Editing Vagus nerve (section)

==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.