Anatomy Of Recurrent Laryngeal Nerve Research Articles

When The Silence Prevails, Images Talk: The Characteristic Ct Features Of Vocal Cord Paralysis, Causes Of Missed Palsy By Radiologists And Mimics Of Vocal Cord Palsy Unveiled.

Causes of vocal cord palsy (VCP) can be identified even before its clinical presentation if a radiologist has knowledge about signs of vocal cord palsy, its various mimics and the anatomy of recurrent laryngeal nerve. Objectives are to know the signs and underlying causes leading to VCP and various mimics which may lead to the false positive diagnosis of VCP. A retrospective cross-sectional pilot study comprising 54 patients with vocal cord palsy proven by IDL was conducted. 3 groups were identified. The first group comprised missed VCP on cross-sectional imaging. The second group was, of missed cause of VCP in patients with clinical diagnoses. The third group was patients with mimics of the palsy. Thirteen (76.5%) patients had missed diagnosis due to lack of knowledge of signs and 23.5% due to lack of time, overwork and tiredness. A vigilant search for the cause was not done in 31.6% of patients and in 68.4% of patients, the cause was identified but not correlated. A total of 8 patients had false positive diagnoses due to failure to differentiate from mimics. There is an increasing trend of missed diagnosis of vocal cord palsy on cross-sectional imaging in patients with established clinical diagnosis due to a lack of knowledge of VCP signs and missed causes along the course of recurrent laryngeal nerve.

Clinical application of modified fistulectomy in the treatment of congenital pyriform sinus fistula based on segmental anatomy of fistula

Objective:To discuss the clinical application and significance of the modified piriform fossa fistulectomy based on segmental anatomy of fistula. Methods:The clinical data of 84 patients with CPSF treated by modified pyriform sinus fistulectomy were analyzed retrospectively. The modified piriform fossa fistula resection adopts the fistula anterograde anatomy method to fine dissect the fistula. The operation procedure can be summarized into four parts: retrograde anatomy of recurrent laryngeal nerve, anatomy of external branch of superior laryngeal nerve, anterograde anatomy of fistula and partial thyroidectomy. Results:All 84 patients successfully completed the operation and discharged from the hospital. The operation time was（64.6±20.0） min, the intraoperative bleeding was（19.6±13.0） mL, and the average hospital stay was（6.8±1.1） d. Postoperative infection occurred in 1 case（1.19%）, temporary vocal cord paralysis in 1 case（1.19%）, no bleeding, pharyngeal fistula, dysphagia, permanent vocal cord paralysis and choking cough. The incidence of complications was 2.3%（2/84）. No complications such as permanent vocal cord paralysis and hypothyroidism occurred. Follow up for 57-106（Median 74） months showed no recurrence. Conclusion:A modified procedure based on segmental dissection of the fistula not only simplifies the traditional procedure, but also procedures the specific steps to provide a targeted and precise resection, which provides a proven surgical solution for complete eradication of the lesion and significantly reduces complications and recurrence.

Anatomy and motor function of extra-laryngeal branching patterns of the recurrent laryngeal nerve; an electrophysiological study of 1001 nerves at risk

Introduction Safe thyroid surgery depends on a deep knowledge of human neck anatomy, including the recurrent laryngeal nerve (RLN). Anatomic variations such as extra-laryngeal terminal branching (ETB) are common. Patients and methods We studied the ETB pattern of 1001 RLNs at risk in 596 patients. We identified and exposed the location of division points on the cervical part of bifid RLN. The function of nerve branches was assessed through intraoperative nerve monitoring (IONM). Results Bifid RLNs was identified in 39.6% of patients. The nerve-based prevalence of ETB was 28.5%. The prevalence of ETB for the right and left RLN was 21.8% and 35.5%, respectively (p < 0.001). The location of the division point was found in the middle, distal, and proximal segments in 48.8%, 33.3%, and 18% of bifid RLNs, respectively. Electrophysiological monitoring revealed motor functions in all anterior and in 7% of posterior branches. The rate of injury was 0.4%, and 1.1% in single trunk and bifid nerves, respectively (p = 0.360), and 3.9% in nerves with proximal branching (p = 0.084). Conclusions The ETB prevalence is high and showing division points in different cervical segments of the RLN. All anterior branches and some posterior branches contain motor fibers. Knowledge and awareness of these anatomic and functional variations are mandatory for every thyroid surgeon to avoid misidentification and misinterpretation of human RLN anatomy.

Varied Recurrent Laryngeal Nerve Course Is Associated with Increased Risk of Nerve Dysfunction During Thyroidectomy: Results of the Surgical Anatomy of the Recurrent Laryngeal Nerve in Thyroid Surgery Study, an International Multicenter Prospective Anatomic and Electrophysiologic Study of 1000 Monitored Nerves at Risk from the International Neural Monitoring Study Group

Background: The recurrent laryngeal nerve (RLN) can be injured during thyroid surgery, which can negatively affect a patient's quality of life. The impact of intraoperative anatomic variations of the RLN on nerve injury remains unclear. Objectives of this study were to (1) better understand the detailed surgical anatomic variability of the RLN with a worldwide perspective; (2) establish potential correlates between intraoperative RLN anatomy and electrophysiologic responses; and (3) use the information to minimize complications and assure accurate and safe intraoperative neuromonitoring (IONM). Methods: A large international registry database study with prospectively collected data was conducted through the International Neural Monitoring Study Group (INMSG) evaluating 1000 RLNs at risk during thyroid surgery using a specially designed online data repository. Monitored thyroid surgeries following standardized IONM guidelines were included. Cases with bulky lymphadenopathy, IONM failure, and failed RLN visualization were excluded. Systematic evaluation of the surgical anatomy of the RLN was performed using the International RLN Anatomic Classification System. In cases of loss of signal (LOS), the mechanism of neural injury was identified, and functional evaluation of the vocal cord was performed. Results: A total of 1000 nerves at risk (NARs) were evaluated from 574 patients undergoing thyroid surgery at 17 centers from 12 countries and 5 continents. A higher than expected percentage of nerves followed an abnormal intraoperative trajectory (23%). LOS was identified in 3.5% of NARs, with 34% of LOS nerves following an abnormal intraoperative trajectory. LOS was more likely in cases of abnormal nerve trajectory, fixed splayed or entrapped nerves (including at the ligament of Berry), extensive neural dissection, cases of cancer invasion, or when lateral lymph node dissection was needed. Traction injury was found to be the most common form of RLN injury and to be less recoverable than previous reports. Conclusions: Multicenter international studies enrolling diverse patient populations can help reshape our understanding of surgical anatomy during thyroid surgery. There can be significant variability in the anatomic and intraoperative characteristics of the RLN, which can impact the risk of neural injury.

Surgical anatomy of recurrent laryngeal nerve during thyroid and laryngeal surgeries

Objective: To determine the anatomic relationship of recurrent laryngeal nerve with inferior thyroid artery, tracheo-oesophageal groove and Berry’s ligament and to determine the thickness and terminal branching pattern of recurrent laryngeal nerve.Material and Methods: Descriptive prospetive study was conducted in the department of Otorhinolaryngology and Head and Neck surgery in BPKIHS, Dharan, between July 2008- June 2009 including all patients undergoing thyroidectomy and total laryngectomy during the study period.Result: RLN frequently passed behind the inferior thyroid artery and occupied the tracheo-oesophageal groove in the left side than on the right. The average diameter of the nerve was 1.88 mm and the nerve commonly terminated as a single trunk.Conclusion: The nerves were commonly found deep to the ITA (96.2% on left side and 88% on right). The segment of RLN vulnerable to surgical injury between the crossing point of ITA to its entry in the larynx was found to be 3.13 cm (SD=0.29cm). The average thickness of the nerve was 1.68mm however the thickness increased as the surgery progressed and at the end of surgery. All the RLNs on the left side were found completely within the TOG while some variations were seen on the right side.

Location of motor fibers within branches of the recurrent laryngeal nerve with extralaryngeal terminal bifurcation; Functional identification by intraoperative neuromonitoring

Extralaryngeal terminal bifurcation (ETB) of the recurrent laryngeal nerve (RLN) is an anatomic variation that threatens the safety of thyroid operation. Therefore, it is important to identify motor function in nerve branches to preserve appropriate motor activity. Intraoperative neuromonitoring (IONM) is an accepted procedure to identify motor function of the RLN. We established the operative anatomy of RLNs with ETB in 47 patients. The main trunk, bifurcation point, and the branches were identified and exposed completely during thyroid operation. The location of motor fibers within nerve branches was investigated by identifying motor function via IONM. Wave amplitudes were recorded after electrophysiologic stimulation. A total of 61 RLNs had ETBs with anterior and posterior branches. Bifurcation occurred early along the pre-arterial (proximal) segment in 13% of bifid RLNs. IONM showed motor function in all anterior branches. IONM identified motor activity in 4 (18%) posterior branches of 22 right, 3 (8%) posterior branches of 39 left, and 7 (12%) posterior branches of all 61 RLNs with ETB. The rate of recorded wave amplitudes of motor function in seven posterior branches was between 14 and 78% of those of corresponding anterior branches. In the RLN, the anterior branch always and the posterior branch uncommonly contain motor fibers. Wave amplitude analysis showed that motor function in the posterior branch is weaker than that in the anterior branch. On the basis of the location of motor fibers in both branches, total exposure and preservation of anatomy and function of all branches of the RLN is mandatory for complication-free thyroid surgery. Electrophysiologic testing may be as an important adjunct to visualization of the nerve with anatomic variation.

3D reconstruction and heat map of porcine recurrent laryngeal nerve anatomy: branching and spatial location.

Recurrent laryngeal nerve palsy is a common post-operative complication of many head and neck surgeries. Theoretically, the best treatment to restore partial function to a damaged recurrent laryngeal nerve would be reinnervation of the posterior cricoarytenoid muscle via anastomosis of the recurrent laryngeal and phrenic nerves. The pig is an excellent model of human laryngeal anatomy and physiology but a more thorough knowledge of porcine laryngeal anatomy is necessary before the pig can be used to improve existing surgical strategies, and develop new ones. This study first identifies the three most common recurrent laryngeal nerve branching patterns in the pig. Secondly, this study presents three-dimensional renderings of the porcine larynx onto which the recurrent laryngeal nerve patterns are accurately mapped. Lastly, heat maps are presented to display the spatial variability of recurrent laryngeal nerve trunks and primary branches on each side of 15 subjects (28 specimens). We intend for this study to be useful to groups using a porcine model to study posterior cricoarytenoid muscle reinnervation techniques.

Bilateral vocal cord paralysis following coronary artery bypass surgery.

Bilateral vocal cord paralysis following coronary artery bypass surgery.

Reply to Dr. Agarwal’s letter to the Editor “Recurrent laryngeal nerve, phonation and voice preservation—energy devices in thyroid surgery—A note of caution”

Sir, Dr. Brij B. Agarwal’s comments to my letter provide many hints for meditation on the overwhelming aggression of new technologies in general surgery [1]. Moreover, it is a clear invitation for the new generation general surgeons to be judicious and prudent before accepting to use any new technological device so smartly offered by the industry. Otherwise, we all know how difficult it is to propose to a patient to enter a prospective randomized control trial which proposes a new surgical procedure, or any related innovation. Surgery is not medicine, and any procedure “is not like an aspirin”. Nevertheless, the new devices proliferate, and many of them have been recently favorably received by the surgical community. The purpose of my letter to the Editor has been to focus the attention to the fact that ultrasonic coagulating– dissectioning systems (HCDS) and electrothermal bipolar vessel sealing systems (EBVSS)—which are now so widely used in thyroid surgery, either traditional or videoscopic [1]— may be potentially more treacherous due to the restricted space in which possible and unrecognized electrical and thermal effects could damage delicate structures such as the recurrent laryngeal nerve (RLN) [2, 3]. I perfectly agree with Dr. Agarwal that in thyroid surgery a meticulous technique during the dissection is absolutely essential; however, if the well-trained surgeon feels confident in using HCDS or EBVSS, possible solutions to avoid lesions due to the involuntary spread of invisible energy from these devices at present are a standardized technique (distance between HCDS or EBVSS shears to the RLN more than 5mm) and to have an intraoperative neuromonitoring (NM) of the preserved function of RLN [1]. Invisible RLN insult from thermal spread by HCDS or EBVSS goes undetected by the surgeon eye and only intraoperative electromyography with NM can exclude such an insult [1, 4]. NM is a new functional dimension of RLN intraoperative management during modern thyroid surgery, superior to visual identification for intraoperative RLN injury [1, 4]. The intraoperative (and not postoperative) assessment of RLN function during thyroid surgery is important for different reasons: clarification of RLN anatomy; intraoperative prediction of postoperative function (prognosis); prevention of bilateral RLN injury (“stage thyroidectomy”); identification of where and how the RLN was injured; early differentiation between RLN related and unrelated voice changes [4, 5]. I do not mean to emphasize new technologies over sound common sense and I do recognize that at present standards for recurrent laryngeal nerve (RLN) management during thyroid surgery are yet extensive knowledge of RLN anatomy, routine visual identification of nerve, cervical exposure of RLN, experience, training, and preand postoperative laryngoscopy [5]. Specific training and caution with NM is essential for optimal use: this modern device requires a senior endocrine surgeon and anesthesiologist with a high level of experience and a standardized approach with routine preand postthyroid resection vagus stimulation [4, 5]. Langenbecks Arch Surg (2009) 394:913–914 DOI 10.1007/s00423-009-0512-x