Stereo-electroencephalography-guided responsive neuromodulation: A propensity-matched cohort study

The optimal pre-implantation evaluation and surgical targeting strategies for responsive neurostimulation (RNS) in patients with unresectable, drug-resistant focal epilepsy continue to be debated. Although stereo-electroencephalography (sEEG) is central to characterizing the seizure-onset zone, its role in preoperative testing for neuromodulation remains undefined. We examined whether sEEG-guided targeting for RNS implantation confers seizure-reduction benefit compared with RNS implantation without sEEG.

We retrospectively reviewed patients who underwent RNS implantation at our institution in 2015-2024. Patients were propensity score-matched based on demographics and epilepsy characteristics to create balanced groups of patients with and without prior sEEG. The primary outcome measure was seizure reduction as a percent change from baseline frequency, determined using linear regression.

Of 99 patients (median ± standard error [SE] follow-up 45.3 ± 2.9 months), 78 (79%) underwent sEEG monitoring before RNS implantation and 21 (21%) did not. Most patients (62%) had no prior interventions for epilepsy and had non-lesional epilepsy (75%). Mean seizure reduction at last follow-up was 72.4% ± 29.3%. There were 21 patients in each propensity-matched group. The use of preoperative sEEG was not associated with greater seizure reduction in the original (p = .835) and propensity score-matched cohorts (p = .914). In the unmatched cohort, female sex (β = 16.7, p = .006,) older age (β = .55, p = .027), thalamic RNS stimulation (β = 18.0, p = .030), and follow-up duration (β = .2, p = .029) were associated with greater seizure reduction on linear regression. Subgroup analyses among epilepsy subtypes (bitemporal, temporal, or extratemporal) found no statistically significant differences in seizure reduction.

In a climate of growing delays in epilepsy care, we did not observe differences in RNS efficacy with or without prior sEEG monitoring in patients with unilateral or bilateral temporal lobe epilepsy, temporal-plus epilepsy, and extratemporal epilepsy. Although prospective data are needed to investigate the relative benefit of preoperative sEEG use, these findings may help guide patient selection and optimize definitive surgical planning.