Abstracts

Rationale: Rationale: Brain-responsive neurostimulation with the RNS?(R) System is a novel, fast evolving treatment that has been demonstrated to be safe and effective for the treatment of refractory partial onset seizures. Treatment is provided by means of a neurostimulator that detects patterns that typically precede an individual patient's seizures and subsequently provides stimulation though leads that are placed according to the seizure focus. In order to determine the seizure focus or foci, patients undergo localization testing that may include monitoring with intracranial electrodes (Phase II). We sought to determine for the patients treated at our center whether RNS detection patterns correlate electrographically with electrographic findings from the Phase II and whether Phase II findings are useful in predicting therapeutic outcomes. Methods: Methods: Ten consecutive patients were treated with the RNS System at University of California, Los Angeles (UCLA); eight had Phase II monitoring prior to implantation. One patient localized without intracranial monitoring had a prior right mesial temporal lobe epilepsy (MTLE) resection and was implanted with left temporal leads, and the other patient had bilateral independent temporal seizures on scalp EEG. The eight patients with temporal lobe onsets were implanted with bilateral or unilateral orthogonally placed depth leads in the entorhinal cortex (EC), and/or hippocampus and/or amygdala. Two patients with seizures originating in proximity to the eloquent cortex had strips placed based on Phase II data. We compared the electrophysiological parameters used to detect seizures by the RNS device in patients who underwent Phase II monitoring prior to lead implantation to determine whether a correlation between the two resulted in a favorable clinical outcome. Results: Results: Our data indicates that patients who undergo Phase II monitoring and in whom seizure onset patterns (onset zone and signature electrical activity) correlated between Phase II and RNS had more favorable clinical outcomes than those patients in whom seizure onset could not be captured during Phase II. Conclusions: Conclusions: Our findings suggest that the data regarding seizure onsets obtained by the RNS System is consistent with seizure onsets defined by intracranial monitoring. In those patients who undergo intracranial monitoring prior to RNS implantation, this data can help to guide lead placement. However, localization of the seizure onset sufficient to guide placement of the RNS leads may be adequately accomplished without intracranial monitoring in some patients, particularly those with seizures of mesial temporal onset. Additional clinical practice will further direct lead placement strategies. Funding: none