Deep brain stimulation

(This article was first printed in the April 2006 issue of the Harvard Mental Health Letter. For more information or to order, please go to http://www.health.harvard.edu/mental.)

The use of electromagnetic devices to treat psychiatric disorders, long confined to electroconvulsive therapy (ECT), has expanded in recent years because of advances in brain imaging, computer control, and microelectronics. Transcranial magnetic stimulation, vagus nerve stimulation, and magnetic seizure therapy have arrived. In early 2006, an electrical technique, deep brain stimulation, is being proposed for patients with severe depression and obsessive-compulsive disorder.

It works this way: A surgeon implants electrodes at precise locations in the brain and connects them with a thin wire to an electrical generator in the chest, sometimes called a brain pacemaker. The generator can interrupt activity or excite inhibitory neurons in the circuits where the electrodes are placed. The apparatus is programmed with a magnetic device passed over the skin that adjusts the current, duration, and frequency of the electrical pulses. Each electrode has several contacts that can be manipulated separately. Stimulation can be continuous or intermittent, and the patient can turn the machine on and off.

As of early 2006, deep brain stimulation already has FDA approval for the treatment of Parkinson’s disease, dystonias (severe muscle spasms), and certain kinds of chronic pain, and it is under investigation for patients with epilepsy and cluster headaches. Testing in obsessive-compulsive disorder and depression has just begun. In one study, the treatment was given to six patients with severe chronic depression who had not been helped by psychotherapy, ECT, or drugs. Four of the six responded well and were still doing well after a year. In another study, four patients with obsessive-compulsive disorder received the treatment. Three of them improved, at least one dramatically and perhaps permanently. The difference was obvious when the stimulus was turned on and off.

The technique could also have potential in the treatment of other severe mental illnesses, and in improving knowledge of the brain circuits affected by those illnesses. Unlike procedures that involve ablation (cutting) of brain tissue — already used in rare cases of obsessive-compulsive disorder — deep brain stimulation is reversible and adjustable. But it is a more drastic measure than other electromagnetic techniques, because of the risks and high cost of brain surgery. Adjusting the apparatus often requires many visits to a doctor, and the battery that fires the pacemaker has to be replaced every two to three years, which means more surgery. So deep brain stimulation is likely to remain a last resort, used only when other possibilities are exhausted.

(This article was first printed in the April 2006 issue of the Harvard Mental Health Letter. For more information or to order, please go to http://www.health.harvard.edu/mental.)

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