Search

Complete and precise knowledge of the neck anatomy and its eventual anomalies is crucial while performing a safe thyroid and parathyroid surgery. Embryo-genetic malformations of the IV branchial arch can lead to an uncommon anatomical alteration known as non-recurrent inferior laryngeal nerve. Its prevalence varies between 0.7% for the dextral branch and 0.04% for the sinistral. In these cases, the inferior laryngeal nerve branches originate directly from the cervical vagus nerve, entering the larynx without hooking, on the right side around the subclavian artery or on the left around the aortic arch. The presence of a non-recurrent laryngeal nerve is challenging, due to the increased risks of iatrogenic damage to the nerve, which results in hoarseness, dysphagia, glottal obstruction, vocal cords palsy, and serious airway impairment. We present the case of a 58-year-old woman. The patient was admitted to our department for a nodule classified as Bethesda IV in the right thyroid lobe. Through the use of intraoperative neuromonitoring (IONM), surgeons detected intraoperatively a non-recurrent laryngeal nerve. A subsequent computed tomography scan confirmed an anomalous right subclavian artery branching from the left aortic arch, the Lusoria Artery. Anatomical variants represent pitfalls in this case and an accurate knowledge of the neck region is imperative while performing thyroid surgery. Devices such as IONM are useful for detecting abnormalities that may lead to iatrogenic damages., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: The purpose of this work was to compare methods of detecting nonrecurrent laryngeal nerves (NRLNs)., Methods: Specificity and sensitivity were compared in three NRLN detection methods: CT, electromyography (EMG), and A-B point comparison., Results: A total of 73 intraoperative pictures and 36 CT details of NRLNs are presented. Incidence of NRLN was 0.39%. Type I NRLN accounted for 50.7%, type IIA 45.2%, type IIB 4.1%. The NRLN median latency was 2.13 ms vs 3.00 ms median in an RLN control group (P < .001). When the threshold was set to 2.5 ms, EMG latency detection had 96.7% sensitivity and 91.6% specificity for detecting NRLN, and the A-B point comparison algrithm had 97.3% sensitivity and 92.5% specificity. Combining EMG latency detection with A-B point comparison achieved 100% sensitivity and specificity for detecting NRLN., Conclusion: This is the largest series of NRLN presented in the literature. Latency shorter than 2.50 ms combined with the A-B point comparison method is the ideal algorithm procedure for early NRLN identification., (© 2018 Wiley Periodicals, Inc.)

Background: Left nonrecurrent laryngeal nerve (LNRLN) is an extremely rare anatomic variant. The development of such anatomic variation requires the regression of both the fourth (aortic arch) and sixth (ductus arteriosus, DA) arches on the left side. Preoperative prediction of this variant is difficult but might reduce risk of nerve injury., Methods: A 34-year-old female was indicated for thyroidectomy for a 2.4 cm follicular neoplasm and Graves' disease. Due to a positive medical history of 22q11.2 microdeletion and unexplained left vocal cord paralysis, a preoperative chest computed tomography (CT) scan was obtained and revealed a right-sided aorta (RSA) and aberrant left subclavian artery (ALSA) without Kommerell's diverticulum. A left-sided NRLN was then highly suspected., Results: Thyroidectomy was performed under general anesthesia with the utilization of intraoperative laryngeal nerve monitoring. A LNRLN was confirmed intraoperatively., Conclusions: Right-sided aorta and ALSA indicate embryologic regression of the left fourth primitive aortic arch. The absence of Kommerell's diverticulum at the origin of the ALSA indicates the lack of high-pressure blood flow from the pulmonary artery to the ALSA through the ductus arteriosus during embryogenesis, suggesting the embryologic regression of the left sixth primitive aortic arch. The presence of all 3 radiologic features thus highly suggests the possibility of a LNRLN.

Background: In thyroid surgery, preserving the recurrent laryngeal nerve (RLN) is crucial for preventing postoperative phonatory dysfunction. Right nonrecurrent laryngeal nerves (NRLNs) are not particularly rare, and they are vulnerable to injury during surgery. This anomaly is associated with a right aberrant subclavian artery. Thus, a right-sided aortic arch with an aberrant left subclavian artery (LSA) suggests a possible left NRLN., Methods: We report the cases of 4 patients with right-sided aortic arch and aberrant LSA. Preoperative imaging studies revealed those anomalies, but no signs of situs inversus. During the surgeries, only 1 of the 4 cases had a left NRLN. We retrospectively evaluated the patients' imaging studies., Results: An aortic diverticulum was found at the point at which the aberrant LSA originated in the 3 patients with left-RLNs, but not in the patient with the left-NRLN., Conclusion: In right-sided aortic arch + aberrant LSA cases, the absence of an aortic diverticulum suggests a left NRLN. © 2016 Wiley Periodicals, Inc. Head Neck 38: First-E2511, 2016., (© 2016 The Authors Head & Neck Published by Wiley Periodicals, Inc.)

The presence of a nonrecurrent laryngeal nerve (NRLN) during carotid endarterectomy (CEA) may significantly limit the exposure of the surgical field during this operation. Although its reported incidence is rare, NRLN typically overlies the carotid bifurcation and failure to recognize this anatomic variation increases the risk of NRLN injury. A retrospective chart review of all patients who underwent CEA for hemodynamically significant extracranial carotid stenosis between January 2005 and December 2014 was performed. All patients with NRLN encountered intraoperatively were identified. Clinical outcomes, surgical techniques, and complications were reviewed and reported. Four left-sided NRLN were identified and 4 were right sided. No cranial nerve deficits or injuries occurred after CEA in patients where NRLN was encountered. Two distinct surgical techniques were used to manage patients with NRLN and they are discussed in detail., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: Nonrecurrent laryngeal nerve (NRLN) is a rare anatomic anomaly, which often co-occurs with aberrant right subclavian artery (ARSA). With this large case series, we present our experience of predicting the presence of NRLN by the means of chest X-ray film, thoracic computed tomography (CT), and ultrasonography., Materials and Methods: A prospective, nonrandomized study has been carried out. A total of 1825 patients with various thyroid disorders scheduled for surgery were recruited between January 2006 and July 2012. All patients underwent preoperative chest X-ray examination. Those suspected with ARSA further underwent thoracic CT scan. Unsuspected patients who had NRLN revealed by surgery were analyzed with ultrasonography postoperatively., Results: A total of 41 patients (2.25%) were suspected to have ARSA by X-ray, of those 19 (46.3%) were confirmed by thoracic CT and proven to have NRLN upon subsequent surgery. No NRLN injury was inflicted. For the remaining 22 cases, CT scan suggested a normal right subclavian artery and none had NRLN upon surgery. For the 1784 unsuspected patients, 4 (0.22%) were discovered to have NRLN upon surgery, of those one was injured. For the 19 predicted NRLN, the time used for identifying the nerve was significantly shorter than the four cases with unsuspected NRLN (t = -15.978; P = 0.000). After the operation, all these unsuspected NRLN were confirmed to have ARSA by ultrasonography., Conclusions: Patients scheduled for thyroid surgery should be screened for ARSA upon routine chest X-ray and thyroid ultrasonography before surgery. Detection of ARSA can accurately predict the existence of NRLN; hence prevent NRLN injury during subsequent surgery., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: The non-recurrent laryngeal nerve is subject to potential injury during thyroid surgery. Intra-operative identification and preservation of this nerve can be challenging. Its presence is associated with an aberrant subclavian artery and the developmental absence of the brachiocephalic trunk. This study aimed to evaluate the incidence of non-recurrent laryngeal nerves and present a new classification system for the course of these nerves., Methods: Non-recurrent laryngeal nerves were identified on the right side in 15 patients who underwent thyroidectomy. The incidence of non-recurrent laryngeal nerves (during thyroidectomy) and aberrant subclavian arteries (using neck computed tomography) was evaluated, and the course of the nerves was classified according to their travelling patterns., Results: The overall incidence of non-recurrent laryngeal nerves was 0.68 per cent. The travelling patterns of the nerves could be classified as: descending (33 per cent), vertical (27 per cent), ascending (20 per cent) or V-shaped (20 per cent)., Conclusion: Clinicians need to be aware of these variations to avoid non-recurrent laryngeal nerve damage. A retroesophageal subclavian artery (on neck computed tomography) virtually assures a non-recurrent laryngeal nerve. This information is important for preventing vocal fold paralysis. Following a review of non-recurrent laryngeal nerve travelling patterns, a new classification was devised.

One of the most important complications of thyroid surgery is inferior laryngeal nerve injury. Variations of inferior laryngeal nerve may increase the risk of iatrogenic injury. Coexistence of ipsilateral nonrecurrent laryngeal nerve and recurrent laryngeal nerve is a very rare variation, and sufficient data are not available on the anatomical and functional relationship of the 2 branches and probable clinical outcomes resulting from the injury of one of them. Herein, we present a case with coexistence of nonrecurrent laryngeal nerve and ipsilateral recurrent laryngeal nerve and discuss the clinical importance of this rare variation.

To delineate the anomaly and frequency of their occurrence in a pig model, we reported the topography of the vagus laryngeal branches and compared the differences with humans. Thirty sides of cervical vagus nerve in 15 fresh cadavers (Sus scrofa) were microdissected. We measured the branch diameters and lengths of the laryngeal branches using a Vernier caliper with a resolution of 0.01 mm. Two patterns of the vagus laryngeal branches were shown: 56.7% with the cranial laryngeal nerve (CLN) and 43.3% without the CLN. The diameters and the length of the CLN were not affected by the side of the neck (P > 0.05), but the diameters of the recurrent laryngeal nerve (RLN) and the nodose ganglion were significantly different between left and right sides (P < 0.05). The left RLN was thinner than the right side in diameter (P < 0.05). Four of the 30 sides had anastomoses between the vagus and the cervical sympathetic chain. There were some differences between the pig anatomy and human anatomy, but the patterns were largely similar. The similarities support the utility of this model, which is closer in size to humans than the standard rodent models.

"Stepladder" surgery for fistula from second or third pharyngeal cleft and pouch is "blind." Neither intraoperative methylene blue injection and probing nor preoperative imaging (fistulogram ultrasound, computed tomography, magnetic resonance imaging) reveal three-dimensional anatomic relations of fistulas. This article describes the most common second and third fistula courses and demonstrates representation of their tracts with wires in human cadavers. A second cleft and pouch fistula, at its external opening, pierces superficial cervical fascia (and platysma), then investing cervical fascia, and travels under the sternocleidomastoid muscle, superficial to the sternohyoid and anterior belly of omohyoid. It ascends along the carotid sheath, and at the upper border of the thyroid cartilage it pierces the pretracheal fascia. Characteristically, it courses between the carotid bifurcation and over the hypoglossal nerve. After passing beneath the posterior belly of the digastric muscle and the stylohyoid, it hooks around both glossopharyngeal nerve and stylopharyngeus muscle. The fistula reaches the pharynx below the superior constrictor muscle. The course of a third cleft and pouch fistula is similar until it has pierced pretracheal fascia; then it passes over the hypoglossal nerve and behind the internal carotid, finally descending parallel to the superior laryngeal nerve, reaching the thyrohyoid membrane cranial to the nerve.

Purpose of the Study: We aimed to highlight a rare anatomical variation involving the recurrent laryngeal nerve, and to emphasise its implications for thyroid surgery., Materials and Methods: Over a period of 13 years, 993 patients underwent thyroid surgery; 1557 recurrent laryngeal nerves (887 on the right side) were exposed., Results: Three non-recurrent laryngeal nerves were found on the right side, associated with a retro-oesophageal subclavian artery. One case was suspected before surgery., Discussion: Several variations in the path and branches of the recurrent laryngeal nerve have been reported in the literature. The frequency of occurrence of a non-recurrent laryngeal nerve is about 1 per cent, for patients undergoing thyroid surgery. Other surgically relevant anatomical variations of the recurrent laryngeal nerve include associations with the inferior thyroid artery and the presence of nerve branches., Conclusion: The recurrent laryngeal nerve must be carefully dissected and totally exposed during thyroid surgery in order to best preserve its function. Moreover, the thyroid surgeon must be aware of the existence of anatomical variations, which are not as rare as one may think.

The identification and prevention of injury to the inferior laryngeal nerve is one of the main issues in thyroid surgery. Sound knowledge of anatomic variants of the nerve is of major importance. In rare cases the nerve does not run the recurrent way and it is therefore difficult to identify the nerve. Abnormal developments of the aortic arch during embryogenesis include malformation of the great vessels and can be the reason for anatomic abnormalities. A cause for a nonrecurrent nerve on the right side is the so-called lusorian artery, a right retroesophageal subclavian artery. Left-sided nonrecurrent nerves are seldom if ever documented. Only two cases have been published so far of patients with situs inversus viscerum, where left nonrecurrent nerves were associated with inverse, left-sided lusorian arteries.

The incidence and possible association of inferior laryngeal nerve and sympathetic anastomotic branch anomalies were evaluated in this study. Non-recurrent inferior laryngeal nerves stem from vascular anomalies involving the right subclavian artery and aortic arches during embryological development. These anomalies usually have no functional consequences (except for occasional dysphagia), but are potentially dangerous during thyroid surgery, occurring in about 1% of cases. Sympathetic-inferior laryngeal anastomotic branches are described in about 1.5% of cases, and may be confused with non-recurrent inferior laryngeal nerves. 1473 patients submitted to total thyroidectomy for benign disease over the period 2001-2006 were evaluated. Four non-recurrent inferior laryngeal nerves (incidence: 0.27%) and 11 sympathetic-inferior laryingeal anastomotic branches (incidence: 0.74%) were observed. Out of a total of 25 definitive inferior laryngeal nerve lesions, 1 occurred in a case of non-recurrent inferior laryngeal nerve. Awareness of the anatomical anomalies described and accurate surgical technique, including a constant search for the inferior laryngeal nerve, are the requirements for identification of non-recurrent inferior laryngeal nerves and sympathetic-inferior laryngeal anastomotic branches. During the pre-operative workup, ultrasonographic study of the right subclavian artery may be advisable in order to rule out alterations of its origin and course.

We present the case of a male patient who needed surgery for a large undefined submandibular schwannoma and a small contralateral thyroid carcinoma associated with cervical lymph nodes of a dubious nature. During the operative procedure all the pathological conditions were resolved, with some remarkable surprises. A non-functioning parathyroid adenoma was found and removed. A fairly unusual anatomical complication was also detected with regard to the right inferior laryngeal nerve, i.e. an anastomotic branch connecting the main trunk to the vagus nerve.

The larynx and its associated structures derive their chief source of innervation from the superior and recurrent laryngeal nerves. Surgery of the larynx requires a sound knowledge of the normal anatomy as well as variations that may be encountered in this region. We report the presence of rare communications between the right external and internal laryngeal nerves as well as between the right external and inferior laryngeal nerves via a thyroid foramen. In addition, we report on bilateral innervation of the respective ipsilateral aryepiglottic, transverse, and oblique arytenoid muscles by the internal laryngeal nerve, which is contrary to the classical descriptions of this nerve. The anatomic features are described and clinical implications are highlighted., (Copyright 2006 Wiley-Liss, Inc.)

The ansa cervicalis is a neural loop in the neck formed by the union of two main nerve roots, namely superior and inferior roots, derived from ventral rami of the cervical nerves. With the expanding use of the ansa cervicalis for reinnervation procedures and the fact that it is located in the vicinity of major nerves and vessels of the neck, knowledge of the topography and morphology of this loop is quite necessary in the modern era. Any variation in the course, contributing roots or branching pattern of the ansa cervicalis, potentially alters and perhaps complicates the course of the procedures involving this nerve such as neurorrhaphy, skull base surgery, neck dissection, and anterior cervical spinal approach. Here, we present an unusual case of an ansa cervicalis encountered upon routine dissection of an adult male cadaver. In this case, the inferior root of the ansa cervicalis was formed by the joining of two rootlets, one originating from spinal accessory nerve and the other from a branch of the cervical plexus to the sternocleidomastoid muscle. The fibers traversing the branch of spinal accessory nerve were derived from the first segments of the cervical spinal cord. This case demonstrates a variant of the spinal accessory nerve plexus that contributed to the formation of the ansa cervicalis. Review of the literature was performed to reveal the possible clinical aspects of this anatomical variation.

Purpose: Damage to the recurrent laryngeal nerve (RLN) during thyroid or parathyroid surgery is the most common iatrogenic cause of vocal cord paralysis. Identification of the RLNs and meticulous surgical technique can significantly decrease the incidence of this complication. Nonrecurrent RLNs (NRRLNs) are exceedingly rare. Surgeons need to be aware of their position to avoid injuries., Patient and Methods: A retrospective review of 263 right RLN exposures (and 251 left RNL) over a 5-year period was performed., Results: Two NRRLNs were encountered, for an incidence of 0.39% (0.76% only for right dissection), without anatomic anomalies on the left side. The nerve anomaly was never preoperatively diagnosed., Conclusion: NRRLNs are rare and is associated with a right subclavian artery arising from distal aortic arch. Awareness of their existence and correct surgical technique will prevent the surgeon from accidentally lesion of NRRLN one if it is encountered during thyroid or parathyroid surgery.

We observed two cases of nonrecurrent inferior laryngeal nerve (NRILN). Case 1, a 71 year old man was diagnosed as having papillary carcinoma. NRILN was found during his operation. It directly branched from the right cervical trunk of the vagus nerve at the level of the cricoid cartilage and then entered the larynx after running behind the thyroid gland. Case 2, a 64 year old woman was diagnosed as having primary hyperparathyroidism. In this patient, the NRILN branched at the level of the inferior pole of the thyroid gland, rose up beside the tracheal wall and entered the larynx. In both patients, preoperative CT scan and postoperative MR angiography revealed the aberrant right subclavian artery. A postoperative barium swallow test showed the compression of the esophagus by this anomalous artery in case 1. Although it is possible to predict the presence of NRILN by preoperative imaging tests, the branching level from the vagus nerve is unpredictable. Surgery must be performed with this point in mind, if the presence of NRILN is suspected.

Aim: Systematic exposure and isolation of the inferior laryngeal nerve in thyroid surgery is a secure method to prevent complications. The knowledge of the nerve anatomy and its anomalies is essential to reduce laryngeal nerve injuries. By a re-examination of literature we underline the importance and some particular anatomical aspects of the anomalies which, even if rare, present an incidence of about 1%., Methods: From January 1995 to December 2002 in our hospital we performed 299 interventions for thyroid diseases: total thyroidectomy (254 cases), partial thyroidectomy (45 cases). In 2 cases we observed a high variant (type I) of non recurrent laryngeal nerve., Results: The global incidence of non recurrent laryngeal nerve was 0.66% (2/299 operations) and 0.72% if we consider the explorations of the cervical right side (2/274) where this anomaly is more frequent. The incidence of nerve injuries was 2/299 (0,66%); we had no complications in the 2 cases of non recurrent nerve observed., Conclusions: Our experience in thyroid surgery confirms the common opinion that only the knowledge of the laryngeal nerve anatomy and the awareness of its anomalies, associated to the systematic exposure of the nerve during surgery can prevent surgical injuries.

The non-recurrent inferior laryngeal nerve (NRILN) is a nerve anomaly that can be associated with an increased risk of vocal fold paralysis. The purpose of this study was to report three new cases of this anomaly, underline the necessity of recognizing its possibility for the prevention of intra-operative nerve damage and a review of the literature. Three cases of thyroid surgery associated with right NRILN are reported. Two patients underwent bilateral thyroidectomy for a multinodular goitre and for a toxic multinodular goitre respectively. The third patient had a right lobectomy and isthmectomy for a thyroid nodule. All patients had identification of the recurrent laryngeal nerve on the left side and NRILN on the right side. The diagnosis of the NRILN was made per-operatively on all cases. A post-operative computed tomography (CT) scan in two patients, showed a retrooesophageal aberrant right subclavian artery. Post-operatively, all patients had normal vocal fold function on laryngoscopy. The NRILN is a rare anomaly but overlooking its possibility may lead to severe operative morbidity. This is an additional argument in favour of systematic dissection of the recurrent inferior laryngeal nerve during thyroid surgery.

A 34-year-old patient with primary hyperparathyroidism and repeated renal stones underwent a parathyroidectomy. During operation, a right superior parathyroid adenoma was found which measured 3.5 x 1.5 x 1.0cm in size. The right nonrecurrent laryngeal nerve passed over the middle of the adenoma, and deformed the parathyroid into a dumbbell shape. Magnetic resonance angiography revealed an absence of the right innominate artery and an independent origin of the right retroesophageal subclavian and common carotid artery. The combination of the parathyroid tumor and nonrecurrent laryngeal nerve is extremely rare, especially in Asia. To avoid surgical complications, it is important to understand the possibility of a nonrecurrent laryngeal nerve developing in such patients.

Background: Injury to the external laryngeal branch of the superior laryngeal nerve during thyroid surgery is not uncommon. Most surgeons tend to avoid rather than expose and identify the external laryngeal nerve (ELN). The aim of the present study was to analyse the frequency and types of ELN crossing the avascular space in relationship to the structures to the upper pole of the thyroid and related thyroid pathology., Methods: One hundred and fifty-one consecutive patients who had thyroid surgery from February 1998 to February 1999 and who met the required preoperative criteria were included into this prospective study. The frequency and type of ELN was documented as it crossed the potential avascular space., Results: A total of 202 ELN (92.7%) nerves were identified during thyroid surgery. The frequency of the ELN documented crossing the avascular space were: type 1 nerve, 35 (17.3%); type 2a, 113 (56%); and type 2b, 54 (26.7%). Sixteen (7.3%) ELN were not seen despite an extensive search; seven (3.2%) were cases of secondary thyroid surgery and six (2.8%) were cases of malignant related pathology. In 78 cases the goitres weighed more than 100 g and the frequencies of ELN distribution seen were: type 1, six (7.7%); type 2a, 32 (41%); and type 2b, 40 (51.3%). There was a considerably higher frequency of type 2b ELN (51.3%) in large goitres of more than 100 g., Conclusions: The various technical problems in preserving the ELN need to be considered. Recognition of the potential avascular space aids the exposure and preservation of ELN. As such every attempt should be made to ensure safe dissection in order to reduce morbidity related to thyroid surgery.

An incidental finding in the anatomy lab showed up a plexus of the external branch of the right superior laryngeal nerve (SLN), including an anastomosis with the recurrent laryngeal nerve (RLN). The external branch of the SLN divided in two extensions: The ventral extension reached the mesopharynx laterally and by supplying the latter, ended at the cricothyroid muscle. The dorsal extension formed a plexus a finger's breadth beneath the inferior margin of the pharynx, on the lateral aspect of the esophagus. The anastomosis ran from the lower part of the plexus to the RLN along the esophagus, laterally., (Copyright 2000 Wiley-Liss, Inc.)

The non-recurrent inferior laryngeal nerve is a rare anomaly (0.34% on th right side, extremely rare on the left side) that increases the risk of damage to the nerve during thyroid and parathyroid surgery. Seven cases of non-recurrent laryngeal nerve are reported, emphasizing the diagnostic accuracy of angio-MR for the anatomical identification of the vascular anomaly that invariably occurs with the nerve malformation.

Purpose: In head and neck surgery, damage to the recurrent laryngeal nerve (RLN) during thyroid surgery is the most common iatrogenic cause of vocal cord paralysis. Identification of the RLNs and meticulous surgical technique can significantly decrease the incidence of this complication. Nonrecurrent RLNs (NRRLNs) are exceedingly rare. Surgeons need to be aware of their position to avoid damage to them., Materials and Methods: A retrospective review of 513 RLN exposures over a 7-year period was performed., Results: Two NRRLNs were encountered, for an incidence of 0.39%., Conclusion: NRRLNs are rare. Awareness of their existence will prevent the surgeon from accidentally severing one if it is encountered during routine thyroid or parathyroid surgery.

The authors report 17 cases of a right non-recurrent inferior laryngeal n. (NRILN) observed during 15 years of practice of thyroid and parathyroid surgery. In their last two cases, the existence of an aberrant right subclavian a., constantly associated with NRILN, was confirmed by MRI angiography. On the basis of the literature and their own experience, the authors review the incidence of this double anomaly, its embryologic explanation and its anatomic and surgical importance. They stress the diagnostic factors and the therapeutic implications, very different in children and adults, of a particular vascular anomaly whose outcome is little understood.

The Authors describe a case of non recurrent inferior laryngeal nerve located on the right side observed during anatomical studies of the innervation of the larynx. The description is accompanied by photographic documentation which shows the anomalous course of the nerve and its abnormal relationship with the right subclavian artery, also anomalous. The embryological nature of such anatomical variations is discussed followed by considerations concerning possible consequences with regard to clinical aspects and thyroid surgery. Furthermore, the Authors indicate clinical signs that may suggest the presence of such anomaly so as to avoid anatomical or functional damage of the nerve which, although anomalous, plays an important role in coordinating breathing and phonation.

There is a lack of appreciation for the fact that, in less than 1 per cent of the general population, the right subclavian artery has an anomalous origin and course. Fortunately, most of these persons do not have symptoms; however, if they should have neck surgery, they may be at increased risk for damage to the right inferior laryngram nerve. The earliest reported description of an anomalous right subclavian artery was that of Hunald in 1735; 52 years passed before the clinical syndrome of dysphagia lusoria was published by Bayford in 1787. Bayford did not mention the associated displacement of the right inferior laryngeal nerve. In 1823, Stedman described the entire anatomical picture.

During surgery on the right thyroid lobe, 15 cases of non-recurrence of the inferior laryngeal nerve were observed, among which two types of equal frequency. Embryologic data explain why this abnormality is always associated with an abnormal origin of the right subclavian artery, directly from the aortic arch. The right subclavian artery generally passes behind the oesophagus in these cases. These 15 cases represent 0,79% of the 1889 cases studied during a short period (1971-1978).

Nineteen cases of non-recurrent inferior laryngeal nerve were identified during 3791 cervicotomies for thyroid or parathyroid excision over the last 7 years, the nervous anomaly being of vascular anomaly origin in all cases. Predisposing factors for its onset during aortic arch development are discussed, together with possible symptomatology and means for preoperative diagnosis. Frequency in the cases reported was 0,54% from 3098 dissections on the right and 0,07% from 2846 dissections on the left. Although rare on the right and exceptional on the left, an aberrant non-recurrent pathway for the inferior laryngeal nerve represents a major, surgical risk during thyroid or parathyroid excision.

In 6307 cervicotomies for thyroid and parathyroid excision, 33 cases of nonrecurrent inferior laryngeal nerve were identified (0.52%). The anomaly was observed in 31 cases from 4921 dissections on the right side (0.63%) and in two cases from 4673 dissections on the left side (0.04%). Of the 31 patients who were initially seen with this anomaly on the right side, no innominate (brachiocephalic) artery was found; the right common carotid artery was arising directly from the aortic arch. The aberrant subclavian artery could always be felt against the vertebral column behind the esophagus. The two patients with the anomaly on the left side had a right aortic arch associated with situs inversus viscerum. In one case of invasive thyroid carcinoma, the nerve had to be sacrificed. In all of the other patients, postoperative laryngoscopic findings were normal. The nervous anomaly was of vascular anomaly origin in all cases. Predisposing factors for its onset during aortic arch development are discussed. Before surgical treatment, the diagnosis may only be made if vascular anomaly is suspected. Impairment of swallowing is the only clinical symptom to be looked for. The retroesophageal subclavian artery may be detected on chest x-ray films (20%) or by the compression and distortion of the esophagus shown during barium swallow tests (97%). Although rare on the right side and exceptional on the left, an aberrant nonrecurrent pathway for the inferior laryngeal nerve represents a major surgical risk. This is an additional argument in favor of systematic dissection of the inferior laryngeal nerve during thyroid or parathyroid excision.

The anomalous position of a nonrecurrent laryngeal nerve predisposes the nerve to injury during thyroidectomy and to compression by a thyroid mass. We present three cases in which a seemingly benign thyroid mass traumatized a nonrecurrent laryngeal nerve resulting in either vocal cord paralysis or a vague pressure sensation over the larynx. Some of these patients feel as if they need to clear a foreign body and present with a chronic cough. Normally the nerve is protected from thyroid masses as it passes through the tracheoesophageal groove. In all three patients, surgical excision of the thyroid mass and release of the nerve resulted in recovery of the nerve and resolution of the symptoms. We have found that small, benign, or otherwise asymptomatic lesions of the thyroid gland have a greater tendency to cause vocal cord paralysis in patients with nonrecurrent laryngeal nerves. The surgeon must always be aware of the possibility of the presence of a nonrecurrent laryngeal nerve.

The etiology of 389 cases of partial or complete bilateral abductor vocal cord paralysis has been determined and classified. One hundred and forty-nine were infants and children 12 years of age and under; 240 were adults, age 13 and older. In the infants and children the paralyses were congenital in 82 cases, of which 43 were associated with other congenital anomalies, and 39 were without associated anomalies. Fifty-nine cases were considered acquired, most being secondary to underlying congenital anomalies, particularly the associated findings of meningomyelocele, Arnold-Chiari malformation, and hydrocephalus. Eight cases of paralysis in this age group were of undetermined etiology. Of the 240 adult cases of bilateral vocal cord paralysis. 138 followed thyroidectomy. Fifty-two cases were associated with various neurologic disorders, including poliomyelitis, Parkinson's disease, cerebrovascular accident, Guillain-Barré syndrome, multiple sclerosis, neoplasms and other miscellaneous neurologic conditions. Sixteen cases were due to malignant neoplasms of the neck and mediastinum. The remaining 34 cases constitute a miscellaneous group which includes foreign bodies, bilateral neck dissection, infection, congenital lesions, trauma, and idiopathic paralyses. The characteristic symptoms of bilateral abductor vocal cord paralysis include normal or near normal phonation with inspiratory stridor which may progress to complete respiratory obstruction. These symptoms are due to the stationary but flaccid midline position of the vocal cords which places them in a phonating position, where they both obstruct the airway and produce a faily clear voice or cry. This paradoxical combination of symptoms was frequently found to be responsible for a failure or delay in diagnosis.

Two cases of a right non-recurrent nerve were encountered in 203 thyroidectomies. In its abnormal, non-recurrent course the nerve passes transversely from under the carotid sheath and takes a position which is at right-angles to the normal recurrent laryngeal nerve.

Congenital anomalies of the parathyroids in cases of cot death have been reported by several workers. Carotid-body hypoplasia also has been noted in typical cases of cot death. Neurally conditioned airway occlusion at the oropharyngeal level has been postulated as a precipitating factor of cot death. All these lines of evidence involve structures derived from the third branchial arch, and it is suggested that developmental arrest of this arch in early gestation may be the pathandemical basis of cot death.

2 cases are described of a right recurrent nerve with abnormal origin and path. Frequency: 0,8%. Both cases ware associated with the presence of an A. lusoria. In the first case, the "non-recurrent" recurrent nerve reached the thyroid gland by its superior pole, in the second case by its inferior pole. In the latter case, there was a close relation between the nerve and the branches of the inferior thyroid artery. The consequences are discussed in relation to the surgical techniques.