Long-term effects of invasive and transcutaneous vagus nerve stimulation in patients with epilepsy: a retrospective cohort study

Abstract Objective To compare the long-term effects of transcutaneous vagus nerve stimulation (tVNS) and invasive vagus nerve stimulation (iVNS) on seizure frequency and tolerability in patients with drug-resistant epilepsies. Methods A retrospective cohort study was conducted to compare the efficacy of iVNS vs. tVNS in patients with drug-resistant epilepsy. Treatment response was defined as a > 50% reduction in seizure frequency. Antiseizure medications (ASM) were continued and changed if deemed clinically necessary. Data were collected during outpatient visits or by telephone interview using a standardized questionnaire. The questionnaire covered various aspects, including seizure frequency, tolerability, adverse effects, mood, and quality of life. Results In total, 75 patients treated with VNS and ASM were included. In the VNS cohort, 18 patients (mean age 40.7 ± 15.49 years) were treated with tVNS and 57 patients (mean age 31.6 ± 11.15 years) used iVNS. The final analysis included 47 patients (53% male, 47% female) who had a follow-up period of 5 years for tVNS and 15 years for iVNS. In the tVNS treatment group the response rate was 30%, while in iVNS users the response rate was 32%. Kaplan–Meier analysis for iVNS and tVNS users revealed comparable effects over a 5-year period, with no statistically significant differences observed in response rates. Under both tVNS and iVNS devices, few and mild adverse effects were reported, and significant improvements in the quality of life were detected. No difference was observed in terms of their impact on mood or concentration. Conclusion Both tVNS and iVNS were found to be a viable and well-tolerated add-on treatment for patients with drug-resistant epilepsy. Both stimulation methods were well tolerated and seemed to be comparably effective in the treatment of epilepsies.