Abstracts

It is widely accepted that surgical outcome in non-lesional epilepsy cases is not comparable to the outcome of anterior temporal lobectomy or amygdalohippocampectomy with MRI documented mesial temporal sclerosis. Fortunately, non-lesional cases make up a small percentage of epilepsy surgery series. In our current communication, we present our experience in treating patients with non-lesional, mainly extra temporal, epilepsy and we also try to identify the prognostic factors that might predict a seizure free outcome. Our retrospective clinical series included 51 patients who were surgically treated in our institution over a period of 11 years (1992-2003). The patients[rsquo] age ranged between 3 and 47 years while their mean age was 22.5 years. Regarding their pre-operative work-up, this included thorough clinical examination with emphasis in the seizure semiology, ictal and interictal surface EEG, invasive EEG monitoring with depth and subdural electrodes and MRI in all of our patients while MEG was obtained in 9 of our patients (17.6%). Based on the patients clinical semiology, EEG and MEG (whenever available) findings the patient underwent surgical resection by employing standard subpial aspiration/resection technique. Engel[rsquo]s modified classification system was used for the evaluation of the surgical outcome at one year post-operatively; 25 patients (49%) were class I, 6 patients (11.7%) were class II, 6 patients (11.7%) were class III while 14 patients (27.4%) were class IV. Regarding their age at surgery, 34 patients were older than 18 years while 17 patients were younger than 18 years; among the older patients, 16 patients (47.0%) were class I while the respective percentage in the younger group of patients was 52.9% (9 out of 51). In regards to the inter-ictal surface EEG findings, among the 13 patients with localizing findings 8 patients (61.5%) had class I outcome while in 38 patients with non-localizing findings 17 patients (44.7%) were seizure free. Regarding the surgical resection site and the outcome, in 24 frontal resections 10 patients (41.6%) were seizure free, in 4 patients with temporal resection 2 (40%) were seizure free, in 3 patients with occipital resection only 1 patient (33.3%) was seizure free, in 5 patients with fronto-temporal resection 4 patients (80%) were seizure free in 8 patients with temporo-parietal resection 5 patients (62.5%) were seizure free and finally in 2 patients with occipito-temporal resection one patient (50%) had class I outcome. Finally, in the group of 9 patients where MEG studies were available, only 2 (22.2%) were seizure free. Our clinical series confirms the inferior surgical outcome of non-lesional cases compared to the one of well-defined temporal lobe seizure foci resection. Early surgery and localizing inter-ictal EEG findings might represent favorable prognostic factors in the surgical outcome of this challenging group of patients.