Abstracts

Rationale: Responsive neurostimulation was approved by the FDA for treatment of refractory epilepsy in 2014, primarily in epilepsies with focal onset. RNS serves as an effective intervention in patients with drug-resistant epilepsy and contraindications to resection. In 2015, patients reported a 44% reduction in seizures after year one, 53% reduction by year two, and a 48% to 66% reduction in years 3 through 6. In 2019, year 9 outcomes showed a median reduction of 75%. We aim to evaluate the efficacy and safety of RNS placement in the population seen at KUMC.

Methods: Data were collected from electronic medical records for patient’s undergoing RNS placement between January 1, 2014, and April 1, 2022. Criteria for inclusion were RNS placement. Collected variables include demographics, seizure types, epilepsy type, number of antiseizure medications before and after the procedure, epilepsy risk factor, neuroimaging findings, seizure freedom, duration of seizure freedom, repeat surgery, and complications. The primary outcome is seizure freedom as defined by Engel and ILAE seizure outcome classification systems. Due to small sample size, the results were analyzed through descriptive statistical analysis methods. Variables were reported as mean or median for numerical variables and percentage for categorical variables.

Results: A total of 50 patients fit inclusion criteria during this time-period. Only 31 were analyzed as 19 patients had less than one year follow-up. Demographic information showed a male predominance (56% males, 44% females). Mean age of the population is 42.10 ± 12.81. The mean age of seizure onset is 20.94 ± 14.41 and the mean age at first surgery is 39.10 ± 12.23, with a mean time from seizure onset to first surgery 18.14 ± 9.57 years. Within the population, 41% had an unknown etiology with each of the remaining etiologies providing 3.2-9.6%. The most common of those were MTS, encephalomalacia, encephalocele, and FCD. Of the 31 evaluated, all reported focal onset of symptoms, except one with generalized onset. Of those patients, 22.6% reached a state of freedom from disabling seizures. 71% of patients underwent only RNS while 19% underwent RNS after other interventions. With 28 total patients getting RNS alone or as a final procedure, 21.4% achieved freedom from debilitating seizures (Engel 1 or ILAE I/II) and 60.7% had a >50% reduction in seizure frequency (ILAE III/IV). No statistical significance was seen when comparing area of RNS placement (bitemporal vs neocortical) between Engel 1 outcomes and Engel 2-4, p = 0.645. It remained insignificant when comparing device location between Engel 1-2 against Engel 3-4 p = 0.428. Within the entire 50 patient cohort, 8% had complications (1 encephalopathy, 2 scalp infections, and one scalp infection with meningitis). The other 92% had no major complications.

Conclusions: Overall, RNS provides worthwhile seizure reduction in most of the population seen at KUMC. Seizure freedom has even been seen in almost one-fifth of the patients. There was no significant difference based on device location. RNS is a well-tolerated procedure with low risk of complication.

Funding: No funding was received in support of this abstract.