Vagus nerve stimulation (VNS) is a procedure in which a pacemaker-like device is implanted underneath the skin in the chest to literally stimulate the nerve. The nerve is enlivened by mild electrical impulses, which can interrupt or suppress abnormal activity and restore the standard neural pathway to the brain. The impulses are also believed to have an affect on the brain's so-called mood centers [source: Mayo Clinic].
According to the American Association of Neurological surgeons (AANS), the typical surgery to implant a pulse generator runs about an hour to 90 minutes and is performed under general anesthesia (patients with any known allergies should apprise the anesthesiologist). However, with improvements in surgical techniques, it's becoming more common to have this operation done under local anesthesia on an outpatient basis, therefore avoiding an expensive overnight hospital stay.
The pulse generator itself is a flat, round piece of metal about the size of a silver dollar, measuring roughly 1.5 inches (3.8 centimeters) wide and 0.47 inches (12 millimeters) thick, though newer models are getting smaller all the time. This battery-run device (see sidebar) emits the impulses that stimulate the nerve's circuitry. The duration of these impulses is set by the surgeon via a programming wand, typically two weeks to a month following surgery, and can be adjusted during future visits. Further, patients (and/or caregivers) can temporarily adjust the impulses by using a handheld magnet.
As with any surgery that requires incisions, there is always a small risk of infection (bringing to mind the old maxim, "The only minor surgery is the surgery that is happening on someone else"). Surgeons must also take special care not to damage the nerve itself or the surrounding blood vessels, including the carotid artery and jugular vein.
There are also certain post-surgical risks. The pulse generator, or the wiring, can detach or prove defective. If you have a stimulator, make sure your doctors and technicians are aware before having a mammogram, ultrasound or MRI (magnetic resonance imaging). The use of a heart defibrillator can also damage the device.