Open-Loop Deep Brain Stimulation Versus Closed-Loop Responsive Neurostimulation in Drug-Resistant Bitemporal Epilepsy: A Narrative Review.

Abstract

Abstract: Drug-resistant bitemporal epilepsy presents a therapeutic challenge when resective surgery is not feasible due to bilateral seizure onset or eloquent cortex involvement. Neuromodulation has emerged as an alternative, with open-loop deep brain stimulation (DBS) and closed-loop responsive neurostimulation (RNS) as implantable strategies. Comparative indications for modality selection remain unclear. A narrative review of articles published from January 2007 to January 2026 was performed in PubMed/MEDLINE. Approximately 120 articles were screened, and 39 studies were included. Due to heterogeneity in study design, findings were synthesized qualitatively. Both DBS and RNS significantly reduce seizure frequency in drug-resistant bitemporal epilepsy, with a median seizure reduction of approximately 60% to 75%. Seizure freedom, however, remained limited, reflecting the palliative nature of these treatments. Open-loop anterior nucleus of the thalamus (ANT) DBS provides network-level modulation with low maintenance, while hippocampal DBS offers localized temporal inhibition. Conversely, closed-loop RNS delivers adaptive focal stimulation via real-time sensing and yields chronic intracranial electroencephalogram data. While both modalities show comparable efficacy, RNS may be advantageous in focal or asymmetric bitemporal epilepsy. Cognitive outcomes were favorable for both techniques, with RNS demonstrating the prevention of memory and language decline. Both DBS and RNS are palliative neuromodulatory options for patients in whom resective surgery is not feasible. Treatment selection should be individualized based on seizure network characteristics, laterality, monitoring needs, participation capacity, and cognitive considerations. The primary goal is to reduce seizure frequency and improve quality of life rather than to achieve seizure freedom. Future multicenter studies and biomarker-driven strategies are needed to refine selection and improve long-term outcomes.