Stimulation: Stimulation du nerf vague

What It Is

The vagus is the tenth cranial nerve, named from the Latin for wandering. It leaves the brainstem and travels down through the neck and chest to the heart, lungs and much of the gut. Vagus nerve stimulation means putting a small electrical signal onto that nerve on purpose. It began as an implanted device for epilepsy and has since taken several forms.

The inflammatory reflex explains why the nerve is studied beyond epilepsy. Work led by Kevin Tracey showed the vagus is part of a loop the body uses to sense inflammation and lower it. Signals traveling up register rising inflammatory molecules; signals traveling down lower the output of those same molecules from immune cells.

The Anatomy Of The Vagus Nerve

1From The Brainstem

The vagus begins in the medulla, low in the brainstem, where a hub called the nucleus tractus solitarius receives the sensory traffic coming up from the body. From there the nerve descends through an opening in the base of the skull and runs down the neck alongside the great vessels.

2Through The Neck And Chest

In the neck it gives off the branch that supplies the voice box, which is why stimulating the nerve can change the voice. It continues into the chest, sending fibers to the heart, where it is the main slowing influence on heart rate, and to the lungs and airways.

3To The Organs And Back

Below the chest it reaches the stomach, gut, liver and other organs. Roughly four in five of its fibers are sensory, carrying information from the organs up to the brain. That sensory traffic feeds the inflammatory reflex.

How It Works

An electrical pulse on the vagus acts in both directions at once, because the nerve runs both ways. Downward, on the parasympathetic side, it can slow the heart and shift the body toward its rest-and-recover setting. Upward, along the larger sensory bundle, it reaches the nucleus tractus solitarius in the brainstem. From there the signal relays to regions that regulate mood, arousal and the release of the brain's own signaling chemicals. The antiseizure and antidepressant effects are thought to arise mainly along this upward route to the brain, and the heart plays little part.

The immune effect runs through the inflammatory reflex. Downward signaling, relayed through the spleen, prompts the release of acetylcholine. Acetylcholine binds receptors on immune cells and lowers their output of inflammatory molecules such as tumor necrosis factor. This is the cholinergic anti-inflammatory pathway, the basis for testing the nerve in an inflammatory disease like rheumatoid arthritis.

There is also a way to the nerve from the surface of the ear. A small branch of the vagus supplies part of the outer ear, so a clip or electrode there reaches the same central projections without surgery. Brain imaging in people shows that stimulating this spot activates the brainstem hub and its onward targets. That is the basis of the non-invasive ear-clip form. The same central hub is also reachable through slow breathing, the gentler everyday route into the system. Vagal tone measures the resting influence of the vagus on the heart, read out as heart rate variability.

What Changed

For its first years the treatment was one specialized procedure, an implanted pulse generator under the collarbone, its lead coiled around the nerve in the neck. It was cleared in the United States in 1997 for epilepsy that had not responded to medication, and a depression approval followed in 2005. Two developments then widened the field: the inflammatory reflex recast the vagus as an influence on the immune system, and the ear branch offered a way in without surgery. That second finding turned a hospital procedure into something a small clinic, or a consumer device maker, could study. Later, pairing brief stimulation with physical therapy was cleared for stroke rehabilitation.

The Forms And Their Evidence

Implanted VNS For Epilepsy And Depression

The implanted device carries the strongest, longest evidence. In drug-resistant epilepsy it reduces seizure frequency by a modest amount. In the pivotal trial, high stimulation cut seizures by about 28 percent over three months, against about 15 percent on low stimulation. It is a standard option when medication and surgery are not enough. For treatment-resistant depression the evidence splits by time frame. The short controlled trial that supported approval did not clearly beat a sham device over ten weeks. The stronger signal is long-term: over years, people with the implant showed higher response and remission rates than those on usual care in a large observational comparison.

Paired VNS For Stroke Rehabilitation

A newer use pairs a brief pulse of stimulation with each movement during rehabilitation. The pulse lands during the window when the brain forms new connections most readily. In the pivotal blinded trial, VNS-REHAB, people who received paired stimulation during arm therapy gained more movement than therapy alone. They were about twice as likely to reach a meaningful improvement. MicroTransponder, the maker of the device, funded that trial. It carries clearance for arm recovery after an ischemic stroke, resting on that one pivotal trial.

Transcutaneous Auricular VNS, The Ear Clip

The non-invasive form, transcutaneous auricular vagus nerve stimulation or taVNS, delivers current through the skin of the ear. It draws the most interest. Many small trials in depression, anxiety, inflammation and atrial fibrillation have reported encouraging results. Three limits run through them:

• they are small;
• they are hard to blind convincingly, because a person can feel the ear clip;
• they vary in how and where on the ear they stimulate.

In depression, an ear-clip protocol reduced symptoms in early trials, including one that matched a standard antidepressant. These trials are small, and that comparison had no dummy device. In atrial fibrillation, low-level ear stimulation lowered the burden of the arrhythmia in small randomized studies.

Everyday Vagal Tone Practices

Outside any device, several practices raise vagal tone. Slow breathing near six breaths a minute is the best supported. It drives the widest, smoothest heart-rate swings, and its mechanism is well understood, covered in full on the breathwork and HRV page. Cold exposure and the diving response also engage the vagus. Humming, chanting and gargling are promoted on the grounds that they use the throat muscles the vagus supplies.

The breathing effect on vagal tone is well established. The claim that humming or gargling treats a disease is not.

Vagal tone measures the resting influence of the vagus on the heart, read out as heart rate variability.

The Research & Studies

Everything here is based on the research we have collected and checked, sorted into groups and ordered with the strongest evidence first. Click any claim to open the studies behind it.

How it works

Les signaux descendants du vague indiquent aux cellules immunitaires de produire moins de TNF, le réflexe inflammatoireStrong · mixed

In plain terms

Le nerf vague est connecté au système immunitaire. Les signaux qui le parcourent réduisent la quantité de molécules inflammatoires que les cellules immunitaires produisent, c'est pourquoi un nerf est étudié pour les maladies inflammatoires.

In detail

Le réflexe inflammatoire, caractérisé dans les travaux menés par Kevin Tracey, est une boucle physiologique dans laquelle le nerf vague détecte à la fois l'inflammation croissante par ses fibres afférentes et la diminue par sa voie efférente cholinergique anti-inflammatoire. L'activité vagale efférente, relayée par le nerf splénique, conduit à la libération d'acétylcholine qui agit sur les récepteurs nicotiniques alpha-7 des macrophages pour réduire la production de facteur de nécrose tumorale et d'autres cytokines. Il s'agit d'un article de mécanisme fondateur et d'une revue du concept, pas d'un essai clinique, donc il établit la voie, pas la taille d'un effet thérapeutique.

The study · 1

Tracey, The inflammatory reflex · Nature 2002;420(6917):853-9

La stimulation de la peau de l'oreille atteint le même centre vagal du tronc cérébral aux scanners cérébrauxModerate · mixed

In plain terms

Une branche du vague atteint l'oreille externe, donc un clip là peut envoyer un signal au même centre du tronc cérébral que cible le dispositif chirurgical, sans aucune opération. Les scanners cérébraux confirment que la voie auriculaire active ce centre.

In detail

L'IRM fonctionnelle chez des personnes saines a montré que la stimulation transcutanée de la conque auriculaire, alimentée par la branche auriculaire du vague, produisait une activation significative dans le noyau du tractus solitaire et les régions connectées incluant le locus coeruleus, correspondant au profil de projection centrale attendu du nerf vague. C'est la base anatomique et d'imagerie de la forme non invasive à clip auriculaire. Elle démontre l'engagement central de la voie, ce qui est la première étape nécessaire, mais pas un résultat clinique.

The study · 1

Frangos, non-invasive access to vagus central projections via the external ear, fMRI evidence · Brain Stimul 2015;8(3):624-36

La stimulation par clip auriculaire déplace le réseau en mode par défaut lié à la dépression aux scanners cérébrauxEmerging · mixed

In plain terms

Les scanners cérébraux montrent que le clip auriculaire modifie l'activité dans un réseau qui se comporte anormalement dans la dépression, ce qui est un mécanisme plausible pour l'effet sur l'humeur. Cela montre que le signal atteint les circuits pertinents, pas que les symptômes s'améliorent.

In detail

Une étude par IRM fonctionnelle chez des patients atteints de trouble dépressif majeur a constaté que la stimulation transcutanée du nerf vague modulait la connectivité du réseau en mode par défaut, notamment son couplage avec des régions impliquées dans la régulation de l'humeur, le déplaçant dans une direction opposée au profil typiquement observé dans la dépression. Cela fournit un pont mécanistique entre la voie auriculaire et les résultats sur l'humeur. En tant qu'étude d'imagerie, elle décrit des effets centraux sur les réseaux cérébraux ; elle ne mesure pas elle-même l'amélioration clinique.

The study · 1

Fang et al., transcutaneous vagus nerve stimulation modulates default mode network in major depressive disorder · Biol Psychiatry 2016;79(4):266-73

Seizure Control

Implanted stimulation cut drug-resistant seizures about 28% versus 15% on low stimulation in its pivotal trialStrong

In plain terms

For epilepsy that medication cannot control, the implanted device is an established, approved treatment. In its pivotal trial it cut seizures about 28 percent against 15 percent on low stimulation, and the benefit tends to grow over the first year or two.

In detail

Implanted vagus nerve stimulation was the first form of the therapy, cleared in the United States in 1997 as an adjunctive treatment for drug-resistant (medication-refractory) focal, or partial-onset, epilepsy. In the pivotal multicenter active-control trial, patients on high stimulation had an average 28 percent reduction in seizure frequency over three months compared with 15 percent on low stimulation (p=0.04). A 2022 systematic review and meta-analysis from the International League Against Epilepsy pooled long-term data and reported a mean seizure reduction of about 35 percent (34.7 percent), with responder rates that improve over years, and concluded that neurostimulation is an effective option for drug-resistant epilepsy. The device reduces how often seizures occur and is used alongside medication.

Who this may not transfer to:The trials enrolled adults and adolescents with focal epilepsy that had not responded to medication, so the figures describe that refractory population and the implanted device, not the non-invasive ear form.

The studies · 2

Touma et al., neurostimulation in people with drug-resistant epilepsy, systematic review and meta-analysis (ILAE Surgical Therapies Commission) · Epilepsia 2022;63(6):1314-1329

Handforth et al., VNS therapy for partial-onset seizures, a randomised active-control trial · Neurology 1998;51(1):48-55

Mood & stress

Sur 10 semaines, l'implant n'a pas battu un simulacre pour la dépression, environ 15 % contre 10 % de réponseModerate · no effect

In plain terms

Au cours de ses dix premières semaines, le dispositif implanté n'a pas clairement battu un dispositif factice éteint pour la dépression résistante au traitement. C'est un point négatif, et c'est pourquoi les preuves à court terme sont plus faibles que le tableau à long terme.

In detail

L'essai contrôlé randomisé en double aveugle de la phase aiguë de la stimulation du nerf vague implantée dans la dépression résistante au traitement comparait la stimulation active à un simulacre (implanté mais ne délivrant pas de thérapie) sur 10 semaines chez 235 participants. Les taux de réponse étaient d'environ 15 % pour l'actif et 10 % pour le simulacre, et la différence sur le critère de jugement principal n'était pas statistiquement significative. Le résultat aigu décevant est au cœur du débat de longue date sur l'approbation du dispositif pour la dépression, qui repose davantage sur des données ouvertes à plus long terme que sur cet essai contrôlé.

The study · 1

Rush et al., VNS for treatment-resistant depression, randomised controlled acute phase trial · Biol Psychiatry 2005;58(5):347-54

Sur 5 ans, 68 % ont répondu à l'implant contre 41 % sous soins habituelsModerate

In plain terms

Sur cinq ans, les personnes avec l'implant ont mieux fait que celles sous soins habituels : environ 68 % ont répondu contre 41 %, avec plus atteignant la rémission. Ce signal à long terme est la principale raison pour laquelle l'utilisation pour la dépression perdure, malgré le faible essai à court terme.

In detail

Un grand registre observationnel de 5 ans a comparé des patients atteints de dépression résistante au traitement traités avec une stimulation du nerf vague implantée adjuvante à ceux recevant un traitement habituel (environ 795 patients dans les deux bras). Le groupe de stimulation a montré un taux de réponse cumulatif plus élevé (environ 68 contre 41 %) et une rémission plus élevée au cours du suivi. L'attribution n'étant pas randomisée, les groupes peuvent avoir différé de façons qui affectent également les résultats, donc la taille du vrai effet est incertaine même si la direction est cohérente.

The study · 1

Aaronson et al., 5-year observational study of VNS versus treatment as usual in treatment-resistant depression · Am J Psychiatry 2017;174(7):640-8

La stimulation par clip auriculaire a soulagé la dépression à parité avec l'antidépresseur citalopram dans un essai de 107 patientsEmerging

In plain terms

La version à clip auriculaire a réduit les scores de dépression dans de petites études précoces, et dans un essai, a fonctionné à peu près aussi bien qu'un antidépresseur courant. Les résultats sont prometteurs mais les essais sont de petite taille et difficiles à aveugler.

In detail

Les essais précoces de stimulation du nerf vague auriculaire transcutanée (taVNS) dans le trouble dépressif majeur ont rapporté des réductions des scores de symptômes, d'abord dans un pilote contrôlé non randomisé et plus tard dans des travaux randomisés. Dans un essai comparatif d'efficacité randomisé de 107 patients, la taVNS administrée pendant huit semaines a produit une amélioration des symptômes similaire à l'antidépresseur citalopram, sans différence significative entre les deux groupes ; les deux bras se sont améliorés, donc une contribution placebo ne peut pas être exclue. Ce sont de petites études, et aveugler de manière convaincante une intervention avec clip auriculaire est difficile, donc l'attente est une préoccupation réelle et la comparaison avec le citalopram utilisait un médicament actif à la place d'un dispositif factice. Les preuves en sont à un stade émergent, encourageant mais non établi.

The studies · 2

Rong et al., effect of taVNS on major depressive disorder, non-randomised controlled pilot · J Affect Disord 2016;195:172-9

Comparative effectiveness of taVNS versus citalopram for major depressive disorder, a randomised trial · Neuromodulation 2022;25(3):450-60

Heart And Vascular

Ear stimulation lowered atrial fibrillation burden about 85% over six months in a 53-person trialEmerging

In plain terms

Gentle stimulation of the ear cut the amount of atrial fibrillation people had in small trials, both in the moment and over six months. The effect is clear in these studies but they are small and single-center.

In detail

In a randomized acute study, low-level transcutaneous stimulation of the tragus suppressed induced atrial fibrillation and lowered inflammatory markers compared with sham. The follow-up TREAT AF randomized clinical trial (about 53 participants) delivered daily ear stimulation over six months and found the median atrial fibrillation burden about 85 percent lower than with sham (p=0.011). These are small, mostly single-center trials in paroxysmal atrial fibrillation, so the direction is encouraging while the magnitude and durability remain uncertain and unconfirmed in large multicenter work.

The studies · 2

Stavrakis et al., low-level transcutaneous electrical vagus nerve stimulation suppresses atrial fibrillation · J Am Coll Cardiol 2015;65(9):867-75

Stavrakis et al., TREAT AF, transcutaneous electrical vagus nerve stimulation to suppress atrial fibrillation, a randomised clinical trial · JACC Clin Electrophysiol 2020;6(3):282-91

Inflammatory Arthritis

In 17 patients, vagus stimulation lowered TNF and eased rheumatoid arthritis, worse when switched offPreliminary

In plain terms

In a tiny early study, an implant that stimulated the vagus lowered inflammation and eased rheumatoid arthritis, and the arthritis worsened again when it was turned off. This is a first demonstration, not a treatment yet.

In detail

A first-in-human open-label study implanted vagus nerve stimulators in a small group of patients with rheumatoid arthritis (about 17 participants) and found that active stimulation reduced whole-blood production of tumor necrosis factor and lowered clinical disease-activity scores, with worsening during a period when the device was switched off. The study was funded by SetPoint Medical, the company developing the implant, a further reason to read a small open-label result with care. This is the clinical demonstration of the inflammatory reflex in an autoimmune disease. With no control group, a small sample and an open-label design, it is an early demonstration that motivates larger controlled trials, not an established therapy.

The study · 1

Koopman et al., VNS inhibits cytokine production and attenuates disease severity in rheumatoid arthritis · Proc Natl Acad Sci USA 2016;113(29):8284-9

Go Deeper

• Breathwork and HRV: the free, best-evidenced way to raise vagal tone, with the protocol and the mechanism.
• Heart rate variability: the number that reads vagal tone, and what it can and cannot tell you.
• Resonance and entrainment: why breathing near the resonance pace couples to the heart the way it does.
• Depression: where implanted and ear-clip stimulation sit among the things studied for low mood.

The Chinese Medicine View

Chinese medicine describes the territory the vagus governs through the breath and the descent of Qi. The Lung governs Qi and controls respiration, 肺主氣，司呼吸, and the breath is where settling the body begins. The instruction 氣沉丹田, sink the Qi to the Dan Tian, directs the breath down into the abdomen. A modern teacher gives the same instruction for slow breathing. The tradition reached it from a different account of the body.

The tradition holds that healthy Qi descends: Lung Qi and Stomach Qi are meant to move downward. When they rebel upward the result is cough, breathlessness, nausea or a restless, ungrounded feeling. That descending, settling direction sits close to what the parasympathetic side does when the vagus quiets the heart. The Heart houses the Shen, the mind and spirit, and a calm, even pulse is read as a settled Shen. A steady, responsive heart rhythm results from that same settling influence in modern terms.

Cautions For This Practice

Everything to be aware of is here, in one place. This practice suits most healthy people; a few situations call for real care.

The ear-clip form is generally well tolerated, mostly mild skin or tingling effects

A systematic review of the safety and tolerability of transcutaneous vagus nerve stimulation in humans gathered adverse events across the published studies and found the intervention generally well tolerated. The most frequently reported effects were mild and local, chiefly skin irritation or redness at the stimulation site, tingling around the ear or face, and occasional headache or dizziness, with serious events rare. Reporting quality varied between the source studies, so the review characterizes a favorable safety picture, not a precise event rate.Redgrave et al., safety and tolerability of transcutaneous vagus nerve stimulation in humans, a systematic review

The implanted device commonly causes a hoarse voice, cough and throat sensations while stimulating

The randomized active-control epilepsy trial (199 implanted, 196 analyzed) documented the side-effect profile of the implanted device. The effects the trial itemized were voice alteration or hoarseness and shortness of breath, arising chiefly during active stimulation; cough and throat or neck sensations are also recognized effects, because the vagus supplies the larynx. They were generally mild, and voice effects in particular tended to lessen over time and could be reduced by adjusting the stimulation parameters. Serious device-related complications were uncommon in the trial.VNS for partial-onset seizures, a randomised active-control trial (Handforth et al.)

The implanted device is surgery

Placing an implanted stimulator is a minor operation and carries the ordinary risks of one, including infection and, rarely, injury to nearby structures. Once it is running, the most common effects come from the stimulation itself: a hoarse or altered voice, a cough, throat tightness and shortness of breath, usually during the seconds the device is active. These tend to be mild and often ease over the first months, and the settings can be adjusted. Weigh these with the specialist managing the device.

The ear clip and the heart

For someone with a cardiac pacemaker, an implanted defibrillator or a known heart-rhythm disorder, ear-clip stimulation is worth a cardiologist's review first. It acts on the same autonomic pathways that influence heart rate and rhythm. Skin irritation or a little redness at the clip is the common minor effect for everyone else.

Not a stand-in for treating serious depression

For someone in a depressive episode, and especially with any thoughts of self-harm, an ear clip is not a substitute for proper care. The implanted form is used under psychiatric supervision for depression that has resisted other treatments, a very different setting from a consumer device. If low mood is severe or persistent, the right first step is a clinician.

Consumer device quality varies widely

The ear-clip devices sold to the public differ a great deal in how well they deliver and target current. Most have not been tested in any published trial. A promising result from a research protocol does not automatically transfer to a given device.

Start slow, be smart, read the research, and consult a professional if you have any concerns. This is here to inform your choice, not make it for you.

Common Questions

Is vagus nerve stimulation safe?

Safety depends on the form. A systematic review of the ear-clip version in people found it generally well tolerated.

Is vagus nerve stimulation FDA approved?

Only the implanted forms are approved, delivered by surgery under specialist care. The ear clips sold to consumers, and the everyday breath-and-cold practices, sit outside that approval. The newest of those approved uses, a paired-stimulation system for arm recovery after stroke, was cleared in 2021.