The Value Of Scalp High Frequency Oscillations To Identify Epileptogenic Zone In Secondary Epilepsy

Objective: comparing the occurrence rate and distribution of spine sharp wave and high frequency oscillations inside and out side the irritative zone and seizure onset zone in secondary epilepsy patients with scalp EEG in order to evaluate the lovation value for epileptogenic zone.Methods: a retrospective analysis of video electroencephalogram(V-EEG) data in our hospital between September 2011 and September 2012,including 37 patients with secondary epilepsy.1.Selecting 30 minutes EEG segments in awake and close eyes or NREM I ~ II with less disturbed, statistics for all patients with interictal spike and sharp waves and HFOs total Occurrence rate of attack; according to interictal spike and sharp wave frequency,patients were divided into high, medium and low group(A, B, C three groups). Analysis the Occurrence quantity of HFOs in each group.2. The Channels with interictal spikes and sharp wave divided as irritability zone, no spike-sharp waves appear as non-irritative zone, We analysis the occurrence rate, quantity,distribution of HFOs and sharp spike and wave in irritation and outside the region. According to the positional relationship between spike-sharp waves and the lesion, the channels will divided into two groups,the lesion area and away from the lesion group(with the same lobe lesion or ipsilateral) the occurrence rate of HFOs were compared in the groups;3. 10 ~ 30 s before the onset of the first to appear ictal discharges(ictal discharge, ID) channels the region as SOZ group, no ID’s channels divided as non-SOZ area group, the occurrence rate and quantity of HFOs inside and outside the SOZ, amounting the channels with HFOs; Comparing the sensitivity, specificity and accuracy of spike-sharp waves and HFOs in positioning SOZ.Results:1.The total occurrence rate of IEDs and Ripple were 100%(37/37) and 48.6%(18/37) in 37 patients. The average channel of IEDs and Ripple were 12.4 ±3.6, 4.2 ±3.6 in every patient( t test, p<0.01), indicate that Ripple is less than the spike-sharp waves, the difference was statistically significant. The higher rate of HFOs in group a with high rate of spike-sharp wave than group b with medium rate,fallow with group c with lower rater(p < 0.05).2.The average rate(times/min) of Ripple in area irritative zone and non-irritative zone were 0.08 ± 0.15, 0.03 ± 0.09,indicated that the average rate(times/min) of Ripple in area irritative zone were higher than non-irritative zone(Chi-square test,p <0.01). The rate of HFOs in lesion group were higher than the far away lesion group(p < 0.05)3.The average rate(times/min) of Ripple in area SOZ and non-SOZ were 0.18± 0.27, 0.02 ±0.07, suggest that SOZ area greater than non-SOZ area(t test, p<0.01). Compared to the IEDs, the ripples were less sensitive(Ripples51.1%, IEDs81.6%),but more specific(Ripples87.9 %,IEDs57.1 %,),and more accuracy(Ripples80.6%,IEDs54%,) in determining the SOZ.Conclusion: High frequency oscillations was closely associated with epileptiform discharges in the epileptogenic zone of secondary epilepsy patients, with higher specificity to identify SOZ. But the sensitivity is too low to take place the IEDs to identify SOZ independently. So it had better to help IEDs to localate epileptogenic zone.