Seizure Outcome After Intraoperative Electrocorticography-Tailored Epilepsy Surgery: A Systematic Review and Meta-Analysis

Abstract

Background and objectives: Tailoring epilepsy surgery using intraoperative electrocorticography (ioECoG) has been debated, and modest number of epilepsy surgery centers apply this diagnostic method. We assessed the current evidence to use ioECoG-tailored epilepsy surgery for improving postsurgical outcome.

Methods: PubMed and Embase were searched for original studies reporting on ≥10 cases who underwent ioECoG-tailored surgery for epilepsy, with a follow-up of at least 6 months. We used a random-effects model to calculate the overall rate of patients achieving favorable seizure outcome (FSO), defined as Engel class I, ILAE class 1, or seizure-free status. Meta-regression was used to investigate potential sources of heterogeneity. We calculated the odds ratio (OR) for estimating variables on FSO:ioECoG vs non-ioECoG-tailored surgery (if included studies contained patients with non-ioECoG-tailored surgery), ioECoG-tailored epilepsy surgery in children vs adults, temporal (TL) vs extratemporal lobe (eTL), MRI-positive vs MRI-negative, and complete vs incomplete resection of tissue that generated interictal epileptiform discharges (IEDs). A Bayesian network meta-analysis was conducted for underlying pathologies. We assessed the evidence certainty using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE).

Results: Eighty-three studies (82 observational studies, 1 trial) comprising 3,631 patients with ioECoG-tailored surgery were included. The overall pooled rate of patients who attained FSO after ioECoG-tailored surgery was 74% (95% CI 71-77) with significant heterogeneity, which was predominantly attributed to pathologies and seizure outcome classifications. Twenty-two studies contained non-ioECoG-tailored surgeries. IoECoG-tailored surgeries reached a higher rate of FSO than non-ioECoG-tailored surgeries (OR 2.10 [95% CI 1.37-3.24]; p < 0.01; very low certainty). Complete resection of tissue that displayed IEDs in ioECoG predicted FSO better compared with incomplete resection (OR 3.04 [1.76-5.25]; p < 0.01; low certainty). We found insignificant difference in FSO after ioECoG-tailored surgery in children vs adults, TL vs eTL, or MRI-positive vs MRI-negative. The network meta-analysis showed that the odds of FSO was lower for malformations of cortical development than for tumors (OR 0.47 95% credible interval 0.25-0.87).

Discussion: Although limited by low-quality evidence, our meta-analysis shows a relatively good surgical outcome (74% FSO) after epilepsy surgery with ioECoG, especially in tumors, with better outcome for ioECoG-tailored surgeries in studies describing both and better outcome after complete removal of IED areas.

Figure 1. PRISMA Flowchart of the Literature Search and Study Selection

Figure 2. Forest Plot for Meta-Analysis of Favorable Seizure Outcome (FSO) Comparing Surgery With ioECoG Tailoring (ioECoG+) With That Without ioECoG Tailoring (ioECoG-)

Pooled results (red diamond) show a higher odds to attain FSO based on ioECoG. FSO = favorable seizure outcome; ioECoG = intraoperative electrocorticography; n = the number of people attaining favorable seizure outcome; N = the total number of people; OR = odds ratio.

Figure 3. Forest Plot for Meta-Analysis of Favorable Seizure Outcome (FSO) Comparing (A) Children With Adults, (B) TL With eTL, and (C) MRI-Positive With MRI-Negative

Results show no statistical difference between children and adults, TL and eTL, and a nonsignificant trend of the chance of FSO being smaller in people with MRI-negative epilepsy compared with those with MRI-positive epilepsy. Each square (blue) represents an independent study, and diamond (red) shows the pooled data with a 95% CI. eTL = extratemporal lobe; FSO = favorable seizure outcome; n = the number of people attaining favorable seizure outcome; N = the total number of people; OR = odds ratio; TL = temporal lobe.

Figure 4. Forest Plot for Meta-Analysis of FSO Comparing Complete With Incomplete Resection of IEDs for Epileptogenic Tissue in the ioECoG

Each square represents an independent study and diamonds show the pooled data with a 95% CI. FSO = favorable seizure outcome; n = the number of people attaining favorable seizure outcome; N = the total number of people; OR = odds ratio.

Figure 5. Results of the Network Meta-Analysis of the Underlying Pathologies Performed on 26 Studies

(A) Forest plot of node-splitting analyses for direct and indirect comparisons of the 5 categories of underlying pathologies was presented. (B) A network diagram of the 5 pathology categories. Each red circle represents a pathology category. Each line is an edge, and its thickness corresponds to the number of studies that included the respective direct estimate. (C) Forest plot of the network meta-analysis for FSO for the different underlying pathology categories, comparing FSO in malformations of cortical development (MCD), mesiotemporal sclerosis (MTS), dual pathology, and others with FSO in tumors. CrI = credible interval; FSO = favorable seizure outcome.