To evaluate current practice of responsive neurostimulation (RNS) in drug-resistant epilepsy associated with focal cortical dysplasia (DRE-FCD) and the potential of personalizing treatment to improve outcomes.
The RNS System involves two intracranial leads placed at the seizure onset zone(s) where they serve to detect abnormal activity and deliver closed-loop electrical stimulation to reduce seizures. FCDs often result in DRE with unique electrographic and imaging signatures that can be leveraged by RNS.
Our scoping review followed a peer-reviewed search to identify relevant studies on epilepsy and RNS across MEDLINE, Embase, and Web of Science, yielding 674, 1,255, and 579 results, respectively. The final protocol was registered with the Open Science Framework. Data on patient and FCD characteristics, pre-implant imaging/intracranial electroencephalography, seizure outcomes, follow-up duration, and past/concurrent resective/neuromodulation procedures were collected. RNS implantation strategies including target selection, lead type, and programming parameters were recorded. Data for subgroups were analyzed using descriptive and inferential statistics.
75 patients across 24 studies were included. Most FCDs were multifocal, located in frontal followed by temporal regions, lead configuration varied between two depth electrodes (54%), two strip electrodes (31%), and a combination of both (15%). Median seizure reduction was 82% [IQR=50, 90.75] at median follow-up of 12 months [IQR=6, 20], including 3 patients achieving seizure freedom. In 13 patients with concurrent RNS implantation and resection, median seizure reduction was 87% [IQR=70, 95]. The 12 patients with thalamic leads had median seizure reduction of 87% [IQR=13, 87.5]. RNS was found to be effective when used in refractory status epilepticus associated with FCDs.
RNS is a flexible therapy that can be tailored to diverse epilepsies and that effectively reduces seizures in DRE-FCD. Future studies are necessary to determine optimal lead configuration and device programming for DRE-FCD and other lesional epilepsies.