S197 Foramen ovale electrodes in epilepsy

Temporal lobe epilepsy is the most prevalent type of epileptic syndrome, and also the most frequent type of surgically treatable epilepsy. But in many cases the laterality is difficult to prove based on non-invasive investigations and scalp EEG. There is broad evidence that suggest that the seizure onset zone may be on the opposite side compared to where the seizure is seen on the scalp EEG due to rapid spread to the contralateral side. Based on these data a technique was developed first by Wieser et al., which allowed direct corticographic recordings from the medial temporal structures without performing invasive surgery. The implantation of foramen ovale (FO) electrode proved to be safe, efficient and very useful in many cases where the seizure onset zone could not be determined on non-invasive data alone. In the last 20 years we have implanted FO electrodes in more tha 100 patients with success. We find using FO electrodes useful in answering the following questions: • Is there an unilateral onset? (laterality vs. Bilateral indenpendent onset?). • Evidence of seizure start in the mediobasal region? (localisation?). • Where is the seizure onset zone over the mediobasal. surface along the anterior – posterior axis? • Seizure propagation routes?