Stimulation of spinal cord less invasive than deep brain stimulation, researchers say
THURSDAY, March 19 (HealthDay News) -- Rodents with Parkinson's-like symptoms walked and moved normally again after their spinal cords were stimulated with high frequency electrical currents, a new study shows.
Researchers said the technique, called dorsal column stimulation, has the potential to be an important new weapon in the arsenal against Parkinson's disease. Spinal cord stimulation could one day replace deep brain stimulation, an effective but highly invasive treatment of last resort for Parkinson's patients.
Researchers plan to begin testing the new technique on primates in a few months and, if successful, begin human testing in about a year.
"If this technology could work in humans, it would provide a completely new option for treating Parkinson's disease," said senior study investigator Dr. Miguel Nicolelis, a professor of neuroscience at Duke University Medical Center, in Durham, N.C.
The study appears in the March 20 issue of Science.
About 1.5 million Americans have Parkinson's disease, and another 60,000 are diagnosed each year, according to the National Parkinson Foundation. Parkinson's, which causes tremors, rigidity, slowed movements and a shuffling gait, is marked by a dying off of brain cells that produce the neurotransmitter dopamine.
Because Parkinson's is degenerative, symptoms can eventually include difficulty swallowing, smiling and speaking, as well as dementia.
During early stages of the disease, symptoms can usually be controlled using the medication levodopa, When combined with another drug, levodopa is converted into dopamine in the brain.
But as the disease progresses, the benefits from levodopa can diminish.
Patients with Parkinson's who are no longer responding well to medications sometimes turn to deep brain stimulation, in which electrodes are placed deep into areas of the brain and programmed to disrupt neurons that are firing incorrectly.
In many patients, blocking the abnormal nerve signals helps alleviate some of the movement problems.
Stimulating the spinal cord could be an improvement over deep brain stimulation because it's considered semi-invasive and the electrodes are easier to implant, Nicolelis said.
In the study, researchers implanted a device to stimulate the dorsal column of the rodents' spinal cords, which carry tactile signals to the brain. While the spinal cord stimulation did not rid the animals of all symptoms, the rodents were able to take 80 percent less medicine.
"We see an almost immediate and dramatic change in the animal's ability to function," Nicolelis said.
Dr. Michael Okun, national medical director of the National Parkinson Foundation, said the results were "interesting."
"Although the observations are preliminary, they are intriguing given our current difficulty in treating dopamine-resistant gait disorders in human sufferers of the disease," Okun said. "More research will be required to confirm these effects before moving into human trials."
For now, deep brain stimulation remains one of the last options for Parkinson's patients. About 71 percent of patients who underwent the procedure experienced an improvement in symptoms, according to a study published in January in the Journal of the American Medical Association.
Doctors don't know precisely why the electrical stimulation works, though a study in the March 19 online issue of Science Express provides some clues.
Researchers from Stanford used a technique called "optogenetics" to study neural circuits in the brain. They found that in rodents with dopamine deficiencies, stimulating the neural wires called axons that converge in the subthalmic nucleas region of the brain had a greater effect on improving Parkinson's symptoms than stimulating the cells in that region of the brain itself.
Because the axons lie closer to the surface of the brain, it's possible the discovery will lead to new, less invasive techniques, researchers said.
"Because these axons are coming from areas closer to the brain's surface, new treatments could perhaps be less invasive than deep brain stimulation," said Dr. Karl Deisseroth, senior study author and an associate professor of bioengineering, psychiatry and behavioral sciences at Stanford University.
The National Parkinson Foundation has more about symptoms and treatments for the disease.
SOURCES: Miguel Nicolelis, M.D., Ph.D., professor, neuroscience, Duke University Medical Center, Durham, N.C.; Michael Okun, M.D., national medical director, National Parkinson Foundation; March 19, 2009, Science Express, online
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