*The translation of this article in French, German and Spanish has been made through machine translation and has not been edited yet. we apologise for any inaccuracies.
As a neurologist, what are your thoughts on vagus nerve stimulation (VNS) therapy? Recent studies have shown that VNS therapy and selective VNS (sVNS) therapy could have significant potential in help treating various neurological disorders including Alzheimer’s disease, Parkinson’s disease, and stroke, among others.
Vagus nerve stimulation treatment, also called VNS therapy, is currently used and FDA-approved for epileptic seizures, depression, and pain management*. In recent years VNS therapy has proven to be effective for many other clinical applications. Due to its therapeutic efficacy, there is considerable pressure to optimise the implementation of VNS and it is currently being explored as a potential treatment for neurological disorders including Alzheimer’s, Parkinson’s, autistic spectrum disorder, traumatic brain injury, and stroke*.
Vagus nerve stimulation involves implanting a small device in a person’s neck that sends regular, mild pulses of electrical energy to the brainstem through the vagus nerve. After reaching the brainstem, the electrical charge is discharged to different areas of the brain and in doing so changes the way brain cells work. The vagus nerve is one of the most promising targets for neuromodulation, being the longest nerve in the autonomic nervous system.
There is one vagus nerve on each side of the body, connected to several organs, including the heart, lungs, larynx, pharynx, stomach, spleen, pancreas, liver, intestines, and ovaries. The vagus nerve also projects to areas within the brain and central nervous system, including the nucleus tractus solitarius, locus coeruleus, thalamus, hippocampus, amygdala and other regions*.
FDA-approved VNS Treatments
Vagus nerve stimulation with electrical impulses was first FDA-approved in the 1980s to treat drug-resistant epilepsy. Since then the technology, the VNS devices, and surgical procedures have evolved. New research and clinical trials have helped researchers develop new frameworks and methods to better stimulate the vagus nerve in ways that targeting specific fiber types within the nerve to produce specific effects.
In 2005, VNS therapy was approved by the FDA for treatment-resistant depression such as severe, recurrent unipolar and bipolar depression. The implanted VNS device sends electrical impulses to the left vagus nerve, stimulating the subcortical, and cortical regions of the brain known to be associated with mood regulation*. The neuromodulation shifts the focus from the monoamine synapse to neural circuitry of the brain, which is dysregulated in depression.
Research and clinical trials continue to better understand exactly how VNS changes brain wave patterns that help reduce or eliminate symptoms of depression. Although this type of treatment is not yet fully understood, it has been proven to s improve quality of life in severely depressed patients.
WHO estimates that 5% of adults suffer from depression globally*. Chronic or severe depression affect up to 1.5% of the general population, and many of these patients obtain little relief from pharmaceutical treatment*. The neurological community continues to investigate the psychiatric benefits of VNS to help improve these numbers.
In recent years, the applications of VNS have also extended to pain management. In 2018, the first non-invasive vagus nerve stimulation (nVNS) device was FDA-approved for migraine and cluster headache. The so called “non-invasive” method describes VNS treatments that do not require any surgical implantation. Instead, the vagus nerve is stimulated with electrical pulses with the help of a device applied directly to the skin. Patients apply gel to the side of their neck, and then hold the VND device to the same area while it dispenses a mild electrical stimulation through the skin and to the vagus nerve. Studies show that patients experienced a 50% reduction in pain, with nearly 40% being pain-free from migraine attacks and cluster headaches after nVNS treatment*.
Selective VNS (sVNS) framework and reduced side effects
As research continues, new methods and applications of VNS are still being discovered. Until recently, vagus nerve stimulation had generally been non-selective, resulting in a range of side effects including throat pain, headaches, difficulty swallowing, voice changes, and infections. selective VNS therapy aims to mitigate this by targeting specific fibre types within the nerve, instead of stimulating the whole nerve, to increase efficacy and specificity of the treatment.
The major challenge of VNS development and achieving better selectivity of VNS is a limited knowledge of functional anatomical organisation of the vagus nerve. Despite extensive research over the last century, this remains poorly understood. To avoid off-target effects and improve overall efficacy of VNS, it will be crucial to optimise electrode array geometry and pulse shape, as well as expanding the applications of selective VNS therapy beyond the current focus on certain disease areas*.
Most of the recent research in sVNS has focused on applications for cardiovascular disease. However, with a better understanding of the vagus nerve and its development in surgical procedures, other areas can be explored, including neurological disorders.
New applications for VNS Therapy, and market outlook
The demand for VNS therapy is steadily increasing. Interest in new VNS treatments, from both the medical community as well the general public has grown immensely in recent years, and is anticipated to continue doing so.
The global vagus nerve stimulation market is expected to grow with a 15% compound annual growth rate (CAGR) between 2022 and 2029, reaching $2,424.01 million USD by 2029*. Some recent areas of focus for new VNS applications include anti-inflammatory treatments. Leading companies of the VNS industry are engaging in various developmental activities and extensive market research will be needed to re-launch updated products in the market. In line with this trend, neurologists will be in high demand to share their expert opinions and help manufacturers gain insight into how to further develop VNS products to improve patient outcomes.
Recent studies of VNS have shown that it has anti-inflammatory properties which has driven more preclinical research aimed at expanding VNS treatment across a wider range of inflammatory disorders such as Crohn’s disease, irritable bowel syndrome, sepsis, lung injury, rheumatoid arthritis, diabetes, and fibromyalgia*.
Because research hasn’t been published yet, the efficacy of VNS treatment for these disorders is currently unknown. However, new preclinical research shows that VNS has significant potential for being applied to a wider range of therapeutic applications, including neurological disorders.
The links below provide further reading on some of the new applications of VNS applications that are currently being explored for neurological disease areas. If you work as a neurologist and are interested in sharing your opinions about treatments and products for neurological disorders, you can sign up below to participate in paid market research studies within neurology.
- Vagus Nerve Stimulation as a Potential Therapy in Early Alzheimer’s Disease (PubMed, 2022)
- Noninvasive vagus nerve stimulation in Parkinson’s Disease (PubMed, 2021)
- Treating Traumatic Brain Injuries with Electroceuticals (MDPI, 2021)
- Neuromodulation of autism spectrum disorders using vagal nerve stimulation (PubMed, 2019)
- Non-invasive Vagus Nerve Stimulation in Cerebral Stroke (PubMed, 2022)
If you have come across any other interesting applications of VNS therapy, please let us know by sharing your thoughts in the comment section below or follow us on LinkedIn for the latest updates.
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