T03. Responsive Neurostimulation Device (RNS) vs. Multiple Hippocampal Transections (MHT) as treatments for refractory Temporal Lobe Epilepsy (TLE) – Outcomes from a single center, the University of California, Davis Medical Center (UCDMC)

Abstract

Temporal lobectomy remains the gold standard for treatment of refractory TLE. However, patients with preserved or significantly asymmetric memory are not considered resection candidates due to the potential of memory deficits postoperatively. In our center these patients are offered placement of RNS or to undergo MHT. Some patients also undergo additional resection wherever possible. There are no head to head studies comparing these two procedures, we retrospectively compared clinical outcomes in patients with refractory TLE who have undergone RNS or MHT. 6 consecutive patients with the seizure onset zone in the dominant temporal lobe underwent either placement of RNS or had MHT at UCDMC. Of these patients, 2 had RNS placement, 2 had MHT only, and 2 had MHT plus resection of other temporal lobe structures. For these 6 patients, we analyzed post procedure clinical outcomes and presence of adverse effects. Median duration following intervention was 29 months in the RNS group and 5 in the MHT group. One of the RNS patients is seizure free 30 months after the implant, while the other showed no changes in seizure frequency or severity 28 months post implant. In that patient, the device was not capturing the seizures as determined by invasive monitoring which both RNS patients had prior to implantation. We were able to change the detection parameters; however not enough clinical data is currently available to determine if this lead to seizure reduction. Alternatively, 3 of 4 MHT patients had significant seizure reduction and 2 are seizure free at 4 and 6 months postoperatively. 2 patients had additional resection (amygdala ± temporal neocortex). 2 of the 4 MHT patients had invasive monitoring prior to the procedure; out of these, 1 is seizure free and 1 did not respond to the procedure. 2 of the 4 MHT patients self-reported word finding difficulties at the last follow up and 3 reported changes in mood and/or behavior. These were worse in the patients who had additional resection. Taking into consideration the limited size of our cohort and short study duration, our results suggest that in patients with refractory dominant TLE who are poor candidates for standard resection, MHT is more likely to lead to significant reduction in seizures; however was also associated with word finding difficulties and changes in mood and behavior. On the other hand, RNS did not result in any deficits and implanting the device offers more flexibility in terms of where the epileptic network maybe stimulated with a goal of optimizing clinical outcomes. Further observations of seizure frequency and standard assessments of higher integrative functions are needed to determine the long term impact of these procedures in order to better delineate who will benefit from one procedure over the other.