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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 27  |  Issue : 2  |  Page : 138-140

Variations in course of laryngeal nerves during thyroid surgery


1 Department of General Surgery, MES Medical College, Perinthalmanna, Kerala, India
2 Department of Surgery, MES Medical College, Perinthalmanna, Kerala, India

Date of Submission28-Jul-2021
Date of Decision05-Sep-2021
Date of Acceptance06-Sep-2021
Date of Web Publication15-Nov-2021

Correspondence Address:
Dr. Hafiz Mohammed
Department of General Surgery, MES Medical College, Perinthalmanna - 679 322, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ksj.ksj_36_21

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  Abstract 


Introduction: Recurrent laryngeal nerve (RLN) is routinely exposed and traced during all thyroid surgeries. The refinement in surgical techniques has made recognition of the RLN and the external branch of superior laryngeal nerve (EBSLN) possible during surgery resulting in lesser morbidity. Aims and Objectives: The aim of this study is to describe the variations in surgical anatomy of both RLN EBSLN in patients undergoing thyroidectomy and to look for proportion of cases with injury to RLN. Methodology: It was a prospective, observational study. The demographic details of the patient, the diagnosis and the surgical findings (variants of EBSLN, branches of RLN and relation of RLN to inferior thyroid artery [ITA]) were recorded. Postoperatively, after 48 h, the vocal cords were assessed by indirect laryngoscopy. The data were analysed using the SPSS software. Results: Cernea type 1 is the most common position of external laryngeal nerve (67.8%). The RLN passes posterior to the ITA in 46.5% on the right side and 44.3% on the left side. RLN gives one branch in 69.3% cases. There was no injury to the laryngeal nerves noted during this study. Conclusion: Very meticulous dissection helps in identifying the RLN and preserving it. The best way to preserve the RLN nerves is to identify the nerve and preserve them rather than staying away.

Keywords: Cernea types, recurrent laryngeal nerve, superior laryngeal nerve, thyroidectomy


How to cite this article:
Mohammed H, Sukumar R, Abid Ali K P. Variations in course of laryngeal nerves during thyroid surgery. Kerala Surg J 2021;27:138-40

How to cite this URL:
Mohammed H, Sukumar R, Abid Ali K P. Variations in course of laryngeal nerves during thyroid surgery. Kerala Surg J [serial online] 2021 [cited 2021 Nov 30];27:138-40. Available from: http://www.keralasurgj.com/text.asp?2021/27/2/138/330400




  Introduction Top


Many surgeons such as Kocher, Billroth and Joll tried to avoid injury to recurrent laryngeal nerves (RLNs) by dissecting away from the nerves.[1] Bier started dissecting the nerve to avoid injuries.[2] The description of capsular technique was given by Halsted, who identified the importance of the inferior thyroid artery (ITA) as the principal means of blood supply to the parathyroid glands. The technique he described utilized ultra-dissection to avoid damage to the parathyroid blood supply by ligating the tertiary branches of the ITA adjacent to the thyroid capsule.[2] In 1937, Coller and Boyden modified their approach to the superior pole of thyroid for preserving the external branch of the superior laryngeal nerve for which individual ligation of the branches of the superior thyroid artery after entering the avascular space between the superior pole and the cricothyroid muscle.[2]

RLN paralysis and the resulting hoarseness may produce serious functional impairment and pose a serious medicolegal concern.[2]

The aim of this study was to assess the importance of dissecting the nerves, identifying their variations in surgical anatomy of the RLN external branch of superior laryngeal nerve (EBSLN) in patients undergoing thyroid surgeries, to look for proportion of cases with injury to RLN and design ways to avoid injury.


  Methodology Top


It was a prospective, observational study conducted in the department of surgery in a tertiary hospital. Patients undergoing thyroid surgeries in 2018 were included. The sample size was calculated as 82 cases using appropriate formula applying an absolute error of 5. The first 82 cases of thyroidectomy meeting the inclusion and exclusion criteria were enrolled after taking written informed consent. Patients with earlier RLN or external branch superior laryngeal nerve palsy and those who had previous thyroid surgery were excluded. The surgical findings (variants of EBSLN, branches of RLN and relation of RLN to ITA) were recorded. Postoperatively after 48 h, the vocal cords were assessed by indirect laryngoscopy. EBSLN was classified according to the CERNEA classification[3] as type 1 crosses superior thyroid artery more than 1 cm above upper pole, Type II A-crosses superior thyroid artery <1 cm above upper pole and Type II B-dorsal to artery and cross STA immediately above upper pole. The branches of RLN and the relation of ITA to RLN were noted-type A-RLN anterior to ITA, type B-RLN posterior to ITA and type-RLN between branches of ITA.

The data were analysed using the SPSS software version 17. Descriptive analysis was done for variants of EBSLN, branches of RLN and relation of RLN to ITA and the findings of indirect laryngoscopy expressed in proportions. Ethical clearance was obtained from the Institutional Ethical Committee.


  Results Top


Genderwise distribution: Among the 92 patients, 72 (79%) were female and 19 (21%) were male.

Age

The mean age of the study population was 40.22 ± 10.6 years. Females had a higher mean age of 40.69 ± 11.24 years compared to males − 38.42 ± 7.9 years. The age and gender wise distribution showed males were higher in age groups 31–40 years (52.6%), females were the highest in the age group of 41–50 years (38.9%). The lowest number of males was seen in 11–20 years' age group and females lowest in same group and above 60 years age group [Table 1].
Table 1: Age and gender wise distribution of patients

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Diagnosis

Most of the patients who underwent thyroidectomy were diagnosed to have colloid goitre [Table 2].
Table 2: Diagnosis and patient distribution

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Type of surgery

Sixty-eight percent of patients in this study underwent total thyroidectomy [Table 3].
Table 3: Type of surgery underwent

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External branch of superior laryngeal nerve

The most common type of EBSLN encountered in this study was type 1 on both sides [Table 4].
Table 4: Type of external branch of superior laryngeal nerve in patients

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Branches of recurrent laryngeal nerve

Most of the patients had only one branch of the RLN on either side, as shown in [Table 5].
Table 5: Number of branches of recurrent laryngeal nerves

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Relationship of recurrent laryngeal nerve to inferior thyroid artery

Nearly half were posterior to the ITA on both sides and a lesser number were seen anterior, as shown in [Table 6].
Table 6: Relationship of recurrent laryngeal nerve to inferior thyroid artery

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Vocal cords

The vocal cords of the all 91 patients were identified to be normal on post-operative assessment.


  Discussion Top


The most accepted classification for variations of EBSLNs is by Cernea et al.[3] The RLNs have different branching pattern the number of branches varies with different individuals so tracing all the branches is required.[4] The knowledge about relation of the recurrent laryngeal nerves with ITA also plays an important role in identifying the nerve before ligating the ITA.[4]

In the present study, we have observed 91 cases of thyroidectomy in which most of the patients (79%) were female and most of the patients were in the age group of 41–50 years, and the mean age of the study population was 40.22 ± 10.6 years. Females were having higher mean age of 40.69 ± 11.24 years when compared to 38.42 ± 7.9 years for males.

We came across 142 EBSLN and 165 RLN, variations of these nerves are discussed here. The present study showed that Cernea type 1 is the most common position of the external laryngeal nerve (67.8%). Similar results were obtained by Pradeep et al. in their studies in the Indian population.[1] In another studies by Chuang et al. in China,[4] Ekhar et al. in India[5] and Hwang et al. in Korea[6] observed that Cernea type 2A EBSLN is more common which is the second most common type as per our study. A study by Rajesh et al.[7] found that Cernea type 2A is most common in Indian population and another study by Pradeep et al. also suggests the same findings.[4]

It was observed that RLN shows variations while branching of which RLN giving one branch is the most common type; similar results were obtained in study conducted by Pradeep et al.[4] in 69.3% cases. Sailaja et al. observed that RLN had two branches in 75% cases in a study on post-mortem specimens.[8]

The results here show that the relation between and ITA and RLN which showed that RLN passes posterior to the ITA in most cases about 46.5% on the right side and 44.3% on the left side. In a study conducted by Thilagavathi et al.[9] in India observed that relation of RLN is anterior to ITA in 51% cases on the right side and posterior to ITA in 51.4% cases on the left side. Pradeep et al.[4] observed RLN posterior to ITA in 65% cases. Similar observation was made by Ngo Nyeki et al. on a study in Cameroon,[10] whereas Calmpos and Henriques observed RLN between the branches of ITA as common in a study on corpses in Brazil.[11]

We did not observe any case of abnormality in the position of RLN postoperatively which means that nerves should be traced and safeguarded for avoiding the incidence of injury to the nerve.


  Conclusion Top


Thyroidectomy is a very common surgery performed but which can cause very serious complications so awareness of anatomy of the gland and the laryngeal nerves are important. Very meticulous dissection and better anatomy helps in identifying the laryngeal nerve and preserving it. Thus, by this, it is concluded that the best way to preserve the laryngeal nerves during thyroidectomy is by identifying the nerve and safeguarding them than staying away from it without seeing it. Every surgeon should make a conscious attempt to look for the nerve during thyroidectomy which will decrease the significant morbidity associated with the injury.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Choong C, Kaye AH. Emil Theodor Kocher (1841-1917). J Clin Neurosci 2009;16:1552-4.  Back to cited text no. 1
    
2.
Bliss RD, Gauger PG, Delbridge LW. Surgeon's approach to the thyroid gland: Surgical anatomy and the importance of technique. World J Surg 2000;24:891-7.  Back to cited text no. 2
    
3.
Cernea CR, Ferraz AR, Nishio S, Dutra A Jr., Hojaij FC, dos Santos LR. Surgical anatomy of the external branch of the superior laryngeal nerve. Head Neck 1992;14:380-3.  Back to cited text no. 3
    
4.
Pradeep PV, Jayashree B, Harshita SS. A closer look at laryngeal nerves during thyroid surgery: A descriptive study of 584 nerves. Anat Res Int 2012;2012:490390.  Back to cited text no. 4
    
5.
Ekhar VR, Ramkumar V, Shelkar RN, Sarode AV. Identification of external branch of superior laryngeal nerve during thyroid surgery: A prospective study. Int J Otorhinolaryngol Head Neck Surg 2018;4:228-32.  Back to cited text no. 5
    
6.
Hwang SB, Lee HY, Kim WY, Woo SU, Lee JB, Bae JW, et al. The anatomy of the external branch of the superior laryngeal nerve in Koreans. Asian J Surg 2013;36:13-9.  Back to cited text no. 6
    
7.
Rajesh PS, Kamalakshy J, Saravanan T. A descriptive study on the surgical anatomy of external laryngeal nerve in patients undergoing thyroidectomies at a tertiary care center in South India. Int Surg J 2017;4:519-24.  Back to cited text no. 7
    
8.
Sailaja K. An observational study on variation in the relations and branches of recurrent laryngeal nerve. Int J Res Med Sci 2016;4:2328-31.  Back to cited text no. 8
    
9.
Thilagavathi J, Anandhi V, Sudha S. A study on the variations in the relationship between the recurrent laryngeal nerve and the vascular pedicle of the thyroid gland. Int J Anat Res 2016;4:2689-91.  Back to cited text no. 9
    
10.
Ngo Nyeki AR, Njock LR, Miloundja J, Evehe Vokwely JE, Bengono G. Recurrent laryngeal nerve landmarks during thyroidectomy. Eur Ann Otorhinolaryngol Head Neck Dis 2015;132:265-9.  Back to cited text no. 10
    
11.
Campos BA, Henriques PR. Relationship between the recurrent laryngeal nerve and inferior thyroid artery: A study in corpses. Rev Hosp Clin 2000;55:6.  Back to cited text no. 11
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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