Robotic Orthogonal Implantation of Responsive Neurostimulation (RNS) Depth Electrodes in the Mesial Temporal Lobe: Case Series

Abstract

BACKGROUND: Responsive neurostimulation (RNS) is a closed-loop neurostimulation modality for treating intractable epilepsy in patients who are not candidates for resection. In the past, implantation of depth electrodes was done through a transoccipital approach that transverses the hippocampus. There have been no descriptions of orthogonal approaches to RNS electrode placement. OBJECTIVE: 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, video electroencephalography, 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. Multiple variables were collected, including age, disease onset, complications, follow-up, semiology, and seizure reduction. RESULTS: There were 8 patients who underwent RNS electrode placement with orthogonal approach. The mean age and follow-up were 44.8 and 1.2 yr, respectively. There were 4 patients with at least 1-yr follow-up. Of them, 1 was seizure free and 2 experienced over 50% reduction in seizures. There were no complications associated with electrode implantation. 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.