Doctors at the University of Maryland School of Medicine in Baltimore are testing a surgically implanted device that could prove to be an innovative new treatment for those who suffer from severe, treatment-resistant depression. The device, which is also used to control epileptic seizures, sends mild electrical impulses to the brain by stimulating the vagus nerve in the neck. The University of Maryland Medical Center is one of 20 research centers around the country participating in the study.
"It's like a pacemaker for the brain," says Mitchel A. Kling, M.D., associate professor of psychiatry and medicine at the University of Maryland School of Medicine. "The intermittent electrical pulses seem to stimulate the areas of the brain that regulate mood," explains Dr. Kling.
The vagus nerve stimulator, known as the NeuroCybernetic Prothesis (NCP) System, consists of a battery powered pulse generator, which is implanted under the skin on the upper left side of the patient's chest. Tiny wires lead to the vagus nerve in the neck, delivering a 30 second pulse of electricity every five minutes. The intensity and duration of the stimulation can be easily adjusted in the doctor's office with a special programming wand and computer.
The 12-week nationwide study involves more than 200 volunteers who suffer from treatment-resistant depression. All will have the vagus nerve stimulator surgically implanted by neurosurgeons, but only half of the devices will be activated. Neither the patients nor the researchers will know which patients are receiving the electrical pulses. After the study period, patients in the control group will have their devices activated so they can receive the treatment. All volunteers will receive long-term follow-up care.
The idea of using vagus nerve stimulation to treat depression came from doctors who were using it to treat patients with epilepsy. The doctors noticed that in addition to having fewer seizures, their patients who had been depressed experienced a dramatic improvement in their mood. In a pilot study involving patients with treatment resistant depression, 40 percent of those who received vagus nerve stimulation experienced significant relief from their depression symptoms.
"This approach has the potential for becoming a breakthrough treatment alternative for patients who have shown only limited improvement with medication and psychotherapy," says Dr. Kling, the study's primary investigator at the University of Maryland and medical director of the Mood Disorder Program at the Baltimore VA Medical Center. "If effective, vagus nerve stimulation could dramatically improve the quality of life for people with treatment-resistant depression."
Depression is a serious psychiatric disorder that affects about 18 million Americans, including about one million who do not respond to anti-depressant medications, such as Prozac. Right now, the most effective treatment for medication resistant depression is electroconvulsive therapy (ECT), which carries the risk of short-term memory problems.
Unlike with ECT and conventional drug treatment, there do not appear to be significant side effects associated with vagus nerve stimulation. Dr. Kling says there is no pain when the stimulation is applied, but some patients experience minor hoarseness or a slight change in voice quality.
The vagus nerve serves as one of many highways of information carrying messages to and from the brain. Nerve fibers in the vagus nerve relay information from several organs, including the heart, lungs and gastrointestinal tract. Researchers believe the vagus nerve is also a route to the limbic structures of the brain associated with the regulation of mood.
The study is being paid for by Cyberonics, Inc., which makes the NCP System. The University of Maryland Medical Center was the first in Maryland to use vagus nerve stimulation for the treatment of epilepsy following FDA approval in 1997.
Dr. Kling's collaborators at the University of Maryland include Howard M. Eisenberg, M.D., professor and chair of the Department of Neurosurgery, Allan Krumholz, M.D., professor of neurology, Elizabeth Barry, M.D., associate professor of neurology, and William Regenold, M.D., assistant professor of psychiatry.
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