Is Spinal Cord Stimulation a Future Treatment for Parkinson's Disease

What Is Spinal Cord Stimulation?

Spinal cord stimulation (SCS) for pain reduction has been around since 1967. How it works is actually a little more complicated that in might seem now that there are almost 50,000 of these surgical procedures performed around the world every year. The purpose of SCS is activation of neurons, making them positive electrically or depolarized so that they can generate action potential.

Theoretically pain messages are sent when the "gate" in the spinal cord dorsal horn is opened and there are more small rather than large diameter fibers active. In SCS it was found that electrical stimulation of peripheral nerves can reduce pain by activating the large diameter gated fibers in the dorsal horn of the spine. It is the opening of the large fiber gates and closing of the small gate which is supposed to prevent the pain signals from reaching the brain.

There are more mechanisms at work such as stimulation at higher frequencies causing the nerve fibers to fail to conduct the action potentials, the inhibition of impulse transmission in the spinothalamic tract and an increase of serontonin, adenosine, GABA and Substance P with a decrase in glutamate and aspartate in the dorsal horn of the spinal cord.

The procedure is to insert the epidural leads and test for 3 to 21 days. If the treatment works a pacemaker-sized generator is implanted and the external remote is provided. The procedure is not a cure of the problems at the root of the pain, the treatment is to reduce the level of pain as it threatens quality of life. Nor does the procedure work for all types of pain.

The use of SCS technology is expanding. One of the most recent areas of focus is Parkinson's disease. At Duke University in North Carolina Dr Miguel Nicolelis, Professor of Neuroscience is investigating using the spinal cord rather than the brain to treat PD symptoms because the spinal cord is the primary pathway by which the body signals the brain and the brain sends signals to the body.

In the lab rodents with induced PD, the scientists found that within 3.5 seconds of getting electrical stimulation the stiff, slow movements became essentially normal. The team experimented with higher and lower levels of electrical stimulation and with a combination of L-Dopa. What they found was that even without levadopa the animals were 26 times more active. When they received two doses of levadopa their ability to move was similar to receiving five doses without stimulation.

Since it is known that eventually L-Dopa will not only cease to work but may exaccerbate symptoms, the modified SCS should enable a serious reduction of meds if successful for the patient.

Dr Nicolelis realized that the brain activity of mice with induced PD was similar to the low frequency oscillations of rodents with seizures and epilepsy which he had previously studied. Furthermore it is felt that these low frequency corticalstriatal oscillations impair motor function so that with electrical stimulation, the activity of the neurons could be normalized and motor function could be restored.

The Duke group is working with a team from Brazil to perform pretrial testing of their device.

references and reading:
"Spinal Cord Stimulation Restores Locomotion in Animal Models of Parkinson's Disease."Romulo Fuentes, Per Petersson, William B. Siesser, Marc G. Caron, and Miguel A. L. Nicolelis.Science 20 March 2009 323: 1578-1582.DOI: 10.1126/science.1164901
http://www.sciencemag.org/cgi/content/abstract/sci;323/5921/1578

Dr Nicolelis has also worked on brain-machine interfaces:
http://www.guardian.co.uk/science/2009/mar/19/parkinsons-disease-spinal-implant-electrical-stimulation