- Vagus Nerve Stimulation
- What is the Vagus Nerve? Function & Related Disorders
- New Paradigms
- Roles and Functions
- Malfunction Causes
- Liver, Pancreas, and Gallbladder
- Kidney and Bladder
- Reproductive Organs
- Mouth and Ears
- Potential Symptoms of Low Vagal Tone
- Conditions that May Improve From Vagus Activation
- Science Confirms That the Vagus Nerve Is Key to Well-being
Vagus Nerve Stimulation
The vagus nerve is one of 12 pairs of cranial nerves that originate in the brain and is part of the autonomic nervous system, which controls involuntary body functions.
The nerve passes through the neck as it travels between the chest and abdomen and the lower part of the brain. It is connected to motor functions in the voice box, diaphragm, stomach and heart and sensory functions in the ears and tongue.
It is connected to both motor and sensory functions in the sinuses and esophagus.
Vagus nerve stimulation (VNS) sends regular, mild pulses of electrical energy to the brain via the vagus nerve, through a device that is similar to a pacemaker.
There is no physical involvement of the brain in this surgery and patients cannot generally feel the pulses.
It is important to keep in mind that VNS is a treatment option limited to select individuals with epilepsy or treatment-resistant depression.
Individuals with any of the following criteria may potentially be unsuitable candidates for VNS:
This procedure, performed by a neurosurgeon, usually takes about 45-90 minutes with the patient most commonly under general anesthesia. It is usually performed on an outpatient basis. As with all surgeries, there is a small risk of infection. Other surgical risks of VNS include inflammation or pain at the incision site, damage to nearby nerves and nerve constriction.
The procedure requires two small incisions. The first one is made on the upper left side of the chest where the pulse generator is implanted (Pulse Generator, Figure 1). A second incision is made horizontally on the left side of the lower neck, along a crease of skin. This is where the thin, flexible wires that connect the pulse generator to the vagus nerve are inserted (Lead, Figure 2).
Pulse Generator (Figure 1)*
Lead (Figure 2)*
The device or implant is a flat, round piece of metal that measures about an inch and a half (4 centimeters) across and 10-13 mm thick, depending on the model used (Pulse Generator, Figure 1).
Newer models may be somewhat smaller. The stimulator contains a battery, which can last from one to 15 years.
When the battery is low, the stimulator is replaced with a less invasive procedure which requires only opening the chest wall incision.
The stimulator is most commonly activated two to four weeks after implantation, although in some cases it may be activated in the operating room at the time of implantation. The treating neurologist programs the stimulator in his or her office with a small hand-held computer, programming software and a programming wand (Programming Wand, Figure 3).
The strength and duration of the electrical impulses are programmed. The amount of stimulation varies by case but is usually initiated at a low level and slowly increased to a suitable level for the individual.
The device runs continuously and is programmed to turn on and shut off for specific periods of time — for example, 30 seconds on and 5 minutes off.
Patients are provided with a handheld magnet (Magnet Bracelet, Figure 4) to control the stimulator at home (which must be activated by the physician to magnet mode).
When the magnet is swept over the pulse generator site, extra stimulation is delivered regardless of the treatment schedule. Holding the magnet over the pulse generator will turn the stimulation off while the magnet is in position. Removing it will resume the stimulation cycle.
All maneuvers performed with the magnet can be done by the patient, family members, friends or caregivers.
Programming Wand (Figure 3)*
Magnet Bracelet (Figure 4)*
Side effects are most commonly related to stimulation and usually improve over time. These may include any of the following:
- Increased coughing
- Changes in voice/speech
- General pain
- Throat or neck pain
- Throat or larynx spasms
- Muscle movements or twitching related to the stimulation
- Nausea or vomiting
- Impaired sense of touch
- Prickling or tingling of the skin
Of these, hoarseness, coughing, throat tickling and shortness of breath are the most common and are usually temporary.
If you have received VNS, you should monitor your condition and overall health closely. If any of the following occur, call your doctor right away:
- Constantly hoarse voice
- Stimulation which becomes painful or irregular
- Stimulation which causes choking, breathing or swallowing difficulties or a change in heart rate
- Changes in your level of consciousness, such as increased drowsiness
- Signs that the pulse generator may not be stimulating properly or that the battery is depleted (the device stops working)
- Any new or unusual changes related specifically to the stimulation
In addition, you should call your physician before you undergo any medical tests that might affect, or be affected by VNS, such as magnetic resonance imaging (MRI), or before you have any other medical devices implanted.
The Food and Drug Administration (FDA) approved VNS as a seizure treatment in 1997.
VNS may be considered as a treatment option in patients who have tried two or more anti-epileptic drugs (AEDs) without adequate control of their seizures or in patients who have not responded to AEDs and cannot undergo brain surgery.
It is important to keep in mind that VNS is used in conjunction with AEDs, not instead of them. In addition, VNS is considered a palliative procedure which can effectively improve seizure control but does not generally produce complete seizure-freedom.
VNS can take up to two years to have an effect on a patient’s seizures. If VNS proves effective, it may enable a patient to decreases dosages of AEDs over time.
The goal of VNS is to reduce the number, length and severity of seizures. VNS may also reduce the time it takes to recover after a seizure. However, VNS is not successful in all patients. The success of this treatment differs — some patients report less frequent seizures, others report a slight reduction, while some patients do not respond at all.
The following results have been noted in select patients with epilepsy:
- Less severe or shorter seizures
- Better recovery after seizures (postictal period)
- Improved sense of well-being
- Improved mood
- Improved alertness, memory and cognitive skills
- Fewer emergency room visits
For people with warnings (auras) before their seizures, activating the stimulator with the magnet when the warning occurs may help shorten or even stop the seizures.
Soon after VNS was approved by the FDA as a seizure treatment, reports indicated a possible decrease in depression symptoms in patients who had the device implanted for seizure control.
electroconvulsive therapy, VNS is believed to work by using electricity to influence the production of brain chemicals called neurotransmitters.
Depression has been tied to an imbalance in those chemicals.
In studies involving more than 200 patients leading to the 2005 FDA approval of VNS for treatment-resistant depression (TRD), the device showed no benefit during the first two or three months.
After one year however, 20-30 percent of patients reported significant improvements, and half of these patients reported that their symptoms had nearly resolved completely. However, other patients did not improve or their symptoms worsened.
VNS has been FDA-approved for people with chronic or recurrent TRD who have failed to respond to four or more adequate treatments.
VNS should not be considered in patients presenting with any of the following:
There is much controversy on the efficacy of VNS as a treatment for TRD and at this stage, more outcomes data is in progress. Currently, VNS is not a covered benefit of most insurers for TRD. However, depending on the results of pending studies it may once again reach the point of insurance coverage.
*Image Credits: Cyberonics, Inc.
The AANS does not endorse any treatments, procedures, products or physicians referenced in these patient fact sheets.
This information is provided as an educational service and is not intended to serve as medical advice.
Anyone seeking specific neurosurgical advice or assistance should consult his or her neurosurgeon, or locate one in your area through the AANS’ Find a Board-certified Neurosurgeon online tool.
What is the Vagus Nerve? Function & Related Disorders
The vagus nerve plays many roles in the body. Scientists think that it drives gut-brain axis communication. Recent research has linked several disorders with vagus nerve problems. In this post, we will review how this “wandering” nerve works and how its activity can affect health.
According to a new scientific paradigm, vagal nerve dysfunction may be at play in people with fatigue, food sensitivities, anxiety, gut problems, “brain fog,” and depersonalization [1, 2, 3].
Researchers suggest that these people may have lower vagal tone–meaning the nerve has a lower ability to perform its functions. Some scientists hypothesize that vagus nerve activity can predict chronic diseases and unhealthy lifestyle choices in general .
Although intriguing, we are still lacking solid research that would back up these hypotheses.
One question scientists face is which aspect of the vagus nerve is malfunctioning and to what extent it is the problem vs. other aspects of a person’s biology.
Additionally, the majority of studies covered in this article deal with associations only, which means that a cause-and-effect relationship hasn’t been established.
For example, just because anxiety has been linked with low vagal tone doesn’t mean that and anxiety is caused by low vagal tone. Data are lacking to make such claims.
Also, even if a study did find that low vagus nerve activity contributes to anxiety, vagal tone is highly unly to be the only causative factor. Complex disorders anxiety always involve multiple possible factors–including brain chemistry, environment, health status, and genetics–that may vary from one person to another.
That said, let’s take a look at exactly what the vagus nerve does in the body.
Roles and Functions
The vagus nerve is part of the parasympathetic nervous system, referred to as the rest-and-digest system. It’s not the only nerve in the parasympathetic system, but it’s the longest one. Scientists also sometimes view it as the most important one because it has such far-reaching effects .
The word vagus means “wanderer,” because this nerve wanders all over the body to reach various important organs.
The vagus nerve affects the brain, gut (intestines, stomach), heart, liver, pancreas, gallbladder, kidney, ureter, spleen, lungs, reproductive organs (female), neck (pharynx, larynx, and esophagus), ears, and tongue [4, 3].
Given its importance for gut health, vagus nerve sluggishness or damage has been implicated in digestive disorders including dyspepsia, gastroparesis, GERD, ulcerative colitis, anorexia, and bulimia, to name a few .
In general, nerves (including the vagus) can be damaged or their activity altered via 3 main pathways [5, 4]:
- Communication from an organ to the brain.
- Communication within the brain.
- Communication from the brain to other areas of the body the heart, liver, and gut.
In the brain, the vagus nerve helps control mood. Limited studies suggest that its imbalance is implicated in anxiety and depression .
The vagus nerve thought to be largely responsible for the mind-body connection since it goes to all the major organs (except the adrenal and thyroid glands) .
Some researchers hypothesize that this nerve might be intimately tied to how we connect with one another–it links directly to nerves that tune our ears to human speech, coordinate eye contact, and regulate emotional expressions. It also influences the release of oxytocin, a hormone that is important in social bonding .
One study suggested that higher vagal tone is associated with greater closeness to others and more altruistic behavior .
Vagus activity of a child may be affected by their mother. Infants of mothers who were depressed, angry, or anxious during pregnancy had lower vagus activity in one study .
Some studies suggested that the vagus nerve is important for getting in the mental state of “flow.” It’s believed that the combination of sympathetic (fight-or-flight) and vagus activation creates the right environment for a flow state .
Vagus nerve stimulation might increase wakefulness (by increasing orexin in the prefrontal cortex). It has been shown to decrease the amount of daytime sleep and rapid eye movement in epilepsy patients with traumatic brain injury. In comatose rats, it seemed to promote the recovery of consciousness after traumatic brain injury .
However, over-activating the vagus nerve has been linked with “sickness behavior” (fatigue, sleepiness, depression, anxiety, appetite loss, pain, lowered motivation, and failure to concentrate) in animals when activated by inflammatory markers in an inflammatory state (IL-1b) .
In the gut, it increases stomach acidity, digestive juice secretion, and gut flow. Since the vagus nerve is important for increasing gut flow (motility), having less vagus activation has been linked with IBS risk and slower flow. Large human studies are needed to confirm these findings .
Scientists are investigating whether stimulating the vagus nerve can increase the release of histamine by stomach cells, which helps release stomach acid. Stomach acid releases the intrinsic factor, which helps absorb vitamin B12 .
Thus, scientists hypothesize that low stomach acidity may be, in part, a vagus nerve problem. They believe that satiety and relaxation following a meal may be partially caused by activation of the vagus nerve’s transmission to the brain in response to food intake .
The vagus nerve is thought to be important in conditions GERD, not only because it controls stomach acidity, but also because it controls the esophagus [6, 15].
Liver, Pancreas, and Gallbladder
In the liver and pancreas, it helps control blood glucose balance .
In the gallbladder, it may help release bile, which helps break down fat and absorb fat-soluble vitamins .
In the heart, it controls heart rate and blood pressure. A promising, small study on heart failure patients suggested that vagal nerve stimulation in addition to conventional therapy may improve symptoms. Larger trials are needed .
Kidney and Bladder
Some research suggests that the vagus nerve promotes general kidney function. It helps with glucose control and increases blood flow, which improves blood filtration. Vagus activation ly also releases dopamine in the kidneys, which helps excrete sodium and, thereby, lower blood pressure. This mechanism is not fully clear in humans, though, and more studies are needed [19, 20].
The vagus nerve also goes to the bladder. A potential side effect of its stimulation is urinary retention. On the other hand, less vagus stimulation may make people urinate more frequently [21, 22].
Certain practitioners hypothesize that their patients who complain about frequent urination may have a vagus nerve issue, in combination with other factors such as low vasopressin, low aldosterone, and high cortisol). Although this is possible, clinical studies about these connections are lacking.
In the spleen, it can reduce inflammation. Note that vagus activation may theoretically affects various organs (by releasing acetylcholine), but when it activates in the spleen the response is thought to be more systemic .
It may affect fertility and orgasms in women by connecting to the cervix, uterus, and vagina. However, the effects of the vagus nerve on women’s health are still largely unknown, and most of what we know comes from animal studies [24, 25].
Mouth and Ears
In the tongue, it helps control taste and saliva; while in the eyes, it helps release tears. It also innervates the ear. Scientists are studying if types of ear stimulation can also activate the vagus nerve while also affecting tinnitus [26, 27].
Potential Symptoms of Low Vagal Tone
The vagus nerve seems to support overall health, particularly affecting the gut-brain axis. Sluggish vagus nerve activity usually points to increased fight-or-flight (sympathetic) activity.
Symptoms and disorders shown here have been associated with vagus nerve dysfunction in limited studies. A cause-and-effect relationship hasn’t been established in most cases. Work with your doctor or other health care professional for an accurate diagnosis.
- Obesity and weight gain 
- IBS 
- Depression 
- Anxiety 
- Chronic fatigue 
- High or low heart rate 
- Difficulty swallowing 
- Gastroparesis, also known as delayed gastric emptying 
- Heartburn 
- Dizziness/fainting 
- B12 deficiency 
- Chronic inflammation 
Conditions that May Improve From Vagus Activation
An implantable vagus nerve stimulator is indicated and FDA-approved only in people with seizures and treatment-resistant depression [35, 36].
Ongoing research is investigating whether various types of vagal stimulation — ranging from implantable devices to manual stimulation or relaxation-induced activity — may be used in :
However, vagus nerve stimulation has not been approved by the FDA for any of the health problems listed above. Large-scale clinical data are still lacking.
Anatomically speaking, people can stimulate or inhibit the vagus nerve in two ways. First, the vagus nerve impulse (activation) can flow from the brain to the rest of the body or from the body to the brain.
When it flows from the brain it’s called a “vagal efferent.” When it flows from other parts of the body to the brain, it’s called a “vagal afferent.” We didn’t use these terms in the article for simplicity.
Also, high-frequency heart rate variability (HRV) is associated with vagus nerve/parasympathetic activity [37, 38].
On the other hand, low-frequency HRV is associated with both sympathetic (fight or flight) and parasympathetic (rest and digest) activation.
Science Confirms That the Vagus Nerve Is Key to Well-being
Dec 19, 2019 · 5 min readIllustration: Kieran Blakey
Take a deep breath. Hug a friend. Reach for the ceiling and stretch your limbs. Each of these simple acts bestows a sense of calm and comfort.
And each works its soothing magic in part by activating a complicated system of nerves that connects the brain to the heart, the gut, the immune system, and many of the organs.
That system is known collectively as the vagus nerve.
The vagus nerve is one of the twelve cranial nerves, which sprawl out from the brain and into the body an intricate network of roots. These nerve networks act as lines of communication between the brain and the body’s many systems and organs. Some of the cranial nerves interpret sensory information collected by the skin, eyes, or tongue. Others control muscles or communicate with glands.
The vagus nerve, also called the “10th cranial nerve,” is the longest, largest, and most complex of the cranial nerves, and in some ways it’s also the least understood.
Experts have linked its activity to symptom changes in people with migraine headaches, inflammatory bowel disease, depression, epilepsy, arthritis, and many other common ailments.
The more science learns about the nerve, the more it seems a better understanding of the vagus nerve function could unlock new doors to treating all manner of human suffering.
Vagus is Latin for “wandering,” which is apt when one considers all the different parts of the body the vagus nerve reaches. “It seems every year somebody finds a new organ or system that it talks with,” says Tiffany Field, PhD, director of the Touch Research Institute at the University of Miami School of Medicine.
“There’s a massive bioelectrical and biochemical series of events that the vagus nerve is responsible for, and all that is almost impossible to map.”
Field says that branches of the vagus nerve are connected to the face and voice.
“We know that depressed people have low vagal activity, and this is associated with less intonation and less-active facial expressions,” she explains.
A separate branch of the vagus nerve runs down to the gastrointestinal tract. Here, low vagal activity is associated with slowed gastric motility, which interferes with proper digestion, she says.
Still other branches of the vagus nerve are connected to the heart, the lungs, and the immune system.
The vagus nerve’s activation or deactivation is tied to the ebb or flow of hormones such as cortisol and the digestive hormone ghrelin, the amount of inflammation the immune system produces, and many other internal processes that shape human health and experience.
“There’s a massive bioelectrical and biochemical series of events that the vagus nerve is responsible for, and all that is almost impossible to map,” Field says.
How could one nerve system control so much? While some aspects of vagal activity are inscrutable, it’s clear that the nerve is the governor of the parasympathetic nervous system, which helps control the body’s relaxation responses.
In simple terms, heightened vagal activity counteracts the stress response, which involves the sympathetic nervous system.
“The sympathetic nervous system is fight or flight, while the parasympathetic nervous system is more chill out,” says Stephen Silberstein, MD, a professor of neurology and director of the Headache Center at Philadelphia’s Thomas Jefferson University Hospitals.
Silberstein co-wrote a comprehensive 2016 review of the research on the vagus nerve. He says that heightened vagal activity slows heart rate and also switches off inflammation, in part by triggering the release of immune system calming chemicals.
There’s also evidence that activating the vagus nerve through electronic stimulation can produce a range of health benefits. “Depending on the frequency of the stimulation, we know it can turn off an asthma attack or an epileptic seizure,” Silberstein says.
“It can turn off a migraine or cluster headache, and it can decrease the perception of acid reflux.”
Pick almost any common medical condition that’s made worse by stress or inflammation — everything from arthritis to inflammatory bowel disease — and there’s research showing that vagus nerve stimulation can help treat it or relieve its symptoms.
In the past, this stimulation required a surgical implant in the chest that transmits electrical pulses directly into the vagus nerve.
But some newer, noninvasive devices — including one that has FDA approval for the treatment of migraine and cluster headaches — are capable of stimulating the vagus nerve when pressed against the skin of the neck.
Silberstein says doctors are exploring the use of vagus nerve stimulation for a wide range of diseases and disorders, including afflictions of the mind.
“More and more, we’re learning how critical vagal activity is to attention and mood,” says Field. Already, there’s evidence that stimulating the vagus nerve may improve working memory or help people with attention deficit hyperactivity disorder. And since the early 2000s, the FDA has approved vagus nerve stimulation for the treatment of some forms of depression.
While electronic stimulation holds promise — and, in some cases, is already providing relief — for people with a range of ailments, Field says there are plenty of ways to stimulate vagal activity without a device or implant. “We know that massage and yoga promote parasympathetic nervous system activity, which is vagal activity,” she says.
Her research has shown that these and many related activities increase vagal activity via pressure receptors buried beneath the surface of the skin — receptors located throughout the body, and ones that only firm pressure or a deep stretch can reach. She points out that light touching or stroking is arousing, while a bear hug or powerful handshake are inherently soothing. “A strong hug or a handshake promote parasympathetic activity,” she says.
Silberstein says that almost anything people find relaxing — meditation, deep breathing — is also associated with heightened vagal activity and parasympathetic nervous system activity. “We did studies in the past showing that patients with migraine have impaired vagal activity,” he says.
“We tried to fix that by doing yoga or deep-breathing meditation, and we found a lot of those things enabled us to activate the vagal nerve.
” On the other hand, stress and anxiety are associated with depressed vagal activity, which may help to explain why these conditions are linked with an increased risk for other maladies.
There’s still a lot about the vagus nerve science doesn’t understand. But as doctors uncover more of its secrets, these discoveries are revealing new and more effective ways to relieve pain, inflammation, sadness, and disease.
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