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.
