Abstracts

Rationale: Neuromodulation therapy such as brain-responsive neurostimulation (RNS system, NeuroPace) is often considered in patients with medically refractory epilepsy who are not candidates for surgical resection or who continue to have seizures despite prior resective surgery. Little is known about the ideal placement of RNS leads. Stereoelectroencephalography (sEEG) may help target the placement of RNS leads. The goal of this study is to report the experience with sEEG and RNS at a comprehensive epilepsy center.  Methods: This retrospective study included adult epilepsy patients evaluated at the Cleveland Clinic with sEEG prior to RNS placement (N=21). Through review of the electronic medical record and sEEG tracings, the following variables were recorded: pre-implantation hypothesis, number of sEEG electrodes, ictal findings, and location of RNS lead placement.   Results: Of patients with RNS placed between 2008 and 2017, 70% (21/30) were evaluated with sEEG. The median age at time of sEEG was 31 years (range 18-60 years), with a median duration of epilepsy of 18 years (range 2-48). 29% of patients (6/21) had a vagus nerve stimulator and 25% of patients (5/21) had prior resective surgery. 81% of patients (17/21) had bilateral sEEG implantation, 10% (2/21) unilateral left, and 10% (2/21) unilateral right. The median number of regions sampled was 14. RNS was implanted bilaterally in 48% of patients (10/21), unilateral left in 29% of patients (6/21), and unilateral right in 24% of patients (5/21). RNS leads were placed in the hippocampus in 11 patients, neocortex in 11 patients, and insula in 1 patient. Individual patient data is displayed in table 1.     Conclusions: This study demonstrates that sEEG can be used to guide the location of RNS leads by targeting structures involved early in the ictal network. Further studies will assess outcomes in these patients.   Funding: No funding was received in support of this abstract.