Vagus nerve stimulation for severe depression

Vagus nerve stimulation for severe depression

Researchers from Washington University School of Medicine in St. Louis are investigating a new method of treating severe depression, that is nerve stimulation. The results are promising and researchers found that  after several months of vagus nerve stimulation changes in brain metabolism occur. Furthermore, it seems that these changes in brain metabolism appear before patients begin to feel better. First author Charles R. Conway, MD, associate professor of psychiatry, said that previous studies involving large numbers of participants have shown that vagus nerve stimulation improves the condition of patients with treatment-resistant depression. He added that however little is known about the mechanism by which vagus nerve stimulation helps treat depression and this is why they focused on those brain regions involved in depression.

Conway and his team conducted a study that included 13 patients who had treatment-resistant depression (that is they have not responded to any of the 5 different medications that they received). Most patients were depressed for about 2 years but there were patients suffering from depression for more than 20 years. All patients underwent surgery to implant a device to stimulate the left vagus nerve, which goes from the brainstem to the abdomen. The stimulator was set to send up to 30-second electronic stimulus every 5 minutes.

Depression

To quantify the effects of treatment, the researchers performed positron emission tomography (PET) imaging  in patients both before brain stimulation and at 3 and 12 months after treatment. The results appeared a few months after the stimulation in 9 of the 13 patients included in the study. In those who responded to this treatment, imaging investigations have shown that electrical stimulation of the vagus nerve led to changes in brain metabolism, and this happened at 3 months after treatment. Conway said that they noticed major changes in brain metabolism long before clinical changes were visible. He explained that it is like as an adaptation process: first, the brain begins to function differently and then the patient begins to feel the changes.

Even though many patients continued therapy with antidepressants after stimulation, those who responded to treatment were able to quit drugs. “Sometimes the antidepressant drugs work in concert with the stimulator, but it appears to us that when people get better, it is the vagus nerve stimulator that is doing the heavy lifting,” Conway stressed. He added  that in treatment-resistant depression an important role is played by dopamine pathways and that these pathways are influenced by the vagus nerve stimulators.