Value Of High-frequency Oscillations Of Electrocorticography For Intraoperative Localization With Symptomatic Epilepsy

Objective: By analyzing the occurrence rate of High-frequencyoscillations(HFOs) of electrocorticography(ECoG) in abnormal dischargearea with non-temporal lobe symptomatic epilepsy, the relationshipbetween HFOs and spikes, and the rate between HFOs and spikes withpostoperative seizure control, to explore the value of HFOs for intraoperativelocalization withnon-temporal lobe symptomatic epilepsy.Methods: A retrospective analysis of137patients with non-temporallobe symptomatic epilepsy in our hospital from August2011to October2013. It was initial positioning of epileptic foci combined clinicalsymptoms, EEG and MRI before operative. After dural incision, the use ofECoG to locate abnormal electrophysiological discharge area with spikes.Set the sampling frequency of2000Hz, and the time constant of240mm/sabout EEG. To analysis spikes(0.5-30Hz) and HFOs, includingripple(R,80-250Hz) and fast ripple(FR,250-500Hz), between inside andoutside of abnormal discharge area. Abnormal discharge in non-functionalarea was with resection/fuser while in functional area was with only fuser. The patients were followed up for2.5years on time, to compare the rate ofseizure free with HFOs and spike.Result:1.137of137cases had spikes, while79of137cases hadHFOs of ECoG:69cases had R alone,10cases had R and FR,0cases hadFR alone. Spikes occur on average207.8±44.2times per minute, R22.8±3.6times per minute and FR0.9±0.3times per minute. There aresignificant difference between HFOs and spikes(p<0.05).2.With in and outof abnormal discharge area, R and FR occur on average24.7±4.2times,1.1±0.4times and16.8±2.9times,0.6±0.1times, there is significantdifference(p<0.05).3. Postoperative seizure free reach Engel I-II of all cases.Postoperative residual spikes in Engel I and II are97cases (89.81%,97/108)and28cases (96.55%,28/29), there is no significant difference(p>0.05).Postoperative residual R in Engel I and II are8cases（7.41%，8/108）、21cases（72.41%，21/29）, there are significant difference(p<0.05). Thenumber of postoperative residual R and spikes in Engel I and II are10.7±3.2times、14.8±1.7times and36.7±10.4times、66.8±17.3times. Thereis significant difference between Engel I and II (p<0.05).Conclusion: In the non-temporal lobe symptomatic epilepsy, theconsistency between HFOs and spikes are well, but the rate and volume ofoccurrence are low. It can not guide intraoperative localization of epilepticfoci independently without spikes by now. Residual HFOs are associatedwith postoperative seizures and HFOs are better than the spikes in predicting postoperative outcome. If we can combine HFOs and spikes forintraoperative positioning, there may be able to get a better outcome.