Abstracts

Rationale:
The gold standard for the management of drug-resistant focal epilepsy (DRE) is surgical resection of the epileptogenic zone. However, in certain patients resective surgery may not be possible because multi-focal epileptogenic zones, the involvement of eloquent cortex as a part of epileptogenic zone or a spatially extensive epileptogenic zone.  For such patients, Responsive neurostimulation (RNS) has emerged as a potential treatment option that safely reduces seizures. The average age of patients undergoing RNS therapy in the pivotal trial and the data since is around 35 years. We live in a rapidly aging society. However, the experience of using RNS has not been studied specifically in older adults. The purpose of our research is to investigate the efficacy, safety, tolerability and outcome of RNS in adults 50 years of age and older.
Method:
We performed a single center retrospective cohort study of patients with DRE who were treated with the RNS System for at least 6 months. All the patients who were surgically implanted with RNS at Cleveland Clinic were included in the study. Patients were then divided into older adults (≥50 years of age) and a younger cohort based on the age at the time of RNS implantation. We assessed the change in seizure frequency compared to pre-implant baseline as the primary outcome. Secondary outcomes included RNS related complications, subsequent resections following RNS and changes in seizure medications after RNS. Categorical variables were described using frequencies and percentages, whereas continuous variables were described using medians and inter-quartile range (IQR; first‐third quartiles). Older adults and the younger cohort were compared using Student’s t-test, Mann-Whitney U test and Fisher’s exact test.
Results:
A total of 57 patients were included in the study, including 12 (21%) individuals who were 50 years or older at the time of RNS implantation. Mean age at the time of RNS implantation was 35.4 years with a mean age of 54.9 among older adults versus 30.2 years among younger adults. 58% (7/12) of the older adults and 56 % (25/45) of the younger adults were female. As noted in Table 1, older adults had seizure onset later in life (25 versus 13.9 years; p< 0.01) and had a long duration of epilepsy (29.9 versus 16.3; p< 0.01) compared to younger adults. There was no significant difference in MRI findings, prior resections, prior VNS implantations, prior intracranial evaluations, and median number of AEDs prior to RNS implantation among the two groups. Eight (67%) of the older adults had > 50% seizure reduction, of whom 3 (25%) became seizure free. Twenty three (52%) of the younger adults had > 50% seizure reduction of whom 5 (11%) became seizure free. Younger adults had more RNS related complications in comparison to older adults (4 versus 0; p< 0.001). Four of the younger adults had battery site infections and a total of 7 had their RNS explanted. None of the older adults had any RNS related complications or explantation of the device.  One of the younger adults had concurrent surgery at the time of RNS placement and 4 of the younger adults had resections following RNS placement.  None of the older adults had concurrent or subsequent resections following RNS implantation.
Conclusion:
Our findings show that RNS is a feasible, and safe therapy for older adults with DRE who cannot undergo epilepsy surgery. The outcomes are comparable to their younger counterparts. Interestingly, unlike younger adults, none of the older adults had RNS complications requiring explantation of the device. Multicenter, larger studies are needed to better elucidate the efficacy and utility of RNS in this patient population.   
Funding:
:None