Robotic Orthogonal Implantation of Responsive Neurostimulation (RNS) Depth Electrodes in Patients With Unilateral Mesial Temporal Lobe Seizure Onset

Abstract

Abstract INTRODUCTION Responsive neurostimulation (RNS) is a closed-loop neurostimulation modality for treating intractable epilepsy in patients who are not candidates for resection. A high number of patients have ictal onsets originating in the temporal lobe. In the past, implantation of depth electrodes have been placed using a transoccipital approach that transverses the long axis of the hippocampus. However, there have been no description of orthogonal approaches to RNS electrode placement into the medial temporal structures in the literature. We aimed to describe our initial experience with placing RNS depth electrodes using an orthogonal approach to target the short axis of the mesial temporal lobe. METHODS Presurgical work up included magnetic resonance imaging (MRI), video electroencephalography (vEEG), and neuropsychological testing. During the procedure, patients were placed with their heads in a neutral position. Electrodes were placed via stereotactic robotic assistance using a unilateral orthogonal approach targeting the amygdala or hippocampus. Patients who underwent RNS electrode implantation via orthogonal approach were identified after a retrospective review of all RNS patients at our institution. Multiple variables were collected, including age, disease onset, complications, follow-up, semiology, and seizure reduction. RESULTS There were 4 patients who underwent RNS implantation with orthogonal electrode placement. The mean age and follow-up were 44.8 and 1.2 yr, respectively. One of 8 patients was seizure free at last follow-up and 2 experienced over 50% reduction in seizures. There was one surgical complication but no mortality. CONCLUSION The initial experience using an orthogonal approach for depth electrode placement for RNS implantation was described. The potential advantages may include better safety, accuracy, and positioning in comparison to a transoccipital approach. Limitations included the retrospective nature of the study and a low sample size. Further research and experience are required to determine the best indications for an orthogonal approach.