Vagus Nerve Stimulation As an Adjunctive Neurostimulation Tool in Treatment-resistant Depression

This method can significantly improve the quality of life in patients with therapy-resistant depression. The main advantage of this technique is that it can be successfully used even if multiple antidepressive drug regiments have failed. Visual demonstration of this method is not difficult, as the different steps of vagus nerve stimulation, or VNS, tuning are easy to learn.

Demonstrating the procedure will be Dr.Merve Aydin, a clinician from the Department of Psychiatry and Psychotherapy from the University of Bonn in Germany. After evaluating for solid compliance and willingness to attend control and tuning visitations, connect the VNS wand to the handheld device and perform lead testing with a minimum of 10 seconds of 0.5 to one milliamp in 25-hertz stimulation. Intraoperative lead testing can be critical because serious side effects, such as bradycardia or even asystole, may occur in some patients.

Place the electrodes inferior through the cardiac branches of the left vagus nerve to avoid such effects. Commence regular VNS dosing two weeks after implantation, starting at 1.5 to three milliamps, a 500 microsecond pulse width, and 20 to 30 hertz for 30 seconds on, five minutes off, and gradually increasing the stimulation 0.25 to 0.5 milliamps per week up to two to three milliamps maximum. In cases of persistent depressive symptoms, end the dosing when a response to VNS is achieved up to a maximum of nine to 12 months.

In cases on non or partial response, instead of increasing the output milliamp current, decrease the signal frequency tuning from 30 to 20 hertz or reduce the off-time to three minutes. If transitory side effects occur, which tend to be directly associated with stimulation of the inferior recurrent laryngeal nerve, reduce the maximum milliamp tuning to no lower than 0.75 milliamps and/or change the on-off timing. If side effects do occur, the patient is able to use his own portable magnet to temporarily stop the VNS stimulation.

In long-term followups on the antidepressive effects of VNS, vagus nerve stimulated patients reported an overall lower degree of depressive severity after treatment. Indeed, the five-year cumulative response and remission rates were significantly higher in the VNS and treatment as usual group than in the treatment as usual only group. While attempting this procedure, it's important to remember that approximately 1/3 of patients with therapy-resistant depression do not adequately respond to VNS and that side effects may limit its therapeutic action.

In cases of insufficient response or intolerable side effects, clinicians can modify the setup of the vagus nerve stimulator. Following this procedure, other indications, like panic or post-traumatic stress disorder, may be future potential psychiatric target for VNS. Don't forget that the fine tuning of the vagus nerve stimulator offers various possibilities for generating desirable effects to different medical conditions.

Future studies to improve VNS efficacy and to reduce side effects should be further evaluated.