Role of the centromedian thalamic nucleus in the genesis, propagation and arrest of epileptic activity. An electrophysiological study in man.

Abstract

Twenty-eight patients underwent electrical stimulation of the centromedian (CM) thalamic nucleus as a neuro-augmentative procedure to control intractable seizures of various types. To assess the correct placement of electrodes, electrical stimulation at 3 and 6 Hz, 1.0 msec and 600-2000 uA pulses in trains of 30-60 sec were used while the EEG was recorded by scalp electrodes. Spontaneous seizure activities of various types were simultaneously recorded. In cases of focal epilepsy depth electrodes were used in order to study the sequence of activation of different structures. Three Hz electrical stimulation induced spike-and-wave complexes accompanied by a typical absence. Eight Hz induced recruiting-like responses with ipsilateral predominance and no clinical manifestations. Interictal spike activity was recorded in the CM in cases of generalized tonic-clonic convulsions (GTCC) and ictal spike pattern in the CM preceded discharges in other areas. In atypical absences cortical and CM discharges occurred simultaneously. It is concluded that the CM participates in the onset of GTCC and typical absences, in the propagation of secondary GTCC but not in myoclonic convulsions.