Beyond the treatment of epilepsy: new applications of vagus nerve stimulation in psychiatry.

Vagus nerve stimulation (VNS) in humans generally refers to stimulation of the left vagus nerve at the cervical level VNS is an established treatment largely devoid of severe side effect for medically refractory partial onset seizures and has been used in more than 16,000 patients. Over the past 5 years, applications in other neuropsychiatric disorders have been investigated with a special emphasis on depression. Recent data from an open-label, multi-center pilot study involving 60 patients suggest a potential clinical usefulness in the acute and maintenance treatment of drug-resistant depressive disorder. The perspective of VNS as along-term treatment with the advantage of assured compliance makes it an interesting technique to potentially treat drug-resistant depression. However, definite therapeutic effects of clinical significance remain to be confirmed in large placebo-controlled trial. Results of clinical pilot studies involving patients suffering from obesity and Alzheimer's disease indicate that VNS might induce weight loss and improve cognition. Besides its clinical usefulness, VNS can be used as a research tool, allowing neurophysiologic investigations of the parasympathetic system and its interactions with other parts of the central nervous system.