Comprehensive long-term outcome of best drug treatment with or without add-on vagus nerve stimulation for epilepsy: a retrospective matched pairs case-control study

Abstract

Purpose: In the treatment of epilepsy, the recommendation to add vagus nerve stimulation (VNS) to the best available drug therapy (BDT) mostly relies on uncontrolled studies which provide limited information about VNS-specific benefits. We report findings from a retrospective matched pairs case-control study comparing the long-term (>2 years) outcomes of BDT with or without VNS.

Methods: Included were adult patients with therapy-refractory epilepsy who had undergone the pre-surgical work-up (baseline) and subsequently received BDT with VNS (BDT+VNS) or BDT alone (BDT group). Patients were matched in pairs for age, gender and follow-up. Health outcomes were assessed at least 24 months after the baseline by comprehensive postal surveys and included established psychometric scales.

Results: We obtained data from 20 matched pairs of case and control patients. In both groups, seizures, health-related quality of life and mood improved over time. More BDT patients experienced a complete cessation of "major" seizures (12/20 vs. 4/20) whereas, in non-seizure free patients, BDT+VNS patients showed better seizure frequency reduction (>50% reduction: 12/19 vs. 7/16). BDT+VNS patients experienced equal drug related and additional VNS related side effects. No clinically relevant effect of VNS treatment was found on any psychological/psychosocial outcome measure.

Conclusion: This retrospective study provided no positive evidence for therapeutic benefits of adding VNS to BDT. The follow-up health status of BDT+VNS patients was slightly worse than in patients receiving BDT alone. Despite minor group differences at baseline the two patient groups who had failed presurgical evaluation were comparable. Therapeutic improvements during long-term BDT alone are often underestimated resulting in a misattribution of positive changes to VNS in uncontrolled studies and reviews. Currently, there is no incontrovertible evidence for the clinical effectiveness of adding VNS to BDT.