Event-related potentials in patients with temporal lobe epilepsy reveal topography specific lateralization in relation to the side of the epileptic focus

Event-related potentials (ERPs) were recorded during a continuous recogniti on memory paradigm in patients with left-sided (LTLE; n = 8) or right-sided temporal lobe epilepsy (RTLE; n = 6), and in healthy control subjects (n = 24). Control subjects and both patient groups exhibited consistent OLD/NEW ERP-differences from 200-600 ms after stimulus onset. ERPs did not differ significantly between LTLE and RTLE patients, with respect to OLD/NEW disti nction or the type of presented material (verbal vs, non-verbal). However, ERP topography showed significant differences between LTLE and RTLE patient s: in lateral fronto-temporal recordings, patients showed larger negativiti es contralateral to the seizure focus, whereas we found larger negativities ipsilateral to the seizure focus in parietal recordings. Differences betwe en the groups were significant from 300 to 600 ms post-stimulus. As a conse quence, the amplitude gradient from frontotemporal to parietal recordings w as higher on the right side in LTLE patients and on the left side in RTLE p atients. Again, differences between LTLE and RTLE patients were highly sign ificant. We assume that ERPs reflect disturbances of a cortico-cortical net work dependent on the side of the seizure focus in temporal lobe epilepsy. Furthermore, scalp-recorded ERPs might be a useful tool in the prediction o f the side of the seizure focus in patients with temporal lobe epilepsy. (C ) 1998 Elsevier Science Ireland Ltd. All rights reserved.