ICTAL PATTERNS IN TEMPORAL-LOBE EPILEPSY RECORDED BY EPIDURAL SCREW ELECTRODES

In a consecutive series of 11 patients with a history of medically ref ractory temporal lobe epilepsy, we studied the appearance of ictal pat terns detected by epidural screw electrodes (ESE) placed in an effort to obviate depth electrode recording. All had prior scalp-sphenoidal m onitoring with significant obscuration of ictal EEG by movement and mu scle artifact. Six to 10 ESE were placed at bilateral temporal locatio ns of the 10% system. Ictal findings in 4-15 partial seizures from 8 p atients with mesiobasal (MBTLE) and 3 patients with neocortical (NCTLE ) epilepsy were correlated with imaging and histology. Five of 8 patie nts with MBTLE had discrete high frequency discharges at onset, evolvi ng within 10 s to focal theta at ESE, before appearing at scalp electr odes. All had Class 1A outcome with mesial temporal sclerosis (MTS). T hree of 8 patients with MBTLE and MTS had less discrete onsets, with C lass 1A, 1B and 3A outcomes. Two patients with NCTLE had lesions; a gr ade II oligoastrocytoma with rhythmic delta at ESE and Class 4 outcome , and an anterior temporal cavernous angioma with variable onsets, som e of which were high frequency, with a Class 1A outcome. The third NCT LE patient demonstrated focal theta as an ictal pattern,had no lesion and a Class 1A outcome, Ictal onsets may be well localized in selected patients by ESE. A majority of patients with MTS display well defined high frequency ictal discharges. (C) 1997 Elsevier Science Ireland Lt d.