In 12 % patients suffering from tumours in the central parietal region or near this area, early compo- nents of cortical median SEPs were enhanced over 12 mV on the affected side in comparison to the healthy side 162–550 %, „absolute enhancement“, 12 cases) or enhanced the amplitude limit of N20-P22 over 2.5 mV (160–367 %, „relative enhancement“, 12 cases). Patients with „absolute enhancement“ of early cortical response suffered more often from simple partial sensorimotor seizures (10 patients, 83 %), sometimes also generalized tonic-clonic ones. Facilitation of the N20-P22 (onset of somatosensory signals at the thalamocortical level) at the C3/4 – Fz exceeding 12 mV is defined as an epileptic marker.

        Key words: SEPs, hemispheral tumours, epileptic seizures, facilitation