Abstracts

Rationale: Surgical results in mesial temporal sclerosis (MTS) decrease when ictal scalp-EEG is topographically discordant from MRI-lesion. In these cases, minimally invasive EEG records (mEEGinv) help to identify the epileptogenic zone (EZ). We describe a case-series of patients with topographically non-concordant electro-imagiological findings evaluated with mEEGinv. Methods: Review of patient database of our epilepsy surgery program, searching for patients who fulfilled the following criteria: MTS on MRI; ictal scalp-video-EEG non-topographically concordant with the MRI-lesion; undergoing mEEGinv.Results: We identified 6 patients, 4 women, mean age 23 years. In the ictal scalp-EEG, 4 patients had seizures in the frontal region ipsilateral to MTS, 2 with controlateral temporal onset. In the first 4 patients, unilateral mEEEGinv were used (1 foramen ovale, 1 depth electrode), in the remainder two, bilateral temporal depth electrodes. In 5/6 patients, all recorded seizures started from the MTS region and have been submitted to surgery (amygdalo-hippocampectomy+temporal lobectomy), with 100% Engel I (mean follow-up 40 months); one patient 2/5 seizures arised away from MTS and surgery was refused. Conclusions: In this small series, by using mEEGinv, we demonstrate that in most of the patients with MTS and ictal scalp-EEG topographically non-concordant with the lesions disclosed in MRI, the seizures in fact start from MTS, with the scalp findings resulting from seizure propagation (falsely localized/ lateralized seizures). A minimally invasive study can be considered in the pre-surgical evaluation of patients with MTS and discordant electro-clinical-imagiological findings, contributing for the good surgical outcome.