Abstracts

Rationale:
Reduction of antiepileptic drugs (AEDs) postoperatively is a measure of success in epilepsy surgery. Responsive neurostimulation (RNS) is proven to safely reduce seizure burden in some patients with medically refractory focal epilepsy who are not candidates for destructive surgery. Its effect on the use of AEDs postoperatively has not been previously investigated. In this study, we aimed to determine if there is a reduction in the cumulative AEDs burden after RNS implantation and evaluate the association with seizure outcomes.
Method:
We performed a retrospective review of patients who underwent RNS placement between November 2004 and April 2019 at our center and had consistent neurostimulation therapy for >1 year. We analyzed the median percentage reduction in disabling clinical seizures (i.e. focal unaware or convulsive) and the responder rate (>50% reduction in disabling seizures), and their association with changes in the number of AEDs postoperatively.
Results:
Thirty-nine patients (64% female) were included in our study. Their median age at the time of implantation was 34 years. They suffered from refractory epilepsy for approximately 15 years with a median pre-implantation seizure frequency of 4.5 per month. 38/39 of these patients had reliable preoperatively AEDs data with a median AEDs burden of 3. 21/39 (54%) were non lesional and 31/38 (82%) had prior invasive investigation. VNS implantation was performed in 11/39 (28%) and resective surgery in 9/39 (23%) of them. 31/39 (79%) had at least one mesial temporal lead implanted. The median duration of RNS therapy was 39 months. 33/39 patients had reliable seizure counts postoperatively with a median post-implantation seizure frequency of 1.5 seizures per month. The median seizure frequency reduction was -75% and the responder rate was 73%. 7/33 (21%) of patients reported being free of disabling seizures, and 15% (5/33) were totally seizure free (including no auras or subclinical electrographic seizures). The median AEDs number post-implantation was 3. Compared to pre-implantation, 24/38 (63%) of the patients had no changes in the total number of AEDs, 4/38 (11%) had a lower number and 10/38 (26%) had a higher number of AEDs. For the patients with reliable pre- and post-implantation AEDs and seizure data, there was no statistically significant association between the seizure outcome and change in the number of AEDs. Even in the seizure-free group, only 1 patient underwent a reduction in the number of AEDs.
Conclusion:
In keeping with the literature, our study confirms the utility of RNS for patients with refractory focal epilepsy who failed or are not good candidates for resective or ablative surgery. Yet, this is not accompanied by a significant reduction in the number of post-implantation AEDs, regardless of favorable response to neurostimulation, even in patients who become seizure free. This practice data may be explained by the longstanding intractability of the implanted cases and reflects the prevailing view of neurostimulation amongst physicians as a palliative rather than curative treatment of refractory epilepsy.
Funding:
:No funding