What are Vagal Nerve Disorders?
The vagus nerves, also called vagal nerves, are long, branching nerves that emerge from the brain and connect to several different parts of the body. The vagus nerve originates at the brain stem and branches to many of the body’s major organs, including the larynx, lungs, heart, liver, stomach, intestine, and kidneys. One of the vagus nerve’s central roles is to serve as part of the body’s parasympathetic nervous system, the network of communication that controls automatic body functions such as breathing, heartbeat, and digestion.
Role of the Vagus Nerves
As part of the parasympathetic nervous system, the vagus nerves help control vital body functions such as:
- Heart rate
- Immune system activity
In addition to its parasympathetic functions, the vagus nerve also plays a role in taste and touch perception, the movement of muscles involved in speech and swallowing, and mood regulation.
Symptoms of Vagal Nerve Disorders
The signs of problems with the vagus nerves vary depending on where and how the nerves are affected. Some common symptoms of vagal nerve issues include:
- Abdominal pain
- Gastric acid reflux
- Swallowing difficulties
- Hoarseness or speech difficulties
- Nausea or vomiting
- Loss of appetite or weight loss
- Dizziness or fainting
- Changes in heart rate
- Changes in blood pressure
Damage to or dysfunction of the vagus nerves can cause specific disorders, including:
- Gastroparesis. In this disorder, food does not move properly from the stomach into the intestines.
- Vasovagal syncope. In this disorder, rapid drops in blood pressure cause dizziness or fainting. The blood pressure changes often result from stressful situations.
What Causes Vagal Nerve Disorders?
The common vagus nerve disorders have varying causes.
Gastroparesis may be caused by several different underlying conditions, including:
Vasovagal syncope is classified as a reflex syncope, a condition in which the parasympathetic nervous system incorrectly regulates blood pressure in response to a stimulus or trigger. Common triggers of vasovagal syncope include:
- Extreme heat
- Long periods of standing
- Long periods of exercise
- Fear or other intense emotion
- Sight of blood
- Straining actions, such as coughing or having a bowel movement
Are Vagal Nerve Disorders Hereditary?
Vagal nerve problems are not necessarily inherited, but some underlying conditions causing them may be passed through families. For example, diabetes, the most common cause of gastroparesis, often runs in families. Some studies have also suggested that there may be a genetic component to vasovagal syncope, although no gene or genes have yet been definitely linked to the condition.
How Are Vagal Nerve Disorders Detected?
Because the vagus nerve is connected to many different parts of the body and is associated with a range of body functions, problems with the vagal system can manifest in many different ways, depending on where and how the nerves are damaged or malfunctioning.
Some potential warning signs of vagal nerve problems include:
- Changes in voice or difficulty speaking
- Problems swallowing
- Low blood pressure
- Low heart rate
- Digestive disruptions
- Nausea or vomiting
- Abdominal pain
- Depression or anxiety
How Are Vagal Nerve Disorders Diagnosed?
Doctors may take several different diagnostic steps when suspecting a patient may have a vagal nerve problem. The exact steps will vary depending on your symptoms. Possible diagnostic procedures include:
- Imaging. Magnetic resonance imaging (MRI), ultrasound, or computerized tomography (CT) scans may be used to look for intestinal blockages.
- Endoscopy. This procedure uses a small camera to examine the digestive tract.
- Echocardiogram or electrocardiogram tests measure heart function.
- Exercise stress tests measure heart function during exertion.
- Laboratory tests may be used to identify conditions such as anemia that could cause dizziness or fainting.
- A tilt table test looks for causes of dizziness related to blood pressure.
How Are Vagal Nerve Disorders Treated?
The type of treatment plan your doctor will prescribe for vagal nerve problems will vary depending on your specific disorder.
Common treatments for gastroparesis include:
- Changes to your diet to encourage emptying of the stomach
- Medications such as metoclopramide or erythromycin to stimulate stomach muscles
- Medications such as diphenhydramine or ondansetron to treat nausea
- Surgical procedures to relieve pressure in the stomach or deliver nutrients to the digestive tract
- Gastric electrical stimulation delivers an electrical pulse that stimulates stomach muscles
Common treatments for vasovagal syncope include:
- Increasing salt intake
- Adjusting medications that lower blood pressure
- Medications such as fludrocortisone acetate or SSRI antidepressants
- Therapies or compression stockings to decrease the pooling of blood in the legs
- Surgical implantation of a pacemaker to regulate heartbeat (used only in rare cases)
How Do Vagal Nerve Disorders Progress?
In most cases, gastroparesis can be managed effectively with lifestyle changes and other treatments. However, the disorder may lead to serious, potentially life-threatening complications if not managed well. Possible complications include:
- Swings in blood sugar levels
- Intestinal blockages
Vasovagal syncope is usually not a serious problem in itself. However, symptoms could indicate a potentially dangerous heart problem, making it important to see your doctor if you experience them. Syncope episodes that cause extreme dizziness or fainting also have the potential to cause injury from falls or accidents.
How Are Vagal Nerve Disorders Prevented?
There is no known way to prevent vagal nerve disorders. However, some lifestyle changes may help lower the risk of developing problems related to your vagus nerves. These changes include:
- Eating a healthy diet
- Getting plenty of exercise
- Practicing relaxation techniques such as yoga or meditation
- Consistently managing underlying conditions such as diabetes or blood pressure problems
Vagal Nerve Disorders Caregiver Tips
Many people with vagal nerve problems also suffer from other brain and mental health-related issues, a condition called co-morbidity. Here are a few of the disorders commonly associated with brain tumors:
Vagal Nerve Disorders Brain Science
In addition to its key role in the parasympathetic nervous system, the vagus nerve is also involved in mood regulation and other important aspects of brain activity. Because of this, researchers have targeted the vagus nerve as they look for new therapies to treat many different brain-related disorders.
Vagus nerve stimulation (VNS) is a procedure that uses a device implanted under the skin to deliver electrical pulses to the vagus nerve. The impulses then travel to the brain and alter electrical activity in parts of the brain associated with certain disorders.
VNS is often used to treat:
- Epilepsy. VNS decreases the atypical brain activity associated with seizures. The therapy has proven effective at treating seizures resistant to medications and other types of therapy.
- Depression. VNS has also shown promise for the treatment of drug-resistant depression, and it has been approved by the FDA to treat the disorder.
Scientists are also looking into the possibility that VNS could be used to treat other brain-related and autoimmune disorders, including:
Vagal Nerve Disorders Research
Title: Non-invasive Vagus Nerve Stimulation in the Treatment of Crohn’s Disease – A Pilot Study (VNS)
Principal investigator: Sashidhar V. Sagi, MD
Crohn’s disease (CD) is a type of inflammatory bowel disease (IBD) characterized by chronic inflammation in the digestive tract. The pathogenesis of IBD involves immunological, genetic, and environmental factors. Currently, there is no cure for Crohn’s disease, and available medical and surgical treatments are expensive and often associated with significant side effects. Anti-tumor necrosis factor-alpha (anti-TNF-α) agents are widely used to treat Crohn’s disease. Electrical neuromodulation is a new treatment approach of bioelectronic medicine, involving molecular medicine, neuroscience, and bioengineering. Multiple possible mechanisms have been proposed for electrical neuromodulation in GI diseases, including central, autonomic, and/or enteric mechanisms. Vagal tone is significantly blunted in IBD and is associated with high TNF- α levels. Animal and preliminary human studies have demonstrated that electrical vagal nerve stimulation (VNS), including non-invasive vagal stimulation (nVNS), exerts an anti-inflammatory effect by harnessing the cholinergic anti-inflammatory pathway. In healthy humans, nVNS has been shown to decrease tumor necrosis factor-α levels. Invasive VNS has been shown to improve inflammation in preliminary studies in patients with Crohn’s disease.
Adult patients with mild to moderate Crohn’s disease will be asked to self-administer transcutaneous vagal nerve stimulation three times per day for 16 weeks. Inflammatory laboratory markers will be compared for each patient against their baseline levels to determine if the intervention helps reduce inflammation caused by their Crohn’s disease. Questionnaires will be administered to evaluate their symptoms, and quality of life over the 16-week treatment period.
Title: Using Transcutaneous Auricular Vagus Nerve Stimulation to Treat Acute Alcohol Withdrawal
Stage: Not Yet Recruiting
Principal investigator: Andrew C. Chen, MD, PhD
Feinstein Institutes for Medical Research
The management of acute alcohol withdrawal is a clinical challenge, partly because there are limited medications available for the condition, and the majority of the medications are controlled substances, which may cause significant adverse effects and can be potentially addictive.
The rationale for using transcutaneous auricular VNS (taVNS) on a specific target area of the ear is based on anatomical studies suggesting that this area is the only place on the human body surface where there is afferent vagus nerve distribution (Mercante et al., 2018). Therefore, direct stimulation of the afferent nerve fibers on the ear can produce an effect similar to that of implanted device-generated VNS yet without the need for surgical intervention. Although taVNS has not been tested for the treatment of AUD, it interestingly appears to be very similar to auricular acupuncture, which has been widely used for AUD. However, acupuncture needs to be administered by medical providers who have undergone long training and have special licensure, usually unavailable in acute detoxification units where patients receive treatment for acute alcohol withdrawal.
The pilot study will enroll 70 evaluable subjects who are in an inpatient detoxification unit randomized to receive single-blind treatment with vagus nerve stimulation or sham stimulation (1:1, VNS: sham). Evaluable subjects are those who complete stimulations (VNS) or sham 5 minutes twice a day for 4 days.
Title: Effects of Respiratory-Gated Transcutaneous Vagal Nerve Stimulation in Major Depression (Phase 1)
Principal investigator: Ronald G. Garcia, MD, PhD
Massachusetts General Hospital
This study will compare the acute effects of respiratory-gated transcutaneous vagus nerve stimulation (tVNS) at different stimulation frequencies and sham stimulation during five sessions within 2 weeks. Heart rate variability (HRV) point process adaptive filtering estimation algorithms will be used to evaluate changes in cardiac autonomic physiology in subjects with major depression in response to tVNS. The effects of tVNS on cardiovagal regulation will be evaluated at rest and in response to an emotion reactivity task. Depression rating scales (Beck’s Depression Inventory) will be used to evaluate the short-term effects of tVNS on depressive symptoms in these subjects. In addition, the study will assess the acute effects of the stimulation on serum levels of pro-inflammatory cytokines. The stimulation frequency that produces the most significant regulatory effects on depressive symptoms and physiological variables in this population will be used in a second longitudinal phase of the study.