Researchers from Duke Medicine have shown that symptoms of Parkinson's disease can be improved with continual spinal cord stimulation. The stimulation will also protect critical neurons from injury or deterioration. The study was conducted in rats and is published in the journal Scientific Reports. The Duke team had in an earlier study found that stimulating the spinal cord with electrical signals temporarily eased symptoms of the neurological disorder in rodents. Parkinson's disease is caused by progressive loss of neurons. Neurons produce an essential molecule in the brain known as dopamine which affect balance, muscle control and movement.
"Finding novel treatments that address both the symptoms and progressive nature of Parkinson's disease is a major priority," said the study's senior author Miguel Nicolelis, M.D., Ph.D., professor of neurobiology at Duke University School of Medicine. "We need options that are safe, affordable, effective and can last a long time. Spinal cord stimulation has the potential to do this for people with Parkinson's disease."
The standard drug treatment for Parkinson's disease is L-dopa, which works by replacing dopamine. L-Dopa may help many people but is also known to cause side effects and it also loses its effectiveness over time. Another valuable therapy that has emerged recently is deep brain stimulation which emits electrical signals from an implant in the brain. However, not more than 5 percent of those with Parkinson's qualify for this therapy.
"Even though deep brain stimulation can be very successful, the number of patients who can take advantage of this therapy is small, in part because of the invasiveness of the procedure," Nicolelis said.
Nicolelis and his colleagues in 2009 had developed a device for rodents that was based on electrical stimulation to the dorsal column, a main sensory pathway in the spinal cord carrying information from the body to the brain, according to their report in the journal Science. The device attached to the surface of the spinal cord in rodents with depleted levels of dopamine mimicked the biological characteristics of someone with Parkinson's disease. The animals' slow, stiff movements were replaced with the active behaviors of healthy mice and rats when the device was turned on
In the present study, Nicolelis and his colleagues investigated the long-term effects of the treatment in rats with the Parkinson's-like disease because research on spinal cord stimulation in animals has been limited to the stimulation's acute effects.
The researchers applied electrical stimulation to a particular location in the dorsal column of the rats' spinal cords twice a week for 30-minute sessions, for six weeks at the end of which they observed a significant improvement in the rats' symptoms including improved motor skills and a reversal of severe weight loss.
The stimulation not only resulted in recovery in clinical symptoms but was also observed to lead to better survival of neurons and a higher density of dopaminergic innervation in two brain regions controlling movement – the loss of which cause Parkinson's disease in humans. The research findings, therefore, lead to the conclusion that this form of treatment protects against the loss or damage of neurons.
A similar application of dorsal column stimulation is currently in use to manage certain chronic pain syndromes in humans. Electrodes implanted over the spinal cord are connected to a portable generator, which produces electrical signals that create a tingling sensation to relieve pain. Studies in a small number of humans worldwide have shown that dorsal column stimulation may also be effective in restoring motor function in people with Parkinson's disease.
"This is still a limited number of cases, so studies like ours are important in examining the basic science behind the treatment and the potential mechanisms of why it is effective," Nicolelis said.
The researchers are continuing to investigate how spinal cord stimulation works, and are beginning to explore using the technology in other neurological motor disorders.
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