INTRACEREBRAL LOW-FREQUENCY ELECTRICAL-STIMULATION - A NEW TOOL FOR THE DEFINITION OF THE EPILEPTOGENIC AREA

Low Frequency (1 Hz) Electrical Stimulation (LFES) has been systematic ally utilized, during stereo-EEG investigations, in 24 consecutive you ng adult patients considered for surgical treatment of severe drug-res istant partial epilepsy.Ninety seizures (1-14/patient) identical to th e spontaneous ones previously recorded were thus obtained in 19 patien ts (79%). LFES is less effective for induction of seizures than high f requency (50 Hz) stimulation (5.9% vs 22.9%), and it also provokes les s ''false positive'' responses (1% vs 17%). The main ''sensitive'' str uctures to LFES are the hippocampus, the amygdala, and the hippocampal gyrus. However, seizures were also induced by stimulating the tempora l lobe white matter, the temporal pole, and the temporal neocortex, as well as the orbito-frontal cortex (in the only patient with fronto-te mporal epilepsy). The more frequently observed electrical pattern is a gradual increase of spikes and spikes and waves frequency, with or wi thout occurrence of low voltage fast activity. The high percentage of early ''subjective'' manifestations similar to the spontaneous ones, t he lack of major electrical artifact, and the good visualization of th e spatial evolution of the induced-discharge, strongly suggest that LF ES is of great help for defining the ''epileptogenic area''.