Abstracts

Rationale: Rationale: A previous multicenter study demonstrated that select patients with medically refractory bilateral mesial temporal lobe epilepsy (MTLE) treated with responsive neurostimulation (RNS) may benefit greatly from eventual resection of the more active side.1 However, there is little data to guide whether to continue RNS therapy following resection and in what manner. Our series aims to address these post-resection stimulation questions in a similar cohort at our institution.

Methods: Methods: A retrospective chart review was performed for patients at our center with bilateral MTLE treated with RNS. Clinical data were collected for patients with bilateral hippocampal (HC) depth electrodes who eventually underwent a unilateral MTL resection. Data obtained included demographics, presurgical workup, clinical course, and surgical outcomes.


Results: Patient demographics and presurgical evaluation are documented in table1. Clinical course and outcomes are documented in table 2. All 4 patients had a modest reduction in seizure burden with RNS, but continued disabling seizures. All experienced remission or near-remission of seizures on the less active side with RNS, leading to eventual decision to perform selective MTL resection on the primary side. Following resection, 3 patients achieved seizure freedom, and the fourth had a 70% seizure reduction, with reemergence of contralateral seizures 2 months after resection. All patients had continuing RNS therapy after resection with the ipsilateral HC depth electrode being used for monitoring only, while the contralateral HC electrode was left in place for both monitoring and stimulation. Two of our patients had transient interruptions of RNS therapy after resection associated with seizure relapse. One had been seizure free 4 years when he suffered a recurrent seizure 1 year after his RNS generator reached end of service at a time of poor AED adherence. After generator replacement and improved AED adherence, he remained seizure free. The other suffered damage to the RNS generator related to electrocautery during resection, prompting replacement surgery within 1 week. She then had two contralateral seizures 2 months afteward when stimulation inadvertently had been disabled. RNS stimulation was eneabled 1 month later and she has since remained seizure free.


Conclusions: Conclusions: Our center's cohort of 4 patients undergoing unilateral MTL resection following RNS with bilateral MTL electrodes had excellent outcomes, similar to those of a prior multicenter series.¹ The outcome findings from our patients also provide clinical examples supporting the continuing need for post resection RNS therapy, an issue not directly addressed by previous research.
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^{1 Hirsch LJ, Mirro EA, Salanova V, Witt TC, Drees CN, Brown MG, Lee RW, Sadler TL, Felton EA, Rutecki P, Shin HW. Mesial temporal resection following long-term ambulatory intracranial EEG monitoring with a direct brain-responsive neurostimulation system. Epilepsia. 2020 Mar;61(3):408-20.}

Funding: No funding for this study.