External trigeminal nerve stimulation: A long term follow up study.

Purpose: External trigeminal nerve stimulation is an emerging noninvasive therapy for drug resistant epilepsy (DRE). The aim of this study is to describe the long-term outcome of a series of patients treated with eTNS. Methods: We present a retrospective observational study of patients with DRE who received eTNS treatment, comparing the monthly seizure frequency during the 3-months period before eTNS initiation with the monthly seizure frequency at 6, 12, 24, 36 and 48 months after eTNS. We analyze the responder rate, the retention rate and the tolerability. Results: 17 patients with highly drug-resistant epilepsy were included. Mean follow-up was 2194 [6-56] months. The responder rate was 35% at 6 months and 12 months, 23% at 24 months, 19% at 36 months, and 14% at 48 months. Retention rates at the same periods were 88%, 53%, 41%, 37.5% and 28.5%. There were no reports of serious adverse events. Four patients reported improvement in sleep and better mood. Conclusion: The effectivity of eTNS is similar to some of the new treatments available, with a retention rate of 52% in the first year and 285% at 4 years. Tolerability is excellent with only mild effects reported by a minority of patients.