Brain stimulation improves mobility in Parkinson's patients

External electric stimulation of the brain can help people with Parkinson's disease (PD) improve mobility, a new study says.

Some people with Parkinson's disease tend to slow down and decrease the intensity of their movements as dopamine neurons generally die on one side of the brain, affecting the ability of the patient to exert effort with the opposite side of the body.

"The loss of dopamine associated with Parkinson's disease makes the effort required to move the affected side of the body seem greater, so the brain is less willing to use that arm to complete tasks," said study senior author Reza Shadmehr, professor of biomedical engineering at the Johns Hopkins University School of Medicine in Baltimore, US.

"Our study suggests that direct current stimulation can compensate somewhat for the loss of dopamine by decreasing the effort the brain has to put into getting its motor neurons to fire," Shadmehr noted.

The study with a small group of patients with PD demonstrated that stimulation of the cortex of the brain using external electrodes corrected some of the distortion and temporarily improved some patients' motor symptoms.

The investigators specifically found that one form of stimulation, known as cathodal transcranial direct-current stimulation

(tDCS), worked best and that the patients who got such stimulation were more willing to engage their affected arm than those who received no stimulation.

Importantly, they observed that the stimulation produced an average improvement of 25 percent in the motor symptoms of the patients, particularly improving rigidity on the affected side.

"As far as we know so far, the effects of tDCS are very temporary, but that's not surprising since no new dopamine cells are being created, which is the root of the problem," Shadmehr cautioned.

"The brain would get used to the stimulation -- just as it adjusts to medications -- and also become less responsive over time, but we are hopeful that continued stimulation might improve symptoms," he noted.

The study was published online in The Journal of Neuroscience.