Abstracts

Rationale: Responsive Neurostimulation (RNS) is an important treatment for drug-resistant epilepsy (DRE) utilizing closed-loop neurostimulation. Although hippocampus is still the most common target, thalamic stimulation has gained favor due to the potential for more widespread network alterations. Given the limited literature on thalamic stimulation, we investigated the comparative efficacy of hippocampal versus thalamic RNS in treating DRE.

Methods: This was a single-center, retrospective study of adult DRE patients implanted with hippocampal RNS (H-RNS) or thalamic RNS (T-RNS) between 2014-2024. Seizure reduction (%) and responder rate ( >50% seizure reduction) were compared between the two groups using Mann-Whitney U and Fisher tests, and in a subset of patients matched for follow-up duration using paired t tests and McNemar’s test.

Results: There were 54 implants including 39 H-RNS (M:F=21:18) and 15 T-RNS (M:F=6:9). The median age was 44 (IQR 34-53) for H-RNS and 30 (IQR 27-39) for T-RNS (p=0.003). The median follow-up was 36 months (IQR 17.0-43.0) for H-RNS and 17 months (IQR 6.5-21.0) for T-RNS, (p=0.009). Overall, H-RNS had greater reductions in median seizure frequency (66.8% vs. 11.1%, p=0.005, Figure 1) and higher responder rates (71.8% vs. 20.0%, p<0.010) than T-RNS. Sub-group analysis matching for follow-up duration between the two groups also revealed greater median seizure reduction (75.0% vs. 11.1% p=0.024) and higher responder rates (73.3% vs. 20.0%, p=0.043) in H-RNS compared to T-RNS (Figure 2). There was no difference in the pre-implant seizure rate between these groups (p=0.267).