Adjusting electrodes may help Parkinson's patients

NEW YORK (Reuters Health) - Patients with Parkinson's disease who have a poor response to brain stimulation therapy may improve if the electrodes are repositioned, even by just a few millimeters.

A poor response can be caused by the misplacement of the electrodes by even just a few millimeters, physicians in France report.

Dr. Mathieu Anheim, at University Hospital, Strasbourg, and colleagues studied seven patients with Parkinson's disease who underwent this procedure in which electrodes are positioned to stimulate the region of the brain called the subthalamic nucleus, a procedure that has been shown to relieve symptoms for many patients.

After the procedure, the seven patients were able to reduce their medication dosage by only a small amount and had little relief from their symptoms. Brain imaging tests showed that 12 of 14 electrodes were misplaced.

The patients underwent a second operation approximately 1.5 years after the first to reimplant the electrodes. One year later, six of the seven patients showed improvements, the authors report in the Archives of Neurology.

The average distance between the contacts and the theoretical effective target decreased from 5.4 to 2.0 mm. Motor symptom scores during stimulation and while off medication fell from 40.1 before reimplantation to 22.2 afterwards, decreasing in parallel with the distance between the electrodes and the target.

The patients' dose of levodopa fell from 1,202 mg per day to 534 mg per day.

For carefully selected patients who have poor results following electrode stimulation and misplaced electrodes are shown on imaging studies, reimplantation closer to the target area should be considered, Anheim and associates advise.

However, they point out that there still will be rare patients who have no clear explanation for poor results on the electrode stimulation technique.

SOURCE: Archives of Neurology, May 2008.