MEMORY FUNCTION DURING LOW-INTENSITY HIPPOCAMPAL ELECTRICAL-STIMULATION IN PATIENTS WITH TEMPORAL-LOBE EPILEPSY

Hippocampal memory dysfunction is a main symptom of mesiotemporal lobe epilepsy (TLE). It may increase after temporal lobectomy for seizure relief. The aim of this study was to assess the ability of psychometry during hippocampal electrical stimulation to predict post-operative m emory deficits and thereby to contribute to lateralization of the epil eptogenic zone, A computerized memory test was performed during low in tensity hippocampal stimulation in nine patients with TLE during invas ive presurgical evaluation. The following results were obtained: speec h dominant hippocampal stimulation induced subtle verbal memory defici ts in patients with the epileptogenic zone in the speech dominant hemi sphere and normal baseline memory performance. Verbal memory deficits could not be induced in patients with the epileptogenic zone in the sp eech dominant hemisphere and pre-existing memory deficits, or if the s eizure origin was contralateral to speech dominance, Thus it was possi ble to lateralize the epileptogenic zone in patients with normal basel ine memory performance by revealing hippocampal dysfunction only durin g electrical stimulation. Post-operative psychometric testing demonstr ated that the individual risk for impairment of verbal memory performa nce following temporal lobectomy could be predicted correctly. In conc lusion, psychometry during hippocampal stimulation may allow predictio n of memory deficits following temporal lobectomy and improve determin ation of the epileptogenic zone.