The vagus nerve is integrally connected to the brain. It plays a very vital role in the functioning of the brain. The vagus nerve cited as the pneumogastric nerve historically. It is the tenth cranial nerve that interfaces with parasympathetic control of the heart, lungs, and digestive tract. The vagus nerves are paired but they are usually referred to in the singular. It is the longest nerve of the autonomic nervous system in the human body. The vagus nerve also has a sympathetic function via the peripheral chemoreceptors. Once the vagus nerve leaves the medulla oblongata between the pyramid and the inferior cerebellar peduncle, it extends through the jugular foramen. It then stretches down to the neck, chest, and abdomen, where it contributes to the innervation of the viscera(the internal organs in the main cavities of the body, especially those in the abdomen, e.g., the intestines.), reaching all the way to the colon.
Besides giving some output to various organs the vagus nerve makes up between 80% to 90% of afferent nerves. It mainly gives sensory information to the central nervous system about the state of the body’s organs. So, the vagus nerve plays a very important role inthe proper functioning of the organs and the central nervous system. Let”s see how the vagus nerve can dysfunction and what are the symptoms of an unhealthy vagus nerve.
Signs of a Vagus Nerve gone Awry
The proper functioning of the vagus nerve is vital to mental and physical well-being. If you feel heavy after eating a meal part of that is due to the vagus nerve. If the vagus nerve begins to malfunction it could be trouble for the whole body. The vagus nerve provides a bidirectional connection between the gut and the brain and it links all major organs. It even plays a role in neurogenesis which is the process of manufacturing new neurons. These are the following ways the vagus nerve affects organs:
- Heart-Decreases heart rate and vascular tone
- Brain-Keeps anxiety and depression away and it fights the sympathetic response to stress
- Liver-Controls insulin secretion (people who have diabetes may have a dysfunctioning vagus nerve) and glucose homeostasis in the liver
- Mouth-Taste data is sent through three central nerves one of those being the vagus nerve. The vagus nerve is needed for the gag reflex, swallowing and coughing.
- Gut-Increases gastric juices, gut motility, and stomach acidic.
- Blood vessels-Decreases vascular tone lowering blood pressure again people who suffer from high blood pressure may have a unhealthy vagus nerve that is not controlling blood pressure properly.
- Inflammation-Stops inflammation by the cholinergic anti-inflammatory pathway
If any of the above functions are disrupted then the vagus nerve is dysfunctioning. Some of the effects of this dysfunction could be fatal.
- Vagus is latin for wandering because the nerve has a long and circuitous path in the body. (It likes to travel)
- Increased vagal tone is associated with increased intimacy (such as with your marriage spouse) and social interaction.Conversely, feeling lonely decreases vagal tone.
- Vagus nerve activity has an antidepressant effect. The hypothalamic-pituitary-adrenal (HPA) axis stress system is out of whack in depression and vagal nerve stimulation normalizes dysregulation of the HPA axis. If the vagus nerve does not regulate this HPA axis depression will set in.
- Vagus nerve dysfunction causes gastrointestinal symptoms. The vagus nerve increases stomach acidity, gut motility and digestive juices. A hypoactive vagus nerve results in delayed gastric emptying. This could cause acid reflux or indigestion.
- The vagus nerve keeps inflammation in check. When the vagus nerve senses inflammatory cytokines it alerts the brain to suppress inflammation via the cholinergic anti-inflammatory pathway. This communication is interrupted the inflammation will set in.
- Vagus nerve stimulation inhibits the synthesis of tumor necrosis factor (TNF) in liver, spleen and heart. Conversely removal of part of the vagus nerve (vagotomy) exacerbates TNF responses to inflammatory stimuli. You may develop cancer if the vagus nerve doesn’t properly inhibit the synthesis of tumors.
- Enterotoxin is responsible for the symptoms of food poisoning. Enterotoxin stimulates the vagus nerve and the vomiting center of the brain, resulting in sickness behavior. You will vomit foreign food matter when this process kicks in. If the vagus nerve doesn’t fulfill its role in the vomiting process you will be in trouble.
Underactive or Overactive Vagus Nerve
In either one of these dysfunctions of the vagus nerve the body will begin to exhibit vagus nerve failure. If an underactive vagus nerve occurs then the body is delayed in gastric emptying. Usually, peristalsis – is a continual contraction and relaxation of the intestinal muscles pushes food into the small intestine for additional digestion. These contractions are supervised by the vagus nerve and if it is damaged these contractions are inhibited. Conversely, if the vagus nerve becomes overactive the heart rate will decrease dramatically causing fainting, and other related symptoms.
Vagus Nerve Functions in Relation to The Parasympathetic Nervous System
- heart rate (decrease) Damaged vagus nerve could cause a heart attack a very serious symptom
- gastrointestinal peristalsis (increase) Damaged vagus nerve will inhibit the process
- sweating (decrease) Dysfunctional vagus nerve will throw the sweating function out of balance
- satiety from food (increase) If the vagus nerve doesn’t regulate satiety you will just go right on eating
- inflammation (decrease) The vagus nerve doesn’t communicate with the brain to block inflammation it will run rampant
- neural processes (decrease) Damaged vagus nerve equals dysfunctioning neural processes
- neurogenesis (increase) Neuron manufacturing may be inhibited by a dysfunctional vagus nerve
- glucose homeostasis and insulin secretion If the vagus nerve is damaged these processes will be harmfully affected
A traumatic experience will trigger excessive vagus nerve activity this in turn will cause a drop in cardiac output which decreases blood flow to the brain. If left untreated the brain could be damaged. Here are some more symptoms of vagus nerve dysfunction:
Weight Gain causing Obesity
There are a few studies that have linked decreased vagus nerve to obesity. This is obvious since the vagus nerve regulates insulin secretion and glucose homeostasis. Like it was mentioned before if the vagus nerve fails to send satiety messages to the brain you will just keep eating. This is because your body will not sense when to stop eating. You will become obese as the weight levels increased. But this theory could be false because when the vagus nerve is removed weight gain and increased appetite do not occur.
If the autonomic nervous system function is disrupted irritable bowel syndrome can occur. If the vagus nerve is damaged then Spaziani R et.will not be the standard autonomic response to rectal distention. This response was hindered in patients with irritable syndrome.Systolic blood pressure increased in response to rectal distension in all participants, but the increase was greater in patients with IBS. IBS patients also had lower baroreceptor sensitivity at rest and throughout rectal distention compared to healthy volunteers. Increase in systolic blood pressure response to rectal distention was higher in patients with irritable bowel syndrome. Also patients with irritable bowel syndrome had lower baroreceptor sensitivity at rest and throughout rectal distention compared to healthy volunteers. Both symptoms of a damaged vagus nerve.
Vagus nerve damage will hinder mood which will lead to depression. Since 1985 clinically induce vagus nerve stimulation has been used. Zabara showed that electrical stimulation from the vagus nerve inhibited neural activity and suppressed seizures in dogs. This implies that this same neural suppression in humans could stop depression. As a result of these findings the FDA has approved therapy for treatment-resistant depression. Vagus nerve stimulation is very invasive. The procedure involves entering the region where the vagus nerve is and transmitting messages to the brain.Because of this the vagus nerve therapy has been reserved for the severely depressed. The vagus nerve, which innervates the upper gut and proximal colon, has been implicated in anxiety and depression. Ingestion of Lactobacillus rhamnosus induced changes in expression of the inhibitory neurotransmitter GABA1b in neurons, associated with reduced levels of corticosteroids and reduced anxious and depressive behaviors. Remarkably, these changes could be blocked by vagotomy. These are all symptoms of a damaged vagus nerve.
The relationship between the vagus nerve and anxiety is well-documented. If the vagus nerve is functioning normally it will fight the sympathetic, fight-or-flight response. But if the vagus nerve is damaged then the sympathetic response is unopposed which leads to hyperarousal, anxiety, insomnia, increased heart rate and decreased rest. Normal vagus nerve activity is needed to keep the fight-or-flight response in check.
Bradycardia is when the heartbeat slows way down below normal levels. This is due to too much vagus nerve activity. This is when the vagus nerve will start to function abnormally. Simply put bradycardia occurs when the heart beats at a rate of below 60 beats per minute. If this should happen it could be fatal so seek medical intervention quickly. Decreased heart rate can lead to syncope or the temporary loss of consciousness. Bradycardia causes inadequate cardiac output, and poor brain perfusion, leading a syncopal episode (fainting).
Difficulty in Swallowing
The main motor distinction of the vagus nerve is the recurrent laryngeal nerve. This nerve key for producing vocal cord adduction during bolus (food) passage and makes possible glottic closure during the cough reflex. If this nerve is damaged it could lead o vocal cord paralysis which could quickly end a singer’s career. The symptoms include:
- dysphagia – difficulty or discomfort swallowing
- weak voice
- poor cough
Vagal nerve injury at or near the skull base produces pharyngeal motor delays and a laryngopharyngeal sensory deficit which increases the risk of aspiration.
Aspiration is the entry of material from the oropharynx or gastrointestinal tract into the voice box and lower respiratory tract.
Gastric deleting Dysfunction
Gastroparesis, also known as delayed gastric emptying, can be rooted in a damaged or compromised under active vagus nerve. The vagus nerve assists in coordinating peristalsis. Peristalsis is the contraction and relaxation of the muscles of the intestine, which creates wavelike movements that push food forward.As was mentioned before.
The symptoms of delayed gastric emptying include:
- stomach pains
- spasms in the stomach
- weight loss
These are some very unpleasant symptoms that we want to avoid. At the first sign of any of these symptoms visit your doctor as quickly as you can.
This is a little-known symptom. Syncope is a quick but complete loss of consciousness. In other words the person will pass out suddenly. It is followed by a prompt and complete recovery which is a very positive fact. The cause of vasovagal syncope (damaged vagus nerve) is characterized by a reflex activation triggering a rapid decrease in heart rate and reduction in vascular tone In the first moments of a vasovagal syncope an empty heart is seen via echocardiography because of the loss of preload (‘empty heart’ syndrome). This is a serious symptom of a damaged vagus nerve. If the person doesn’t wake up promptly this could lead to extensive brain damage and it could be fatal.
Bye Bye to B12
If the part of the vagus nerve is surgically removed it will lead to a B12 deficiency. The following reason why: The vagus nerve routinely activates parietal cells in the stomach to secrete acid and intrinsic factor. This allows for the normal production of B12 in the body. Intrinsic factor is vital to the absorption of vitamin B12. Vagotomy ( partially removing the vagus nerve surgically) reduces intrinsic factor secretion, which inhibits vitamin B12 absorption. Vitamin B12 deficiency – if untreated – results in nerve damage, dementia, and death. Dementia is a serious byproduct of a dysfunctional vagus nerve.
Chronic inflammatory supposedly is a nebulous term used by people who really don’t know what it means according to one expert. But there is really no other way to put it if the vagus nerve becomes damaged. Supposedly local inflammatory in healthy individuals will correct itself promptly. People with a dysfunctional vagus nerve have quite the different reaction to inflammation activation. The following quote defines the reaction of the person with a damaged vagus nerve.
“But the innate immune response can become disrupted resulting in continual pro-inflammatory cytokine activity. This state of chronic inflammations underpins a wide range of disease states, including sepsis, rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, and possibly even Alzheimer’s disease.” This means that if inflammation is allowed to progress it could lead to the above mentioned harmful conditions. In some cases it could be fatal.
The following is an explanation of what happens when a cough is impaired by a dysfunctional vagus nerve: “Afferent nerve endings richly innervate the pharynx, larynx, and airways to the level of the terminal bronchioles and extend into the lung parenchyma. They may also be located in the external auditory meatus (the auricular branch of the vagus nerve, or the Arnold nerve) and in the esophagus. Sensory signals travel via the vagus (inhibited if the vagus nerve is damaged) and superior laryngeal nerves to a region of the brainstem in the nucleus tractus solitarius vaguely identified as the “cough center.” (These sensory signals will not reach the “cough center” if they don’t have a clear pathway through the vagus nerve.) The cough reflex involves a highly orchestrated series of involuntary muscular actions,(which are immobilized if the sensory signal doesn’t reach this area to activate these involuntary muscular actions) with the potential for input from cortical pathways as well. The vocal cords adduct, leading to transient upper-airway occlusion. Expiratory muscles contract, generating positive intrathoracic pressures as high as 300 mmHg. With sudden release of the laryngeal contraction, rapid expiratory flows are generated.” (These flows will not be generated if the vagus nerve is damaged preventing the whole coughing mechanism to take place.)
The first clinical use of vagus nerve stimulation was for refractory epilepsy. How exactly vagus nerve stimulation terminates seizures is not well understood, but some hypotheses have been developed. Here are three theories that attempt to explain why vagus nerve stimulation suppresses convulsions:
- Synchronization theory. Cervical vagus nerve stimulation induces EEG desynchronization. Desynchronization of overly synchronized neuronal activity may confer antiepileptic effects.
- Neurotransmitter theory. Krahl et al. found that lesioning hte locus ceruleus prevents the anticonvulsant effects of vagus nerve stimulation. Depleting norepinephrine in the brain also eliminates the anti-seizure effects of the vagus nerve stimulation. Finally, Ben-Menachem et al. observed increased GABA and decreased glutamate following vagus nerve stimulation.
- Cerebral blood flow theory. Henry showed that vagus nerve stimulation alters blood flow to numerous brain regions and may activate inhibitory structures in the brain. Excess vagus nerve activity induces fainting (syncope); this hypothesis is an extension of that observation.
The above theories attempt to explain how vagus stimulation may stop seizures but this technology is not completely understood.
Remedies for Vagus Nerve Dysfunction
- Exercising the pharynx
- Surgically removing the vagus nerve
- Partially removing the vagus nerve
- Re-aligning the vagus nerve by a chiropractor
- Exercise the soft palate
- A combination of vocalizations, breathing techniques and movements, the exercises could activate the vagus nerves, helping to alleviate some of the symptoms.
The symptoms of vagus nerve dysfunction are varied and widespread. They can appear in the body totally unexpected and some of them are minor while others could be very serious. It seems like not a lot of doctors are familiar with this condition or its symptoms. Which could lead to the conclusion they may not know how to treat it. But it is a real condition that affects a lot of the parts and organs of the body. Some of the symptoms of vagus nerve dysfunction could be fatal.