View source for Recurrent laryngeal nerve

{{short description|Nerve in the human body}}
{{redirect|Recurrent nerve|the supply to the [[thenar eminence]]|recurrent branch of the median nerve}}
{{good article}}

{{Infobox Nerve
| Name = Recurrent laryngeal nerve
| Latin = nervus laryngeus recurrens
| Image = Recurrent laryngeal nerve.svg
| Caption = Course of the left recurrent laryngeal nerve
| Alt = A diagram showing the recurrent laryngeal nerve
| Image2 = Gray622.png
| Caption2 = Posterior view of [[Vertebrate trachea|tracheal]] and [[bronchus|bronchial]] lymph glands, with the left and right recurrent nerves visible on either side.
| Alt2 = A diagram showing lymph glands and the recurrent laryngeal nerve
| Innervates = [[Larynx]]<br />[[Posterior cricoarytenoid muscle|posterior cricoarytenoid]] <br />[[Lateral cricoarytenoid muscle|lateral cricoarytenoid]] <br />[[Arytenoid muscle|arytenoid]] <br />[[Thyroarytenoid muscle|thyroarytenoid]] <br />[[Aryepiglottic muscle|aryepiglottis]] <br /> [[esophagus]] <br /> [[heart]]<br /> [[trachea]]<br /> [[inferior pharyngeal constrictor muscle]]
| BranchFrom = [[Vagus nerve]]
| BranchTo = 
}}

The '''recurrent laryngeal nerve''' ('''RLN'''), also known as '''nervus recurrens''', is a branch of the [[vagus nerve]] ([[cranial nerve]] X) that supplies all the [[Larynx#Intrinsic|intrinsic muscles]] of the [[larynx]], with the exception of the [[cricothyroid muscle]]s. There are two recurrent laryngeal nerves, right and left.  The right and left nerves are not symmetrical, with the left nerve looping under the aortic arch, and the right nerve looping under the [[subclavian artery|right subclavian artery]], then traveling upwards. They both travel alongside the trachea. Additionally, the nerves are among the few nerves that follow a ''recurrent'' course, moving in the opposite direction to the nerve they branch from, a fact from which they gain their name.

The recurrent laryngeal nerves supply sensation to the larynx below the vocal cords, give cardiac branches to the [[deep cardiac plexus]], and branch to the trachea, esophagus and the inferior constrictor muscles. The [[posterior cricoarytenoid muscle]]s, the only muscles that can open the vocal folds, are innervated by this nerve.

The recurrent laryngeal nerves are the nerves of the sixth [[pharyngeal arch]]. The existence of the recurrent laryngeal nerve was first documented by the physician [[Galen]].

== Structure ==
[[File:Gray505.png|thumb|right|alt=The vagus nerves and major blood vessels|Passing under the [[subclavian artery]], the right recurrent laryngeal nerve has a much shorter course than the left which passes under the [[aortic arch]] and [[ligamentum arteriosum]].]]

The recurrent laryngeal nerves branch from the [[vagus nerve]], relative to which they get their names; the term "recurrent" from {{langx|la|re-}} (back) and ''currere'' (to run),<ref>{{cite web |url= http://www.merriam-webster.com/dictionary/recur |title= Recur |work= Free Dictionary |publisher= Merriam-Webster |access-date= March 1, 2013 }}</ref> indicates they run in the opposite direction to the vagus nerves from which they branch.<ref>{{cite web |url= http://www.merriam-webster.com/medical/recurrent?show=0&t=1362154002 |title= Recurrent |work= Medical definition and more |publisher= Merriam-Webster |access-date= March 1, 2013 }}</ref> The vagus nerves run down into the thorax, and the recurrent laryngeal nerves run up to the larynx.<ref name=GRAYS2005>{{cite book| vauthors = Drake RL, Vogl W, Mitchell AW |title=Gray's Anatomy for Students |year=2005|publisher=Elsevier/Churchill Livingstone|location=Philadelphia|isbn=978-0-8089-2306-0 }}</ref>{{rp|930–931}}

The vagus nerves, from which the recurrent laryngeal nerves branch, exit the skull at the [[jugular foramen]] and travel within the [[carotid sheath]] alongside the [[carotid artery|carotid arteries]] through the neck. The recurrent laryngeal nerves branch off the vagus, the left at the [[aortic arch]], and the right at the right [[subclavian artery]]. The left RLN passes in front of the arch, and then wraps underneath and behind it. After branching, the nerves typically ascend in a groove at the junction of the [[Vertebrate trachea|trachea]] and [[esophagus]].<ref name=Schwartz9th>{{cite book | vauthors = Brunicardi FC, Brunicardi F, Andersen D, Raphael EP, Billiar T, Dunn D, Hunter J, Matthews J, Pollock RE | display-authors = 6 |title= Schwartz's Principles of Surgery |url= https://books.google.com/books?id=zGVIyHiqL5wC |edition=9th |date= September 11, 2009 |publisher= McGraw Hill Professional |isbn= 978-0-07-154769-7}}</ref>{{rp|1346–1347}} They then pass behind the posterior, middle part of the outer lobes of the [[thyroid gland]] and enter the [[larynx]] underneath the [[inferior constrictor muscle]],<ref name="GRAYS2005"/>{{rp|918}} passing into the larynx just posterior to the cricothyroid joint.<ref>{{cite book|last1=Agur|first1=A. M. R. |last2=Dalley|first2=Arthur F. |title=Grant's Atlas of Anatomy|url=https://books.google.com/books?id=H20V4pCpACYC&pg=PA770|year=2009|publisher=Lippincott Williams & Wilkins|isbn=978-0-7817-7055-2|page=770}}</ref> The terminal branch is called the ''inferior laryngeal nerve''.<ref name="RossLamperti2006">{{cite book|last1=Ross|first1=Lawrence M. |last2=Lamperti|first2=Edward D. |title=Thieme Atlas of Anatomy: Neck and Internal Organs|url=https://books.google.com/books?id=n0jqG0Lv2CAC&pg=PA19|year=2006|publisher=Thieme|isbn=978-1-58890-443-0}}</ref>{{rp|19}}

Unlike the other nerves supplying the larynx, the right and left RLNs lack [[bilateral symmetry]].<ref>{{cite book|last=Aronson|first=Arnold Elvin|title=Clinical Voice Disorders|url=https://books.google.com/books?id=wOhkGWBzG2UC&pg=PA74|year=2009|publisher=Thieme|isbn=978-1-58890-662-5|page=74}}</ref> The left RLN is longer than the right, because it crosses under the [[aortic arch|arch of the aorta]] at the [[ligamentum arteriosum]].<ref name="Schwartz9th"/>{{rp|1346–1347}}

=== Nucleus ===
The [[General somatic efferent fibers|somatic motor fibers]] that innervate the [[laryngeal muscles]], and [[pharyngeal muscles]] are located in the [[nucleus ambiguus]] and emerge from the [[medulla oblongata|medulla]] in the [[Cranial root of accessory nerves | cranial root of the accessory nerve]]. Fibers cross over to and join the vagus nerve in the [[jugular foramen]].<ref name="Shulte2007" />{{rp|86–88}} Sensory cell bodies are located in the [[Inferior ganglion of vagus nerve|inferior jugular ganglion]],<ref name="Alberstone2009">{{cite book|last=Alberstone|first=Cary D.|title=Anatomic Basis of Neurologic Diagnosis|url=https://books.google.com/books?id=7VG1om3OmyUC&pg=PA260|year=2009|publisher=Thieme|isbn=978-0-86577-976-1|pages=260–261}}</ref> and the fibers terminate in the [[solitary nucleus]].<ref name="Shulte2007" />{{rp|86–88}} [[Parasympathetic nervous system|Parasympathetic fibers]] to segments of the trachea and esophagus in the neck originate in the [[Dorsal nucleus of vagus nerve|dorsal nucleus of the vagus nerve]].<ref name="Alberstone2009" />

=== Development ===
During human and all [[vertebrate]] development, a series of [[pharyngeal arch]] pairs form in the developing [[embryo]]. These project forward from the back of the embryo towards the front of the face and neck. Each arch develops its own artery, nerve that controls a distinct muscle group, and skeletal tissue. The arches are numbered from 1 to 6, with 1 being the arch closest to the head of the embryo, and the fifth arch only existing transiently.<ref name = LARSEN1993 />{{rp|318–323}}

Arches 4 and 6 produce the laryngeal cartilages. The nerve of the sixth arch becomes the recurrent laryngeal nerve. The nerve of the fourth arch gives rise to the superior laryngeal nerve. The arteries of the fourth arch, which project between the nerves of the fourth and sixth arches, become the left-sided arch of the aorta and the right subclavian artery. The arteries of the sixth arch persist as the [[ductus arteriosus]] on the left, and are obliterated on the right.<ref name = LARSEN1993 />{{rp|318–323}}

After birth, the ductus arteriosus regresses to form the [[ligamentum arteriosum]]. During growth, these arteries descend into their ultimate positions in the chest, creating the elongated recurrent paths.<ref name=LARSEN1993 >{{cite book |last= Larsen |first= William J. |title=Human embryology |year=1993 |publisher= Churchill Livingstone |url=https://books.google.com/books?id=6KxqAAAAMAAJ |access-date=February 26, 2013 |isbn=0-443-08724-5}}</ref>{{rp|318–323}}

===Variation===
In roughly 1 out of every 100&ndash;200&nbsp;people, the right inferior laryngeal nerve is nonrecurrent, branching off the vagus nerve around the level of the [[cricoid cartilage]]. Typically, such a configuration is accompanied by variation in the arrangement of the major arteries in the chest; most commonly, the right subclavian artery arises from the left side of the aorta and crosses behind the esophagus. A left nonrecurrent inferior laryngeal nerve is even more uncommon, [[situs inversus|requiring the aortic arch be on the right side]], accompanied by an arterial variant which prevents the nerve from being drawn into the chest by the left subclavian.<ref>{{cite book| vauthors = Duh QY, Clark OH, Kebebew E |title=Atlas of Endocrine Surgical Techniques|url=https://books.google.com/books?id=Rf93TdGdC5gC&pg=PA10|access-date=March 6, 2013|date=October 14, 2009|publisher=Elsevier Health Sciences|isbn=978-1-4160-4844-2}}</ref>{{rp|10, 48}}

In about four people out of five, there is a connecting branch between the ''inferior laryngeal nerve'', a branch of the RLN, and the [[internal laryngeal nerve]], a branch of the [[superior laryngeal nerve]]. This is commonly called the ''anastomosis of Galen'' ({{langx|la|ansa galeni}}), even though [[anastomosis]] usually refers to a [[blood vessel]],<ref>{{cite journal | vauthors = Naidu L, Ramsaroop L, Partab P, Satyapal KS | title = Galen's "anastomosis" revisited | journal = Clinical Anatomy | volume = 25 | issue = 6 | pages = 722–728 | date = September 2012 | pmid = 22162120 | doi = 10.1002/ca.22011 | s2cid = 23512491 }}</ref><ref name="Langmore2001">{{cite book| vauthors = Langmore SE |title=Endoscopic Evaluation and Treatment of Swallowing Disorders|url=https://books.google.com/books?id=tWy7yYpzRZoC&pg=PA35|date=January 2001|publisher=Thieme|isbn=978-0-86577-838-2}}</ref>{{rp|35}} and is one of several documented [[anastomoses]] between the two nerves.<ref>{{cite journal | vauthors = Sañudo JR, Maranillo E, León X, Mirapeix RM, Orús C, Quer M | title = An anatomical study of anastomoses between the laryngeal nerves | journal = The Laryngoscope | volume = 109 | issue = 6 | pages = 983–987 | date = June 1999 | pmid = 10369294 | doi = 10.1097/00005537-199906000-00026 | s2cid = 26161510 }}</ref>

As the recurrent nerve hooks around the [[subclavian artery]] or [[aorta]], it gives off several branches. There is suspected variability in the configuration of these branches to the [[cardiac plexus]], trachea, esophagus and [[inferior pharyngeal constrictor muscle]].<ref name="medscape2023"" />

== Function ==
The recurrent laryngeal nerves control all [[Larynx#Intrinsic|intrinsic muscles of the larynx]] except for the [[cricothyroid muscle]].<ref name="medscape2023"/>{{efn|Namely, the [[Posterior cricoarytenoid muscle]]s, [[Lateral cricoarytenoid muscle]]s, [[Transverse arytenoid muscle]]s, [[Oblique arytenoid muscle]]s, [[Thyroarytenoid muscle]]s and [[Vocalis muscle]]}} These muscles act to open, close, and adjust the tension of the vocal cords, and include the [[posterior cricoarytenoid muscle]]s, the only muscle to open the vocal cords.<ref name=HYDMAN2008 />{{rp|10–11}} The nerves supply muscles on the same side of the body, with the exception of the [[interarytenoid muscle]], which is innervated from both sides.<ref name="medscape2023">{{cite web |title=Laryngeal Nerve Anatomy: Introduction, Vagus Nerve (Cranial Nerve X), Superior Laryngeal Nerve |url=https://emedicine.medscape.com/article/1923100-overview |access-date=3 August 2024 |date=28 November 2023}}</ref>

The nerves also carry sensory information from the mucous membranes of the larynx below the lower surface of the [[vocal fold]],<ref name=Moore3rd>{{Cite book|title= Clinically Oriented Anatomy |year= 1992 | vauthors = Moore KL |publisher= Williams & Wilkins |edition= 3rd |isbn= 0-683-06133-X }}</ref>{{rp|847–9}} as well as sensory, secretory and motor fibres to the cervical segments of the [[esophagus]] and the [[Vertebrate trachea|trachea]].<ref name="Shulte2007">{{cite book| vauthors = Schulte E, Schumacher U, Rude J  |title=Thieme Atlas of Anatomy: Head and Neuroanatomy|url=https://books.google.com/books?id=wlGDPwz_7KoC&pg=PA86|year=2007|publisher=Thieme|isbn=978-1-58890-441-6}}</ref>{{rp|142–144}}

==Clinical significance==

===Injury===
[[File:Rekurrens.png|thumb|Recurrent laryngeal nerve visible during resection of a [[goitre]]|alt=An image of a surgical procedure in which the recurrent laryngeal nerve is visible]]
The recurrent laryngeal nerves may be injured as a result of trauma, during surgery, as a result of tumour spread, or due to other means.<ref name=HYDMAN2008 />{{rp|12}} Injury to the recurrent laryngeal nerves can result in a weakened voice ([[hoarseness]]) or loss of voice ([[aphonia]]) and cause problems in the [[respiratory tract]].<ref>{{cite journal | vauthors = Aljammal J, Hussain I, Ahmad S | title = Management of Recurrent Laryngeal Nerve Injury During Radiofrequency Ablation of Thyroid Nodules | language = English | journal = AACE Clinical Case Reports | volume = 8 | issue = 2 | pages = 102 | date = 2022-03-01 | pmid = 35415225 | pmc = 8984510 | doi = 10.1016/j.aace.2022.02.004 }}</ref><ref name=HYDMAN2008 />{{rp|11–12}} Injury to the nerve may paralyze the [[posterior cricoarytenoid muscle]] on the same side. This is the sole muscle responsible for opening the vocal cords, and paralysis may cause difficulty breathing ([[dyspnea]]) during physical activity.<ref name="Hartl2005">{{cite journal | vauthors = Hartl DM, Travagli JP, Leboulleux S, Baudin E, Brasnu DF, Schlumberger M | title = Clinical review: Current concepts in the management of unilateral recurrent laryngeal nerve paralysis after thyroid surgery | journal = The Journal of Clinical Endocrinology and Metabolism | volume = 90 | issue = 5 | pages = 3084–3088 | date = May 2005 | pmid = 15728196 | doi = 10.1210/jc.2004-2533 | doi-access = free }}</ref> Injury to both the right and left nerve may result in more serious damage, such as [[aphonia|the inability to speak]]. Additional problems may emerge during healing, as nerve fibres that re-anastamose may result in ''vocal cord motion impairment'', uncoordinated movements of the vocal cord.<ref name=HYDMAN2008 />{{rp|12–13}}

===Surgery===
The nerve receives close attention from surgeons because the nerve is at risk for injury during neck surgery, especially [[thyroid]] and [[parathyroid]] surgery; as well as esophagectomy.<ref>{{cite journal | doi=10.1213/XAA.0000000000000601 | title=Successful Assessment of Vocal Cord Palsy Before Tracheal Extubation by Laryngeal Ultrasonography in a Patient After Esophageal Surgery | date=2017 | last1=Yamamoto | first1=Natsuhiro | last2=Yamaguchi | first2=Yoshikazu | last3=Nomura | first3=Takeshi | last4=Yamaguchi | first4=Osamu | last5=Goto | first5=Takahisa | journal=A & A Case Reports | volume=9 | issue=11 | pages=308–310 | doi-access=free }}</ref><ref name=Schwartz9th /> Nerve damage can be assessed by [[laryngoscopy]], during which a [[stroboscope|stroboscopic]] light confirms the absence of movement in the affected side of the vocal cords. The right recurrent laryngeal nerve is more susceptible to damage during thyroid surgery because it is close to the bifurcation of the right inferior thyroid artery, variably passing in front of, behind, or between the branches.<ref name=Moore3rd />{{rp|820–1}} Similarly, thermal injury can occur with the use of radio frequency ablation to remove thyroid nodules.<ref>{{cite journal | vauthors = Hussain I, Zulfiqar F, Li X, Ahmad S, Aljammal J | title = Safety and Efficacy of Radiofrequency Ablation of Thyroid Nodules-Expanding Treatment Options in the United States | journal = Journal of the Endocrine Society | volume = 5 | issue = 8 | pages = bvab110 | date = August 2021 | pmid = 34258495 | pmc = 8271212 | doi = 10.1210/jendso/bvab110 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Muhammad H, Santhanam P, Russell JO | title = Radiofrequency ablation and thyroid nodules: updated systematic review | journal = Endocrine | volume = 72 | issue = 3 | pages = 619–632 | date = June 2021 | pmid = 33449296 | doi = 10.1007/s12020-020-02598-6 | s2cid = 231611505 }}</ref><ref>{{cite book | vauthors = Allen E, Minutello K, Murcek BW | chapter = Anatomy, Head and Neck, Larynx Recurrent Laryngeal Nerve |date=2022 | chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK470179/ | title = StatPearls |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29261997 |access-date=2022-05-24}}</ref>  The nerve is permanently damaged in 0.3&ndash;3% of thyroid surgeries, and transient paralysis occurs in 3&ndash;8% of surgeries; accordingly, recurrent laryngeal nerve damage is one of the leading causes of [[medical law|medicolegal]] issues for surgeons.<ref>{{cite journal | vauthors = Hayward NJ, Grodski S, Yeung M, Johnson WR, Serpell J | title = Recurrent laryngeal nerve injury in thyroid surgery: a review | journal = ANZ Journal of Surgery | volume = 83 | issue = 1–2 | pages = 15–21 | date = January 2013 | pmid = 22989215 | doi = 10.1111/j.1445-2197.2012.06247.x | s2cid = 8581189 | doi-access = free }}</ref> A 2019 [[systematic review]] concluded that the available evidence shows no difference between visually identifying the nerve or utilizing intraoperative [[neuroimaging]] during surgery, when trying to prevent injury to recurrent laryngeal nerve during surgery.<ref>{{cite journal | vauthors = Cirocchi R, Arezzo A, D'Andrea V, Abraha I, Popivanov GI, Avenia N, Gerardi C, Henry BM, Randolph J, Barczyñski M | display-authors = 6 | title = Intraoperative neuromonitoring versus visual nerve identification for prevention of recurrent laryngeal nerve injury in adults undergoing thyroid surgery | journal = The Cochrane Database of Systematic Reviews | volume = 1 | issue = 1 | pages = CD012483 | date = January 2019 | pmid = 30659577 | pmc = 6353246 | doi = 10.1002/14651858.CD012483.pub2 | collaboration = Cochrane Metabolic and Endocrine Disorders Group }}</ref>

===Tumors===
The RLN may be compressed by tumors. Studies have shown that 2&ndash;18% of [[lung cancer]] patients develop hoarseness because of recurrent laryngeal nerve compression, usually left-sided.<ref name="Spiro2007">{{cite journal | vauthors = Spiro SG, Gould MK, Colice GL | title = Initial evaluation of the patient with lung cancer: symptoms, signs, laboratory tests, and paraneoplastic syndromes: ACCP evidenced-based clinical practice guidelines (2nd edition) | journal = Chest | volume = 132 | issue = 3 Suppl | pages = 149S–160S | date = September 2007 | pmid = 17873166 | doi = 10.1378/chest.07-1358 }}</ref> This is associated with worse outcomes, and when found as a presenting symptom, often indicates inoperable tumors. The nerve may be severed intentionally during lung cancer surgery in order to fully remove a tumor.<ref name="CarbonePass2010">{{cite book | vauthors = Carbone DP, Pass HI, Johnson DH, Minna JD |title=Principles and Practice of Lung Cancer: The Official Reference Text of the IASLC|url=https://books.google.com/books?id=Ggmy0Sj-Bg4C&pg=RA1-PA3 |access-date=August 12, 2013 |year=2010 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-7365-2 }}</ref>{{rp|330}} The RLN may also be damaged by tumors in the neck, especially with malignant lymph nodes with extra-capsular extension of tumor beyond the capsule of the nodes, which may invade the area that carries the ascending nerve on the right or left.

===Other disease===
In [[Ortner's syndrome]] or cardiovocal syndrome, a rare cause of left recurrent laryngeal nerve [[wikt:palsy|palsy]], expansion of structures within the [[heart]] or major blood vessels impinges upon the nerve, causing symptoms of unilateral nerve injury.<ref name="HeikkinenMilger2012">{{cite journal | vauthors = Heikkinen J, Milger K, Alejandre-Lafont E, Woitzik C, Litzlbauer D, Vogt JF, Klußmann JP, Ghofrani A, Krombach GA, Tiede H | display-authors = 6 | title = Cardiovocal Syndrome (Ortner's Syndrome) Associated with Chronic Thromboembolic Pulmonary Hypertension and Giant Pulmonary Artery Aneurysm: Case Report and Review of the Literature | journal = Case Reports in Medicine | volume = 2012 | pages = 230736 | year = 2012 | pmid = 23424588 | pmc = 3477763 | doi = 10.1155/2012/230736 | doi-access = free }}</ref>

== Other animals==
Horses are subject to ''equine recurrent laryngeal neuropathy'', a [[axonopathy|disease of the axons]] of the recurrent laryngeal nerves. The cause is not known, although a genetic predisposition is suspected. The length of the nerve is a factor since it is more common in larger horses, and the left side is affected almost exclusively. As the nerve cells die, there is a progressive paralysis of the larynx, causing the airway to collapse. The common presentation is a sound, ranging from a musical whistle to a harsh roar or heaving gasping noise ([[stertorous]]), accompanied by worsening performance. The condition is incurable, but surgery can keep the airway open. Experiments with nerve grafts have been tried.<ref>{{cite book| vauthors = Munroe G, Weese S |title=Equine Clinical Medicine, Surgery and Reproduction|url=https://books.google.com/books?id=Cu-XUjVS85QC&pg=PA421|access-date=March 2, 2013|date=March 15, 2011|publisher=Manson Publishing|isbn=978-1-84076-608-0}}</ref>{{rp|421–426}}

Although uncommon in dogs, bilateral recurrent laryngeal nerve disease may be the cause of wheezing ([[stridor]]) when middle-aged dogs inhale.<ref>{{cite book| vauthors = Slatter DH |title=Textbook of Small Animal Surgery|url=https://books.google.com/books?id=B_nh6zSr4wUC&pg=PA771|access-date=March 2, 2013|year=2003|publisher=Elsevier Health Sciences|isbn=978-0-7216-8607-3}}</ref>{{rp|771}}

In [[sauropod]] dinosaurs, the [[vertebrate]]s with the longest necks, the total length of the vagus nerve and recurrent laryngeal nerve would have been up to {{convert|28|m|ft}} long in ''[[Supersaurus]]'', but these would not be the longest neurons that ever existed: the neurons reaching the tip of the tail would have exceeded {{convert|30|m|ft}}.<ref>{{cite journal| vauthors = Wedel MJ |title=A Monument of Inefficiency: The Presumed Course of the Recurrent Laryngeal Nerve in Sauropod Dinosaurs|journal=Acta Palaeontologica Polonica|date=June 2012|volume=57|issue=2|pages=251–256|doi=10.4202/app.2011.0019|doi-access=free}}</ref>

==Evidence of evolution==
The extreme detour of the recurrent laryngeal nerves, about {{convert|15|ft|m|order=flip}} in the case of [[giraffe]]s,<ref>{{Cite book | title=Mammal Anatomy: An Illustrated Guide | year=2010 | publisher=Marshall Cavendish Corporation | isbn=978-0-7614-7882-9 |url=https://books.google.com/books?id=mTPI_d9fyLAC&q=%22laryngeal+nerve%22}}</ref>{{rp|74–75}} is cited as [[evidence of evolution]], as opposed to [[intelligent design]]. The nerve's route would have been direct in the fish-like ancestors of modern [[tetrapod]]s, traveling from the brain, past the heart, to the [[gills]] (as it does in modern fish). Over the course of evolution, as the neck extended and the heart became lower in the body, the laryngeal nerve remained in its original course.

==History==
Ancient Greek physician [[Galen]] demonstrated the nerve course and the clinical syndrome of [[Vocal fold paresis|recurrent laryngeal nerve paralysis]], noting that pigs with the nerve severed were unable to squeal. Galen named the nerve the ''recurrent nerve'', and described the same effect in two human infants who had undergone surgery for [[goiter]].<ref name=HYDMAN2008>{{cite book| vauthors = Hydman J |title=Recurrent laryngeal nerve injury |year=2008 |location=Stockholm |isbn=978-91-7409-123-6}}</ref>{{rp|7–8}}<ref>{{cite journal | vauthors = Gross CG |date=May 1998 |title= Galen and the Squealing Pig |journal= Neuroscientist |volume=4 |issue=3 |pages= 216–221 |issn= 1073-8584 |doi= 10.1177/107385849800400317 |s2cid= 72125962 }}</ref>  In 1838, five years before he would introduce the concept of [[Homology (biology)|homology]] to biology, anatomist [[Richard Owen]] reported upon the dissection of three giraffes, including a description of the full course of the left recurrent laryngeal nerve.<ref>{{Cite book| vauthors = Owen R |author-link=Richard Owen|title=Transactions of the Zoological Society of London|chapter-url=https://books.google.com/books?id=4ulEAQAAIAAJ&pg=PA217|access-date=February 27, 2013|year=1841|publisher=Zoological Society of London|pages=217–248|chapter=Notes on the dissection of the Nubian giraffe}}</ref><ref name="BerryHallam1986">{{cite book| vauthors = Berry RJ, Hallam A |author-link2=Anthony Hallam|title=The Collins Encyclopedia of Animal Evolution|url=https://books.google.com/books?id=z1ZnQgAACAAJ|access-date=February 27, 2013|year=1986|publisher=HarperCollins Publishers Limited|isbn=978-0-00-219818-9|pages=82–83}}</ref> Anatomists [[Andreas Vesalius]] and [[Thomas Willis]] described the nerve in what is now regarded as an anatomically standard description, and doctor [[Frank Lahey]] documented a way for its interoperative identification during thyroid operations.<ref>{{cite journal | vauthors = Ardito G, Revelli L, D'Alatri L, Lerro V, Guidi ML, Ardito F | title = Revisited anatomy of the recurrent laryngeal nerves | journal = American Journal of Surgery | volume = 187 | issue = 2 | pages = 249–253 | date = February 2004 | pmid = 14769313 | doi = 10.1016/j.amjsurg.2003.11.001 }}</ref>

==Notes==
{{notelist}}

== References ==
{{Reflist|2}}

== External links ==
* {{SUNYAnatomyFigs|21|04|01}}
* {{NormanAnatomy|cranialnerves}} ({{NormanAnatomyFig|X}})
* [http://www.dailymotion.com/video/xdm5he_richard-dawkins-demonstrates-laryng_tech#from=embed Dissection of a giraffe displaying the laryngeal nerve] ([https://www.youtube.com/watch?v=cO1a1Ek-HD0 youTube])

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

[[Category:Vagus nerve]]
[[Category:Human throat]]
[[Category:Nerves of the head and neck]]