How activating a nerve in the neck could reduce movement difficulties for those with Parkinson’s

Parkinson’s disease is a neurodegenerative disorder, meaning that brain cells are damaged and this damage spreads to other cells, particularly in areas of the brain that control movement. People with Parkinson’s disease experience many movement-related symptoms, such as walking slowly, using small steps and falling. Many also experience mental problems, such as forgetting memories. Previous research has found that repetitive activation of the Vagus Nerve (a nerve that communicates with different parts of the brain and controls many bodily functions) may help to reduce these symptoms. Activating the Vagus Nerve can be done by holding a small device to the side of the neck. This technique is called non-invasive vagus nerve stimulation (nVNS).

Why is the study important?

This study aimed to provide further support for the role of nVNS in reducing symptoms of Parkinson’s disease and to understand how nVNS works, as this is unclear. Current Parkinson’s disease treatments (such as Levodopa) can lessen a patient’s symptoms but do not fix the underlying cause of the symptoms (the brain cell damage) so cannot stop the disease spreading to other cells and getting worse. Therefore, if nVNS is found to improve patient’s symptoms by reducing their brain cell damage, it may be a more effective treatment option for Parkinson’s disease.

What did the authors do and how did they do it?

This study included 21 people with Parkinson’s disease, who were given nVNS, lasting two minutes per session, three times a day for a month. To make sure that any changes in the patients were due to the nerve activation, for an additional month, the patients were also given a placebo version of nVNS (which looked the same but could not cause nerve activation). After each month of device use, the patients underwent tests to understand whether there were any changes in their movement or mental functioning (for instance, better memory). The patients also had blood tests to determine whether there were certain chemicals present that would indicate that the condition of the brain cells were deteriorating or recovering.

What are the results?

This study showed that after the patients underwent the real version of nVNS, movement had slightly improved (for instance, the patients were able to take bigger steps and walk faster) and the blood tests showed that brain cells may be recovering. Specifically, indicators of neuroinflammation (when the immune system attacks brain cells) and oxidative stress (when there are too many ‘killer’ chemicals in the brain) in the blood were lowered, and an indicator of neuroplasticity (when brain cells make new connections with other brain cells) was increased.

When patients underwent the placebo version of nVNS, movement did not improve, and the blood test indicators suggested that the brain cells may still have been deteriorating. However, it is important to note that some other parts of movement (like stopping mid-walk), some other indicators of brain cell damage/ recovery and mental functioning did not change after using the real or the placebo version of nVNS.

What do the findings mean going forward for people with the disease?

These results suggest that nVNS has potential to improve movement in people with Parkinson’s disease by stopping damage to the brain cells and encouraging the cells to recover. The researchers believe that nVNS could reduce brain cell damage by bringing down two processes that have been linked to Parkinson’s disease (neuroinflammation and oxidative stress), and increasing neuroplasticity, potentially reversing the deterioration of brain cells caused by Parkinson’s disease.

The patients in this study reported that nVNS was only mildly painful and easy to use, therefore it could be a good treatment option for patients with Parkinson’s disease. However, as this was a relatively short study that contained just a small number of participants, longer studies with more participants are needed to be certain of this.

This study can be found at
https://doi.org/10.3389/fnagi.2023.1331575

Paper title
Effects of non-invasive vagus nerve stimulation on clinical symptoms and molecular biomarkers in Parkinson’s disease

Lead Authors
Banashree Mondal, Hrishikesh Kumar and colleagues

Publication details including date of publication
Frontiers in Aging Neuroscience, Volume 15, February 2024