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.