Safety and Efficacy of Brain-Responsive Neurostimulation Treatment With Depth Leads Placed in the Neocortex

INTRODUCTION: Responsive neurostimulation (RNS) is efficacious in treating medically refractory epilepsy arising from neocortical foci. During clinical trials, most patients with neocortical seizure foci received cortical strip leads, perhaps due to intracranial monitoring with subdural grids/strips. Stereo-electroencephalography (sEEG) has become more widely utilized since the trials, resulting in increased placement of neocortical RNS depth leads. This is also an appealing approach when dural adhesions make strip lead implantation difficult. METHODS: We conducted retrospective chart review of adult patients with refractory epilepsy at seven institutions who underwent placement and connection of at least one RNS depth lead in the neocortex. RESULTS: 61 neocortical depth leads were connected to the RNS neurostimulator in 53 patients. 33 patients had additional depth leads in a non-neocortical focus, and 12 had an additional neocortical strip lead. Median follow-up was 2.2 years (range: 0.4 – 5.2 years). Median clinical seizure reduction in seizures was 63% at 1 y and 75% at last follow-up. 12 patients (23%) were seizure-free at last follow-up; a majority of these (83%) were seizure-free for >6 mo, with five patients seizure-free for >1 y. There were two (3.8%) scalp infections. One patient (1.9%) had each of the following: chemical meningitis, epidural hematoma, post-surgical status epilepticus (resolved with stimulation), new-onset non-epileptic seizures, and stimulation-related nausea (resolved with programming). CONCLUSIONS: Our multicenter series of 53 patients with neocortical-onset epilepsy treated with neocortical RNS depth leads demonstrated 75% median seizure reduction at 2 y of follow-up with a similar safety profile to placement of deep brain electrodes for movement disorders. Neocortical depth leads may be preferred with the RNS system following sEEG evaluation and/or if strip placement poses increased surgical risk.