JUn 1, 2007
Researchers are using a process known as deep brain stimulation to try and treat patients with severe depression. Shown are X-rays of a brain and the locations of where electrodes are implanted for the treatment.
Stimulating different parts of the brain with implanted electrodes could help treat the nearly two million people in the United States who suffer from severe depression but fail to respond to conventional treatment.
"It's a very dangerous disorder. Twenty percent of patients suffering from major depression commit suicide," said Thomas Schlaepfer, professor of psychiatry and psychotherapy at University Hospital in Bonn, Germany and associate professor of psychiatry and mental health at Johns Hopkins University School of Medicine in Baltimore.
Schlaepfer and his team are among a handful of researchers using deep brain stimulation — a therapy successfully used to treat tremors associated with Parkinson's disease — to treat depression. The idea is to reset disordered neural activity in the brain in a similar way to how a person might reboot a computer to override a glitch.
The system consists of a neurostimulator, a device about the size of a hockey puck, that is implanted in the chest wall. Wires attached to the stimulator run under the skin to two electrodes that are inserted through tiny holes in the skull and glued to the bone.
The stimulator, which can be switched on or off by the patient, delivers electrical current to the electrodes. Depending on its intensity and frequency (parameters that are controlled by a medical team member), the current influences brain activity in a particular region.
Because an important symptom of major depression is anhedonia — the inability to find pleasure from activities previously experienced as pleasurable — Schlaepfer's group focused on the brain's reward center, a region called the nucleus accumbens, which responds to stimuli from such things as food, sex, and some drugs.
During their most recent study, the researchers surgically implanted the system into three individuals who suffered from major depression and who had not responded to other treatments, including drugs or electroconvulsive therapy.
The patients all reported that they felt no sensations when the stimulator was turned on. Curiously enough, they also reported feeling no changes to their condition after the stimulator was turned on. Yet all of them almost spontaneously began planning pleasurable activities.
One patient visited the Cologne Cathedral the day following the operation. Another patient mentioned taking up bowling, a favorite pastime from 12 years past.
Focusing on the accumbens region of the brain not only makes sense from a theoretical point of view but also from an experimental point view because it could be one node in a larger circuit that affects depression, said Helen Mayberg, professor of psychiatry and neurology at Emory University School of Medicine in Atlanta.
But focusing on the the brain's pleasure center could also have some unpleasant side effects.
"The nucleus accumbens has been modeled as an area of craving. Could you get habituated to the chronic stimulation?" She asked. "Sometimes side effects are worse than your primary symptoms."
Still, Mayberg added that the deeper the understanding about how the brain functions, the better the treatments.
"If there's buy-in scientifically and conceptually to the idea of a circuit and that some nodes are more important than others, the engineers will advance the technology," said Mayberg.
Schlaepfer is currently working with the stimulator's manufacturer, Minneapolis, Minn.-based Medtronic, to complete a clinical trial that could meet government approval within about five years.