WHAT IS VNS?
VNS uses electrical impulses to stimulate centers in the brain that regulate mood, sleep, appetite and motivation. VNS was initially approved by the U.S. Food and Drug Administration for the treatment of epilepsy. In 2005, VNS was approved for the treatment of both chronic or recurring depression and bipolar disorder. VNS has been described as a “pacemaker for the brain,” because it delivers subtle electrical stimulation directly to the brain at regular intervals.
A battery-operated, computer-controlled device the size of a pocket watch, called a pulse generator, is surgically implanted in the upper chest, just below the collarbone. Wires attach it to the left vagus nerve, which runs from the brain through the neck and into several major organs. Electrical pulses travel from the generator to the vagus nerve. When stimulated, the nerve sends signals to the brain.
IS VNS EFFECTIVE?
VNS has only been studied and approved for those who have failed to respond to more traditional treatments. Although scientists do not yet know exactly how VNS works to alleviate the symptoms of depression, studies have shown that it is effective in many cases. VNS has been shown to be significantly helpful in about 30% of patients treated for chronic depression or Type II bipolar affective disorder, improving mood, sleep, energy, motivation and overall quality of life. Patients treated with VNS have also been shown to have lower relapse rates for depressive episodes.
The therapeutic effects of VNS appear to accumulate over time, with some patients needing up to a year of treatment to see a full effect. Studies have also shown that the improvement can be long lasting. Patients who saw improvement within 12 months showed nearly a 70% chance of retaining a positive response after two years. Although VNS patients often continue to require medication, for some people the variety and quantity of medications may be reduced over time.
WHEN IS VNS RECOMMENDED?
VNS can help those patients who have not found adequate relief from depression with any other treatment method. The U.S. Food and Drug Administration has approved VNS for patients 18 years and older who have long term, chronic depression that has lasted two or more years, recurrent or severe depression, or depression that has not improved after the use of other treatments.
VNS is not for everyone. In order to be a candidate, a patient must have tried at least four different medication therapies from at least two different classes (two different mechanisms of interacting with the brain’s chemistry), including at least two combination therapies, coupling two medications which act differently when taken together. These treatments must have been attempted for a significant length of time at appropriate dosages.
It is also recommend that patients have had an adequate course of evidence-based psychotherapy for depression, such as Cognitive Behavioral Therapy (CBT) or Interpersonal Therapy (IPT). Patients are also strongly encouraged to try an adequate course of Electroconvulsive Therapy (ECT) as well before considering VNS.
Some psychiatric conditions exclude patients from consideration for VNS therapy, including acute suicidal thinking or behavior, rapid cycling bipolar disorder, schizophrenia, schizoaffective disorder, severe personality disorder, and ongoing substance/alcohol abuse.
Since the vagus nerve is associated with several major organs, some medical conditions exclude patients from receiving VNS Therapy. These include: previous brain injury, progressive neurological disorders, severe lung disorders, vasovagal syncope (a fainting syndrome), ulcers, dysautonomias (an imbalance of the autonomic nervous system) and heart arrhythmias (irregular heartbeat). VNS therapy can also cause or worsen obstructive sleep apnea. Patients who have had one or both vagus nerves removed are not candidates for VNS.
WHAT IS INVOLVED IN THE PROCEDURE?
An outpatient surgical procedure lasting one to two hours is required to implant the VNS system, and most patients go home the same day. The surgery involves making two small incisions: one in the upper chest area, where the pulse generator is placed (just beneath the skin below the collarbone, similar to where cardiac pacemakers are placed) and another on the left side of the neck, where the wires are attached to the vagus nerve. Because the incisions are small, they typically heal with very little visible scarring.
A week or two after the surgery, the doctor will turn on the stimulator during an office visit, and will gradually adjust the strength of stimulation over several weeks. The stimulator is programmed to deliver intermittent electrical impulses to the nerve throughout the whole day. Stimulation lasts for 30 seconds and occurs every 5 minutes. Sometimes this is noticeable as a tickling sensation or slight hoarseness to the voice. Patients are supplied with a magnet to temporarily turn off the device if they find that the period stimulation disrupts them when they are participating in particular activities, such as giving a speech, singing, or exercising heavily.
ARE THERE SIDE EFFECTS?
VNS does not cause the side effects encountered with many medications, such as memory loss, sleep difficulty, weight gain or sexual dysfunction. There are some side effects associated with VNS, but most patients find them to be relatively minor and to decrease over time. During the 30-second stimulations, patients may experience temporary voice changes and hoarseness, difficulty swallowing, tightness in the throat, increased muscle tension, difficulty breathing with exertion, headache, nausea, neck pain, numbness and tingling at the incision site, coughing, dizziness, chest pain and/or a sore throat.
A very small percentage of patients experience vocal cord paralysis while the device is stimulating the nerve. Although uncommon, VNS therapy may lead to hypomanic or manic states in patients suffering from bipolar disorder.
IS VNS SAFE?
The treatment requires surgery, making it more invasive than other treatments for depression. Any medical procedure involving anesthesia carries some risk.
WHAT COMES AFTER VNS?
VNS is not a quick fix, and it is not a cure for depression. Patients may not feel any effect for several months. VNS is considered a long-term therapy, and while many patients may require less medication as a result of VNS, they may still need some drug therapy to manage their symptoms. Some patients may have no improvement, or even worsen with VNS therapy.
After several years, the batteries in the VNS device must be replaced, which involves another short outpatient surgical procedure. Although the pulse generator can be removed, the wires remain permanently attached to the vagus nerve.