Anatomical variations of recurrent laryngeal nerve: a systematic review and meta-analyses.

PURPOSE: The aim of this systematic review and meta-analysis was to systematically review and perform a meta-analysis on the anatomical variations of the RLN. METHODS: We performed online research for studies that addressed anatomical variations of the RLN and laterality, published between 2015 and 2021. We found 230 articles, and nine were included. RESULTS: Eight variations were found, with Type I prevailing (41.17%; 95% CI 19.44-64.88), extra laryngeal divergence of the RLN. The other types were: II-fan shape; III-distance greater than 5 mm to the cricothyroid joint; IV-thickening and adipopexy in the elderly; V-non-recurrent laryngeal nerve; VI-intracranial branch; VII-tortuous ascending RLN; and VIII-combination between the inferior branch of the NV and the ascending trunk of the RLN. Types I (p = 0) and III (p < 0.01) prevailed on the left and types II (p < 0.01) and V (p < 0.01) on the right. CONCLUSIONS: It was observed that variations occurred due to the path of the RLN to the entrance to the larynx, its shape, and the age of the evaluated individual. The most frequent variation and side were, respectively, Type I, extra laryngeal divergence and left.

Patient Perception of Swallowing after Thyroidectomy in the Absence of Laryngeal Nerve Injury.

INTRODUCTION: Swallowing and voice alterations may manifest in patients with thyroid disease, especially after thyroidectomy. OBJECTIVE: To identify the prevalence of patients with complaints of swallowing disorders after thyroidectomy and to evaluate patients' perceptions regarding swallowing before and after the procedure. METHODS: A prospective longitudinal study was performed with 26 consecutive patients undergoing a private service thyroidectomy, in which the presence of swallowing dysfunction was evaluated using validated questionnaires that addressed the perception of swallowing by patients before (on the day of surgery) and after the surgery (on the first postoperative day). RESULTS: Of the 26 patients, 18 (69.2%) were subjected to total thyroidectomy and 8 to partial thyroidectomy. Analysis of the domains of the Swallowing Handicap Index questionnaire showed higher scores when evaluated on the first postoperative day, demonstrating a significant worsening in swallowing after the procedure. The same result was demonstrated for the final score of swallowing perception, with 15.3 and 30.8% of patients reporting moderate alterations before and after the thyroidectomy, respectively, and 11.5% reporting the alterations as severe. Swallowing and vocal symptoms on the first postoperative day were more prevalent in the procedure than previously mentioned. Eight patients (30.8%) noted swallowing alterations before the procedure, compared with 80.8% (21 cases) after thyroidectomy. CONCLUSION: There was a prevalence of 42.3% in swallowing complaints on the first postoperative day, regardless of the lesion in the laryngeal innervation, and this prevalence was significantly higher than that prior to the procedure.

O tubérculo de Zuckerkandl pode auxiliar na localização do nervo laríngeo inferior durante tireoidectomias? / Can the Zuckerkandl tubercle assist in the location of the inferior laryngeal nerve during thyroidectomies?

RESUMO Objetivo: avaliar se a projeção lateral da glândula tireoide, chamada tubérculo de Zuckerkandl (TZ), pode auxiliar o cirurgião na identificação do nervo laríngeo inferior durante a tireoidectomia convencional aberta. Métodos: estudo prospectivo de 51 pacientes submetidos à tireoidectomia, com um total de 100 lobos tireoidianos ressecados, e observação da presença ou não do TZ em dimensões suficientes para ser identificado sem magnificação de imagem, suas dimensões de base e altura, sua localização na glândula e sua relação anatômica com o nervo laríngeo inferior. Resultados: o TZ estava presente em 68 dos 100 lobos de tireoide analisados (68%). A dimensão média da base foi 6,7mm no lado direito e 7,1mm no lado esquerdo, e a altura média foi 5,7mm no lado direito e 6,1mm no lado esquerdo. Na maioria dos lobos estudados, o tubérculo tinha altura mínima de 5mm (55,9%) sem diferença significativa entre o lobo direito e esquerdo da glândula tireoide. Durante a cirurgia, 100% dos TZ identificados estavam anteriores ao nervo laríngeo inferior, imediatamente abaixo da entrada do nervo na laringe. Conclusão: o TZ é bastante frequente e em dimensões suficientes para ser usado como referência anatômica na localização intraoperatória do nervo laríngeo inferior, próximo à sua entrada na laringe, junto com as demais referências anatômicas.

ABSTRACT Objective: to evaluate whether the lateral projection of the thyroid gland, called Zuckerkandl's tubercle (ZT), can assist the surgeon in identifying the inferior laryngeal nerve during conventional open thyroidectomy. Methods: we conducted a prospective study with 51 patients submitted to thyroidectomy, with a total of 100 resected thyroid lobes, and observed the presence or absence of ZT in sufficient dimensions to be identified without image magnification, its base and height, its location in the gland, and its anatomical relationship with the inferior laryngeal nerve. Results: ZT was present in 68 of the 100 thyroid lobes analyzed (68%). The mean base was 6.7mm on the right side and 7.1mm on the left side, and the average height was 5.7mm on the right side and 6.1mm on the left side. In most of the lobes studied, the tubercle had a minimum height of 5mm (55.9%), with no significant difference between the right and left lobes of the thyroid gland. During surgery, 100% of the identified ZTs were anterior to the inferior laryngeal nerve, just below the nerve entry in the larynx. Conclusion: the ZT is a quite frequent entity and large enough to serve as an intraoperative anatomical reference for the inferior laryngeal nerve, next to its entry in the larynx, along with other anatomical references.

Injury of the external branch of the superior laryngeal nerve in thyroid surgery.

The external branch of the superior laryngeal nerve (EBSLN) innervates the cricothyroid muscle (CTM) to promote lengthening and thinning of the vocal fold, thus increasing voice pitch. The close relation with the superior thyroid vessels (STV) puts the EBSLN in risk every time the superior pole of the thyroid is dissected. It travels downward to innervate the CTM, lateral to the thyroid cartilage and to the inferior pharyngeal constrictor muscle (IPCM), being eventually covered by this muscle fibers as it approaches its entry point. During its descending course, the EBSLN curves and crosses the STV posteriorly. The lower this crossing occurs in the neck, the higher the risk of surgical damage to the nerve by transection, traction, entrapment, thermal damage or disrupted blood supply. The chances of surgical trauma are also increased by size and weight of the specimen, shorter neck length and non-white ethnicity. Voice changes following thyroid surgery are common and multifactorial. The actual rate of vocal impairment due to EBSLN injury is unclear, since changes to the everyday speaking voice can be minimal and laryngeal findings are usually subtle and controversial. CTM electroneuromyography (EMG) is the most accurate tool to diagnose abnormal EBSLN conductivity, but it is technically difficult and barely applicable in routine practice. Recommended approaches to prevent injury include: (I) individual distal ligature of the STV by the thyroid capsule; (II) visual identification of the nerve and its trajectory and (III) electrostimulation with either observation of CTM twitch or intraoperative nerve monitoring (IONM) via dedicated endotracheal tube electrodes. There is accumulating evidence that a combination of visual and standardized electrophysiological EBSLN identification with meticulous division of the STV improves preservation rates. IONM bears the additional benefits of prognostication, quantification and documentation of neural function once it allows intraoperative laryngeal EMG.

Anatomic relation between the external branch of the superior laryngeal nerve and the thyroid gland / Relação anatômica entre o ramo externo do nervo laríngeo superior e a glândula tireoide

AIM: This prospective study investigated the anatomic relations between the external branch of the superior laryngeal nerve (EBSLN), the superior thyroid artery (STA) and the thyroid gland in human cadavers. MATERIAL AND METHODS: Twenty-two human cadavers aged over 18 years old, less than 24 hours after death. RESULTS: The mean distance between the EBSLN and the superior pole of the thyroid gland was 7.68 ±3.07 mm. A tangent to the inferior edge of the thyroid cartilage between the EBSLN and the STA measured 4.24 ±2.67 mm. A line from the intersection of the EBSLN - related to the STA - to the superior pole of the thyroid gland measured 9.53 ±4.65 mm. A line from the EBSLN to the midline of the most caudal point of the thyroid cartilage measured 19.70 ±2.82 mm. A line from the RENLS to the midline on the most cranial point of the cricoid cartilage was 18.35 ±3.66 mm. CONCLUSION: There is a variable proximity relation between the EBSLN and the superior pole of the thyroid gland; this distance ranges from 3.25 to 15.75 mm. There was no evidence of significant variation between the measures in the ethnic groups comprising the sample.

OBJETIVO: Descrever, prospectivamente, a relação anatômica entre o ramo externo do nervo laríngeo superior (RENLS), a artéria tireoidea superior (ATS) e a glândula tireoide em cadáveres humanos. MATERIAL E MÉTODO: Foram dissecados 22 cadáveres humanos com idade superior a 18 anos, com menos de 24 horas de pós-morte. RESULTADOS: A medida entre o RENLS e o polo superior da glândula tireoide foi 7,68 +/- 3,07mm; entre o RENLS e a ATS foi de 4,24 +/- 2,67mm numa linha tangente ao bordo inferior da cartilagem tireoide; entre o cruzamento da ATS com o RENLS e o polo superior tireoidiano foi 9,53 +/- 4,65mm; entre o RENLS e a linha mediana do pescoço no ponto mais caudal da cartilagem tireoide foi 19,70 +/- 2,82mm; e entre o RENLS e a linha mediana do pescoço no ponto mais cranial da cartilagem cricoide foi 18,35 +/- 3,66mm. CONCLUSÕES: Há uma relação de proximidade variável entre o RENLS e o polo superior da glândula tireoide, variando de 3,25 a 15,75mm. Não constatou-se variações significativas entre as medidas para as diferentes etnias que compõem a amostra.

Análise retrospectiva das tireoidectomias realizadas por residentes de cirurgia geral em hospital universitário / Retrospective analysis of the thyroidectomies performed by general surgery resident in a university hospital

Introdução: Com o objetivo de avaliar as complicações das tireoidectomias realizadas no Hospital Geral do Grajaú, da Faculdade de Medicina da UNISA, durante o período de novembro de 2000 a agosto de 2003, foram analisados retrospectivamente 105 prontuários. Métodos: Todas as cirurgias foram realizadas pelo residente do segundo ano de Cirurgia Geral sob a supervisão de um especialista. Os pacientes foram analisados de acordo com o gênero, idade, duração média da cirurgia, tempo de internação pós-operatório e complicações apresentadas. Resultados: Na série estudada, 85,7% dos pacientes (90 casos), era do gênero feminino. A idade média dos pacientes foi de 50,5 anos, tendo um predomínio de doenças benignas (84% dos casos). A tireoidectomia total foi realizada em 77,1% dos pacientes (81 casos) e 96% dos pacientes receberam alta em até 48 horas após a cirurgia. As complicações encontradas foram: hipocalcemia definitiva em 0,95% (um caso); paralisia transitória do nervo laríngeo recorrente em 2,85% (três casos) e definitiva em 1,9% (dois casos); hematoma com posterior necessidade de reabordagem em 1,9% (dois casos) e desenvolvimento de hipotireoidismo em 50% dos casos que foram submetidos à tireoidectomia não total e nenhum óbito. Conclusão: A tireoidectomia é um procedimento com baixa morbimortalidade, sendo segura, mesmo quando realizado por cirurgiões em treinamento, desde que sob a supervisão direta de um especialista.

Introduction: In order to evaluate the thyroidectomies done in Grajaú General Hospital - UNISA - Medical University from November, 2000 to August, 2003, 105 patients were retrospectively analyzed. Methods: All surgeries were performed by the general surgery 2nd year resident under a specialist supervision. The patients were analyzed according to the gender, age, average duration of the surgery, postoperative permanence into the hospital, and diagnosed complication. Results: In the analyzed series, 85.7% of the patients (90 cases), were women. The age average was 50.5 years-old with a predominance of benign pathology (84.4% of the cases). The total thyroidectomy was performed in 77.1% (81 cases) and 96% of the patients were discharged from hospital in 48 hours after surgery. The following complications were found: definitive hypocalcemia in 0.95% (1 case); transitory palsy of the laryngeal nerve in 2.85% (3 cases); definitive palsy of the laryngeal nerve in 1.9% (2 cases); hematoma with posterior need of reoperation in 1.9% (2 cases); development of hypothyroidism in 50% of the cases which underwent to non total thyroidectomy. There was no death. Conclusion: The thyroidectomy is a low morbimotality procedure and it is safe, even when performed by surgeons in training, since under straight specialist supervision.

Análise quantitativa das fibras mielínicas dos nervos laríngeos em humanos de acordo com a idade / Quantitative analysis of myelinic fibers in human laryngeal nerves according to age

INTRODUÇÃO E OBJETIVO: Realizar análise morfométrica das fibras mielínicas dos nervos laríngeos com a finalidade de verificar modificações quantitativas decorrentes do processo de envelhecimento. FORMA DE ESTUDO: Clínico e experimental. Material e Método: Foi coletado fragmento de 1cm dos nervos laríngeos superiores e nervos laríngeos recorrentes de 12 cadáveres do sexo masculino. A amostra foi dividida em dois grupos: idade inferior a 60 anos (Adulto) e idade igual ou superior a 60 anos (Idoso). O material foi avaliado em microscópio de luz acoplado a sistema analisador de imagem. RESULTADOS: O número total de fibras mielínicas do nervo laríngeo superior foi semelhante nos dois grupos etários, mas com tendência para o maior número de fibras de 1µm no grupo adulto (p=0,0744). O grupo adulto apresentou maior número total de fibras mielínicas no nervo laríngeo recorrente (p=0,0006), e esta diferença ocorreu nas fibras com diâmetros de 1-3µm (p<0,007). O grupo adulto apresentou maior número total de fibras mielínicas nos nervos laríngeos (soma das fibras dos nervos laríngeos superiores e dos nervos laríngeos recorrentes) que o grupo idoso (p<0,0091). CONCLUSÃO: O número total de fibras mielínicas dos nervos laríngeos é maior no grupo com idade inferior a 60 anos.

INTRODUCTION AND AIM: To carry out a morphometric analysis of myelinic fibers in laryngeal nerves aiming to identify quantitative changes as a result of aging. Study design: Clinical and experimental. MATERIAL AND METHOD: A 1cm fragment was collected from the superior laryngeal nerves and recurrent laryngeal nerves taken from twelve male cadavers. The sample was divided into two groups: those aged below 60 years (Adult) and those aged 60 years or more (Elderly). The material was evaluated under light microscopy coupled with an image analysis system. RESULTS: The total number of myelinic fibers from the superior laryngeal nerve was similar in both age groups; there was, however, a trend for a higher number of 1ìm fibers in the adult group (p=0.0744). The adult group had a higher total number of myelinic fibers in the recurrent laryngeal nerve (p=0.0006), and this difference was seen in fibers with diameters betwee 1-3ìm (p<0.007). The adult group had a higher total number of myelinic fibers in the laryngeal nerves (sum of superior laryngeal nerves and recurrent laryngeal nerves fibers) compared to the elderly group (p<0.0091). CONCLUSION:The total number of myelinic fibers in laryngeal nerves is higher for the group aged below 60 years.

Superior laryngeal nerve anatomy in corpses not preserved in formaldehyde: contribution to the operative technique / Anatomia do nervo laríngeo superior em cadáver não formalizado. Contribuição para a técnica operatória

PURPOSE: To carry out an anatomic study of superior laryngeal nerve in not preserved in formaldehyde and not frozen corpses. METHODS: Thirty-eight male corpses from the Minas Gerais Medico-legal Institute (IML) were studied. In 18 corpses dissection was performed bilaterally and in 20 only on the left side, total number 56 nerves dissected. Their descriptive segments measurements and the anatomic relations with the cervical structures of the region were described. This nerve was statistically analyzed; the variables were corpse side (Friedmanïs test (p<0.05), height (Pearson), racial group (Kruskal-Wallis). RESULTS: The superior laryngeal nerve presented a definite anatomical disposition in all the 56 nerves studied, emerging from the nervus vagus inferior ganglion. The superior laryngeal nerve trunk was in average longer in corpses over 25 years old (p<0.05). Significant differences (p<0.05) between the internal and external branches were observed in all racial groups, and the internal branch average was inferior to the external branch average. There were not significant differences between the 18 studied corpses' left and right sides paired measurements. CONCLUSIONS: Concerning emergence, trunk, bifurcation and major branches, the 56 studied nerves disposition had a definite anatomic pattern. The superior laryngeal nerve trunk was in average longer in corpses over 25 years old. In this study, the external branch of the laryngeal nerve was in average longer than the internal branch.(AU)

OBJETIVO: Realizar um estudo anatômico do nervo laríngeo superior através da dissecção em cadáver não formolizado e não congelado. MÉTODOS: 38 cadáveres do sexo masculino, provenientes do Instituto Médico-Legal de Minas Gerais (IML), foram estudados. Em 18 cadáveres a dissecção foi realizada bilateralmente e em 20 somente do lado esquerdo, totalizando 56 nervos. Foram registradas as medidas descritivas dos seus segmentos e as relações anatômicas com as estruturas cervicais da região. Este nervo foi analisado sob o ponto de vista estatístico, com as variáveis: lado (teste de Friedman p<0,05), altura e idade (Pearson) e etnia (Kruskal-Wallis). RESULTADOS: O nervo laríngeo superior apresentou uma disposição anatômica definida em todos os 56 nervos estudados, emergindo do gânglio inferior do nervo vago. O tronco do nervo laríngeo superior foi em média mais longo nos cadáveres acima de 25 anos de idade (p<0,05). Foram observadas diferenças significativas (p<0,05) entre as medidas do ramo interno e do ramo externo em todos os grupos étnicos, sendo que a média do ramo interno foi inferior à média do ramo externo. As medidas pareadas dos lados direito e esquerdo não apresentaram diferenças significativas nos 18 cadáveres estudados. CONCLUSÕES: A disposição dos 56 nervos laríngeos superiores mostrou um padrão anatômico definido, quanto à emergência, ao tronco, à bifurcação e aos ramos principais. O tronco do nervo laríngeo superior foi em média mais longo nos cadáveres acima de 25 anos de idade. O comprimento do ramo externo do nervo laríngeo superior foi em média maior do que o do ramo interno, neste estudo.(AU)

Protocolo anatômico-cirúrgico das relações entre os nervos laríngeos recorrentes e as artérias tireóideas inferiores: estudo em 79 tireoidectomias / Anatomical-surgical protocol of the relation between recurrent laringeal nerves and inferior thyroidal artery in 79 thyroidectomies

INTRODUÇÃO: Os cuidados com as preservações dos nervos laríngeos recorrentes e das glândulas paratireóides, nas tireoidectomias, continuam desafiando os cirurgiões em razão das graves complicações que podem ocorrer quando são manipulados inadequadamente. O trabalho teve como objetivo, no curso das tireoidectomias totais e parciais, estabelecer protocolo anatômico-cirúrgico das relações anatômicas entre os nervos laríngeos recorrentes com as artérias tireóideas inferiores, identificar-preservar esses nervos e as glândulas partireóides. MÉTODO: Os registros fotográficos durante os trans-operatórios foram obtidos de 79 pacientes submetidos às tireoidectomias totais e parciais (lobectomia total direita ou esquerda e istmectomia), respectivamente, com as identificações dos nervos e artérias bi ou unilateralmente, propondo expor as relações anatômicas entre essas estruturas, operados entre janeiro de 2005 e julho de 2006. RESULTADOS: Os registros fotográficos foram adaptados aos desenhos esquemáticos para estabelecer os principais pontos de referências anatômicas dos nervos laríngeos recorrentes em relação às artérias tireóideas inferiores, totalizando 116 nervos laríngeos recorrentes. CONCLUSÃO: A íntima relação dos nervos laríngeos recorrentes e as artérias tireóideas inferiores podem se apresentar de diversas formas, incluindo as anomalias congênitas, como a do laríngeo não recorrente, as duplicações e triplicações pré-laríngeas do nervo, sem dúvida, algumas vezes, dificultando a identificação dessas estruturas. São imperativas as claras identificações dessas estruturas e das glândulas paratireóides para preservá-las, no curso das tireoidectomias totais e parciais, a fim de evitar as complicações pós-operatórias.

BACKGROUND: Care in preserving the recurrent laryngeal nerves and the parathyroids glands, during thyroidectomies, continue to challenge surgeons because of the serious complications, which can occur when they are inadequately handled. The work aimed at establishing a surgical-anatomical protocol of the relations between the recurrent laryngeal nerves with the lower thyroidal arteries and identify and preserve the nerves and the parathyroids glands, in the course of total and partial thyroidectomies. METHODS: The photographic records during the surgery have been obtained from 79 patients who were submitted to total and partial thyroidectomies (total right or left lobectomy and istmectomy) respectively, with identification of the nerves and arteries, both unilateral and bilateral, proposing to expose the anatomical relations between these structures, operated on between January 2005 and July 2006. RESULTS: The photographic records were adapted to the schematic drawings so as to establish the major anatomical points of reference of the recurrent laryngeal nerves vis-à-vis the inferior thyroidal arteries were completed in a total of 116 recurrent laryngeal nerves. CONCLUSION: The intrinsic relation of the nerves with the arteries can occur in different forms, including the congenital abnormalities, as that of the non-recurrent laryngeal, the prelaryngeal duplications and triplications of the nerve, undoubtedly hindering the identification of such structures. Even under the protection of the anatomic and surgical difficulties, a clear identification of the nerve, artery and the parathyroid glands is imperative to preserve them in the course of total and partial thyroidectomies in order to avoid post-surgical complications.