A new technique could soon help alleviate some of the most debilitating symptoms of Parkinson's disease. Scientists hope the process, in which gentle shocks were applied to the surface of the brain in baboons, could be a dramatic improvement over the more extreme and complex surgical treatments that are currently the only recourse for patients with the worst symptoms.
In Parkinson's patients, a depletion of the neurotransmitter dopamine causes neurons in the basal ganglia to fire abnormally. This decreases the activity of neurons in the motor cortex and leads to a host of problems including slowness of movement, rigidity, and tremors.
Although most patients benefit from drugs that increase the levels of dopamine in the brain, others require a complex treatment known as deep brain stimulation, in which surgeons implant a pacemaker-like device that delivers pulses of electricity to the basal ganglia. The procedure can be highly effective, although its use is limited by the difficulties in placing electrodes properly in such tiny regions located deep within the brain.
A new procedure, described in the 2 December issue of Neuron, may prove to be a powerful alternative. Stéphane Palfi, a neuroscientist and neurosurgeon at Henri Mondor Hospital and the Centre National de la Recherche Scientifique in Paris and colleagues focused on the more accessible motor cortex. Using baboons afflicted with a form of Parkinson's disease, the researchers placed a flat electrode between the brain and the skull directly over the motor cortex. Low-voltage electrical stimulation (about the strength of a AA battery) delivered through the electrodes dramatically improved the baboons' ability to walk and climb. The baboons didn't appear to have any significant side effects from the stimulation.
Additional experiments suggested that the treatment had prompted neurons in the basal ganglia to resume a normal pattern of activity and had restored some activity in the baboons' previously sluggish motor cortex. Palfi says phase I clinical trials are currently under way in France on about 10 patients to determine whether the procedure is safe to try in humans.
This study could "suddenly open up surgical therapy for Parkinson's patients everywhere," says Gary Heit, a neurosurgeon at the Permanente Medical Group in Redwood City, California. "If the clinical trial works, this will be a very big deal."