Comparative Effectiveness of Stereotactic Electroencephalography Versus Subdural Grids in Epilepsy Surgery

Abstract

Objective: The aim was to compare the outcomes of subdural electrode (SDE) implantations versus stereotactic electroencephalography (SEEG), the 2 predominant methods of intracranial electroencephalography (iEEG) performed in difficult-to-localize drug-resistant focal epilepsy.

Methods: The Surgical Therapies Commission of the International League Against Epilepsy created an international registry of iEEG patients implanted between 2005 and 2019 with ≥1 year of follow-up. We used propensity score matching to control exposure selection bias and generate comparable cohorts. Study endpoints were: (1) likelihood of resection after iEEG; (2) seizure freedom at last follow-up; and (3) complications (composite of postoperative infection, symptomatic intracranial hemorrhage, or permanent neurological deficit).

Results: Ten study sites from 7 countries and 3 continents contributed 2,012 patients, including 1,468 (73%) eligible for analysis (526 SDE and 942 SEEG), of whom 988 (67%) underwent subsequent resection. Propensity score matching improved covariate balance between exposure groups for all analyses. Propensity-matched patients who underwent SDE had higher odds of subsequent resective surgery (odds ratio [OR] = 1.4, 95% confidence interval [CI] 1.05, 1.84) and higher odds of complications (OR = 2.24, 95% CI 1.34, 3.74; unadjusted: 9.6% after SDE vs 3.3% after SEEG). Odds of seizure freedom in propensity-matched resected patients were 1.66 times higher (95% CI 1.21, 2.26) for SEEG compared with SDE (unadjusted: 55% seizure free after SEEG-guided resections vs 41% after SDE).

Interpretation: In comparison to SEEG, SDE evaluations are more likely to lead to brain surgery in patients with drug-resistant epilepsy but have more surgical complications and lower probability of seizure freedom. This comparative-effectiveness study provides the highest feasible evidence level to guide decisions on iEEG. ANN NEUROL 2021;90:927-939.

Figure 1:

Patient distribution across the different study arms. *some patients had multiple fields with missing data.

Figure 2.

Standardized differences for baseline covariates for patients who underwent invasive EEG (the “resection analysis cohort”, panel 2A), for patients who had resective surgery (the “seizure outcomes cohort”, panel 2B), and for the complications analysis cohort (panel 2C) before and after propensity score matching.

Figure 3.

Panel A. Odds ratio estimates (with 95% confidence intervals) for resection in the resection analysis cohort before and after propensity score matching. Odds ratio here describes the odds of resection in SDE patients as compared to SEEG. Higher OR indicates higher probability of resection after SDE. The “unadjusted” estimate fails to account for the large separation in baseline covariate distributions across the SDE and SEEG groups within this cohort. Panel B. Odds ratio estimates (with 95% confidence intervals) for seizure-free status in the seizure outcomes cohort before and after propensity score matching. Odds ratio here describes the odds of seizure-freedom in SEEG patients as compared to SDE. Higher OR indicates higher probability of seizure freedom after SEEG. The “unadjusted” fails to account for the large separation in baseline covariate distributions across the SDE and SEEG groups within patients who had resective surgery after iEEG in this cohort. Panel C. Odds ratio estimates (with 95% confidence intervals) for incidence of surgical complications (defined by composite outcome of any one of post-operative infection, symptomatic intracranial hemorrhage, or complication resulting in a permanent neurologic deficit) before and after propensity score matching. Odds ratio here describes the odds of complications in SDE patients as compared to SEEG. Higher OR indicates higher probability of complications after SDE. The “unadjusted” fails to account for the large separation in baseline covariate distributions across the SDE and SEEG groups within the complications analysis cohort.