Vagus Nerve Stimulation acts like a “pacemaker for the brain”. The vagus nerve is defined as the nerve that produces inhibition of neural processes, which can alter the brains electrical activity.
VNS was first considered for treatment-resistant depression because:
1. clinical observations of improved cognition and mood during studies of patients with epilepsy.
2. the fact that several anti-convulsant medications are used to treat mood disorders.
The most common side effects that have been reported in research studies and clinical trials as possibly, probably, or definitely related to stimulation were hoarseness, throat pain, headache, shortness of breath, general pain, and neck pain. In general, stimulation-related effects were mild and well tolerated, and they have occurred only when stimulation was on. Hypomania has been caused through Vagus Nerve Stimulation, but has subsided with stimulation reduction.
In many ways, VNS is much like the very common practice of implanting cardiac pacemakers. In both cases, a generator sends an electrical signal to an organ through an implanted electrode.
Vagus Nerve Stimulation is delivered through an implantable, multiprogrammable, bipolar pulse generator (the size of a pocket watch) that is implanted in the left chest wall to deliver electrical signals to the left vagus nerve through a bipolar lead. With VNS, the electrode is wrapped around the vagus nerve in the neck, near the carotid artery using a separate incision, and then connected to the generator.
The software, along with a personal computer, provide telemetric communication with the pulse generator, which enables non-invasive programming, functional assessments and data retrieval. The system includes mechanical and electrical safety features that minimise the possibility of high-frequency stimulation that could lead to tissue damage. In addition, each patient is given a magnet that, when held over the pulse generator, turns off stimulation. When the magnet is removed, normal programmed stimulation resumes.