Posts tagged nerve stimulation
Posts tagged nerve stimulation
For nearly a decade, doctors have used implanted electronic stimulators to treat severe depression in people who don’t respond to standard antidepressant therapy.
Now, preliminary brain scan studies conducted by researchers at Washington University School of Medicine in St. Louis are beginning to reveal the processes occurring in the brain during stimulation and may provide some clues about how the device improves depression. They found that vagus nerve stimulation brings about changes in brain metabolism weeks or even months before patients begin to feel better.
The findings will appear in an upcoming issue of the journal Brain Stimulation and are now available online.
“Previous studies involving large numbers of people have demonstrated that many with treatment-resistant depression improve with vagus nerve stimulation,” said first author Charles R. Conway, MD, associate professor of psychiatry. “But little is known about how this stimulation works to relieve depression. We focused on specific brain regions known to be connected to depression.”
Conway’s team followed 13 people with treatment-resistant depression. Their symptoms had not improved after many months of treatment with as many as five different antidepressant medications. Most had been depressed for at least two years, but some patients had been clinically depressed for more than 20 years.
All of the participants had surgery to insert a device to electronically stimulate the left vagus nerve, which runs down the side of the body from the brainstem to the abdomen. Once activated, the device delivers a 30-second electronic stimulus to the vagus nerve every five minutes.
To establish the nature of the treatment’s effects on brain activity, the researchers performed positron emission tomography (PET) brain imaging before the initiation of stimulation, and again three and 12 months after stimulation had begun.
Eventually, nine of the 13 subjects experienced improvements in depression with the treatment. However, in most cases it took several months for improvement to occur.
Remarkably, in those who responded, the scans showed significant changes in brain metabolism following three months of stimulation, which typically preceded improvements in symptoms of depression by several months.
“We saw very large changes in brain metabolism occurring far in advance of any improvement in mood,” Conway said. “It’s almost as if there’s an adaptive process that occurs. First, the brain begins to function differently. Then, the patient’s mood begins to improve.”
Although the patients remained on antidepressants for several months after their stimulators were implanted, Conway says many of those who responded to the device eventually were able to stop taking medication.
“Sometimes the antidepressant drugs work in concert with the stimulator, but it appears to us that when people get better, it is the vagus nerve stimulator that is doing the heavy lifting,” Conway explained. “Stimulation seems to be responsible for most of the improvement we see.”
Additionally, the PET scans demonstrated that structures deeper in the brain also begin to change several months after nerve stimulation begins. Many of those structures have high concentrations of brain cells that release dopamine, a neurotransmitter that helps control the brain’s reward and pleasure centers and also helps regulate emotional responses.
There is a consensus forming among depression researchers that problems in dopamine pathways may be particularly important in treatment-resistant depression, according to Conway. And he said the finding that vagus nerve stimulators influence those pathways may explain why the therapy can help and why, when it works, its effects are not transient. Patients who respond to vagus nerve stimulation tend to get better and stay better.
“We hypothesized that something significant had to be occurring in the brain, and our research seems to back that up,” he said.
Wearing a nerve stimulator for 20 minutes a day may be a new option for migraine sufferers, according to new research published in the February 6, 2013, online issue of Neurology®, the medical journal of the American Academy of Neurology.
The stimulator is placed on the forehead, and it delivers electrical stimulation to the supraorbital nerve.
For the study, 67 people who had an average of four migraine attacks per month were followed for one month with no treatment. Then they received either the stimulation 20 minutes a day for three months or sham stimulation, where they wore the device but the stimulation given was at levels too low to have any effect.
Those who received the stimulation had fewer days with migraine in the third month of treatment compared to the first month with no treatment. The number of days with migraine decreased from 6.9 days to 4.8 days per month. The number did not change for those who received the sham treatment.
The study also looked at the number of people who had 50 percent or higher reduction in the number of days with migraine in a month. That number was 38 percent for those who had the stimulation compared to 12 percent of those who received the sham treatment.
There were no side effects from the stimulation.
“These results are exciting, because the results were similar to those of drugs that are used to prevent migraine, but often those drugs have many side effects for people, and frequently the side effects are bad enough that people decide to quit taking the drug,” said study author Jean Schoenen, MD, PhD, of Liège University in Belgium and a member of the American Academy of Neurology. The study was supported by the Walloon Region, Department of Economy, Employment and Research in Belgium.
Researchers at the University of Glasgow are hoping to help victims of stroke to overcome physical disabilities by helping their brains to ‘rewire’ themselves.
Doctors and scientists from the Institute of Cardiovascular and Medical Sciences will undertake the world’s first in-human trial of vagus nerve stimulation in stroke patients. Stroke can result in the loss of brain tissue and negatively affect various bodily functions from speech to movement, depending on the location of the stroke.
The study, which will be carried out at the Western Infirmary in Glasgow, will recruit 20 patients who suffered a stroke around six months ago and who have been left with poor arm function as a result.
Each participant will receive three one-hour sessions of intensive physiotherapy each week for six weeks to help improve their arm function.
Half of the group will also receive an implanted Vivistim device, a vagus nerve stimulator, which connects to the vagus nerve in the neck. When they are receiving physiotherapy to help improve their arm, the device will stimulate the nerve.
It is hoped that this will stimulate release of the brain’s own chemicals, called neurotransmitters, that will help the brain form new neural connections which might improve participants ability to use their arm.
Lead researcher Dr Jesse Dawson, a Stroke Specialist and Clinical Senior Lecturer in Medicine, said: “When the brain is damaged by stroke, important neural connections that control different parts of the body can be damaged which impairs function.
“Evidence from animal studies suggests that vagus nerve stimulation could cause the release of neurotransmitters which help facilitate neural plasticity and help people re-learn how to use their arms after stroke; particularly if stimulation is paired with specific tasks. A slightly different type of vagus nerve stimulation is already successfully used to manage conditions such as depression and epilepsy.
“This study is designed to provide evidence to support whether this is the case after stroke but our primary aim is to assess feasibility of vagus nerve stimulation after stroke.
“It remains to be seen how much we can improve function, but if we can help people perform even small actions again, like being able to hold a cup of tea, it would greatly improve their quality of life.”
July 19, 2012 By Emily Martinez
(Medical Xpress) — UT Dallas researchers recently demonstrated how nerve stimulation paired with specific experiences, such as movements or sounds, can reorganize the brain. This technology could lead to new treatments for stroke, tinnitus, autism and other disorders.
Dr. Michael Kilgard helped lead a team that paired vagus nerve stimulation with physical movement to improve brain function.
In a related paper, UT Dallas neuroscientists showed that they could alter the speed at which the brain works in laboratory animals by pairing stimulation of the vagus nerve with fast or slow sounds.
A team led by Dr. Robert Rennaker and Dr. Michael Kilgard looked at whether repeatedly pairing vagus nerve stimulation with a specific movement would change neural activity within the laboratory rats’ primary motor cortex. To test the hypothesis, they paired the vagus nerve stimulation with movements of the forelimb in two groups of rats. The results were published in a recent issue of Cerebral Cortex.
After five days of stimulation and movement pairing, the researchers examined the brain activity in response to the stimulation. The rats who received the training along with the stimulation displayed large changes in the organization of the brain’s movement control system. The animals receiving identical motor training without stimulation pairing did not exhibit any brain changes, or plasticity.
People who suffer strokes or brain trauma often undergo rehabilitation that includes repeated movement of the affected limb in an effort to regain motor skills. It is believed that repeated use of the affected limb causes reorganization of the brain essential to recovery. The recent study suggests that pairing vagus nerve stimulation with standard therapy may result in more rapid and extensive reorganization of the brain, offering the potential for speeding and improving recovery following stroke, said Rennaker, associate professor in The University of Texas at Dallas’ School of Behavioral and Brain Sciences.
“Our goal is to use the brain’s natural neuromodulatory systems to enhance the effectiveness of standard therapies,” Rennaker said. “Our studies in sensory and motor cortex suggest that the technique has the potential to enhance treatments for neurological conditions ranging from chronic pain to motor disorders. Future studies will investigate its effectiveness in treating cognitive impairments.”