The Value Of High Gamma In The Ecog In The Location Of Epileptogenic Zone

Objective: To compare the occurrence rate and distribution of the high gamma(65-100Hz)and the spike inside and outside the irritative zone and around the focal by analyzing the intraoperative electrocorticography(ECo G)of patients with refractory temporal lobe epilepsy in order to evaluate the localization value for epileptogenic zone.Methods: A retrospective analysis study of intraoperative electrocorticography data in our hospital from January 2013 to January2019 including 21 patients with refractory temporal lobe epilepsy was carried out.The channels with interictal epileptiform discharges(IEDs)were defined as area A(i.e.irritated area)and those without IEDs were defined as area B(i.e.non-irritated area).Combined with preoperative imaging data,intraoperative navigation and neurosurgeon’s judgment,dividing the monitoring cortical area into area C(the focal area),area D(the perifocal area),and area E(areas away from the focus).Compare the occurrence rate and distribution characteristics of IEDs(filter range: 1～30Hz)and High gamma(filter range: 65 ～ 100 Hz),and analyze the distribution of High gamma inside and outside the irritative zone,and the incidence of High gamma around the focal.Results:(1)The total occurrence rates of IEDs and High gamma in 21 patients were 100.0%(21/21)and 100.0%(21/21),respectively.The average channel number of IEDs,High gamma,Gamma+IEDs were(9.50±2.80),(8.14±2.93),(6.60±2.40)respectively,suggesting that the channel number of IEDs was significantly higher than High gamma,and higher than Gamma+IEDs by one-way ANOVA.(2)The average channel number of High gamma and the event rate of High gamma in area A and area B were(6.60±2.40),(1.50±1.30);(0.42±0.30);(0.20±0.20),respectively.Suggesting that area A was significantly higher than area B by paired t-test.(3)The number of High gamma events in area C,D and E were(46.00±42.00),(33.40±32.90),(8.40±9.40),and the event rates are(0.40±0.30),(0.37±0.38),(0.10±0.10).There was no significant difference in the number events and the event rate of High gamma in the area C and D by paired t-test,area C and D were significantly higher than area E respectively by paired t-test.Conclusion: Traditional IEDs are still important markers to guide the range of resection in epilepsy surgery by intraoperative ECo G.High gamma has great consistency with IEDs and focal,and the identification of epileptogenic zone is more accurate than IEDs.Therefore,IEDs combined with High gamma may have a higher value in locating epileptogenic zone.