Dec. 15, 1999 (Cleveland) -- An implantable device that is about the size of a stopwatch may put a stop to depression in patients who have failed treatment with antidepressants or shock therapy. Depression affects about 18 million Americans, but about 1 million of those people have severe treatment-resistant depression that lasts for years and is a disabling condition.
The experimental treatment works by way of a generator implanted in the chest. Wires attach the device to the vagus nerve, which runs from the neck into a brain region believed to be important for regulating mood. The generator then sends tiny electric shocks to the nerve.
The treatment, called a vagus nerve stimulator, is already FDA-approved for severe epilepsy. But the results of a multi-center study on its effect on depression were presented at the annual meeting of the American College of Neuropsychopharmacology in Acapulco earlier this week and published online Wednesday by Biological Psychiatry.
"Typically the surgery is done as an outpatient procedure that takes about an hour or two," says lead researcher A. John Rush, MD.
Rush, vice chairman for research in the department of psychiatry at the University of Texas Southwestern Medical Center in Dallas, tells WebMD that 40% of the 30 patients enrolled in the open treatment trial had at least a 50% improvement in their depression at the end of an eight-week course of treatment.
Rush says, "We have followed some of these patients for 10 months now, and we can report that those who responded during the early phase have held the response, and some patients who didn't respond during the eight-week trial responded later. So the long-term results are actually slightly more optimistic than the eight-week results that were reported in this paper."
The results are particularly compelling given the severity of depression, he says. "Twenty-one patients had major depressive disorder and nine were bipolar [formerly known as manic depressive]," he says. More than half of the patients had received ECT-- the so-called electro-shock therapy -- and all the patients failed to respond to at least two robust antidepressant medication trials.
"A typical side effect would be a raspy-sounding voice during stimulation, because the [vocal cords are] also affected," says Rush. The electrical current is on for 3 seconds and then off for 5 minutes, and this cycle is constant 24 hours a day, Rush says. "At the same time, the patient is maintained on the baseline medication regimen. This is an unusual approach for psychiatry, but we are considering this as an add-on therapy," he says.
Although he is enthusiastic, Rush emphasizes the preliminary nature of the findings. Asked to comment on the study, Thomas Thompson, MD, director of the ECT program at Wesley Woods Geriatric Hospital in Atlanta and assistant professor of psychiatry at Emory University School of Medicine, echoed that cautious note. Thompson tells WebMD, "This is very preliminary work, and the findings need to be replicated in a larger study. A lot more work still needs to be done."
If the results are proven in larger studies (the FDA has given approval to enroll another 30 patients in the ongoing trial), Rush says that the stimulator may prove a good alternative to ECT. He says that he and his fellow researchers did some testing that indicates the vagus nerve device may actually improve some mental functioning.
One of the main criticisms of ECT is that it sometimes leaves patients with sluggish responses and impaired memory. Rush says, however, that the improvement may be related to the improvement in depression.
That explanation makes sense to Thompson, who says that although ECT is associated with some changes in mental functioning around the time of the treatments, "We actually see improvements when we retest after treatment if there has been an improvement in the depression." He says that the vagus nerve stimulator may work the same way.
Using the treatment for depression is experimental, but Rush estimates that if it becomes an approved therapy the cost will be "about $10,000 to $12,000 for the device and about $4,000 to $5,000 for the surgery." In this study, all surgeries were "done by neurosurgeons who have implanted [the vagus nerve stimulator] for epilepsy," Rush says.
The study was partially funded by Cyberonics of Houston, manufacturer of the stimulator.
- Depression affects 18 million Americans, and about 1 million of those do not respond to conventional treatment.
- An implanted device that stimulates the vagus nerve has been shown to be effective in some of these treatment-resistant patients.
- The vagus nerve stimulator, which is an approved epilepsy treatment, requires outpatient surgery that lasts about two hours.