Abstracts

Rationale: Neurostimulation is a treatment option for patients with focal epilepsy resistant to at least two medication trials. The first two devices FDA-approved for treatment of refractory focal epilepsy were vagal nerve stimulation (VNS) and responsive neurostimulation (RNS System). [1,2] Both devices were evaluated independently in clinical trials, but no studies have evaluated safety and efficacy of dual therapy, despite hundreds of patients who have both devices. [3,4,5] The mechanism of action of both devices is poorly understood. VNS is thought to work primarily through long-term neuromodulation, but can also function acutely to abort seizures. Scant prior evidence suggests that acute VNS stimulation may reduce epileptiform activity and cause EEG desynchronization on electrocorticography (ECoG). [6,7,8,9] Our study aims to isolate effects of VNS on ECoG as recorded by RNS System in patients with both devices, by recording ECoG samples with and without acute VNS stimulation. Methods: ECoG samples from 9 individuals were obtained. Five pairs of “off” recordings of 60-second baseline ECoGs were compared to “on” recordings of 60-second ECoGs with acute VNS stimulation and were analyzed for differences in spectral content. Results: Preliminary analysis shows decreasing trends across all power spectra bands (desynchronization) during acute VNS stimulation, not reaching statistical significance. The strongest trends were in theta band (87 uV2 decrease) and total power (202 uV2 decrease). Conclusions: Results suggest that ECoGs recorded by RNS System show evidence of desynchronization as a mechanism of action of VNS. As more patients receive dual neurostimulators, it is crucial to understand isolated effects of each device, which may inform programming optimization to maximize benefit. Funding: No funding