Vagus Nerve Stimulation in Humans: Neurophysiological Studies and Electrophysiological Monitoring

Abstract

Evidence from studies of experimental animals indicates that electrical stimulation of the vagus nerve alters behavioral and electrographic seizure activity. We report on effects of electrical stimulation of the vagus nerve in five patients with medically intractable seizures as part of a clinical trial of chronic vagal stimulation for control of epilepsy. The mechanism of action of the vagal antiepileptic effect is unknown, and it is hoped that analysis of electrophysiological effects of vagal nerve stimulation will help elucidate which brain areas are affected. Stimulation of the left vagus nerve in the neck was accomplished with a programmable implanted stimulator. Effects of stimulus amplitude, duration, and rate were studied. Noncephalic reference recording of the vagus-nerve-evoked potential showed some unusual properties: a scalp negative component occurred with latency of 12 ms, very high amplitude (up to 60 microV), and widespread scalp distribution. Field distribution studies indicate that this potential is generated in the neck, in the region of the stimulating electrodes. Muscle paralysis confirms this observation. Stimulation at various frequencies had no noticeable effect on electroencephalographic (EEG) activity regardless of whether the patient was under general anesthesia, awake, or asleep.

Controlling Bursting in Cortical Cultures with Closed-Loop Multi-Electrode Stimulation

“…Epileptic seizures in human cortex, although probably originating from very different causes, have a strikingly similar phenomenology: ensemble bursts extending over large areas of neural tissue (Lopes da Silva et al, 2003). Electrical stimulation has been used in several experimental therapies for epilepsy; stimulation of the vagus nerve is the most well known example (Penfield and Jasper, 1954;Hammond et al, 1995;BenMenachem et al, 1994;Fisher et al, 1997;Handforth et al, 1998;Koo, 2001). Alternatively, animal and modeling studies suggest that focal stimulation at the site of the seizure can terminate seizures after they have started (Lesser et al, 1999;Franaszczuk et al, 2003;Slutzky et al, 2003).…”

Evolution of Neuromodulation

“…In 1985, Zabara [79] demonstrated that such stimulation could also infl uence strychnine seizures, again in the dog. This led Terry et al [80] to design a stimulator with fl exible intermittent parameters and an appropriate electrode that was used in an encouraging clinical study in epilepsy [81] . FDA approval was obtained in 1997, and vagal nerve stimulation has become commonplace in epilepsy management.…”

Vagus Nerve Stimulation Therapy and Epilepsy Surgery

“…At seizure onset, however, VNS has terminated both the clinical and the EEG seizure activity [32]. At seizure onset, however, VNS has terminated both the clinical and the EEG seizure activity [32].…”