Surgical Anatomy of Non-Recurrent Inferior Laryngeal Nerves Observed Between 2011–2023

Surgical Anatomy of Non-Recurrent Inferior Laryngeal Nerves Observed Between 2011–2023 | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Surgical Anatomy of Non-Recurrent Inferior Laryngeal Nerves Observed Between 2011–2023 Koki Sato, Keizo Sugino, Masahiro Nishihara, Yukari Kawasaki, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4173995/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Purpose: To avoid complications during thyroid surgery, it is important to be aware of anatomical variations. This study aimed to analyze the clinical aspects of non-recurrent inferior laryngeal nerves (NRILNs) at a hospital in Japan. Methods: We retrospectively analyzed thyroid surgery cases at our institution over the last 12 years (2011–2023). The study included 2187 patients (1676 women, 76.6%) who underwent total thyroidectomy (TT; N = 512) or hemithyroidectomy (HT; N = 1611). The HT group included 850 right and 761 left thyroidectomies, and 82 patients underwent complementary TTs (40 right and 42 left). The total number of inferior laryngeal nerves identified during surgery was 2717 (1402 right and 1315 left). All patients underwent preoperative neck and thoracic computed tomography (CT) and neck ultrasonography (US). NRILN is classified into two types: Type 1, in which the NRILN branches at the level of the inferior thyroid artery and ascends along the trachea; and Type 2, in which the NRILN branches at the level of the superior pole of the thyroid gland and runs directly to the larynx. Results: We identified 12 NRILN cases. The nerve anomaly was diagnosed preoperatively in all patients. Of these cases, eight were Type 1 and four were Type 2. No inferior laryngeal nerve injury was observed after surgery. Conclusion: To avoid inferior laryngeal nerve injury, preoperative diagnosis of NRILNs is essential. NRILN is associated with an aberrant right subclavian artery; hence, its presence should be evaluated using routine US and CT before surgery. thyroid operation aberrant right subclavian artery nonrecurrent inferior laryngeal nerve preoperative diagnosis vagal nerve Figures Figure 1 Figure 2 Introduction Recurrent laryngeal nerve (RLN) injury is a severe complication during thyroid surgery that can significantly affect a patient’s quality of life. Therefore, a comprehensive understanding of anatomical variations by thyroid surgeons is crucial to prevent complications. A non-recurrent inferior laryngeal nerve (NRILN) is a rare anatomical variant, first reported in 1823 by Stedman [ 16 ], that occurs when the inferior laryngeal nerve branches directly from the vagus nerve. An NRILN is associated with an anomalous right subclavian artery (ARSA) origin [ 9 , 21 ]. The origin of the subclavian artery is at the left part of the aortic arch, which crosses the posterior wall of the esophagus (Fig. 1 ). The preoperative detection of ARSA using computed tomography (CT) or ultrasonography (US) is an indicator of NRILN and may reduce the incidence of iatrogenic nerve injury [ 9 ]. We have previously classified NRILNs into two subtypes based on their course: Type 1 (Fig. 2 A) crosses in close proximity to the inferior thyroid artery and enters the larynx ascending along the trachea, while Type 2 (Fig. 2 B) enters the larynx directly from the superior pole of the thyroid gland [ 18 ]. The purpose of this study was to retrospectively evaluate the incidence and anatomical features of NRILNs over the past 12 years (2011–2023) at our institution. Materials and Methods Thyroid surgeries performed at Tsuchiya General Hospital between January 2011 and April 2023 were retrospectively evaluated. Before surgery, all patients had undergone neck CT (from the upper mediastinum to the axillary sinus level), cervical US, and chest radiography. The nerves were identified based on anatomical landmarks. A peripheral nerve stimulator (Fisher & Paykel) had been used in all cases since before 2011. Furthermore, intraoperative nerve monitoring (IONM) had been introduced in 2019 and used in 274 patients with large tumors, tumors adjacent to the inferior recurrent nerve, or those suspected of nerve invasion. Comprehensive informed consent for the use of all radiographic, pathological, and laboratory data for research purposes was obtained from all patients who had undergone surgery at the hospital, with institutional approval. Results and Discussion Between January 2011 and April 2023, 2205 thyroid surgeries were performed at Tsuchiya General Hospital, including 512 total thyroidectomies, 850 right hemithyroidectomies, 761 left hemithyroidectomies (LHT), and 82 complementary total thyroidectomies. Out of a total of 2717 inferior laryngeal nerves at risk, NRILNs were identified in 12 asymptomatic cases (0.44% overall, 0.86% of the right nerves), which involved two men and ten women (Table 1 ). In all patients, the anomaly involved the right laryngeal nerve. In case 9, LHT + D1 central lymphadenectomy was performed for papillary thyroid carcinoma in the left lobe of the thyroid gland. NRILNs on the right side were confirmed by dissection of the right III lymph node. In eight cases, the non-recurrent laryngeal nerve originated from the vagus nerve and descended into the larynx with the superior pole of the thyroid lobe (Type 1), whereas in four cases, it crossed in close proximity to the inferior thyroid artery (Type 2). In all cases, preoperative CT confirmed ARSA, and cervical US revealed loss of the normal bifurcation of the right common carotid artery and right subclavian artery. Surgery was initiated based on the preoperative diagnosis of NRILN in all cases. IONM, which was introduced in our hospital in 2019, allowed the detection of NRILNs during thyroid surgery in five cases. No nerve lesions or postoperative vocal-fold deficits were observed in any patients. The abnormal formation of the subclavian artery during fetal development is implicated in the pathogenesis of NRILN [ 7 ]. The heart, which is located in the neck during early fetal development, descends into the thoracic cavity as fetal development progresses. Under normal conditions, the right subclavian artery is formed from the right fourth aortic arch, and the ductus arteriosus is formed from the left sixth branchial arch. The laryngeal nerve withdraws into the thoracic cavity as the heart descends. Then, the nerves present as the recurrent nerves that turn around the right subclavian artery and aortic arch, respectively. However, when the right fourth aortic arch is abnormally lost in the early embryonic stage, an ARSA is formed by a compensatory seventh intersegmental artery [ 15 ]. As a result, the right inferior laryngeal nerve does not pass into the thoracic cavity and branches directly from the cervical vagus nerve without forming a recurrent loop [ 22 ]. The ARSA most commonly follows a retroesophageal course (80–84%), which is between the trachea and esophagus (12.7–15%), or a pretracheal course (4.2–5%) [ 11 , 12 ]. NRILN mostly occurs on the right side, occurring on the left side only when there is a situs inversus or right aortic arch [ 7 ]. Only six cases of left NRILN have been reported [ 5 ]. The incidence of this abnormality ranges from 0.3–1.6% in the right non-recurrent laryngeal nerve. However, the exact incidence is difficult to determine because few surgical reports are available [ 20 ]. A series of more than 1000 published cases is summarized in Table 2 , with incidence rates ranging from 0.34–1.04% [ 1 , 3 , 4 , 6 , 7 , 10 , 13 , 14 , 17 , 20 ]. Although NRILNs occur infrequently, head and neck surgeons may often encounter this variation, and preoperative detection is important. Deveze et al. [ 4 ] reported 104 patients with NRILNs showing abnormally running arteries, emphasizing the need to consider the presence of NRILNs in these patients. Satoh et al. reported that the sensitivity and specificity of CT for detecting NRILN are both 100% (abnormalities of the right subclavian artery were noted in all 10 NRILN cases in 1086 patients who underwent preoperative CT), indicating the usefulness of preoperative CT [ 14 ]. Iacobone et al. have found that the preoperative performance of US to identify arterial abnormalities significantly decreases NRILN morbidity. Demonstrating the absence of the brachiocephalic trunk, with the right carotid artery arising from the aortic arch independently and separated from the right subclavian artery, is a more rapid and easier method than direct identification of the origin of the aberrant lusorian artery from the left side of the aortic arch because of its deep location. The absence of the brachiocephalic artery predicts NRILN with a sensitivity and negative predictive value of 100% and a specificity of 97.7% [ 8 , 9 ]. However, the positive predictive value for NRILN due to the absence of the brachiocephalic artery on US has been reported as 45.9% [ 8 ]. In cases where the right brachiocephalic artery branches from the central side (closer to the aortic arch), evaluating the absence of branching of the right brachiocephalic artery using US angled caudally at the sternal notch may be insufficient. Prior to the present study, we encountered one case in which the absence of the brachiocephalic artery could not be detected by preoperative US, and NRILN was found intraoperatively. Therefore, in addition to preoperative cervical US, all patients underwent CT, which revealed abnormalities in the running of the artery, thus predicting the presence of NRILNs in our hospital. F: female, M: male, PTC: papillary thyroid carcinoma, CTT: completion total thyroidectomy, TT: total thyroidectomy, RHT: right hemithyroidectomy, LHT: left hemithyroidectomy, STT: subtotal thyroidectomy, D1: central lymphadenectomy, RASA: right aberrant subclavian artery. Table 2 Incidence of nonrecurrent inferior laryngeal nerve in large published series Author Year Number of operations Number of NRILN Frequency (%) Stewart [ 8 ] 1972 1776 * 6 0.34 Henry [ 5 ] 1988 6307 *** 33 0.52 Proye [ 9 ] 1991 6961 *** 56 0.80 Defechereux [ 10 ] 2000 2517 *** 20 0.79 Deveze [ 11 ] 2003 19868 *** 104 0.52 Toniato [ 7 ] 2004 6000 ** 31 0.51 Satoh [ 12 ] 2013 1561 * 11 0.70 Gong [ 13 ] 2014 1825 ** 23 1.26 Barcynzki [ 14 ] 2015 2500 ** 9 0.37 Le [ 15 ] 2019 2158 ** 16 0.74 This study 2023 1402 * 12 0.86 * Number of right recurrent nerves identified at surgery ** Number of thyroidectomies *** Number of neck explorations (cervicotomies) However, the course of non-RLNs may vary. Two main types are defined by Cangnol et al. [ 2 ], Toniato et al. [ 20 ], and Sugino et al. [ 18 ]. Henry et al. [ 7 ] have classified the types as superior, middle, or inferior based on the nerve running pattern. Le et al. [ 10 ] have identified a V-shaped type and classified the four traveling patterns. Toniato et al. [ 20 ] have classified NRILNs as Type 1 (from the superior pole) or Type 2 (from the inferior pole). We followed the classification reported by Sugino et al. in 1998 [ 18 ], in which Type 1 is defined as the inferior pole and Type 2 as the superior pole. The ratio of cases involving Type 1 to Type 2 branching from the lower branching level has been reported as 26:7 by Henry et al. [ 7 ], 26:5 by Toniato et al. [ 20 ], 6:1 by Satoh et al [ 14 ], 10:2 by Le et al. [ 10 ], and 5:2 by Terao et al. [ 19 ], indicating a higher incidence of branching from the lower pole level. Similarly, in this study, Type 1 bifurcation from the lower pole was more common than Type 2 bifurcation from the upper pole (eight vs. four patients, respectively). Toniato et al. [ 20 ] have reported a higher incidence of nerve damage in cases with branching from the superior pole (three out of five cases). Even if preoperative identification of NRILN is possible, the specific running pattern cannot be predicted. Therefore, comprehensive vascular treatment of the upper pole of the thyroid gland should be carefully performed, focusing on the branches of the superior thyroid artery along the thyroid gland capsule. NRILN, encountered in approximately 1% of thyroid surgeries, is not extremely rare. In many cases, NRILNs are injured during the early stages of perithyroid dissection. Literature indicates that RLN injury occurs in approximately 3–7% of patients following thyroid surgeries, while the incidence of NRLN injury may reach as high as 12.9% [ 10 ]. To minimize the risk of damaging NRILN and ensure safer surgical procedures, the following measures are recommended: (1) preoperative evaluation of ARSA via US and CT; (2) not dissecting the nerve-like tissue that enters the superior pole of the right lobe from the lateral side during surgery on the right lobe of the thyroid gland until the right recurrent nerve is identified; (3) if the right recurrent nerve is not easily identified, the carotid sheath and cervical vagus nerve should be exposed and carefully examined to determine the presence of NRLN leading toward the thyroid gland; and (4) after confirming the presence of the right recurrent nerve, right lobectomy should be performed. Conclusion Predicting NRILN before thyroid surgery is important to prevent injury to the inferior laryngeal nerve. ARSA induces NRILN; hence, ARSA must be evaluated using US and CT before surgery. Declarations Acknowledgements: None. Author Contributions Conception and design: all authors. Acquisition of data: K.S. Analysis and interpretation of data: K,S. Drafting the article: K.S.K,S. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors. Study supervision: K.S. Competing Interests: None declared. Informed consent and research ethics: Informed consent was obtained from all individual participants included in the study. Institutional approval was obtained from Tsuchiya General Hospital. Funding: None. Compliance with ethical requirements: All authors comply with the journal’s ethical policies. References Barczyński M, Stopa M, Konturek A, Nowak W (2016) The overwhelming majority but not all motor fibers of the bifid recurrent laryngeal nerve are located in the anterior extralaryngeal branch. World J Surg 40:629-635. https://doi.org/10.1007/s00268-015-3257-4 Cagnol G, Santini J, Demard F (1987) Anatomy of the recurrent nerve. Descriptive anatomy, trajectory and relationships, variations. Acta Oto-Rhino-Laryngol Belg 41:821-827 Defechereux T, Albert V, Alexandre J, Bonnet P, Hamoir E, Meurisse M (2000) The inferior non recurrent laryngeal nerve: a major surgical risk during thyroidectomy. Acta Chir Belg 100:62-67 Devèze A, Sebag F, Hubbard J, Jaunay M, Maweja S, Henry JF (2003) Identification of patients with a non-recurrent inferior laryngeal nerve by duplex ultrasound of the brachiocephalic artery. Surg Radiol Anat 25:263-269. https://doi.org/10.1007/s00276-003-0135-9 Furukawa T, Otsuki N, Tomotsu M, Tatehara S, Morita N, Kojima Y, Teshima M, Shinomiya H, Nibu KI (2021) Left non-recurrent inferior laryngeal nerve in a patient with right-sided aortic arch and aberrant left subclavian artery. Auris Nasus Larynx 48:317-321. https://doi.org/10.1016/j.anl.2020.02.011 Gong RX, Luo SH, Gong YP, Wei T, Li ZH, Huang JB, Li ZL, Li-Ling J, Zhu JQ (2014) Prediction of nonrecurrent laryngeal nerve before thyroid surgery--experience with 1825 cases. J Surg Res 189:75-80. https://doi.org/10.1016/j.jss.2014.02.010 Henry JF, Audiffret J, Denizot A, Plan M (1988) The nonrecurrent inferior laryngeal nerve: review of 33 cases, including two on the left side. Surgery 104:977-984 Iacobone M, Citton M, Pagura G, Viel G, Nitti D (2015) Increased and safer detection of nonrecurrent inferior laryngeal nerve after preoperative ultrasonography. Laryngoscope 125:1743-1747. https://doi.org/10.1002/lary.25093 Iacobone M, Viel G, Zanella S, Bottussi M, Frego M, Favia G (2008) The usefulness of preoperative ultrasonographic identification of nonrecurrent inferior laryngeal nerve in neck surgery. Langenbecks Arch Surg 393:633-638. https://doi.org/10.1007/s00423-008-0372-9 Le VQ, Ngo QD, Ngo XQ (2019) Nonrecurrent laryngeal nerve in thyroid surgery: frequency, anatomical variations according to a new classification and surgery consideration. Head Neck 41:2969-2975. https://doi.org/10.1002/hed.25771 Natsis K, Didagelos M, Gkiouliava A, Lazaridis N, Vyzas V, Piagkou M (2017) The aberrant right subclavian artery: cadaveric study and literature review. Surg Radiol Anat 39:559-565. https://doi.org/10.1007/s00276-016-1796-5 Pramesh CS, Saklani AP, Parmar V, Acharya S, Badwe RA (2003) Aberrant subclavian artery causing difficulty in transhiatal esophageal dissection. Dis Esophagus 16:173-176. https://doi.org/10.1046/j.1442-2050.2003.00322.x Proye CA, Carnaille BM, Goropoulos A (1991) Nonrecurrent and recurrent inferior laryngeal nerve: a surgical pitfall in cervical exploration. Am J Surg 162:495-496. https://doi.org/10.1016/0002-9610(91)90271-e Satoh S, Tachibana S, Yokoi T, Yamashita H (2013) [Preoperative diagnosis of nonrecurrent inferior laryngeal nerve--usefulness of CT and ultrasonography]. Nihon Jibiinkoka Gakkai Kaiho 116:793-801. https://doi.org/10.3950/jibiinkoka.116.793 Shindo K, Nagai E, Nabae T et al (2017) Successful video-assisted thoracoscopic surgery in prone position in patients with esophageal cancer and aberrant right subclavian artery: report of three cases. Surg Case Rep 3:86. https://doi.org/10.1186/s40792-017-0360-9 Stedman GW (1823) A singular distribution of some of the nerves and arteries in the neck, and the top of the thorax. Edinb Med Surg J 19:564-565 Stewart GR, Mountain JC, Colcock BP (1972) Non-recurrent laryngeal nerve. Br J Surg 59:379-381. https://doi.org/10.1002/bjs.1800590513 Sugino K, Okamoto H, Fudaba Y, Asahara T (1998) The significance of confirmation for nonrecurrent inferior laryngeal nerve in thyroid surgery (in Japanese). Endocr Surg 15:121-126 Terao K, Toda M, Murata K (2000) [A clinical study of the nonrecurrent inferior laryngeal nerve in seven patients]. Nihon Jibiinkoka Gakkai Kaiho 103:1205-1211. https://doi.org/10.3950/jibiinkoka.103.1205 Toniato A, Mazzarotto R, Piotto A, Bernante P, Pagetta C, Pelizzo MR (2004) Identification of the nonrecurrent laryngeal nerve during thyroid surgery: 20-year experience. World J Surg 28:659-661. https://doi.org/10.1007/s00268-004-7197-7 Watanabe A, Kawabori S, Osanai H, Taniguchi M, Hosokawa M (2001) Preoperative computed tomography diagnosis of non-recurrent inferior laryngeal nerve. Laryngoscope 111:1756-1759. https://doi.org/10.1097/00005537-200110000-00017 Zheng V, Rajeev R, Pinto D, de Jong MC, Sreenivasan DK, Parameswaran R (2023) Variant anatomy of non-recurrent laryngeal nerve: when and how should it be taught in surgical residency? Langenbecks Arch Surg 408:185. https://doi.org/10.1007/s00423-023-02928-y Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4173995","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":286116311,"identity":"7133e7e2-e635-47e8-943a-a25232f761ce","order_by":0,"name":"Koki Sato","email":"","orcid":"","institution":"Akane-Foundation, Tsuchiya General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Koki","middleName":"","lastName":"Sato","suffix":""},{"id":286116313,"identity":"47c68a0f-237c-4c9b-a35b-583dd9c4d672","order_by":1,"name":"Keizo 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contrast.\u003c/p\u003e\n\u003cp\u003eThe right subclavian artery is located at the level of the aortic arch and crosses and subsequently compresses the posterior wall of the esophagus (arrow).\u003c/p\u003e","description":"","filename":"figure.11.png","url":"https://assets-eu.researchsquare.com/files/rs-4173995/v1/da7ffea0a389f74818f91dca.png"},{"id":53970067,"identity":"0f60024b-49fd-4346-8cc9-b57710d1b847","added_by":"auto","created_at":"2024-04-02 20:40:04","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":55745,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA\u003c/strong\u003e Schematic presentation of non-recurrent inferior laryngeal nerves (NRILNs). \u003cstrong\u003eA)\u003c/strong\u003e Type 1: The NRILN (arrow) runs down to the level of the inferior thyroid artery, rises beside the tracheal wall, and enters the larynx. \u003cstrong\u003eB)\u003c/strong\u003e Type 2: The NRILN (arrow) runs through the superior pole of the thyroid gland and directly enters the larynx\u003c/p\u003e","description":"","filename":"figure.21.png","url":"https://assets-eu.researchsquare.com/files/rs-4173995/v1/e20e8cf3784ffb15b020e8fd.png"},{"id":54050609,"identity":"b349bb58-270f-419a-bc3f-91387defed69","added_by":"auto","created_at":"2024-04-03 21:22:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":390073,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4173995/v1/d96b21d7-f419-413d-8ee5-155bb523bec5.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Surgical Anatomy of Non-Recurrent Inferior Laryngeal Nerves Observed Between 2011–2023","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRecurrent laryngeal nerve (RLN) injury is a severe complication during thyroid surgery that can significantly affect a patient\u0026rsquo;s quality of life. Therefore, a comprehensive understanding of anatomical variations by thyroid surgeons is crucial to prevent complications. A non-recurrent inferior laryngeal nerve (NRILN) is a rare anatomical variant, first reported in 1823 by Stedman [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], that occurs when the inferior laryngeal nerve branches directly from the vagus nerve. An NRILN is associated with an anomalous right subclavian artery (ARSA) origin [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The origin of the subclavian artery is at the left part of the aortic arch, which crosses the posterior wall of the esophagus (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The preoperative detection of ARSA using computed tomography (CT) or ultrasonography (US) is an indicator of NRILN and may reduce the incidence of iatrogenic nerve injury [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWe have previously classified NRILNs into two subtypes based on their course: Type 1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA) crosses in close proximity to the inferior thyroid artery and enters the larynx ascending along the trachea, while Type 2 (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB) enters the larynx directly from the superior pole of the thyroid gland [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe purpose of this study was to retrospectively evaluate the incidence and anatomical features of NRILNs over the past 12 years (2011\u0026ndash;2023) at our institution.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eThyroid surgeries performed at Tsuchiya General Hospital between January 2011 and April 2023 were retrospectively evaluated. Before surgery, all patients had undergone neck CT (from the upper mediastinum to the axillary sinus level), cervical US, and chest radiography. The nerves were identified based on anatomical landmarks. A peripheral nerve stimulator (Fisher \u0026amp; Paykel) had been used in all cases since before 2011. Furthermore, intraoperative nerve monitoring (IONM) had been introduced in 2019 and used in 274 patients with large tumors, tumors adjacent to the inferior recurrent nerve, or those suspected of nerve invasion.\u003c/p\u003e \u003cp\u003eComprehensive informed consent for the use of all radiographic, pathological, and laboratory data for research purposes was obtained from all patients who had undergone surgery at the hospital, with institutional approval.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003eBetween January 2011 and April 2023, 2205 thyroid surgeries were performed at Tsuchiya General Hospital, including 512 total thyroidectomies, 850 right hemithyroidectomies, 761 left hemithyroidectomies (LHT), and 82 complementary total thyroidectomies. Out of a total of 2717 inferior laryngeal nerves at risk, NRILNs were identified in 12 asymptomatic cases (0.44% overall, 0.86% of the right nerves), which involved two men and ten women (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). In all patients, the anomaly involved the right laryngeal nerve. In case 9, LHT\u0026thinsp;+\u0026thinsp;D1 central lymphadenectomy was performed for papillary thyroid carcinoma in the left lobe of the thyroid gland. NRILNs on the right side were confirmed by dissection of the right III lymph node. In eight cases, the non-recurrent laryngeal nerve originated from the vagus nerve and descended into the larynx with the superior pole of the thyroid lobe (Type 1), whereas in four cases, it crossed in close proximity to the inferior thyroid artery (Type 2). In all cases, preoperative CT confirmed ARSA, and cervical US revealed loss of the normal bifurcation of the right common carotid artery and right subclavian artery. Surgery was initiated based on the preoperative diagnosis of NRILN in all cases. IONM, which was introduced in our hospital in 2019, allowed the detection of NRILNs during thyroid surgery in five cases. No nerve lesions or postoperative vocal-fold deficits were observed in any patients.\u003c/p\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003c/table\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003eThe abnormal formation of the subclavian artery during fetal development is implicated in the pathogenesis of NRILN [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]. The heart, which is located in the neck during early fetal development, descends into the thoracic cavity as fetal development progresses. Under normal conditions, the right subclavian artery is formed from the right fourth aortic arch, and the ductus arteriosus is formed from the left sixth branchial arch. The laryngeal nerve withdraws into the thoracic cavity as the heart descends. Then, the nerves present as the recurrent nerves that turn around the right subclavian artery and aortic arch, respectively. However, when the right fourth aortic arch is abnormally lost in the early embryonic stage, an ARSA is formed by a compensatory seventh intersegmental artery [\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]. As a result, the right inferior laryngeal nerve does not pass into the thoracic cavity and branches directly from the cervical vagus nerve without forming a recurrent loop [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]. The ARSA most commonly follows a retroesophageal course (80\u0026ndash;84%), which is between the trachea and esophagus (12.7\u0026ndash;15%), or a pretracheal course (4.2\u0026ndash;5%) [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]. NRILN mostly occurs on the right side, occurring on the left side only when there is a situs inversus or right aortic arch [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]. Only six cases of left NRILN have been reported [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe incidence of this abnormality ranges from 0.3\u0026ndash;1.6% in the right non-recurrent laryngeal nerve. However, the exact incidence is difficult to determine because few surgical reports are available [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e]. A series of more than 1000 published cases is summarized in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, with incidence rates ranging from 0.34\u0026ndash;1.04% [\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e]. Although NRILNs occur infrequently, head and neck surgeons may often encounter this variation, and preoperative detection is important. Deveze et al. [\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e] reported 104 patients with NRILNs showing abnormally running arteries, emphasizing the need to consider the presence of NRILNs in these patients. Satoh et al. reported that the sensitivity and specificity of CT for detecting NRILN are both 100% (abnormalities of the right subclavian artery were noted in all 10 NRILN cases in 1086 patients who underwent preoperative CT), indicating the usefulness of preoperative CT [\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]. Iacobone et al. have found that the preoperative performance of US to identify arterial abnormalities significantly decreases NRILN morbidity. Demonstrating the absence of the brachiocephalic trunk, with the right carotid artery arising from the aortic arch independently and separated from the right subclavian artery, is a more rapid and easier method than direct identification of the origin of the aberrant lusorian artery from the left side of the aortic arch because of its deep location. The absence of the brachiocephalic artery predicts NRILN with a sensitivity and negative predictive value of 100% and a specificity of 97.7% [\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e]. However, the positive predictive value for NRILN due to the absence of the brachiocephalic artery on US has been reported as 45.9% [\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e]. In cases where the right brachiocephalic artery branches from the central side (closer to the aortic arch), evaluating the absence of branching of the right brachiocephalic artery using US angled caudally at the sternal notch may be insufficient. Prior to the present study, we encountered one case in which the absence of the brachiocephalic artery could not be detected by preoperative US, and NRILN was found intraoperatively. Therefore, in addition to preoperative cervical US, all patients underwent CT, which revealed abnormalities in the running of the artery, thus predicting the presence of NRILNs in our hospital.\u003c/p\u003e\u003cp\u003e\u003cimg src=\"https://myfiles.space/user_files/122228_c8a1650c59388082/122228_custom_files/img1712075069.png\"\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003eF: female, M: male, PTC: papillary thyroid carcinoma, CTT: completion total thyroidectomy, TT: total thyroidectomy, RHT: right hemithyroidectomy, LHT: left hemithyroidectomy, STT: subtotal thyroidectomy, D1: central lymphadenectomy, RASA: right aberrant subclavian artery.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eIncidence of nonrecurrent inferior laryngeal nerve in large published series\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAuthor\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eYear\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNumber of operations\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNumber of NRILN\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFrequency\u003c/p\u003e\n \u003cp\u003e(%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eStewart [\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1972\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1776\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.34\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHenry [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1988\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6307\u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eProye [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1991\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6961\u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.80\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDefechereux [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2000\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2517\u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.79\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDeveze [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19868\u003csup\u003e***\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e104\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eToniato [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6000\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.51\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSatoh [\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2013\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1561\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.70\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eGong [\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2014\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1825\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.26\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBarcynzki [\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2015\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2500\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLe [\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2019\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2158\u003csup\u003e**\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.74\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThis study\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2023\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1402\u003csup\u003e*\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.86\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003e* Number of right recurrent nerves identified at surgery\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003e** Number of thyroidectomies\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003e*** Number of neck explorations (cervicotomies)\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eHowever, the course of non-RLNs may vary. Two main types are defined by Cangnol et al. [\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e], Toniato et al. [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e], and Sugino et al. [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e]. Henry et al. [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e] have classified the types as superior, middle, or inferior based on the nerve running pattern. Le et al. [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e] have identified a V-shaped type and classified the four traveling patterns. Toniato et al. [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e] have classified NRILNs as Type 1 (from the superior pole) or Type 2 (from the inferior pole). We followed the classification reported by Sugino et al. in 1998 [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e], in which Type 1 is defined as the inferior pole and Type 2 as the superior pole. The ratio of cases involving Type 1 to Type 2 branching from the lower branching level has been reported as 26:7 by Henry et al. [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e], 26:5 by Toniato et al. [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e], 6:1 by Satoh et al [\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e], 10:2 by Le et al. [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e], and 5:2 by Terao et al. [\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e], indicating a higher incidence of branching from the lower pole level. Similarly, in this study, Type 1 bifurcation from the lower pole was more common than Type 2 bifurcation from the upper pole (eight vs. four patients, respectively). Toniato et al. [\u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e] have reported a higher incidence of nerve damage in cases with branching from the superior pole (three out of five cases). Even if preoperative identification of NRILN is possible, the specific running pattern cannot be predicted. Therefore, comprehensive vascular treatment of the upper pole of the thyroid gland should be carefully performed, focusing on the branches of the superior thyroid artery along the thyroid gland capsule.\u003c/p\u003e\n\u003cp\u003eNRILN, encountered in approximately 1% of thyroid surgeries, is not extremely rare. In many cases, NRILNs are injured during the early stages of perithyroid dissection. Literature indicates that RLN injury occurs in approximately 3\u0026ndash;7% of patients following thyroid surgeries, while the incidence of NRLN injury may reach as high as 12.9% [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eTo minimize the risk of damaging NRILN and ensure safer surgical procedures, the following measures are recommended: (1) preoperative evaluation of ARSA via US and CT; (2) not dissecting the nerve-like tissue that enters the superior pole of the right lobe from the lateral side during surgery on the right lobe of the thyroid gland until the right recurrent nerve is identified; (3) if the right recurrent nerve is not easily identified, the carotid sheath and cervical vagus nerve should be exposed and carefully examined to determine the presence of NRLN leading toward the thyroid gland; and (4) after confirming the presence of the right recurrent nerve, right lobectomy should be performed.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003ePredicting NRILN before thyroid surgery is important to prevent injury to the inferior laryngeal nerve. ARSA induces NRILN; hence, ARSA must be evaluated using US and CT before surgery.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e None.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConception and design: all authors. Acquisition of data: K.S. Analysis and interpretation of data: K,S. Drafting the article: K.S.K,S. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors. Study supervision: K.S.\u003c/p\u003e\n\u003cp\u003eCompeting Interests: None declared.\u003c/p\u003e\n\u003cp\u003eInformed consent and research ethics: Informed consent was obtained from all individual participants included in the study. Institutional approval was obtained from Tsuchiya General Hospital.\u003c/p\u003e\n\u003cp\u003eFunding: None.\u003c/p\u003e\n\u003cp\u003eCompliance with ethical requirements: All authors comply with the journal\u0026rsquo;s ethical policies.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBarczyński M, Stopa M, Konturek A, Nowak W (2016) The overwhelming majority but not all motor fibers of the bifid recurrent laryngeal nerve are located in the anterior extralaryngeal branch. World J Surg 40:629-635. https://doi.org/10.1007/s00268-015-3257-4\u003c/li\u003e\n\u003cli\u003eCagnol G, Santini J, Demard F (1987) Anatomy of the recurrent nerve. Descriptive anatomy, trajectory and relationships, variations. Acta Oto-Rhino-Laryngol Belg 41:821-827\u003c/li\u003e\n\u003cli\u003eDefechereux T, Albert V, Alexandre J, Bonnet P, Hamoir E, Meurisse M (2000) The inferior non recurrent laryngeal nerve: a major surgical risk during thyroidectomy. Acta Chir Belg 100:62-67\u003c/li\u003e\n\u003cli\u003eDev\u0026egrave;ze A, Sebag F, Hubbard J, Jaunay M, Maweja S, Henry JF (2003) Identification of patients with a non-recurrent inferior laryngeal nerve by duplex ultrasound of the brachiocephalic artery. Surg Radiol Anat 25:263-269. https://doi.org/10.1007/s00276-003-0135-9\u003c/li\u003e\n\u003cli\u003eFurukawa T, Otsuki N, Tomotsu M, Tatehara S, Morita N, Kojima Y, Teshima M, Shinomiya H, Nibu KI (2021) Left non-recurrent inferior laryngeal nerve in a patient with right-sided aortic arch and aberrant left subclavian artery. Auris Nasus Larynx 48:317-321. https://doi.org/10.1016/j.anl.2020.02.011\u003c/li\u003e\n\u003cli\u003eGong RX, Luo SH, Gong YP, Wei T, Li ZH, Huang JB, Li ZL, Li-Ling J, Zhu JQ (2014) Prediction of nonrecurrent laryngeal nerve before thyroid surgery--experience with 1825 cases. J Surg Res 189:75-80. https://doi.org/10.1016/j.jss.2014.02.010\u003c/li\u003e\n\u003cli\u003eHenry JF, Audiffret J, Denizot A, Plan M (1988) The nonrecurrent inferior laryngeal nerve: review of 33 cases, including two on the left side. Surgery 104:977-984\u003c/li\u003e\n\u003cli\u003eIacobone M, Citton M, Pagura G, Viel G, Nitti D (2015) Increased and safer detection of nonrecurrent inferior laryngeal nerve after preoperative ultrasonography. Laryngoscope 125:1743-1747. https://doi.org/10.1002/lary.25093\u003c/li\u003e\n\u003cli\u003eIacobone M, Viel G, Zanella S, Bottussi M, Frego M, Favia G (2008) The usefulness of preoperative ultrasonographic identification of nonrecurrent inferior laryngeal nerve in neck surgery. Langenbecks Arch Surg 393:633-638. https://doi.org/10.1007/s00423-008-0372-9\u003c/li\u003e\n\u003cli\u003eLe VQ, Ngo QD, Ngo XQ (2019) Nonrecurrent laryngeal nerve in thyroid surgery: frequency, anatomical variations according to a new classification and surgery consideration. Head Neck 41:2969-2975. https://doi.org/10.1002/hed.25771\u003c/li\u003e\n\u003cli\u003eNatsis K, Didagelos M, Gkiouliava A, Lazaridis N, Vyzas V, Piagkou M (2017) The aberrant right subclavian artery: cadaveric study and literature review. Surg Radiol Anat 39:559-565. https://doi.org/10.1007/s00276-016-1796-5\u003c/li\u003e\n\u003cli\u003ePramesh CS, Saklani AP, Parmar V, Acharya S, Badwe RA (2003) Aberrant subclavian artery causing difficulty in transhiatal esophageal dissection. Dis Esophagus 16:173-176. https://doi.org/10.1046/j.1442-2050.2003.00322.x\u003c/li\u003e\n\u003cli\u003eProye CA, Carnaille BM, Goropoulos A (1991) Nonrecurrent and recurrent inferior laryngeal nerve: a surgical pitfall in cervical exploration. Am J Surg 162:495-496. https://doi.org/10.1016/0002-9610(91)90271-e\u003c/li\u003e\n\u003cli\u003eSatoh S, Tachibana S, Yokoi T, Yamashita H (2013) [Preoperative diagnosis of nonrecurrent inferior laryngeal nerve--usefulness of CT and ultrasonography]. Nihon Jibiinkoka Gakkai Kaiho 116:793-801. https://doi.org/10.3950/jibiinkoka.116.793\u003c/li\u003e\n\u003cli\u003eShindo K, Nagai E, Nabae T et al (2017) Successful video-assisted thoracoscopic surgery in prone position in patients with esophageal cancer and aberrant right subclavian artery: report of three cases. Surg Case Rep 3:86. https://doi.org/10.1186/s40792-017-0360-9\u003c/li\u003e\n\u003cli\u003eStedman GW (1823) A singular distribution of some of the nerves and arteries in the neck, and the top of the thorax. Edinb Med Surg J 19:564-565\u003c/li\u003e\n\u003cli\u003eStewart GR, Mountain JC, Colcock BP (1972) Non-recurrent laryngeal nerve. Br J Surg 59:379-381. https://doi.org/10.1002/bjs.1800590513\u003c/li\u003e\n\u003cli\u003eSugino K, Okamoto H, Fudaba Y, Asahara T (1998) The significance of confirmation for nonrecurrent inferior laryngeal nerve in thyroid surgery (in Japanese). Endocr Surg 15:121-126\u003c/li\u003e\n\u003cli\u003eTerao K, Toda M, Murata K (2000) [A clinical study of the nonrecurrent inferior laryngeal nerve in seven patients]. Nihon Jibiinkoka Gakkai Kaiho 103:1205-1211. https://doi.org/10.3950/jibiinkoka.103.1205\u003c/li\u003e\n\u003cli\u003eToniato A, Mazzarotto R, Piotto A, Bernante P, Pagetta C, Pelizzo MR (2004) Identification of the nonrecurrent laryngeal nerve during thyroid surgery: 20-year experience. World J Surg 28:659-661. https://doi.org/10.1007/s00268-004-7197-7\u003c/li\u003e\n\u003cli\u003eWatanabe A, Kawabori S, Osanai H, Taniguchi M, Hosokawa M (2001) Preoperative computed tomography diagnosis of non-recurrent inferior laryngeal nerve. Laryngoscope 111:1756-1759. https://doi.org/10.1097/00005537-200110000-00017\u003c/li\u003e\n\u003cli\u003eZheng V, Rajeev R, Pinto D, de Jong MC, Sreenivasan DK, Parameswaran R (2023) Variant anatomy of non-recurrent laryngeal nerve: when and how should it be taught in surgical residency? Langenbecks Arch Surg 408:185. https://doi.org/10.1007/s00423-023-02928-y\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"thyroid operation, aberrant right subclavian artery, nonrecurrent inferior laryngeal nerve, preoperative diagnosis, vagal nerve","lastPublishedDoi":"10.21203/rs.3.rs-4173995/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4173995/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose:\u003c/h2\u003e \u003cp\u003eTo avoid complications during thyroid surgery, it is important to be aware of anatomical variations. This study aimed to analyze the clinical aspects of non-recurrent inferior laryngeal nerves (NRILNs) at a hospital in Japan.\u003c/p\u003e\u003ch2\u003eMethods:\u003c/h2\u003e \u003cp\u003eWe retrospectively analyzed thyroid surgery cases at our institution over the last 12 years (2011\u0026ndash;2023). The study included 2187 patients (1676 women, 76.6%) who underwent total thyroidectomy (TT; N\u0026thinsp;=\u0026thinsp;512) or hemithyroidectomy (HT; N\u0026thinsp;=\u0026thinsp;1611). The HT group included 850 right and 761 left thyroidectomies, and 82 patients underwent complementary TTs (40 right and 42 left). The total number of inferior laryngeal nerves identified during surgery was 2717 (1402 right and 1315 left). All patients underwent preoperative neck and thoracic computed tomography (CT) and neck ultrasonography (US). NRILN is classified into two types: Type 1, in which the NRILN branches at the level of the inferior thyroid artery and ascends along the trachea; and Type 2, in which the NRILN branches at the level of the superior pole of the thyroid gland and runs directly to the larynx.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e \u003cp\u003eWe identified 12 NRILN cases. The nerve anomaly was diagnosed preoperatively in all patients. Of these cases, eight were Type 1 and four were Type 2. No inferior laryngeal nerve injury was observed after surgery.\u003c/p\u003e\u003ch2\u003eConclusion:\u003c/h2\u003e \u003cp\u003eTo avoid inferior laryngeal nerve injury, preoperative diagnosis of NRILNs is essential. NRILN is associated with an aberrant right subclavian artery; hence, its presence should be evaluated using routine US and CT before surgery.\u003c/p\u003e","manuscriptTitle":"Surgical Anatomy of Non-Recurrent Inferior Laryngeal Nerves Observed Between 2011–2023","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-02 20:40:00","doi":"10.21203/rs.3.rs-4173995/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3bbdbd17-769d-4f25-ad5f-8069c5ea38fe","owner":[],"postedDate":"April 2nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-04-03T21:14:36+00:00","versionOfRecord":[],"versionCreatedAt":"2024-04-02 20:40:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4173995","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4173995","identity":"rs-4173995","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}