Abstracts

Rationale: Autoimmune-associated epilepsy (AAE) is mediated by neural autoantibodies and is often refractory to multiple antiseizure medications (ASM). Little is known about the role of neuromodulation therapy in patients with refractory AAE. This study examines the efficacy and safety of brain responsive neurostimulation (RNS) therapy in a small sample of patients with refractory AAE.

Methods: We searched medical records of 85 adult patients treated with the RNS system at Mayo Clinic (Arizona, Florida, and Minnesota) to identify patients with AAE. We then collected clinical data, including demographics, epilepsy history, prior evaluations including brain imaging and EEG findings, prior epilepsy treatment data including ASM and immunotherapies, Responsive Neurostimulation (RNS) System implantation and lead information, long term ambulatory electrocorticography data, and seizure burden. Inclusion criteria were: 1) confirmed neural antibodies or 2) negative autoimmune panel with Antibody Panel in Epilepsy (APE) score ≥ 4. All patients must have at least six months of follow-up after RNS implantation. Primary endpoints were 1) seizure reduction by at least 50%, and 2) adverse events related to the RNS therapy.

Results: Of the 85 patients, nine (10.5%) patients (8 females, 1 male) met the inclusion criteria. The average age of onset 28.7 yo (range 9 - 59). Mean implant duration was 26.9 months (range = 13 - 48). Three patients had GAD65 antibodies (range = 123-2074mg/dl), one had biopsy-proven Rasmussen's encephalitis, five had negative or no antibody panel but APE score ≥ 4. The median number of ASMs used was 5 (range = 4 - 8). The majority (n=5, 55%) had received at least one form of immunotherapy in adjunct to ASM therapy; three received steroids, three received IVIg, one received plasmapheresis, and three were on chronic immunosuppressants (mycophenolate, azathioprine, and rituximab, respectively). The majority (n=5, 55%) had bi-hippocampal implantation of the RNS electrodes; one with a left insula and hippocampal depth electrodes; one with a left hippocampal depth and a left parietococciptal strip; one with insular depth and a right superior temporal strip; one with two left temporal strips. Mean RNS charge density for therapy was 2.36 (range = 1.5 - 4.25uC/cm2). Six patients (67%) had > 50% reduction in seizures, and two patients had between 25% - 49% reduction in seizures, and one patient reported no significant improvement. Two patients had minor complications, one had a post-surgical headache, and the other had a superficial wound infection at the implant site. There were no serious adverse events reported.

Conclusions: The findings from our study suggest that RNS therapy is a safe and efficacious treatment option for drug‐resistant AAE. Future prospective studies with larger sample sizes are needed to validate the results of our study further.

Funding: Please list any funding that was received in support of this abstract.: none.