Abstracts

Rationale: Surgical resection and Laser Interstitial Thermal Therapy (LiTT) for refractory epilepsy can be restricted by eloquent cortex and multifocality of seizures. The RNS System can be used in conjunction with resective surgery (RNS+R) or LiTT (RNS+LiTT), which allows the offering of new combination treatments for these patients. Methods: Patients that had RNS+R or RNS+LiTT at UT Southwestern were included in this study. Patients who received RNS+R had both a resective surgery and RNS System placement in the same procedure. Patients who received RNS+LiTT were prescribed both but had a several days gap between the LiTT (occurring first) and RNS System placement due to neurosurgical logistics (range: 11-53 days). Clinical seizure outcomes at last follow-up were collected for patients that had the RNS System placed for at least 7 months. Seizure frequency counts at the last follow-up were compared to the pre-implant baseline seizure frequency to calculate the median percent change. The intracranial monitoring findings, prior surgeries, resection limitations, RNS System lead locations, and safety data were collected for all patients. Results: Four patients underwent RNS+LiTT without intra- or post-operative complications. Twelve patients underwent RNS+R, with 1 patient having a non-RNS System related complication (stroke) several days after surgery. Fourteen patients had at least 1 RNS System lead placed at the margins of the resection or ablation; 5/14 had the second lead placed at a separate onset location. Two patients had RNS System leads that were entirely placed in a different onset location(s) than the resection margins. Thirteen patients had the device for at least 7 months. All patients had stimulation enabled due to electrographic and/or clinical seizures after the RNS+LiTT or RNS+R. One patient from this subset was excluded because they were not able to provide seizure count data due to mental health issues. The median percent seizure reduction at the last clinical evaluation for the remaining 12 patients was 96% (mean: 75%, range: 0-100%), with a mean of 13mo (range: 7-25mo) since surgery and a mean of 11mo (range: 4-25) of responsive stimulation therapy. The subset of RNS+R patients (n=9) had a median seizure reduction of 100% (mean: 89%, range: 50-100%). All of the RNS+R patients reported a >= 50% reduction, seven (78%) reported a 90% reduction, and five (56%) reported a 100% seizure reduction. The 3 RNS+LiTT patients reported seizure reductions of 0, 0, and 100%. One RNS+LiTT patient (Pt#14) was seizure free for over a year after the procedure. Seizures resumed that were initially provoked possibly by a vaccination and continued after being medication noncompliant. Conclusions: Our experience with the safety and efficacy of RNS+R in this small group has been excellent. The safety experience with RNS+LiTT has also been excellent but efficacy results are mixed and need to be further studied. Overall, these patients had a median 96% seizure frequency reduction. Offering the RNS System in conjunction with a traditional resective surgery or Laser Interstitial Thermal Therapy has allowed us to offer a more tailored treatment when a full resection is not possible or more than one seizure focus exists. Funding: No funding