Retrospective analysis of variables favouring good surgical outcome in posterior epilepsies.

AIM: to determine variables favouring good surgical outcome in posterior epilepsies. METHODS: Fourteen patients submitted to epilepsy surgery were included in the study. The epileptogenic zone was located in temporo-parieto-occipital areas as assessed by both invasive and non-invasive pre-surgical evaluation. Several variables (age at first seizure; age at surgery; disease duration; type, frequency and clinical semiology of seizures; presence of lesion; scalp ictal and interictal EEG; localization and extension of epileptogenic zone; completeness of surgical resection) were compared (Fisher's exact test) with freedom from seizures to determine whether surgical outcome (Engel's classification) could be related to any of them. RESULTS: Seven patients were seizure free (Ia) and very satisfying results were obtained for 3 patients (2 Ib, 1 Ic). New post-surgical visual deficits occurred only in 3 patients. Surgical outcome was related significantly to two variables: scalp ictal EEG (focal versus non-focal; p: 0.014) and completeness of surgical resection of epileptogenic zone (p: 0.0023). A significant trend towards a better outcome for focal interictal intracranial activity versus a non-focal one (p: 0.07) was found. CONCLUSIONS: The correlation between completeness of epileptogenic zone resection and surgical outcome suggests that a presurgical protocol, allowing a precise definition of the area of resection, could help in obtaining more satisfying results in posterior epilepsies.

The human supplementary motor area-proper does not receive direct somatosensory inputs from the periphery: data from stereotactic depth somatosensory evoked potential recordings.

Somatosensory evoked potentials to median nerve (MN) stimulation were recorded by stereotactically implanted electrodes in the frontal lobe of two epileptic patients in order to evaluate whether short-latency cortical responses could be generated in the supplementary motor area (SMA)-proper. In both patients two potentials, called P20 and N30 responses, showed a decreasing amplitude from the most superficial to the deepest contacts and were recorded in the white as well in the grey matter of the frontal lobe. Furthermore, no phase reversal of both P20 and N30 potentials was identifiable along electrode trajectories. Our results suggest that short-latency somatosensory evoked responses recorded in the SMA-proper contralateral to MN stimulation are volume conducted from remote cortical generators.