Abstracts

Rationale: Evaluate clinical seizure reductions in patients with medically-refractory epilepsy and a regional neocortical seizure onset zone treated with the RNS® System. Methods: This was a retrospective review of patients with regional neocortical seizure onset zones who were treated with the RNS System at the University of California, San Francisco (UCSF). A regional seizure onset zone was defined as a seizure focus spanning > 1 centimeter (cm). The lead implantation approaches are described and the post-implant seizure frequency reductions were calculated relative to the pre-RNS System treatment baseline. Results: Twelve (12) patients with one regional seizure onset zone was treated with the RNS System at UCSF, comprising 30% of the total RNS System experience at UCSF. The median follow-up duration was 1.9 years (range: 0.4–4.1 years). Seven (58%) of these patients had the RNS Neurostimulator and leads implanted immediately at the conclusion of intracranial monitoring, and five (42%) at the time of a concurrent resection. Nine patients (75%) had strip leads only, one (8%) had depth leads only, and two (17%) had one strip and one depth lead. The mean distance between the two leads was 3.3 cm (range: 1.2–6.0 cm). The median percent seizure reduction in this group was 80% (mean: 77%, range: 40–100%). In all cases, there was a clear seizure onset pattern detectable on at least one lead connected to the neurostimulator. Conclusions: Seizure onset zones in patients with refractory focal epilepsy are occasionally localized to areas of the neocortex that are too extensive for a resective surgery. In this small retrospective series, brain-responsive neurostimulation delivered to the neocortex across leads placed at distances up to 6.0 cm apart achieved median percent seizure reductions that ranged from 40-100%. This experience supports brain-responsive stimulation as a treatment option for patients with regional neocortical seizure onsets. Funding: None