Role of epileptogenicity index in the epileptogenic zone and network localization

Abstract

Objective To propose a novel stereo-electroencephalography(SEEG) quantitative measure analyzing ictal high frequency (60-90 Hz) and calculating high frequency epileptogenicity index (HFEI) to localize epileptogenic zone and evaluate epileptogenic network. Methods The clinical presurgical evaluation and SEEG data of 15 patients who were performed SEEG electrodes implantation from April 2015 to March 2016 were analyzed retrospectively. Post-implantation head CT images and 3D MRI data were fused for accurately identifying and locating each electrode contact. Ictal SEEG quantitative measure HFEI was calculated and threshold was set. The epileptogenic network was divided into focal, regional, multiple regional and bilateral ones and the results were compared with the pathological results. Results The epileptogenic network was focal for four patients, regional for four patients, multiple regional for six patients and bilateral for one patient (7/15). In terms of the pathology, two cases with hippocampal sclerosis both showed regional network. In four cases with cerebral malacia, two cases showed multiple regional network and the other two cases showed focal network. In six cases with cortical malformation, three cases showed multiple regional network, the other three cases showed focal, regional and bilateral networks respectively. Conclusions We explored a novel SEEG quantitative measure based on the high frequency power analysis, which is objective and could localize epileptogenic zone and evaluate the epileptic network. Key words: Epilepsy; Electroencephalography; Nerve net