Introduction: Patients with medically refractory bitemporal epilepsy are candidates for neuromodulation procedures. While vagus nerve stimulation (VNS) was historically the procedure of choice for this condition, in recent years the responsive neurostimulation system (RNS) has come into favor for its more targeted approach. While both VNS and RNS have been reported to have good efficacy in bitemporal epilepsy, the outcomes of these two procedures have not been directly compared. The goal of this study was to compare outcomes following VNS versus RNS for bitemporal epilepsy.
Methods: We retrospectively reviewed the records of all patients with bitemporal epilepsy who underwent VNS or RNS placement at Massachusetts General Hospital between 2003 and 2018. The primary outcome was change in seizure frequency. Other outcomes included Engel score, change in anti-epileptic medications, and complications. Continuous variables were compared using a two-sample t-test and categorical variables were compared using chi-square test.
Results: Twenty-six patients met inclusion criteria. Of these, 11 were treated with VNS and 15 with RNS. At baseline, the two groups were statistically similar in terms of age at surgery, epilepsy duration, and pre-operative seizure frequency (33.5 ± 33.2 and 33.4 ± 50.0 per month). Mean follow-up length was 76.6 ± 44.6 months in the VNS group and 35.5 ± 38.6 months in the RNS group. At last follow-up, both groups displayed reduced seizure frequency (mean 46.3% reduction for the VNS group and 56.7% reduction for the RNS group, p = 0.73). Response rate (defined as seizure reduction greater than 50%), Engel score, and change in anti-epileptic medications were also statistically similar between groups. 13.3% (n = 2) of the RNS group experienced infection requiring re-operation, compared to 0.0% of the VNS group.
Conclusions: Despite their different mechanisms, VNS and RNS resulted in similar seizure control for patients with bilateral temporal lobe epilepsy.
Patient Care: A better understanding of the contemporary neuromodulatory modalities will help guide clinical decision-making in challenging epilepsy cases. Longitudinally, we hope this area of research will mitigate the significant morbidity and mortality associated with medically refractory epilepsy.
Learning Objectives: Participants should be able to:
1) Describe the considerations for VNS versus RNS, including predictors for response to treatment as reported in the literature.
2) Compare the complication profiles for the two treatments.
3) Discuss the current evidence for efficacy for the two procedures.