Abstracts

Rationale: Responsive neurostimulation (RNS) reduces seizure frequency in patients with refractory focal epilepsy. There is limited data in the literature regarding RNS treatment in eloquent cortex, defined as primary motor, sensory, visual, and language areas. This study evaluates if RNS stimulation parameters are limited in patients with electrodes in eloquent cortex due to adverse effects compared to patients with electrodes in non-eloquent areas and if such limitation results in lower seizure frequency reduction.

Methods: This is a retrospective analysis of adult patients with medically refractory focal epilepsy who underwent RNS placement between 2007-2023 at the Jefferson Comprehensive Epilepsy Center. Stimulation parameters, quality of life, and presence of adverse effects were evaluated at 3 months, 6 months, 1 year, 2 years, 5 years, and final visits. Baseline and last follow-up monthly seizure frequency was calculated using the preceding 3 months if patients had ≥ 1 seizure/month, and using the preceding 12 months if they had < 1 seizure/month. Focal to bilateral tonic-clonic seizures, focal seizures with impaired awareness, and focal aware seizures that patients considered disabling were included. Seizure frequency reduction, maximum charge density, and quality of life were compared between patients with RNS leads in eloquent cortex and those with electrodes in other areas. GraphPad Prism was used for statistical analysis.

Results: Fifteen patients with stimulation of eloquent cortex and 33 patients with stimulation of non-eloquent cortex were included. Significant differences between the two groups were noted in age at RNS placement, stimulated lobe, epilepsy surgery history, treatment duration, and baseline seizure frequency (Table 1). When comparing patients with eloquent cortex stimulation to those with non-eloquent cortex stimulation, there was no significant difference in seizure frequency reduction or quality-of-life change. Maximum charge density was significantly different between the two groups (p=0.045, Table 2). Two patients with eloquent cortex stimulation (frontal, occipital lobe) had side effects attributed to device stimulation (motor, visual effects respectively) which limited current. Despite limitations, these two patients still experienced a 41% and 52% total seizure frequency reduction, respectively.

Conclusions: RNS is an effective and well tolerated treatment for refractory focal epilepsy in eloquent cortex. Adverse effects directly limiting stimulation parameters are infrequent and should be managed according to individual need.

Funding: N/A