Autostimulation in Vagus Nerve Stimulator Treatment: Modulating Neuromodulation

Until now, the vagus nerve stimulation (VNS) treatment in epilepsy has consisted of two different modes: normal and magnet stimulation. A new vagus nerve stimulator model (106 AspireSR®, LivaNova, Houston, TX, USA) also allows automatic stimulation (AutoStim). The purpose of this study is to examine the effect of autostimulation on seizure frequencies together with energy consumption.

The study material consisted of 14 patients whose former stimulator model (102/103) was replaced with model 106. We calculated the theoretical charge (Q) in Coulombs for one day in both of those groups. We evaluated the follow-up data of the patients' seizure counts, with a mean follow-up time of 18.1 months (SD 8.1).

The total charge, "VNS dose," was reduced with model 106 in comparison with models 102 or 103 (p = 0.001, Mann-Whitney test). The average charge (Q_total ) for one day with AutoStim was 142.56 mC; without AutoStim, it was 321.09 mC. We were able to assess seizure diaries in 11 out of 14 patients. Four patients (36%) had >50% seizure reduction and two patients (18%) experienced a reduction in seizure severity with VNS with autostimulation. Five patients (46%) remained unchanged. In three out of four patients with improved seizure control, the duty cycle was maintained at the original level. The patients whose duty cycle was modified for a more prolonged OFF-time had unchanged seizure frequencies.

VNS with AutoStim achieves maintenance of prior-established seizure control with markedly less energy consumption and can also improve seizure control as compared to former stimulator model.