An Epileptogenic Network Study Of Occipital Lobe Epilepsy Based On Stereo-electroencephalography

Objective: To identify the epileptogenic areas in occipital and extraoccipital regions,using a multi-disciplinary discussion and high frequency epileptogenic index(HFEI)based on the multimodal epilepsy preoperative accurate assessment system supported by stereoelectroencephalography(SEEG),MSC was used to calculate the connectivity between epileptic areas,and the epileptic network of occipital lobe epilepsy was classified to study the clinical characteristics,transmission characteristics and surgical treatment effect of different subtypes of epileptic network.Materials and methods: A retrospective analysis was conducted from December2016 to 2020 In July,10 patients with occipital lobe epilepsy underwent standardized and standardized multimodal pre-operative accurate assessment of epilepsy in the fourth ward of Neurosurgery,the second hospital of Lanzhou University.The data included detailed history,epilepsy sequence MRI,PET-CT,VEEG,image postprocessing image and neuropsychological examination.The analysis of SEEG data was based on HFEI proposed by Yuquan Hospital of Tsinghua University.According to the comprehensive analysis of clinicians and HFEI,defined a pure occipital group and an occipital “plus” group,the latter including two further subgroups,occipitotemporal and occipitoparietal.Surgical intervention(including simple epileptogenic region resection,epileptogenic region resection + transection of transverse fiber,radiofrequency thermocoagulation)was carried out according to the principle of treatment.The patients were followed up for more than 6 months.Engel grade was used to evaluate the prognosis.Engel grade I was defined as good prognosis and Engel grade II-IV as poor prognosis.Results: A total of 10 patients were included in this study,including 5 males(50%)and 5 females(50%);(1)All the 10 patients underwent intracranial electrode implantation,the total number of implanted electrodes was 72,3 damaged electrodes were removed,and the average effective electrodes was 6.9 ± 1.37;the total number of implanted leads was 932,34 damaged leads were removed,and the average number was 89.8 ± 22.04.All leads were calculated by HFEI.The results showed that there were 85 epileptogenic leads and 119 epileptogenic leads by professional electrophysiologists.The average sensitivity and specificity of HFEI algorithm were39.01 ± 7.83% and 95.22 ± 2.43%.(2)The results of single patient and 10 patients’ MSC analysis showed that the PP value was the largest,the PN value was the second,and the NN value was the smallest,showing that the connectivity between epileptic electrodes was the strongest,the connectivity between epileptic electrodes and non epileptic electrodes was the second,and the connectivity between non epileptic electrodes was the weakest,indicating the possibility of increased connectivity between epileptic areas and surrounding brain areas.(3)Results of network analysis:2 patients(20%)with pure occipital lobe network were involved in epileptogenic structures,including lingual gyrus,fusiform gyrus,talar fissure and cuneus with high HFEI value.After surgical treatment,1 patient had a good prognosis and 1 patient had a poor prognosis.There were 6 cases(60%)with occipitotemporal network,the epileptogenic structures included lateral occipital gyrus,hippocampus head,hippocampus body,cauda equina,superior temporal gyrus and inferior temporal gyrus,the spread was fusiform gyrus → lateral occipital gyrus → temporal lobe.The prognosis was good in 3 cases and poor in 3 cases.There were 2 cases(20%)with occipitoparietal network.The epileptogenic structures included fusiform gyrus,lateral occipital dorsal gyrus,accessory motor area,precuneus and posterior cingulate gyrus.The spread was fusiform gyrus → lateral occipital dorsal gyrus → precuneus →accessory motor area or posterior cingulate gyrus.The prognosis of 2 cases was good.Conclusion: 1.There are three types of epileptogenic network in occipital lobe epilepsy,including pure occipital lobe type,occipitotemporal type and occipitoparietal type,which respectively represent that the early epileptogenic network is limited in occipital lobe,ventral spreading type and dorsal spreading type.2.In the early spread of occipitotemporal epilepsy,fusiform gyrus and lateral occipital gyrus are important network nodes,while in occipitoparietal epilepsy,fusiform gyrus and lateral occipital dorsal gyrus are important network nodes.