Tiny electrical zaps to the brain appear to soothe the herky-jerky movements of people with Parkinson's disease. Findings from a pilot experiment, described in this month's issue of Nature Medicine, suggest a potential new therapy for the disease, which affects roughly 1% of elderly Americans.
Parkinson's is a motor disorder that causes rigidity and problems initiating movement. The disease is triggered by the death of dopamine-producing cells in the brain, an event that leads to changes in the brain's architecture that affect neural communications. In particular, an area at the end of the basal ganglia, the globus pallidus, steps up its suppression of activity in other brain regions. "It's like a brake on a car," explains Andres Lozano, a neurosurgeon at Toronto Hospital. "Parkinson's patients' motions are slow, erratic, and jerky--it's like they are driving with their brakes on." As a last resort, doctors sometimes destroy the globus pallidus of Parkinson's patients who fail to respond to drug therapy aimed at replacing the lost dopamine.
Taking a different tack, Lozano's team inserted electrodes into the globus pallidus of 21 Parkinson's volunteers. Using a positron emission tomography (PET) scanner to measure electrical activity, Lozano's team found that sending rapidly oscillating electrical pulses to the globus pallidus triggered increased blood flow to the premotor cortical areas, brain regions that are responsible for planning and initiating movement. At the same time, the researchers found, the subjects' motions became quicker and more fluid.
The mechanism for this beneficial effect is a mystery. "It's still unclear what's happening," says Mahlon DeLong, a neurologist at Emory University in Atlanta. He thinks that the electric shocks may temporarily depolarize and thus disable neurons in the globus pallidus, allowing the premotor cortical areas to resume normal function.
DeLong says a larger study is needed to compare the benefits of electrode therapy with surgical ablation of the globus pallidus. But he predicts that electrode therapy will gain favor as an improved understanding and visualization of the brain allows for more precise interventions. "We're on a fresh wave of significant new treatments of Parkinson's and other movement disorders," he says, leading to "restoring large numbers of patients to a higher quality of life."