• Alvin Y Chan, Diem Kieu Tran, Michelle R Paff, Kamran Urgun, HsuFrank P KFPKComprehensive Epilepsy Program, Department of Neurological Surgery, University of California, Irvine, California., and Sumeet Vadera.
• Comprehensive Epilepsy Program, Department of Neurological Surgery, University of California, Irvine, California.
• Oper Neurosurg (Hagerstown). 2020 Jul 1; 19 (1): 19-24.

BackgroundResponsive 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.ObjectiveTo describe our initial experience with placing RNS depth electrodes using an orthogonal approach to target the short axis of the mesial temporal lobe.MethodsPresurgical 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.ResultsThere 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.ConclusionThe 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.Copyright © 2019 by the Congress of Neurological Surgeons.

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