Cardiac-based vagus nerve stimulation reduced seizure duration in a patient with refractory epilepsy

Purpose: A novel vagus nerve stimulation (VNS) device was recently approved in Europe which rapidly detects increases in heart rates (HR) and applies an additional stimulus if HR-increases exceed a given threshold. The effects of HR-triggered VNS-pulses on seizures were not reported yet under controlled conditions. Here, we quantified the effects of HR-triggered VNS-pulses on the seizure duration in one patient. Methods: The novel VNS device was implanted in a 29-year old man with refractory epilepsy. After implantation, the patient underwent video-EEG telemetry for 68 h with no changes in anticonvulsant drugs. On the first day the patient only received sham-stimulation. During the following 46 h HR-related VNS-stimulation was set to 2 mA. Seizure duration was determined based on clinical signs. Results: Twelve stereotypical seizures were recorded (six during sham- and six during the active stimulation). The VNS device recognised a total of 139 events as a seizure and correctly identified 11 seizures. The HR-triggered VNS-stimulation significantly reduced the total seizure duration from 33.2 +/- 4.8 s to 26.5 +/- 5 s and the remaining seizure duration after the onset of the extra-stimulation from 27.8 +/- 4.3 s to 16.2 +/- 3.2s. With the given configuration in this patient, sensitivity and specificity of HR-based seizure-detection amounted to 92% and 13.5%, respectively. Conclusions: This case illustrates that VNS-stimulation in response to seizure-related HR-increases is able to significantly reduce seizure duration. Despite the limitations of our case, its promising results should prompt larger studies to confirm the clinical benefit of this novel device. (C) 2015 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.