Study On The Application Of SEEG Electrophysiological Indexes In The Location Of Epileptogenic Zone Of Refractory Epilepsy And The Analysis Of Epileptogenic Network

Objective: The precise location of epileptogenic zone(EZ)is the most important step in the preoperative assessment for patients with refractory epilepsy(RE),The purpose of this study is to locate the epileptogenic zone and analyze the epileptogenic network based on the multimodal preoperative precise evaluation of epileptic surgery,and further explores the relation between SEEG electrophysiological indexes and prognosis of patients.Data and Methods: Data of preoperative assessment and EEG data during SEEG attack of 26 patients with intractable epilepsy(RE)who were implanted with deep electrodes in the brain in the premise of the preoperative precise assessment of multimodal epileptic surgery in the Department of Functional Neurosurgery of the Second Hospital Attached to Lanzhou University from December,2017 to December,2019 were analyzed retrospectively.The image post-processing technology was used to fuse the skull CT after implantation of electrode,preoperative MRI and PET images for 3D reconstruction.The technology combined with such three electrophysiological indexes as high frequency oscillations(HFOs),DC shift and epileptogenic index(EI)recorded and calculated,the critical value of EI ≥ 0.3 was defined as a significant positive EI value and analyze the epileptogenic network,and perform individuated surgical treatment after the precise positioning of epileptic electrode contact.The epileptogenic network scope is categorized as follows: epileptogenic contact is limited to one gyrus or brain structure is limited,that more than two gyrus are limited to one lobe belongs to brain regions,more than one lobe is limited to one hemisphere,which is multi brain regions,and those involving two hemispheres are bilateral.The results were compared with the pathological results of patients.After a follow-up of more than 3 months,the prognosis of epilepsy was evaluated by Engel grading method as: good prognosis group(Engel Ⅰ),poor prognosis group(Engel II-IV).Results: 26 patients underwent the preoperative precise assessment of multimodal epilepsy surgery and the surgical intervention.Twenty males(76.9%)and six females(23.0%)were followed up for an average of 13.43 ± 5.01 months(3-23 months).Preoperative epileptic sequence MRI showed that 22 of 26 cases had different types of MRI abnormal signals,4 cases had no abnormal MRI,and interictal PET-CT examination showed that there were different degrees of metabolic abnormalities around the lesions or the brain regions.There were 184 electrodes implanted in 26 patients,the average number of electrodes implanted in each patient was 7.1 ± 1.26,the total number of electrode contacts was 2214,and the average number of electrode contacts in each patient was 85.1 ± 18.61.Among the 26 cases,11(42.3%)were temporal lobe epilepsy,9(34.6%)frontal lobe epilepsy,4(15.4%)insular cortex epilepsy,1(3.8%)parietal lobe epilepsy and 1(3.8%)temporal parietal occipital junction epilepsy.Among the 26 patients,19 had HFOs at the onset of SEEG attack,3 only had DC shift at the onset,23 cases with positive EI value in the algorithm of onset basis.The analysis of epileptogenic network showed that among 11 patients with temporal lobe epilepsy,the epileptogenic network scope was limited in 5 cases,brain regions in 3 cases,multi brain regions in 2 cases,being bilateral in 1 case;in 9 patients with frontal lobe epilepsy,the epileptogenic network scope was brain regions in 4 cases,multi brain regions in 5 cases;the epileptogenic network of 4 patients with insular cortex epilepsy,1 patient with parietal lobe epilepsy and 1 patient with temporal parietal occipital junction epilepsy was multi brain regions.The pathological results of 26 patients showed that 14 cases of FCD,3 cases of DNT,2 cases of hippocampal sclerosis,1 cases of GG(WHO Ⅰ grade),1cases of cavernous hemangioma,4 cases of radiofrequency thermocoagulation and 1 cases of simple pia meningeal dissection there were no pathological reports.According to the follow-up results,22 patients(84.6%)were in the good prognosis group(Engel I),and 4 patients(15.4%)were in the poor prognosis group(Engel II-IV).Statistical analysis showed that electrophysiological index HFOs and positive EI value,pathological type FCD,MRI positive results had statistical significance for the good prognosis of patients.Conclusion:1.Based on the precise location of multimodal epilepsy surgery,the application of SEEG,HFOs,DC shift and EI can assist the location of EZ and guide the formulation of individuated surgical procedures,so as to improve the operation effect.2.In the prognosis of epileptic patients,we found that HFOs,positive EI value,pathological type FCD and MRI positive results were significantly related to the good prognosis of patients.