Re-evaluating the role of electrocorticography-guided resections in neurosurgery

Electrocorticography (ECoG) has long guided epilepsy surgery, yet its role remains contested. Recent studies – particularly those integrating high-frequency oscillations (HFOs) – compel a reappraisal of its value. Here, we argue that ECoG with HFO analysis represents a promising but under-standardized tool, and we outline priorities for future research[1]. This manuscript has been written in line with TITAN guidelines[2]. A 2024 multicenter meta-analysis by Guo et al reviewed outcomes after intraoperative ECoG in epilepsy surgery. They report that seizure freedom (Engel class I) rates at 1 year range from 60% to 76% when epileptogenic tissue is precisely delineated and removed. This confirms that ECoG guidance remains associated with good outcomes, but also that variability persists across centers[3]. HFOs, particularly fast ripples, have emerged as promising biomarkers of epileptogenicity. In a large study of 648 patients, van Klink et al evaluated whether intraoperative HFOs could guide resections. They showed that patients with resected HFO-generating tissue had better postoperative seizure control than those in whom HFOs were incompletely removed. The study strengthens the argument that ECoG guided by both classical interictal epileptiform discharges (IEDs) and HFOs is superior to reliance on IEDs alone[4]. Tumor-related epilepsy (TRE) is another domain where ECoG may offer enhanced benefits. Feyissa et al examined awake patients undergoing surgery for brain tumor-associated epilepsy. They found that the presence of HFOs correlated with preoperative seizure frequency and tumor grade (WHO) status. Importantly, the study suggested that intraoperative detection of HFOs in TRE provides prognostic information and can potentially guide more effective resection margins[5]. Conversely, several studies raise caution. Wray et al investigated 52 children: 37 had residual discharges at the end of resection, and 73% of these were seizure-free; 15 had no residual discharges, and 60% of these were seizure-free. This suggests that post-resective interictal discharges are not uniformly predictive of outcome, at least in the pediatric population[6]. An important study in temporal lobe epilepsy (TLE), especially MRI-negative TLE, by Burkholder et al, demonstrated that complete resection of baseline ECoG IEDs was associated with better surgical outcomes. Among 87 MRI-negative TLE patients, those with unilateral-only scalp EEG IEDs and complete ECoG IED resection had excellent outcomes in 71% of cases. This provides strong evidence that ECoG IEDs are actionable in this setting[7]. Taken together, these data assert that ECoG-guided resections – especially incorporating HFO metrics – deliver superior outcomes in seizure control, particularly when complete resection of IEDs or HFO-generating cortex is feasible. Yet, several unresolved issues and potential pitfalls remain. Several limitations temper the promise of ECoG. Definitions of HFOs, recording protocols, and electrode configurations remain inconsistent, making cross-study comparisons difficult[8]. Post-resective discharges, particularly in pediatric series, show weak and inconsistent correlation with long-term seizure freedom, suggesting that broader network dynamics often outweigh focal activity[9]. In TRE, epileptogenic zones may extend beyond visible tumor margins, and while HFOs correlate with seizure burden and tumor grade, their role in guiding resections remains unproven[5]. Outcome data are also limited by short follow-up, with late seizure recurrence and tumor progression underrepresented[10,11]. Finally, ECoG – especially when incorporating HFOs – adds surgical time, technical demands, and costs that may challenge its adoption in resource-limited settings[12]. Future studies should prospectively compare traditional IED-based ECoG with HFO-integrated approaches, stratified by age, pathology, and imaging profile. Technical consensus on HFO definitions, recording protocols, and signal processing is urgently needed. Multicenter collaborations with long-term follow-up are essential to determine whether HFO-guided resections should become standard practice[13–15]. In conclusion, ECoG – particularly when integrated with HFO analysis – has clear potential to improve seizure outcomes in both epilepsy and TRE. The evidence base is growing, but progress will stall without methodological standardization and prospective multicenter validation. Establishing these standards should now be a priority if ECoG is to become a global neurosurgical tool for maximizing seizure freedom and preserving function.