Prospective and “live” fast ripple detection and localization in the operating room: Impact on epilepsy surgery outcomes in children

Objective Fast ripples (FR, 250–500 Hz) are proposed biomarkers of the epileptogenic zone on the basis of several retrospective reports linking postoperative seizure freedom to their complete resection. There are no clinical trials or prospective reports validating the use of FR as characterized by electrocorticography (ECoG), to guide the scope of epilepsy surgery, and to inform prognosis thereafter. We set out to prospectively evaluate the utility of FR resection to predict postoperative epilepsy outcomes, and examine the feasibility of “live” intraoperative FR ascertainment. Methods FR were prospectively reviewed in 30 consecutive pediatric cases including 11 reviewed “live” during surgery. Intraoperative ECoG studies were recorded at 2000 Hz sampling rate, interpreted conventionally to guide surgical resection, and visually inspected for FR. Seizure outcome was tallied for all 30 children. Results Median age at surgery was 9.1 years (interquartile range [IQR] 4.7–13.2), median ECoG duration was 10.5 min (IQR 8.0–13.2), and median postoperative follow-up was 58.4 months (IQR 25.7–79.0). FR were identified in 24 of 30 ECoG studies. The incomplete resection of FR was strongly linked to postoperative seizures (hazard ratio 11.6, p = 0.005). “Live” ECoG review in the operating room to ascertain FR proved feasible and did not differ from conventional FR ascertainment. Significance: In a prospective fashion, including “live” review, FR were detected in 80% of pediatric ECoG studies, and incomplete resection of FR cortex predicted postoperative seizures. These findings extend the notion that interictal FR are surrogate markers of the epileptogenic zone, and that their intraoperative localization could be used to inform prognosis and guide surgical resections in children.