Vagus Nerve and Its Role Post-Viral Syndromes
The persistent presence of symptoms after an acute viral infection, lasting months and sometimes years, indicates the occurrence of a post-viral syndrome. These syndromes can cause a feeling of fatigue and weakness, digestive issues, heart rate abnormalities, pain, difficulty concentrating and headaches resulting from reduced vagal tone, caused by persistent inflammation of the vagus nerve. In some cases, this can result in more serious conditions such as dysautonomia, or even autoimmune disorders like adrenal insufficiency. The vagus nerve is responsible for the parasympathetic response of the nervous system, regulating functions such as heart rate, digestion, immune response, metabolic rate which can become impaired and contribute to¹:
Heart Rate Variability (HRV) Reduction
Post-Viral syndromes, known for reducing vagal tone and impairing autonomic function, often disrupt the vagus nerve. This disruption leads to an imbalance toward sympathetic dominance and a prolonged stress response. Impairment of the vagus nerve is measured by decreased heart rate variability (HRV) resulting from the inability of its efferent fibres to effectively send signals from the brain to the heart, leading to decreased parasympathetic control of the heart rhythm².
Stress Response
Post-viral syndromes can cause dysregulation of the vagus nerve, due to excessive activation of the sympathetic nervous system, which can lead to long-term oxidative stress and immune system dysfunction. Impairment of the Vagus Nerve disturbs the functioning of the hypothalamic-pituitary-adrenal (HPA) axis with prolonged release of stress hormones such as cortisol. While initial cortisol release is anti-inflammatory, prolonged elevation due to ongoing stress (including infections) can lead to cortisol resistance at the cellular level. This resistance contributes to chronic inflammation and leads to post-infection complications, such as fatigue, depression, brain fog³.
Dysautonomia
Neurological symptoms accompanying viral diseases, such as COVID-19, HIV, hepatitis C and B, Lyme disease, both in their acute phases and as part of long-term syndromes, may lead to dysautonomia, a dysfunction of the autonomic nervous system. This condition is associated with vagus nerve inflammation. The vagus nerve, a major component of this system, with its dysfunction can contribute to various symptoms, including fatigue, sudden changes in heart rate, episodes of acute diarrhoea, fainting, and sleep disturbances in affected patients. The immune system's response to these viruses cause inflammation or direct damage to autonomic nerves, including the vagus nerve⁴.
Brain-Gut Axis
Even after recovery from infection, scientists observed the long-term persistence of viral interferons in the intestinal environment. These interferons interrupt the uptake of tryptophan, a key precursor of the neurotransmitter serotonin. This persistent interference with tryptophan absorption may contribute to damage to the vagus nerve, characterised by dysfunction of the autonomic nervous system, which can cause fatigue, increased stress, depression and even cardiovascular problems. The vagus nerve plays an integral role in the neuroendocrine-immune axis connecting the central nervous system (CNS) with the gut. As a result, affecting the vagus nerve can lead to symptoms such as gastrointestinal problems like bloating, gastroparesis, reflux and diarrhoea³'⁵.
Inflammation and immune response
The vagus nerve can transmit signals related to the body's inflammatory response (the hypothalamic-pituitary-adrenal (HPA) axis and the cholinergic anti-inflammatory pathway (CAP)). During a viral infection, the body's immune system releases various cytokines and inflammatory molecules. These signals can affect the vagus nerve and contribute to symptoms of fatigue, malaise and brain fog seen in post-viral syndromes⁶'⁷.
- Rangon C.M., & Niezgoda A. (2022). Understanding the Pivotal Role of the Vagus Nerve in Health from Pandemics. Bioengineering (Basel). 29, 9(8):352.
- Taman H., Mageed N., et al. (2023). Heart rate variability as an indicator of COVID-19 induced myocardial injury: a retrospective cohort study. BMC Anesthesiol. 10, 23(1):17.
- Breit S., Kupferberg A., et al. (2018). Vagus Nerve as Modulator of the Brain–Gut Axis in Psychiatric and Inflammatory Disorders. Frontiers in Psychiatry, 9.
- Woo M.S., Shafiq M., et al. (2023). Vagus nerve inflammation contributes to dysautonomia in COVID-19. Acta Neuropathol 146, 387–394.
- Andrea C., Wong Ashwarya S., et al. (2023). Serotonin reduction in post-acute sequelae of viral infection. Cell, 186(22), 4851-4867.
- Falvey A. (2022). Vagus nerve stimulation and inflammation: expanding the scope beyond cytokines. Bioelectron Med 8, 19.
- Kavanagh E. (2022). Long Covid brain fog: a neuroinflammation phenomenon?, Oxford Open Immunology 3, 1.
Nurosym improves regulatory functions of the vagus nerve, effectively mitigating excessive post-viral symptoms, as indicated by improved HRV. The observable increase in HRV during Nurosym stimulation indicates a more pronounced parasympathetic “rest and digest” activity, connected with anti-inflammatory response with reduced markers of oxidative stress, and reduced norepinephrine. Nurosym's role in improving HRV addresses these issues by reestablishing autonomic control processes, leading to a reduction in symptoms such as fatigue, brain fog, heart rhythm changes, sleep disturbances, persistent cough, joint pain, and mood fluctuations.
Nurosym normalises the autonomic nervous system, reducing sympathetic overactivity and enhancing parasympathetic activity, thereby mitigating the physiological effects of stress on cognitive function. Nurosym has anti-inflammatory effects, leading to reduced cytokine levels. This influence correlates with the modulation of the HPA axis, which results in the increased stress resilience. Furthermore, Nurosym has demonstrated an antioxidative stress response by effectively neutralising reactive oxygen species (ROS), indicated by hydrogen peroxide (H2O2). These combined effects can improve stress resilience and cell regeneration, and alleviate post-viral symptoms.
By enhancing the function of the vagus nerve, Nurosym effectively counteracts the effects of inflammation and direct damage to the nervous system caused by viral infections such as COVID-19, HIV, hepatitis C and B, and Lyme disease. The stimulation provided by Nurosym improves vagal tone, which can lead to relief from symptoms commonly associated with dysautonomia, such as chronic fatigue, irregular heart rates, acute diarrhoea episodes, fainting, and sleep disturbances. Furthermore, it helps reduce inflammation and the immune system's overreactivity, key factors in the development and prolongation of dysautonomia following viral infections.
Nurosym normalises the functioning of the vagus nerve. Vagus Nerve is essential in the neuroendocrine-immune axis connecting the central nervous system (CNS) with the digestive system, counteracting inflammation and enabling the production of serotonin. This can lead to a reduction in symptoms such as fatigue, gastrointestinal problems, stress, depression and cardiovascular problems that are often related to neurotransmitter disruption.
Nurosym research has shown decrease of inflammation in the body, which can be useful in the context of post-viral syndrome. Nurosym activates the cholinergic anti-inflammatory pathway, in which the vagus nerve plays a key role in controlling inflammation that increases following viral infections. This action helps reduce levels of pro-inflammatory cytokines such as TNF-α. Reducing systemic inflammation, facilitated, may consequently alleviate cognitive impairment and symptoms such as brain fog, fatigue, pain joint, and dyspnea that are often reported with post-viral syndrome.
Nurosym Research-Based Evidence
77% of patients using Nurosym reported a decrease in Long-Covid symptoms including brain fog, fatigue, gastrointestinal problems, stress, depression, within one month of treatment leading to mood improvement and a reduction in future-related complications in post-viral syndrome.
Another Nurosym finding highlights significant remission of debilitating symptoms, particularly the alleviation of brain fog, pain, depression and fatigue in all long-COVID patients enrolled in the investigation by 40%.

Fig. Evolution of the severity of the syndrome, during treatment (day 0, day 5, day 10), and 1 week after ending Nurosym neuromodulation (follow-up). The individual values and the median are shown. Non parametric Friedman statistics for paired comparisons were used and followed by post-hoc Dunn’s multiple comparisons test (Parasym Clinical Trials, 2021).
Additionally, After 2 weeks of Nurosym neuromodulation therapy, patients experienced an average of 57% improvement in cognition related to ME/CFS.
Reduced HRV is associated with worse performance in cognitive domains. Patients using Nurosym observed HRV enhancements and the research has indicated 61% improvement.

Fig (A, B, C D). The response of autonomic function measured by HRV in Nurosym or Placebo conditions over time: (A) HF, (B) RMSSD, (C) pRR50, (D) SDRR. With Nurosym, the measurements of HF, RMSSD, PRR50 and SDRR were significantly higher than those in Placebo (Parasym Clinical Trials, 2022).
During Parasym trials, reduction of 45% on the Beck Depression Inventory score was observed, directly correlating with mood improvement.

Fig. Evolution of the Beck depression scale scores during Nurosym treatment (day 0, day 5 and day 10). The individual values and the median are shown. Non parametric Friedman statistics for paired comparisons were used and followed by post-hoc Dunn’s multiple comparisons test. (Parasym Clinical Trial, 2021).
48% fatigue improvement was evident in the research findings, reflecting positive outcomes on patients' energy.

Fig. The Pichot fatigue scale scores during Nurosym therapy (D0: day 0, D5: day 5 and D10: day 10). Significant improvement in fatigue scores after Nurosym treatment was observed (D0 vs. D10, p<0.0001). (Parasym clinical trial, 2021).
Another Nurosym finding highlights 78% reduction in inflammation (cytokines levels like IL-8, Il-6, TNF-α). This reduction in inflammation is correlated with a decrease in pain perception and an improvement in gastrointestinal and cardiovascular function. It is worth noting viruses’ interferons can persist in the intestines for an extended period causing chronic inflammation, dysautonomia, and disrupting their proper function, including reduction of neurotransmitter production.

Fig. (A, B) In a three-month study employing the Nurosym device for heart failure patients, notable improvements (*P<0.05) were noted in inflammatory biomarkers: (A) Tumor Necrosis Factor (TNF)‐α exhibited a ~23% reduction, while (B) Interleukin (IL)‐8 showed a marked ~61.3% reduction. The investigation specifically targeted participants with elevated baseline inflammation levels (Parasym Clinical Trial, 2022).
Long-Covid, characterised by persistent symptoms after the acute phase of the illness, frequently includes cognitive dysfunction. In clinical trials conducted by Parasym, individuals exhibited an improvement within 5 days, showing a 32% enhancement in memory and a 26% boost in learning performance with the use of Nurosym.

Fig (A, B). Nurosym has shown to enhance memory in learning tasks relative to a placebo. (A) Across all test questions, Nurosym's neuromodulation demonstrated a notable advantage over placebo. (B) Specifically, this improvement was largely due to the significant impact of Nurosym neuromodulation on memory-related questions (Parasym Clinical Trial, 2020).

Fig (A, B). In the study, pairing Nurosym neuromodulation with training notably enhanced speed performance in the Automaticity learning task (significantly, *p<0.05), compared to placebo controls. Additionally, Nurosym neuromodulation significantly improved accuracy, as measured by the percent correct, in the Decoding learning task when compared to controls (*p < 0.05) (Parasym Clinical Trial, 2020).
In clinical trials involving participants with dysautonomia due to viral infection, assessments at baseline (Day 0), post-intervention (Day 10), and a 1-month follow-up revealed a 17% improvement in overall Fluid Cognition.

(Fig). The Fluid Cognition Score represents cognitive performance across several domains, including Pattern Comparison Processing Speed, Pattern Sequencing Memory, and List Sorting Working Memory. The study showed significant increases from baseline to post-intervention and follow-up (p < 0.01). Friedman’s test indicated a significant main effect of time (p = 0.001) across all composite cognitive scores (Parasym Clinical Trials, 2024).
Nurosym neuromodulation indicated lower neuropeptide Y (NPY) levelsby approximately 38% compared to the placebo group, potentially influencing neuroinflammation in the context of infection.

(Fig). Significant reduction in circulating neuropeptide Y (NPY) concentrations was observed after 6 months of Nurosym treatment. NPY is associated with inflammatory disease progression (Parasym Clinical Trials, 2020).
Doctors about Nurosym
Patients about Nurosym
“I’ve struggled with Lyme disease, autonomic issues, EBV, pituitary problems including adrenal insufficiency, fatigue, insomnia and gastrointestinal issues. It was very serious, in and out of hospitals, I needed a wheelchair and was practically bed bound for several years. Many days I couldn’t even lift my head off the pillow due to my fatigue and Postural tachycardia syndrome (PoTS). I’ve seen so many doctors and taken so many different medications and supplements. With the Parasym I now have a tool I can use myself at home which doesn’t have the nasty side effects medications do. My PoTS, although still present, is much more manageable”
“I'm a long COVID sufferer…I had a lot of muscle spasms, and I was also overly sensitive to external stimuli. So some days I couldn't do anything but just lay down with noise cancelling headphones and dim the light. And that changed after I started using [Nurosym; formerly Parasym] on a daily basis… So, for me, it has been an excellent treatment and I'm thankful for that.”
Tatiana
“Nurosym helped soothe the multiple inflammatory conditions I had developed after covid, such as arthritis, myocarditis, thyroiditis and brain fog. As I now feel better, I do not need to use it every day anymore, but I still incorporate it in my routine whenever I feel the need to relax and restore my nervous system and my whole body.”
Who is for it?
Nurosym is suitable for people with post-viral syndrome, which is characterised by a series of persistent symptoms such as fatigue, cognitive impairment and autonomic dysfunction resulting from a viral infection. Nurosym restores balance to the autonomic nervous system, reduces inflammation and alleviates neurological symptoms, making it a suitable therapy for people suffering from the long-term effects of viral infections. Nurosym effectively improves cognitive and physiological functions of people struggling with post-viral syndrome, especially since pharmacological solutions fall short, merely treating symptoms temporarily without improving the body's autonomic efficiency.
Protocol - How to Use
Based on research findings and patient feedback, it is recommended to conduct Nurosym sessions for treating long-COVID and other post-viral syndromes for at least 30 minutes twice daily, typically in the morning and before bedtime to improve vagal tone. Reducing inflammatory processes in the body requires a longer time of therapy.
The settings of the Nurosym device should be adjusted to each patient's response, starting with the tingling point that indicates the point of stimulation of the vagus nerve. Some patients may begin to notice improvement within 5 days. However, the best results are typically achieved by 4 weeks of therapy. It’s worth continuing therapy to achieve anti-oxidative properties for further health implications.
How often
Nurosym is recommended for use twice daily based on clinical research and patient feedback. This regimen ensures optimal energy balancing and nervous system calming.
How long
Users should allocate 30 minutes in the morning and 60 minutes before sleep for Nurosym therapy sessions. Consistency in application is key to achieving desired results.
Results
Positive outcomes from Nurosym therapy may become noticeable within a relatively short timeframe. Many individuals report improvements within days of starting treatment.