Editing Vagus nerve

{{Short description|Main nerve of the parasympathetic nervous system}}
{{Use dmy dates|date=December 2024}}
{{Infobox nerve
| Name        = Vagus nerve
| Latin       = nervus vagus
| Image       = Gray791.png
| Caption     = Plan of the upper portions of the [[glossopharyngeal nerve|glossopharyngeal]], vagus, and [[accessory nerve]]s.
| Image2      = Gray793.png
| Caption2    = Course and distribution of the [[glossopharyngeal nerve|glossopharyngeal]], vagus, and [[accessory nerve]]s.
| Innervates  = [[Levator veli palatini]], [[Salpingopharyngeus muscle|salpingopharyngeus]], [[Palatoglossus muscle|palatoglossus]], [[Palatopharyngeus muscle|palatopharyngeus]], [[superior pharyngeal constrictor]], [[middle pharyngeal constrictor]], [[Inferior pharyngeal constrictor muscle|inferior pharyngeal constrictor]], [[Organ (biology)#Viscera|viscera]]
| BranchFrom  =
| BranchTo    =
}}
The '''vagus nerve''', also known as the tenth [[Cranial nerves|cranial nerve]] (CN X), plays a crucial role in the [[autonomic nervous system]], which is responsible for regulating involuntary functions within the human body. This nerve carries both sensory and motor fibers and serves as a major pathway that connects the brain to various organs, including the heart, lungs, and digestive tract. As a key part of the [[parasympathetic nervous system]], the vagus nerve helps regulate essential involuntary functions like heart rate, breathing, and digestion. By controlling these processes, the vagus nerve contributes to the body's "rest and digest" response, helping to calm the body after stress, lower heart rate, improve digestion, and maintain homeostasis.  

The vagus nerve consists of two branches: the right and left vagus nerves. In the neck, the right vagus nerve contains approximately 105,000 fibers, while the left vagus nerve has about 87,000 fibers, according to one source. However, other sources report slightly different figures, with around 25,000 fibers in the right vagus nerve and 23,000 fibers in the left.<ref>{{Cite journal |last1=Hoffman |first1=Henry Harland |last2=Schnitzlein |first2=Harold Norman |date=March 1961 |title=The numbers of nerve fibers in the vagus nerve of man |url=https://onlinelibrary.wiley.com/doi/10.1002/ar.1091390312 |journal=The Anatomical Record |language=en |volume=139 |issue=3 |pages=429–435 |doi=10.1002/ar.1091390312 |pmid=13963923 |issn=0003-276X}}</ref><ref>{{Cite journal |last1=Neuhuber |first1=Winfried L. |last2=Berthoud |first2=Hans-Rudolf |date=2022-10-01 |title=Functional anatomy of the vagus system: How does the polyvagal theory comply? |url=https://linkinghub.elsevier.com/retrieve/pii/S0301051122001685 |journal=Biological Psychology |volume=174 |pages=108425 |doi=10.1016/j.biopsycho.2022.108425 |pmid=36100134 |issn=0301-0511}}</ref>

The vagus nerve is the longest nerve of the [[autonomic nervous system]] in the human body, consisting of both sensory and motor fibers. The sensory fibers originate from the [[jugular ganglion|jugular]] and [[nodose ganglion]], while the motor fibers are derived from neurons in the dorsal motor nucleus of the vagus and the [[nucleus ambiguus]].<ref name="Walker">{{cite book |title=Clinical Methods: The History, Physical, and Laboratory Examinations. |vauthors=Walker HK |publisher=Butterworths |year=1990 |isbn=9780409900774 |edition=3rd |chapter=Cranial Nerve XI: The Spinal Accessory Nerve |pmid=21250228 |access-date=2019-05-30 |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK387/ |via=NCBI Bookshelf}}</ref> Historically, the vagus nerve was also known as the pneumogastric nerve, reflecting its role in regulating both the lungs and digestive system.

== Structure ==
Upon leaving the [[medulla oblongata]] between the [[Olivary body|olive]] and the [[inferior cerebellar peduncle]], the vagus nerve extends through the [[jugular foramen]], then passes into the [[carotid sheath]] between the [[internal carotid artery]] and the [[internal jugular vein]] down to the [[neck]], [[chest]], and [[abdomen]], where it contributes to the innervation of the [[viscera]], reaching all the way to the [[Large intestine|colon]]. Besides giving some output to various organs, the vagus nerve comprises between 80% and 90% of [[afferent nerve fiber]]s conveying [[sense|sensory]] information about the state of the body's organs to the [[central nervous system]].<ref>{{cite journal|vauthors=Berthoud HR, Neuhuber WL|title=Functional and chemical anatomy of the afferent vagal system|journal=Autonomic Neuroscience|volume=85|issue=1–3|pages=1–17|date=December 2000|pmid=11189015|doi=10.1016/S1566-0702(00)00215-0|s2cid=30221339}}</ref>

The right and left vagus nerves descend from the cranial vault through the jugular foramina,<ref>{{Cite journal|last1=Freitas|first1=Carlos Alberto Ferreira de|last2=Santos|first2=Luiz Roberto Medina Dos|last3=Santos|first3=Andreza Negreli|last4=Amaral Neto|first4=Augusto Barreto do|last5=Brandão|first5=Lenine Garcia|date=2020|title=Anatomical study of jugular foramen in the neck|journal=Brazilian Journal of Otorhinolaryngology|volume=86|issue=1|pages=44–48|doi=10.1016/j.bjorl.2018.09.004|issn=1808-8686|pmc=9422587|pmid=30348503}}</ref> penetrating the carotid sheath between the internal and external carotid arteries, then passing posterolateral to the common carotid artery. The cell bodies of [[General visceral afferent fibers|visceral afferent]] fibers of the vagus nerve are located bilaterally in the [[Inferior ganglion of vagus nerve|inferior ganglion of the vagus nerve]] (nodose ganglia).The vagus runs parallel to the common carotid artery and internal jugular vein inside the carotid sheath.  

[[File:Slide6rom.JPG|thumb|Vagus nerve]]

[[File:Slide1EBA.JPG|thumb|Vagus nerve]]

'''Right Vagus Nerve:''' The right vagus nerve gives rise to the right [[recurrent laryngeal nerve]], which hooks around the right [[subclavian artery]] and ascends into the neck between the [[trachea]] and [[esophagus]]. The right vagus then crosses anterior to the right subclavian artery, runs posterior to the [[superior vena cava]], descends posterior to the [[right main bronchus]], and contributes to [[cardiac plexus|cardiac]], [[pulmonary plexus|pulmonary]], and [[esophageal plexus]]es.  It forms the [[posterior vagal trunk]] at the lower part of the esophagus and passes through the [[thoracic diaphragm|diaphragm]]  to enter the abdomen through the [[esophageal hiatus]].

'''Left Vagus Nerve:''' The left vagus nerve enters the [[thorax]] between [[left common carotid artery]] and left [[subclavian artery]] and descends on the [[aortic arch]].  It gives rise to the left [[recurrent laryngeal nerve]], which hooks around the [[aortic arch]] to the left of the [[ligamentum arteriosum]] and ascends between the trachea and esophagus. The left vagus further gives off thoracic cardiac branches, breaks up into the [[pulmonary plexus]], continues into the esophageal plexus, and enters the abdomen as the [[anterior vagal trunk]] by way of the esophageal hiatus of the diaphragm.

===Branches===
* [[Pharyngeal branch of vagus nerve|Pharyngeal nerve]]
* [[Superior laryngeal nerve]]
* [[Aortic nerve]]
* [[Superior cervical cardiac branches of vagus nerve]]
* [[Inferior cervical cardiac branch]]
* [[Recurrent laryngeal nerve]]
* [[Cardiac branches of the vagus nerve|Thoracic cardiac branches]]
* Branches to the [[pulmonary plexus]]
* Branches to the [[esophageal plexus]]
* [[Anterior vagal trunk]]
* [[Posterior vagal trunk]]

===Nuclei===
The vagus nerve includes [[axon]]s which emerge from or converge onto four [[cranial nerve nucleus|nuclei]] of the medulla:
# The [[dorsal nucleus of vagus nerve]]  – sends [[parasympathetic nervous system|parasympathetic]] output to the viscera, especially the intestines
# The [[nucleus ambiguus]] – gives rise to the branchial efferent motor fibers of the vagus nerve and preganglionic parasympathetic neurons that innervate the heart
# The [[solitary nucleus]] – receives afferent taste information and primary afferents from visceral organs
# The [[spinal trigeminal nucleus]] – receives information about deep/crude touch, pain, and temperature of the outer ear, the [[dura mater|dura]] of the [[posterior cranial fossa]] and the mucosa of the larynx

==Development==
The [[motor system|motor]] division of the glossopharyngeal nerve is derived from the [[Basal plate (neural tube)|basal plate]] of the [[embryo]]nic [[medulla oblongata]], while the [[sensory system|sensory]] division originates from the [[cranial neural crest]].<ref>{{cite book|doi=10.1016/B978-0-12-821736-8.00024-8|chapter=Embryology|title=Epidemiology of Brain and Spinal Tumors|date=2021|last1=Moini|first1=Jahangir|last2=Avgeropoulos|first2=Nicholas G.|last3=Samsam|first3=Mohtashem|pages=65–79|isbn=978-0-12-821736-8}}</ref> The development of the vagus nerve begins early in embryonic life, around the third to fourth week of gestation. It forms from two key structures: [[neural crest]] cells, which contribute to its sensory components, and the [[neural tube]], which forms its motor components in the brainstem (specifically in the [[medulla oblongata]]). By weeks 4 to 5, the vagus nerve begins to connect with the fourth and sixth [[Pharyngeal arch|pharyngeal arches]], which give rise to muscles involved in swallowing and speaking. Around weeks 5 to 6, specialized nuclei in the brainstem develop to manage the nerve’s motor and sensory functions.<ref>{{Cite journal |last1=Ratcliffe |first1=E. M. |last2=Farrar |first2=N. R. |last3=Fox |first3=E. A. |date=October 2011 |title=Development of the vagal innervation of the gut: steering the wandering nerve |journal=Neurogastroenterology and Motility |volume=23 |issue=10 |pages=898–911 |doi=10.1111/j.1365-2982.2011.01764.x |issn=1365-2982 |pmc=3173572 |pmid=21851506}}</ref> These centers are essential for regulating vital automatic processes like breathing, digestion, and heart rate. Between weeks 6 and 9, the vagus nerve extends its branches to various organs, including the heart, lungs, and gastrointestinal tract, as well as sensory areas like the ear and throat.<ref>{{Cite journal |last1=Cerritelli |first1=Francesco |last2=Frasch |first2=Martin G. |last3=Antonelli |first3=Marta C. |last4=Viglione |first4=Chiara |last5=Vecchi |first5=Stefano |last6=Chiera |first6=Marco |last7=Manzotti |first7=Andrea |date=2021-09-20 |title=A Review on the Vagus Nerve and Autonomic Nervous System During Fetal Development: Searching for Critical Windows |journal=Frontiers in Neuroscience |language=English |volume=15 |doi=10.3389/fnins.2021.721605 |doi-access=free |pmid=34616274 |pmc=8488382 |issn=1662-453X}}</ref> As the [[fetus]] grows, the vagus nerve matures into a crucial part of the parasympathetic nervous system, helping maintain the body's internal balance. This process shows how a single nerve can become so important for multiple systems in the body.<ref>{{Citation |last1=Kuwar Chhetri |first1=Parvat |title=Neuroanatomy, Neural Tube Development and Stages |date=2025 |work=StatPearls |url=https://www.ncbi.nlm.nih.gov/books/NBK557414/ |access-date=2025-04-14 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=32491346 |last2=Das |first2=Joe M.}}</ref>

== Function ==
The vagus nerve supplies motor [[parasympathetic]] fibers to all the organs (except the [[adrenal]] glands) from the [[neck]] down to the second segment of the [[transverse colon]]. The vagus also controls a few [[skeletal muscle]]s, including:
* [[Cricothyroid muscle]]
* [[Levator veli palatini muscle]]
* [[Salpingopharyngeus muscle]]
* [[Palatoglossus muscle]]
* [[Palatopharyngeus muscle]]
* Superior, middle and inferior [[pharyngeal constrictor]]s
* Muscles of the [[larynx]] ([[Speech communication|speech]]).

This means that the vagus nerve is responsible for such varied tasks as [[heart rate]], gastrointestinal [[peristalsis]], [[sweating]], and quite a few muscle movements in the mouth, including [[Speech communication|speech]] (via the [[recurrent laryngeal nerve]]). It also has some afferent fibers that innervate the inner (canal) portion of the [[outer ear]] (via the auricular branch, also known as [[Auricular branch of vagus nerve|Arnold's or Alderman's nerve]]) and part of the [[meninges]].<ref>{{cite book|vauthors=Eljamel S|title=Problem Based Neurosurgery|page=66|doi=10.1142/7830|year=2011|isbn=978-981-4317-07-8|s2cid=78277439}}</ref> The vagus nerve is also responsible for regulating inflammation in the body, via the [[inflammatory reflex]].<ref name="Forbes 2023">{{cite web|last1=Haseltine|first1=William|title=Electrically Stimulating The Vagus Nerve May Be Able To Reverse Chronic Inflammation|url=https://www.forbes.com/sites/williamhaseltine/2023/06/29/electrically-stimulating-the-vagus-nerve-may-be-able-to-reverse-chronic-inflammation/?sh=7688f3eb5001|website=Forbes|access-date=26 October 2023}}</ref>

[[Efferent nerve fiber|Efferent]] vagus nerve fibers innervating the pharynx and back of the throat are responsible for the [[gag reflex]]. In addition, [[5-HT3 receptor|5-HT<sub>3</sub> receptor]]-mediated afferent vagus stimulation in the gut due to [[gastroenteritis]] is a cause of [[vomiting]].<ref>{{cite web|vauthors=Mandal A|title=Vomiting Mechanism|url=http://www.news-medical.net/health/Vomiting-Mechanism.aspx|website=News Medical|access-date=27 June 2015|archive-url=https://web.archive.org/web/20150104162002/http://www.news-medical.net/health/Vomiting-Mechanism.aspx|archive-date=4 January 2015|date=25 September 2013}}</ref> Stimulation of the vagus nerve in the [[Cervix|cervix uteri]] (as in some medical procedures) can lead to a [[vasovagal response]].

The vagus nerve also plays a role in satiation following food consumption.<ref name="pmid18482776">{{cite journal|vauthors=Berthoud HR|title=The vagus nerve, food intake and obesity|journal=Regulatory Peptides|volume=149|issue=1–3|pages=15–25|date=August 2008|pmid=18482776|pmc=2597723|doi=10.1016/j.regpep.2007.08.024}}</ref> Knocking out vagal nerve receptors has been shown to cause [[Polyphagia|hyperphagia]] (greatly increased food intake).<ref name="pmid25161883 ">{{cite journal|vauthors=de Lartigue G, Ronveaux CC, Raybould HE|title=Deletion of leptin signaling in vagal afferent neurons results in hyperphagia and obesity|journal=Molecular Metabolism|volume=3|issue=6|pages=595–607|date=September 2014|pmid=25161883|pmc=4142400|doi=10.1016/j.molmet.2014.06.003}}</ref> Neuroscientist [[Ivan De Araujo]] and colleagues have shown that the vagus nerve transmits reward signals from the body to the brain,<ref name="pmid23950538">{{cite journal|vauthors=Tellez LA, Medina S, Han W, Ferreira JG, Licona-Limón P, Ren X, Lam TT, Schwartz GJ, de Araujo IE|title=A gut lipid messenger links excess dietary fat to dopamine deficiency|journal=Science|volume=341|issue=6147|pages=800–2|date=August 2013|pmid=23950538|doi=10.1126/science.1239275|bibcode=2013Sci...341..800T|s2cid=38293563}}</ref><ref name="pmid30245012">{{cite journal|vauthors=Han W, Tellez LA, Perkins MH, Perez IO, Qu T, Ferreira J, Ferreira TL, Quinn D, Liu ZW, Gao XB, Kaelberer MM, Bohórquez DV, Shammah-Lagnado SJ, de Lartigue G, de Araujo IE|title=A Neural Circuit for Gut-Induced Reward|journal=Cell|volume=175|issue=3|pages=665–678.e23|date=October 2018|pmid=30245012|pmc=6195474|doi=10.1016/j.cell.2018.08.049}}</ref> potentially explaining how stimulation of the nerve leads to emotional changes.

=== Cardiac effects ===
[[File:Sinoatrial node high mag.jpg|thumb|[[H&E stain]]ed fibers of the vagus nerve (bottom right) innervate the [[sinoatrial node]] tissue (middle left)]]

Parasympathetic innervation of the heart is partially controlled by the vagus nerve and is shared by the [[thoracic ganglia]]. Vagal and spinal ganglionic nerves mediate the lowering of the [[heart rate]]. The right vagus branch innervates the [[sinoatrial node]]. In healthy people, parasympathetic tone from these sources is well-matched to sympathetic tone. Hyperstimulation of parasympathetic influence promotes [[bradyarrhythmias]]. When hyperstimulated, the left vagal branch predisposes the heart to [[heart block|conduction block]] at the [[atrioventricular node]].

At this location, neuroscientist [[Otto Loewi]] first demonstrated that nerves secrete substances called [[neurotransmitters]], which have effects on receptors in target tissues. In his experiment, Loewi electrically stimulated the vagus nerve of a frog heart, which slowed the heart. Then he took the fluid from the heart and transferred it to a second frog heart without a vagus nerve. The second heart slowed without electrical stimulation. Loewi described the substance released by the vagus nerve as [[vagusstoff]], which was later found to be [[acetylcholine]]. 

Drugs that inhibit the [[muscarinic receptor]]s ([[anticholinergic]]s) such as [[atropine]] and [[Hyoscine hydrobromide|scopolamine]], are called vagolytic because they inhibit the action of the vagus nerve on the heart, gastrointestinal tract, and other organs.  Anticholinergic drugs increase heart rate and are used to treat [[bradycardia]].

=== Urogenital and hormonal effects ===
Excessive activation of the vagal nerve during [[emotional stress]], which is a parasympathetic overcompensation for a strong [[sympathetic nervous system]] response associated with stress, can also cause [[Reflex syncope|vasovagal syncope]] due to a sudden drop in [[cardiac output]], causing [[Brain ischemia|cerebral hypoperfusion]]. Vasovagal syncope affects young children and women more than other groups. It can also lead to temporary [[urinary incontinence|loss of bladder control]] under moments of extreme fear.

Research has shown that women having had complete [[spinal cord injury]] can experience [[orgasm]]s through the vagus nerve, which can go from the [[uterus]] and [[cervix]] to the brain.<ref>{{cite magazine|url=http://archive.wired.com/medtech/health/news/2007/01/72325|magazine=Wired|title=Exploring the Mind-Body Orgasm|date=2007-01-10|url-status=live|archive-url=https://web.archive.org/web/20150919100602/http://archive.wired.com/medtech/health/news/2007/01/72325|archive-date=19 September 2015}}</ref><ref>{{cite journal|vauthors=Komisaruk BR, Whipple B, Crawford A, Liu WC, Kalnin A, Mosier K|title=Brain activation during vaginocervical self-stimulation and orgasm in women with complete spinal cord injury: fMRI evidence of mediation by the vagus nerves|journal=Brain Research|volume=1024|issue=1–2|pages=77–88|date=October 2004|pmid=15451368|doi=10.1016/j.brainres.2004.07.029|author2-link=Beverly Whipple|s2cid=9202518|author1-link=Barry Komisaruk}}</ref>

[[Insulin]] signaling activates the [[adenosine triphosphate]] (ATP)-sensitive potassium (KATP) channels in the [[arcuate nucleus]], decreases AgRP release, and through the vagus nerve, leads to decreased glucose production by the liver by decreasing gluconeogenic enzymes: [[phosphoenolpyruvate carboxykinase]], [[glucose 6-phosphatase]].<ref>{{cite journal|vauthors=Pocai A, Lam TK, Gutierrez-Juarez R, Obici S, Schwartz GJ, Bryan J, Aguilar-Bryan L, Rossetti L|display-authors=6|title=Hypothalamic K(ATP) channels control hepatic glucose production|journal=Nature|volume=434|issue=7036|pages=1026–1031|date=April 2005|pmid=15846348|doi=10.1038/nature03439|s2cid=4414624|bibcode=2005Natur.434.1026P}}</ref><ref>{{cite journal|vauthors=Pagotto U|title=Where does insulin resistance start? The brain|journal=Diabetes Care|volume=32|issue=Suppl 2|pages=S174–S177|date=November 2009|pmid=19875547|pmc=2811464|doi=10.2337/dc09-S305}}</ref>

==Clinical significance==
===Stimulation===
{{Main|Vagus nerve stimulation}}
{{update|section|date=January 2023}}
[[Vagus nerve stimulation]] (VNS) therapy via a [[Neurostimulation|neurostimulator]] implanted in the chest has been used to control [[seizure]]s in [[epilepsy]] patients and has been approved for treating drug-resistant [[clinical depression]].<ref>{{cite journal|vauthors=Nemeroff CB, Mayberg HS, Krahl SE, McNamara J, Frazer A, Henry TR, George MS, Charney DS, Brannan SK|display-authors=6|title=VNS therapy in treatment-resistant depression: clinical evidence and putative neurobiological mechanisms|journal=Neuropsychopharmacology|volume=31|issue=7|pages=1345–1355|date=July 2006|pmid=16641939|doi=10.1038/sj.npp.1301082|doi-access=free}}</ref> Several noninvasive VNS devices that stimulate an afferent branch of the vagus nerve are available. GammaCore is recommended by [[National Institute for Health and Care Excellence|The National Institute for Health and Care Excellence (NICE)]] for cluster headaches.<ref>{{cite journal|last1=O’Connell|first1=Susan|last2=Dale|first2=Megan|last3=Morgan|first3=Helen|last4=Carter|first4=Kimberley|last5=Morris|first5=Rhys|last6=Carolan-Rees|first6=Grace|title=gammaCore for Cluster Headaches: A NICE Medical Technologies Guidance|journal=PharmacoEconomics – Open|date=December 2021|volume=5|issue=4|pages=577–586|doi=10.1007/s41669-021-00276-5|pmid=34322861|pmc=8611122}}</ref>

VNS may also be achieved by one of the ''[[vagal maneuver]]s'': holding the breath for 20 to 60&nbsp;seconds, dipping the face in cold water, coughing, humming or singing, or tensing the stomach muscles as if to bear down to have a bowel movement.<ref name="vagal">{{cite web|vauthors=Davis, MD CP|veditors=Shiel Jr WC|title=Supraventricular Tachycardia|website=eMedicineHealth.com|date=2005-08-22|url=http://www.emedicinehealth.com/supraventricular_tachycardia/page7_em.htm|access-date=2008-11-28|url-status=live|archive-url=https://web.archive.org/web/20081216084703/http://www.emedicinehealth.com/supraventricular_tachycardia/page7_em.htm|archive-date=16 December 2008}}</ref> Patients with [[supraventricular tachycardia]],<ref name="vagal"/> [[atrial fibrillation]], and other illnesses may be trained to perform vagal maneuvers (or find one or more on their own).{{cn|date=January 2023}}

Vagus nerve blocking (VBLOC) therapy is similar to VNS but used only during the day. In a six-month [[open-label trial]] involving three medical centers in Australia, Mexico, and Norway, vagus nerve blocking helped 31&nbsp;obese participants lose an average of nearly 15&nbsp;percent of their excess weight. {{As of | 2008}}, a yearlong [[Blind experiment#Double-blind trials|double-blind]], [[Clinical trial#Phase II|phase&nbsp;II]] trial had begun.<ref>
{{cite press release|url=http://www.mayoclinic.org/news2008-rst/4892.html|publisher=Mayo Clinic|title=Device blocking stomach nerve signals shows promise in obesity|archive-url=https://web.archive.org/web/20090308033402/http://www.mayoclinic.org/news2008-rst/4892.html|archive-date=8 March 2009|quote=Dr. Camilleri says a follow-up double-blinded study, which will involve up to 300&nbsp;patients at multiple medical centers including a limited number from Mayo Clinic, will be important for gauging the device's true effectiveness.}}</ref>

===Vagotomy===
[[Vagotomy]] (cutting of the vagus nerve) is a now obsolete therapy that was performed for [[peptic ulcer disease]] and now superseded by oral medications, including H2 antagonists, proton pump inhibitors and antibiotics. Vagotomy is currently being researched as a less invasive alternative weight-loss procedure to [[gastric bypass surgery]].<ref>{{cite web|url=http://www.nbcnews.com/id/19563617|archive-url=https://web.archive.org/web/20131215043341/http://www.nbcnews.com/id/19563617/|url-status=dead|archive-date=15 December 2013|title=Ulcer surgery may help treat obesity – Diet and nutrition|publisher=NBC News}}</ref> The procedure curbs the feeling of hunger and is sometimes performed in conjunction with putting bands on patients' stomachs, resulting in an average of 43% of excess weight loss at six months with diet and exercise.<ref>{{Cite news|title=Could nerve-snip spur weight loss?|url=http://www.cnn.com/2007/HEALTH/conditions/07/09/obesity.nerve.ap/index.html|archive-url=https://web.archive.org/web/20070713084325/http://www.cnn.com/2007/HEALTH/conditions/07/09/obesity.nerve.ap/index.html|archive-date=2007-07-13|url-status=dead|publisher=CNN}}</ref>

One serious side effect of vagotomy is a [[Vitamin B12|vitamin B<sub>12</sub>]] deficiency later in life – perhaps after about 10 years – that is similar to [[pernicious anemia]]. The vagus normally stimulates the stomach's [[parietal cell]]s to secrete acid and intrinsic factor. [[Intrinsic factor]] is needed to absorb vitamin B<sub>12</sub> from food. The vagotomy reduces this secretion and ultimately leads to deficiency, which, if left untreated, causes nerve damage, tiredness, dementia, paranoia, and ultimately death.<ref>{{cite web|url=http://www.pernicious-anaemia-society.org|title=The Pernicious Anemia Society|archive-url=https://web.archive.org/web/20100724201702/http://www.pernicious-anaemia-society.org/|archive-date=24 July 2010}}</ref>

Researchers from [[Aarhus University]] and Aarhus University Hospital have demonstrated that vagotomy prevents (halves the risk of) the development of [[Parkinson's disease]], suggesting that Parkinson's disease begins in the gastrointestinal tract and spreads via the vagus nerve to the brain.<ref>{{cite web|url=http://medicalxpress.com/news/2015-06-parkinson-disease-gut.html|title=Parkinson's disease may begin in the gut.|author=Aarhus University|publisher=Medical Xpress|archive-url=https://web.archive.org/web/20150627170446/http://medicalxpress.com/news/2015-06-parkinson-disease-gut.html|archive-date=27 June 2015}}</ref> Or giving further evidence to the theory that dysregulated environmental stimuli, such as that received by the vagus nerve from the gut, may have a negative effect on the dopamine reward system of the [[substantia nigra]], thereby causing Parkinson's disease.<ref>{{cite journal|vauthors=Liu B, Fang F, Pedersen NL, Tillander A, Ludvigsson JF, Ekbom A, Svenningsson P, Chen H, Wirdefeldt K|display-authors=6|title=Vagotomy and Parkinson disease: A Swedish register-based matched-cohort study|journal=Neurology|volume=88|issue=21|pages=1996–2002|date=May 2017|pmid=28446653|pmc=5440238|doi=10.1212/WNL.0000000000003961}}</ref>

===Vagus nerve pathology===
The sympathetic and parasympathetic components of the autonomic nervous system (ANS) control and regulate the function of various organs, glands, and involuntary muscles throughout the body (e.g., vocalization, swallowing, heart rate, respiration, gastric secretion, and intestinal motility).  Hence, most of the signs and symptoms of vagus nerve dysfunction, apart from vocalisation, are vague and non specific. Laryngeal nerve palsy results in paralysis of an ipsilateral vocal cord and is used as a pointer to diseases affecting the vagus nerve from its origin down to termination of its branch of the laryngeal nerve.

* '''Sensory neuropathy'''

The hypersensitivity of vagal afferent nerves causes refractory or idiopathic cough.

[[Auricular branch of vagus nerve|Arnold's nerve]] ear-cough reflex, though uncommon, is a manifestation of a vagal sensory neuropathy and this is the cause of a refractory chronic cough that can be treated with [[gabapentin]]. The cough is triggered by mechanical stimulation of the external auditory meatus and accompanied by other neuropathic features such as throat irritation (laryngeal paresthesia) and cough triggered by exposure to nontussive triggers such as cold air and eating (termed allotussia). These features suggest a neuropathic origin to the cough.<ref>{{cite journal|vauthors=Ryan NM, Gibson PG, Birring SS|title=Arnold's nerve cough reflex: evidence for chronic cough as a sensory vagal neuropathy|journal=Journal of Thoracic Disease|volume=6|issue=Suppl 7|pages=S748–S752|date=October 2014|pmid=25383210|pmc=4222929|doi=10.3978/j.issn.2072-1439.2014.04.22}}</ref>

* '''Motor neuropathy'''

Pathology of the vagus nerve proximal to the laryngeal nerve typically presents with symptom hoarse voice and physical sign of paralysed vocal cords.  Although a large proportion of these are the result of idiopathic vocal cord palsy but tumours especially lung cancers are next common cause.  Tumours at the apex of right lung and at the hilum of the left lung are the most common oncological causes of vocal cord palsy.  Less common tumours causing vocal cord palsy includes thyroid and proximal oesophageal malignancy.

==History==
===Etymology===
The [[Latin]] word ''vagus'' means literally "wandering" (the words ''[[vagrancy (people)|vagrant]]'', ''[[vagabond (person)|vagabond]]'', ''[[vague]]'', and [[wikt:divagation|''divagation'']] come from the same root). Sometimes the right and left branches together are spoken of in the plural and are thus called '''vagi''' ({{IPAc-en|ˈ|v|eɪ|dʒ|aɪ}} {{respell|VAY|jy}}).  The vagus was also historically called the ''pneumogastric'' nerve since it innervates both the lungs and the stomach.

== Additional illustrations ==
<gallery>
File:Brain human normal inferior view with labels en.svg|Inferior view of the human brain, with the cranial nerves labeled.
File:Gray384.png|Section of the neck at about the level of the sixth cervical vertebra
File:Gray503.png|Transverse section of thorax, showing relations of pulmonary artery
File:Gray505.png|The arch of the aorta, and its branches
File:Gray567.png|Dura mater and its processes exposed by removing part of the right half of the skull, and the brain
File:Gray622.png|The tracheobronchial lymph glands
File:Gray694.png|Section of the medulla oblongata at about the middle of the olive
File:Gray719.png|Hind- and mid-brains; postero-lateral view
File:Gray792.png|Upper part of medulla spinalis and hind- and mid-brains; posterior aspect, exposed in situ
File:Gray838.png|The right sympathetic chain and its connections with the thoracic, abdominal, and pelvic plexuses
File:Gray848.png|The celiac ganglia with the sympathetic plexuses of the abdominal viscera radiating from the ganglia
File:Gray1032.png|The position and relation of the esophagus in the cervical region and in the posterior mediastinum, seen from behind
File:Gray1174.png|The thyroid gland and its relations
File:Gray1178.png|The thymus of a full-term fetus, exposed in situ
File:Internal carotid artery.jpg|Vagus nerve – dissection
</gallery>

== See also ==
{{Anatomy-terms}}
* [[Porphyria]] – A rare disorder can cause seizures and damage to the vagal nerve.
* [[Vagovagal reflex]]
* [[Inflammatory reflex]]
* [[Vagus ganglion]]
* [[Vagus nerve stimulation]]
* [[Vagusstoff]]
* [[Polyvagal theory]]
* [[Gastroparesis]]
* [[Reflex syncope]] – Vasovagal syncope is one of the major types of reflex syncope.

== References ==
{{Reflist}}

== External links ==
{{Commons category|Nervus vagus}}
* {{LoyolaMedEd|grossanatomy/h_n/cn/cn1/cn10.htm}}
* {{cite web|url=http://www.yale.edu/cnerves/cn10/cn10_1.html|title=10-1|publisher=[[Yale School of Medicine]]|work=Cranial Nerves|archive-url=https://web.archive.org/web/20160303222022/http://www.yale.edu/cnerves/cn10/cn10_1.html|archive-date=2016-03-03}}
* {{NormanAnatomy|cranialnerves}} ({{NormanAnatomyFig|X}})

{{Cranial nerves}}
{{Authority control}}

{{DEFAULTSORT:Vagus Nerve}}
[[Category:Vagus nerve| ]]
[[Category:Cranial nerves]]
[[Category:Autonomic nervous system]]
[[Category:Thorax (human anatomy)]]
[[Category:Abdomen]]
[[Category:Gustatory system]]
[[Category:Human head and neck]]
[[Category:Nervous system]]
[[Category:Nerves of the head and neck]]
[[Category:Innervation of the tongue]]