Vagus nerve stimulation, an effective epilepsy treatment, has produced encouraging preliminary results for patients suffering from "treatment-resistant depression," and a study beginning at University Medical Center of Arizona and a handful of other U.S. sites may verify the promising new therapy. Approximately 18 million Americans suffer from depression, and about 1 million of whom have severe treatment-resistant depression.
FDA Approval
FDA approval for the Vagal Nerve Stimulator (VNS) came July 1997 as adjunctive treatment of complex partial seizures for patients over 12 years old. As with any approved treatment, "off label" use is permitted and epileptologists have already implanted children younger than 12 (three y.o.), and treated patient with other than complex partial seizures (absences, Lennox-Gastuat).
FDA approval for the VNS Therapy System as depression treatment approach was received on July 15, 2005. This device is indicated for the adjunctive long-term treatment of chronic or recurrent depression for patients eighteen years of age or older who are experiencing a major depressive episode and have not had an adequate response to four or more adequate antidepressant treatments.
How VNS works?
There's one vagus nerve on each side of your body. The nerve runs from your brainstem through your neck and down to your chest and abdomen. Information travels through this nerve to and from your central nervous system. The pulse generator sends electrical signals along your vagus nerve up into your brain, where it's hoped that these electrical signals will create a reaction that improves your mood and reduces depression symptoms.
The principal components of the VNS Therapy System are an implantable pulse generator and lead, and an external programming system. The procedure usually lasts about 50 to 90 minutes with the patient under general anesthesia. Sometimes a hospital stay of one night is required. Some surgeons have performed the procedure with local anesthesia and the patient has been discharged the same day.
The study patients are implanted with a NeuroCybernetic Prosthesis (NCP) System, which consists of a battery-powered generator implanted in the chest and a lead attached, at neck level, to the vagus nerve leading to the brain. The device delivers an automatic, periodic electrical stimulation to the vegus nerve. A physician can adjust the intensity, duration and frequency of the stimulation, which may be minimally noticeable by the patient, in follow-up visits.
The Vagus Nerve Stimulation device costs $12,000 and the cost of surgery to implant the device can run as high as $15,000.
Side Effects
The possible side-effects that have been reported at some time during treatment that were significantly increased, were
- voice alteration/hoarseness,
- cough,
- throat pain,
- nonspecific pain,
- dyspnoea,
- paraesthesia,
- dyspepsia,
- vomiting and
- infection.
However, VNS does not cause the side effects normally associated with depression medications, such as weight gain, loss of sexual function, cognitive impairment and insomnia.
Medical Coverage
In May 2007, US Department of Health and Human Services issued a memo, claiming that there is sufficient evidence to conclude that vagus nerve stimulation is not reasonable and necessary for treatment of resistant depression. Accordingly, it has been issued the following national coverage determination: Vagus nerve stimulation is not covered for treatment resistant depression.
During the surgery
Surgery to implant the vagus nerve stimulation device is done either on an outpatient basis, allowing you go to home that same day, or on an inpatient basis, requiring an overnight stay in the hospital. The surgery usually takes one to two hours. It may be done under local or general anesthesia. The FDA recommends that the surgery be done by a neurosurgeon with expertise in implanting the device.
Surgery to implant the vagus nerve stimulation device is done either on an outpatient basis, allowing you go to home that same day, or on an inpatient basis, requiring an overnight stay in the hospital. The surgery usually takes one to two hours. It may be done under local or general anesthesia. The FDA recommends that the surgery be done by a neurosurgeon with expertise in implanting the device.
The surgery doesn't involve your brain. The pulse generator is surgically implanted in the upper left side of your chest. The device is meant to be a permanent implant, but it can be removed if necessary. The pulse generator is about the size of a stopwatch and runs on battery power. A lead wire is connected to the pulse generator. The lead wire is guided under your skin from your chest up to your neck, where it's attached to the left vagus nerve through a second incision.
After the procedure
The pulse generator is activated during a visit to your doctor's office a few weeks after surgery. The pulse generator can be programmed to deliver electrical impulses to the vagus nerve at various durations, frequencies and currents. Vagus nerve stimulation usually starts at a low level and gradually increases, depending on your symptoms and side effects.
The pulse generator is activated during a visit to your doctor's office a few weeks after surgery. The pulse generator can be programmed to deliver electrical impulses to the vagus nerve at various durations, frequencies and currents. Vagus nerve stimulation usually starts at a low level and gradually increases, depending on your symptoms and side effects.
Stimulation typically lasts for 30 seconds and occurs every five minutes. You may have some tingling sensations or slight pain in your neck during episodes of nerve stimulation.
You are given a hand-held magnetic device so that you can control the stimulation yourself at home. This enables you to temporarily turn off the vagus nerve stimulation, which may be necessary when you engage in such activities as public speaking, singing or exercising, or when you're eating if you have swallowing problems.
You must visit your doctor periodically to make sure that the pulse generator is working correctly and that it hasn't shifted out of position.
Maintenance of the Device
The device comes with a programming wand and software, which are used to program the device or turn it off if necessary. You will eventually need surgery to replace the generator when the battery wears out. How quickly the battery wears out depends upon its settings, but on the average it lasts about six years. Replacement of the generator is generally an outpatient procedure under local anesthetic that takes about one hour to complete.
What can you expect?
Vagus Nerve Stimulation hasn't been on the market that long, so long-term studies aren't available. That's why it's extremely important to discuss the pros and cons of VNS Therapy with your psychiatrist and other doctors. As mentioned earlier, the FDA advises that VNS be used only along with traditional depression treatments such as antidepressants and psychotherapy.
It may take several weeks to months before a VNS patient notices improvement in their depression symptoms. And since VNS didn't perform any better than a placebo in clinical trials, it's possible a patient won't experience any improvement at all. In fact, the FDA advises that, in some cases, depression could worsen with VNS therapy. The most common adverse effect (side-effects) associated with VNS is voice alteration or hoarseness, throat pain and cough. Dyspnea and paresthesia are also reported side-effects of Vagus Nerve Stimulation. Vagal nerve stimulation has not been reported to cause cognitive impairment.
One Happy Customer
One news report cites Lauri Sandoval, 42, a participant in the pilot study, who has tried almost every antidepressant available and was set to start electroconvulsive therapy: "I was so desperate and depressed that I wasn't even scared of it, even though it hadn't been studied before."
Lauri had suffered from depression for 30 years and was having trouble holding down a job. It took her three months after receiving the implant to feel the change, and 18 months later, she reported feeling dramatically better: "I used to be a hermit and I tried to pretend that I wasn't depressed. I would stay in bed as long as I could. I would get up to go to work, or to walk my dogs, but after a while that would even be difficult."
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