Overall, deep brain stimulation patients were nearly four times as likely to have serious post-surgery problems, such as infections, disorders of the nervous system, or psychiatric problems. Ten percent of surgery patients developed infections in the surgical site, and one person died. Serious falls also were more common among deep brain stimulation patients during the six months after surgery.

People who had deep brain stimulation were also more likely to develop depression, confusion, and anxiety, although these changes were minor, according to Weaver and her colleagues, and it’s not yet clear how much of an effect they had on patients.

The surgery is extremely complex, Weaver notes; first, patients must have the electrodes implanted in the brain, which has to happen while they are awake so the surgeon can test the effects of touching various brain regions in order to make sure they are putting the device in the right place. Then patients undergo surgery to implant the pacing device, usually in the chest, which must be done under general anesthesia. If a patient develops an infection, it may be necessary to remove the device and replace it with a new one.

The fact that the study included a relatively high number of people over 70 may have contributed to the high rate of adverse events, Weaver explains. But the benefits seen for patients—including the older people, who fared as well as the younger patients—are “great news,” Dr. Charles says.

Anyone considering deep brain stimulation should keep these risks in mind and work with his or her physician to determine if the benefits will outweigh these relatively rare—but significant—dangers, Weaver advises.

More than 1 million people in the United States have Parkinson’s disease, and 50,000 new cases are diagnosed each year. Actor Michael J. Fox is arguably the most famous person with the disease; he was diagnosed in 1991.

In 1998, Fox underwent a type of brain surgery called a thalamotomy, in which a tiny portion of brain tissue is destroyed. This type of surgery gives a similar result to deep brain stimulation, but is not reversible. With deep brain stimulation, doctors can halt the electrical impulses if necessary. More than 35,000 deep brain stimulation procedures have been performed around the world, according to the American Association of Neurological Surgeons, and the procedure is being studied as a treatment for depression and other conditions as well.

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