A Scoping Review of Responsive Neurostimulation in Focal Cortical Dysplasia-Related Epilepsy

Responsive Neurostimulation (RNS) is a closed-loop neuromodulation therapy approved for treating drug resistant epilepsy (DRE) with 1 or 2 seizure foci, but its potential utility for treating complex seizure networks, such as in focal cortical dysplasia (FCD), remains uncertain. This review and commentary discuss the current practice of RNS use in focal cortical dysplasia-related drug-resistant epilepsy(FCD-DRE), and the potential of individualized approaches.

Our scoping review followed a search to identify relevant studies on epilepsy and RNS across MEDLINE, Embase, and Web of Science, yielding 674, 1,255, and 579 results, respectively followed by abstract and full text review to include FCD-DRE. Data on history, imaging, intracranial EEG, RNS implantation and programming strategies were recorded.

78 patients with FCD-DRE across 25 studies were included. The most common lead configuration was two depth electrodes in 53 % (19/36). The median seizure reduction was 85 % [IQR = 66, 96] with a median follow up of 17 months., including 6 patients (7.6 %) achieving seizure freedom for a median 15 months. In 17 patients with resections and RNS implantation, median seizure frequency reduction was 87 % (N = 15), not significantly different from the group with RNS only. 8 patients with cortical and thalamic leads had median seizure frequency reduction of 87 % [IQR = 51, 92]. RNS was effective when used in refractory status epilepticus associated with FCDs.

RNS is a flexible therapy that effectively reduces seizures in FCD-DRE. Electrographic and imaging signatures can potentially be leveraged. Hybrid resection with RNS approaches and the role in refractory status epilepticus associated with FCD is highlighted. Future studies are necessary to optimize RNS therapy in FCD-DRE.