Relationship Of Residual Epileptiform Discharges In Intraoperative Electrocorticography With Seizure Recurrence In Patients After Epilepsy Surgery

Objective : To investigate the relationship of residual epileptiform discharges including spikes,ripples and fast ripples(FR)in post-resection intraoperative electrocorticography(ECoG)in the patients with refractory focal epilepsy with seizure recurrence after epilepsy surgery.Methods:We studied,retrospectively,ECoG recorded after resection in a total of 71 patients with refractory focal epilepsy treated in our neurosurgery department from January 2010 to January 2015.Follow-up period was within 1 to 5 years after surgery.Patients were sub-divided into positive(+)and negative(-)groups depending on whether they had onset of residual events.We analyzed occurrence and number of residual spikes(1~40 Hz,spike group),ripples(80~250Hz,R group)and FR(250~500Hz,FR group)within the last minute of each recording and compared these to seizure recurrence.Results : The mean postoperative follow-up period was 2.3 ± 1.5years.Among 71 patients,26 patients had recurrent seizures(Engel Ⅰb~Ⅳ)and 45 patients were seizure free(EngelⅠa).1.The seizure recurrence was significantly higher in FR(+)vs FR(-)patients(12/17 vs 14/54,P<0.01),and its positive predictive value(PPV)was 70.59%,negative predictive value(NPV)was 74.07%.Also,the patients with recurrent seizures had higher FR rates than seizure-free patients(7.62±1.19 vs 5.24 ±1.30,P<0.01).2.The seizure recurrence was higher but no significant difference in R(+)vs R(-)patients(19/44 vs 7/27,P=0.14),and its PPV was 43.18%,NPV was 74.07%.Also,the patients with recurrent seizures had higher R rates than seizure-free patients(9.39± 4.01 vs 8.06 ± 3.09,P=0.13)3.The seizure recurrence was higher but no significant difference in Spike(+)vs Spike(-)patients(21/52 vs 5/19,P=0.28),and its PPV was40.38%,NPV was 73.68%.Also,the patients with recurrent seizures had higher spike rates than seizure-free patients(14.38 ± 5.82 vs 13.81 ±4.62,P=0.23).Conclusion:Residual FR in post-resection intraoperative ECoG may be an electrophysiological marker for seizure recurrence in the patients with refractory focal epilepsy.Moreover,the higher residual FR is closely associated with seizure recurrence after surgery.