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Invasive vagus nerve stimulation has been demonstrated to be an effective treatment in major depressive episodes. Recently, a novel non-invasive method of stimulating the vagus nerve on the outer canal of the ear has been proposed. In healthy subjects, a prominent fMRI BOLD signal deactivation in the limbic system was found. The present pilot study investigates the effects of this novel technique of auricular transcutaneous electric nerve stimulation in depressed patients for the first time. A total of 37 patients suffering from major depression were included in two randomized sham controlled add-on studies. Patients were stimulated five times a week on a daily basis for the duration of 2 weeks. On days 0 and 14, the Hamilton Depression Rating Scale (HAMD) and the Beck Depression Inventory (BDI) were assessed. In contrast to sham-treated patients, electrically stimulated persons showed a significantly better outcome in the BDI. Mean decrease in the active treatment group was 12.6 (SD 6.0) points compared to 4.4 (SD 9.9) points in the sham group. HAMD score did not change significantly in the two groups. An antidepressant effect of a new transcutaneous auricular nerve stimulation technique has been shown for the first time in this controlled pilot study. Regarding the limitations of psychometric testing, the risk of unblinding for technical reasons, and the small sample size, further studies are necessary to confirm the present results and verify the practicability of tVNS in clinical fields.

Background: Olfactory and gustatory functions were investigated before and during vagus nerve stimulation (VNS) in a group of 9 patients with therapy-resistant depression, implanted with a VNS system., Methods: Gustation and olfaction were tested using standard sniffing tests. Subjects participated in 2 sessions with the vagal stimulator switched on and off, respectively., Results: Under conditions of stimulation of the VNS, there were statistically significant differences of the threshold of perception, with an intensification of the taste "sweet" (Z = -2.0; p = 0.048) and "bitter" (Z = - 2.5; p = 0.011) compared to the "off-mode". A statistical trend (Z = - 1.7; p=0.098) for increased intensity of the taste "salty" was observed, however, these results would supposedly disappear after correction for multiple testing presumably due to the large number of variables and the small sample size. There were no statistically relevant differences concerning olfactory perception., Conclusions: The changes of gustatory perception under conditions of vagal nerve stimulation observed in this study show another important central nervous effect of vagal stimulation on the limbic system that might be of importance in the elucidation of mechanisms of action of VNS especially on refractory depression., (© Georg Thieme Verlag KG Stuttgart · New York.)