Early seizure detection in rats based on vagus nerve activity

Continuous, scheduled vagus nerve stimulation (VNS) is used for the treatment of refractory epilepsy. On-demand VNS, started prior to or at the onset of a seizure may improve the effect of the treatment, however, this requires seizures to be predicted or detected early. This study investigates the possibility of early seizure detection based on the cervical vagus electroneurogram (VENG). Fourteen anesthetized rats received an intravenous infusion (IV) of either saline (control, n = 6) or pentylenetetrazol (PTZ) diluted in saline (PTZ-treated, n = 8). A cardiac-related VENG profile (CrVENG) was derived by using R-peak triggered averaging of the VENG energy. Following, changes in this profile were evaluated as a seizure predictor. Using left nerve VENG, seizures were detected in all PTZ-treated rats 103 ± 51 s (mean ± SD) before they developed tonic seizures. Control rats did not develop seizures and our method did also not detected seizures in these rats. Seizures can be early detecting based on left nerve VENG in anesthetized rats. Preictal CrVENG changes may reflect central-mediated changes and/or changes in the relation between the respiration and the cardiac cycle. Further research is needed to evaluate the method in awake and freely moving animals and eventually in humans.