What is vagus nerve stimulation by TENS?
Vagus nerve stimulation (VNS) using transcutaneous (through the skin) electrical nerve stimulation (TENS) is a therapeutic approach that involves applying low-voltage electrical stimulation to the vagus nerve through the skin. The vagus nerve is a major component of the parasympathetic nervous system which is part of the autonomous nervous system. The autonomous nervous system controls involuntary bodily functions such as heart rate, respiration, digestion. The autonomous nervous system is divided in two main branches, the sympathetic nervous system and the parasympathetic nervous system.
The sympathetic nervous system is often associated with the so-called “fight or flight” response, it regulates the bodies response to stress situations. The parasympathetic nervous system is often associated with the so-called “rest and digest”, it is active during periods of recovery and rest and promotes relaxation after the sympathetic response. As a component of the parasympathetic nervous system, the vagus nerve is a major mediator of the parasympathetic response.
During the procedure electrodes are placed on the skin, typically in the ear or neck area, targeting specific branches of the vagus nerve. Low-voltage electrical impulses are then delivered through the electrodes, aiming to stimulate the vagus nerve, and thereby influencing its activity.
Vagus nerve stimulation by TENS is used for various therapeutic purposes
Vagus nerve stimulation has an impact on the release of neurotransmitters (biochemical messengers) like serotonin and norepinephrine, which are implicated in pain sensation. It can have a relaxing and stress reducing effect through the parasympathetic response. Due to its influence on the parasympathetic nervous system, a stimulation of the vagus nerve may have beneficial effects on conditions that are associated with a dysfunction of the autonomic nervous system. Moreover, vagus nerve stimulation by TENS has been associated with anti-inflammatory effects and a positive effect on mood regulation.
Based on these implications, vagus nerve stimulation is approved for the treatment of drug resistant epilepsy and endogenous depression (see infobox) in Switzerland. In epileptic patients it may reduce the frequency and intensity of seizures, while patient suffering from depression could benefit from its effects on mood regulation and neurotransmission. Furthermore, it has been discussed for treatment of chronic pain (e.g., in fibromyalgia or migraine) and inflammatory disorders. However, research in these areas is still ongoing.
It's important to note that while vagus nerve stimulation by TENS seems to be promising in various applications, more research is needed to fully understand its mechanisms and optimize its use for different medical conditions. Additionally, the application of this therapy should be done under the supervision of qualified healthcare professionals.
Position of the vagus nerve and depiction of the organs connected to it.
What are potential implications for vagus nerve stimulation by TENS in Long COVID?
As mentioned previously, Long COVID has been associated with a dysregulation of the autonomic nervous system. Vagus nerve stimulation may help modulate the activity of this part of the nervous system. Moreover, the vagus nerve plays a role in regulating inflammation and immune responses, which could help lingering symptoms of Long COVID patients.
While electrical stimulation of the vagus nerve for the treatment of Long COVID has been discussed for quite a while, clinical evidence is still scarce. A recently published study from Spain showed that vagus nerve dysfunction is likely to contribute to Long COVID. The study compared 30 Long COVID patients with symptoms suggesting vagus nerve dysfunction with 14 individuals who had fully recovered from COVID-19 and 16 individuals who have never been infected with SARS-CoV-2. The study found that neck ultrasounds of participants with Long COVID were more likely to show thickening of the vagus nerve and a hyperechogenic vagus nerve (appearing brighter than the surrounding tissue, which indicates that the tissue is denser).
Currently only one study has published results on electronical vagus nerve stimulation as a treatment for Long COVID. The US study assessed supervised, at-home, self-administered transcutaneous auricular vagus nerve stimulation (taVNS, stimulation through the skin (transcutaneous) applied by the ear (auricular)) to manage Long COVID symptoms in 12 individuals. Six participants were randomized to get active taVNS while the rest received a sham-control (see infobox). The treatment appeared to be safe, however, efficacy could not be determined due to the small participant number. The authors reported a small trend suggesting that the treatment might have been beneficial.
Some smaller studies (Laura Uehara et al., Carlos Tornero et al., Claire-Marie Rangon et al.) have assessed vagus nerve stimulation for acute COVID-19. The studies showed that the treatment is safe and suggested some benefits for the short-term outcomes of acute infection.
What are potential risks for Long COVID patients?
Responses to interventions such as vagus nerve stimulation can vary widely among individuals. Long COVID patients may have different symptom profiles, and what works for one person may not work the same way for another.
Nevertheless, current evidence suggests that the treatment is safe, even though its efficacy is still to be determined. It is important to discuss potential side effects based on your individual health condition with your health care professionals.
Since Long COVID patients can be especially sensitive to stimulating treatments, it is important to start at a very low dose. Providers of TENS equipment often recommend sessions of 30-60 min per day. These recommendations are NOT directly translatable to Long COVID patients! If you want to try vagus nerve stimulation, please discuss with a health care professional, which intensity and duration might be suitable. To increase safety, it is better to start at a very low intensity and duration. If you don’t experience any negative side effects, you can slowly increase the intensity or duration.
Join our forum to share your personal experiences with vagus nerve stimulation with other people affected with Long COVID. There is an ongoing discussion about the topic: Follow this link!
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