoclonic seizures where CM complete discharges and individual spike-wave complexes significantly lead those of the surface. Brief tonic-atonic spasms clinically undistinguishable from "real" epileptic seizures showed no EEG counterparts at CM and surface. Interictal CM spike-wave complete discharges and individual spike-wave complexes showed variable amplitude-temporal patterns. Amplitude emphasis on CM and frontopolar regions was observed in most of complete discharges, however, and phase shifts between CM and frontopolar regions were observed in individual spike-wave complexes.