Trans-ear VNS device ‘too smart’ for Parkinson’s disease

Transauricular vagus nerve stimulation (taVNS) is feasible, well tolerated, and may improve motor function in patients with Parkinson’s disease (PD), new research suggests.

The field of noninvasive brain stimulation in PD is still in its infancy, but emerging research shows that it is a promising approach for some patients, according to lead study author Vanessa K. University of South Carolina, Charleston, said Medscape Medical News.

“It’s a very clever approach for someone who may be intolerant of oral drugs or invasive surgery, and therefore needs to be explored further,” Henson said.

The Results are displayed At the International Conference on Parkinson’s Disease and Movement Disorders (MDS) 2022.

Rating Scale Improvement

Dr. Vanessa Henson

The vagus nerve, a major component of the sympathetic and parasympathetic nervous systems, is involved in important neurophysiological functions. The small auricular branch connects to the main nerve, which sends information to brain structures important for Parkinson’s disease, including the locus coeruleus, substantia nigra, hippocampus, thalamus, and prefrontal cortex.

Hinson’s group has previously shown that VNS can improve locomotion in animal models of PD. The stimulation enhanced the neurochemicals noradrenaline and dopamineand reduced cell loss in parts of the brain that occurs in Parkinson’s, she reported.

She added that neuroinflammation and oxidative stress were also reduced in the animals after the intervention.

Since these results were published, Henson said, the field has “began to explode” in terms of interest in pursuing this intervention clinically — particularly because the VN can be stimulated noninvasively in the outer ear.

The current study included 30 participants (100% white) aged 40-79 years with mild to moderate Parkinson’s disease, Hoehn & Yahr stage 2-3, and a Montreal Cognitive Assessment score of 24 or greater.

All were randomly assigned to 10 active or sham stimulation (1 hour each) over a two-week period. For the active stimulation group, electrodes were attached to the outer ear, connected to the auricle.

Henson noted that the strength of the electric current was individual. “At the time when they can feel the stimulation, which is called the perception threshold, you increase the current a little higher,” she said.

She added that patients felt a “tingling” in the ear – and likened it to transcutaneous electrical nerve stimulation (TENS), which is used to stimulate muscles in physical therapy.

In the sham group, electrodes were attached to the earlobe. Henson reported that these participants felt the same tingling sensation and were unable to tell that they were not receiving active stimulation.

She explained that the results showed that all patients tolerated the treatment well, adding that they did not consider the stimulation painful or annoying. Because the vagus nerve is connected to the heart, the researchers also examined the effect of the stimulation on blood pressure and heart rate and found no negative effects.

There was an improvement of three or more points on the Standardized Parkinson’s Disease Rating System III scale in 8 members of the active group compared to 4 members of the placebo group. The most symptomatic improvement in respondents was bradykinesia, followed by tremor.

External result?

Interestingly, there were significant differences between groups in semantic fluency, which necessitates the creation of words in a category such as “fruits” within a certain time period, and in phonemic fluency, such as naming words beginning with the letter “F.” In fact, there was a decrease in these scores in the active group and an improvement in the sham group.

This may be due to the stimulation’s effect on the prefrontal cortex, a brain structure “that oversees word-finding and word generation,” Henson said. “Here, the nerve may be overstimulated and produce positive effects on movement and possibly diminish cognitive performance.”

She stressed, however, that the study was small and that this finding could be out of the ordinary. “If you stimulate 100 patients, you may not see that effect,” she said.

As Henson said, these cognitive effects were transient and “not something they personally observed.”

However, this finding “tells us that we need to learn more about the parameters of the stimulus: how strong the stimulus is and for how long,” she said.

Henson noted that future studies will use household appliances and evaluate the effects of stimulation for a period of 6 months. From the use of VN stimulation in treatment resistance depression And the epilepsy“We are learning that it usually takes a few months to achieve maximum benefit,” she said..

Additionally, for future analyses, patients will be evaluated while in a functional magnetic imaging scanner so the researchers can “see exactly which brain structures are being stimulated.” [instead of] Just going by our assumptions about who we are Think Henson said.

Apart from a temporary effect on semantic and vocal fluency, there were no group differences on other cognitive tests or subjective measures of cognitive performance, fatigue, freezing gait, and sleep quality.

Henson noted that this generally non-surgical intervention may be ideal for older patients with Parkinson’s disease. If a doctor has this type of patient, she said, “the last thing you want is to treat them with 10 different medications that may all interact with each other.”

Some older patients may also have neuropsychological problems such as depression and anxiety, and therefore may not tolerate oral medications well, and are poor candidates for invasive stimulation methods such as deep brain stimulationshe added.

Small but intriguing

Comment on Medscape Medical NewsEthan Brown, Assistant Professor of Neuroscience, Weill Institute for Neurosciences, University of California San Francisco, said this study is small but intriguing.

“It demonstrates the potential effectiveness of an entirely new approach to improving symptoms in people with Parkinson’s,” said Brown, who was not involved in the research.

He added that if trans-auricular stimulation proves effective in future studies, “it could be broadly applicable to patients who cannot tolerate more invasive procedures or with drug complications.”

However, as the researchers “importantly” pointed out, this approach has potential side effects such as affecting cognitive tests – and this is something future studies should pay attention to, Brown concluded..

The study received funding from the Center on Aging at the Medical University of South Carolina and the Murray Center for Research in Parkinson’s Disease and Related Disorders at the Medical University of South Carolina.. Henson and Brown reported no related financial relationships.

International Conference on Parkinson’s Disease and Movement Disorders (MDS) 2022: Abstract 727. It was introduced on September 16, 2022.

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