April 12, 2005 -- Deep brain stimulation appears to reduce uncontrolled movements in people with Parkinson's disease.
Valerie Anderson, PhD, and colleagues report their findings in April's Archives of Neurology.
Deep brain stimulation suppresses uncontrolled movements by using electrical impulses to block signals from the brain that cause these movements. Surgery is required to implant tiny wire electrodes that produce the electrical impulses. The device can be turned on or off as needed.
Parkinson's disease affects certain brain cells that make dopamine, a chemical messenger that helps direct movement. As those cells are destroyed, dopamine decreases, garbling the brain's movement signals.
Symptoms include shaking (tremor), stiff muscles (rigidity), and slow movement (bradykinesia). Parkinson's usually starts in middle age or later, progressing gradually. Although there is no cure, medications (and sometimes surgery) can help manage symptoms. Deep brain stimulation is an option in patients with advanced Parkinson's disease whose movements cannot be controlled with medication or have intolerable side effects from their medication.
Testing the Technique
Anderson's team randomly assigned 23 Parkinson's patients to get deep brain stimulation in one of two brain areas: the globus pallidus interna (GPi) or subthalmic nucleus (STN).
Participants were tested before the operation and again three, six, and 12 months later. Ten patients from each group finished the study.
After the surgery, both groups had reduced abnormal movements while off their Parkinson's drugs. Uncontrolled motion improved in both groups 12 months after surgery.
Slow movement tended to improve more with STN stimulation than GPi stimulation, says the study.
Several people in the STN group experienced memory and concentration difficulties and behavioral side effects after the procedure.
Three had mild delirium that faded in a few days. Two others had a brief bout of anxiety, and another had hallucinations that disappeared after levodopa doses were adjusted.
No mood or thinking changes were noted in the GPi group.
Reduced Drug Use
After a year of deep brain stimulation, the STN group cut their medication use by 38%, compared with 3% in the GPi group.
"Medication reduction is desirable but should not be the primary goal of surgery," says an Archives of Neurology editorial written by doctors including Michael Okun, MD, of the University of Florida's neurology and neurosurgery department.
Longer follow-up is needed to see if drug decreases last, say Okun and colleagues. They note that among their own patients who've had STN stimulation, those who completely stopped their Parkinson's drugs eventually needed them again and that many patients need to notch up their medication as the disease progresses.
Which site is better for deep brain stimulation? The verdict isn't in yet.
"There is no clear superiority of STN over GPi stimulation," the researchers say. "Preliminary experience suggests that both may be effective," agrees Okun.
Further tests may show if one site works better for certain patients, say the researchers, noting that the study was limited by its small size.
They say GPi stimulation may be better for the patients who suffer from abnormal movements due to medication side effects, while STN stimulation may be better for the younger patients who suffer with prominent symptoms of slow movement.