Correlation between the cernea classification of external branch of superior laryngeal nerve in relation to the ultrasound-based volume of thyroid gland

Background. The external branch of the superior laryngeal nerve innervates a cricothyroid muscle, which provides tension in vocal cords and formation of high-frequency sounds. When the nerve is damaged during surgery, patients may notice hoarseness, inability to utter high pitched sounds, “rapid fatigue” of the voice, and dysphagia. According to literature, paresis of an external branch of the superior laryngeal nerve reaches up to 58% after thyroid surgery. Aim: to identify permanent landmarks and topographic variations of the external branch of the superior laryngeal nerve. Materials and methods. The study is based on the autopsy material (21 complexes organs of the neck) and on identification of variations of 40 external branches of the superior laryngeal nerve. We identified two permanent landmarks that are located at the minimum distance from nerve and we made metrical calculations relative to them: oblique line of thyroid cartilage and tendinous arch of the inferior pharyngeal constrictor muscle. Results. The piercing point of the nerve is always located at the inferior pharyngeal constrictor muscle without protruding beyond the oblique line of thyroid cartilage superiorly and tendinous arch of the inferior pharyngeal constrictor muscle anteriorly. The nerve had the parallel direction in 92.8% of cases (angel less than 30 degrees) relative to the oblique line and in 85.7% cases it was in close proximity to this line (at distance up to 4 mm). The proposed topographic classification of the location of the external branch of the superior laryngeal nerve is based on localization of the piercing point of the nerve relative to the length of the oblique line of thyroid cartilage and the risk of nerve damage. In 14.2% of cases, the piercing point was in the front third of the line (type I), and in 50% it was in the middle third of this line (type II). These variations of the external branch of the superior laryngeal nerve was in close proximity to the upper pole of the thyroid gland, which could have lead to its damage during surgery. In type III and IV (35.8%) – the piercing point in the muscle was located as far as possible from the upper pole of the thyroid gland and the greater part of the nerve was covered with the fibers of inferior pharyngeal constrictor muscle. Conclusion. We identified the main orienteers for the search and proposed anatomical classification of the location of the external branch on the superior laryngeal nerve.

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Assessment of Relation between External Branch of Superior Laryngeal Nerve & Thyroid Gland- A Cadaveric Study

Academia Anatomica International ◽

10.21276/aanat.2020.6.2.16 ◽

2020 ◽

Vol 6 (2) ◽

pp. 73-76

Author(s):

Anurag ◽

Vishnu Gupta

Keyword(s):

Thyroid Gland ◽

Cricoid Cartilage ◽

Superior Laryngeal Nerve ◽

Laryngeal Nerve ◽

The Body ◽

Superior Thyroid Artery ◽

Group I ◽

External Branch ◽

The Mean ◽

Group Ii

Background: The thyroid gland is essential for normal growth of the body. This study assessed relation of external branch of superior laryngeal nerve to the superior pole of the thyroid gland. Subjects and Methods: This study was conducted on 25 human cadavers having 50 superior thyroid poles of both genders. Cadavers were classified based on age groups, group I was those with age less than 39 years and group II cadavers were those with age more than 40 years of age. Various measurements were performed on cadavers. Results: 14 cadavers were I group I and 11 were in group II. The mean mass was 67.2 Kgs in group I and 59.5 Kgs in group II, time elapsed after death was 481.5 minutes in group I and 476.4 minutes in group II, mean height was 1.74 meters in group I and 1.69 meters in group II, mean BMI found to be 22.3 kg/m2in group I and 20.1 kg/m2in group II. Height found to be significant between both groups (P< 0.05). The mean distance from EBSLN to cranial point of the thyroid gland was 6.66 mm in group I and 8.96 mm in group II. The mean transverse distance from superior thyroid artery to EBSLN was 3.55 mm in group I and 5.12 mm side in group II. The mean distance of the crossing point between the most cranial point of the thyroid lobe was 6.40 mm in group I and 11.47 mm in group II. The mean distance from the EBSLN to the midline of the neck was 19.80 mm in group I and 18.58 mm in group II. The mean distance from the EBSLN to the midline of the neck on the most cranial point of the cricoid cartilage was 18.77 mm in group I and 17.80 mm in group II. Conclusion: Authors found variation in measurements in left and right side in both group I and group II.

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Improving classification of the external branch of the superior laryngeal nerve with neural monitoring: a research appraisal and narrative review

Gland Surgery ◽

10.21037/gs-21-518 ◽

2021 ◽

Vol 10 (9) ◽

pp. 2847-2860

Author(s):

Yishen Zhao ◽

Zihan Zhao ◽

Daqi Zhang ◽

Yujia Han ◽

Gianlorenzo Dionigi ◽

...

Keyword(s):

Superior Laryngeal Nerve ◽

Laryngeal Nerve ◽

Narrative Review ◽

External Branch ◽

Neural Monitoring

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Study of Some “Intrinsic Risk Factors” that Can Enhance an Iatrogenic Injury of the External Branch of the Superior Laryngeal Nerve

Otolaryngology ◽

10.1067/mhn.2003.11 ◽

2003 ◽

Vol 128 (3) ◽

pp. 396-400 ◽

Cited By ~ 23

Author(s):

Julio Cesar Furlan ◽

Anói Castro Cordeiro ◽

Lenine Garcia Brandã

Keyword(s):

Risk Factors ◽

Thyroid Gland ◽

Analysis Of Variance ◽

Study Design ◽

Statistical Significance ◽

Superior Laryngeal Nerve ◽

Laryngeal Nerve ◽

Human Adult ◽

External Branch ◽

Anatomic Relationship

OBJECTIVE: This study evaluates some “intrinsic risk factors” for a surgical injury of the external branch of superior laryngeal nerve (EBSLN) based on its anatomic relationship with the thyroid gland. STUDY DESIGN AND SETTING: Seventy-two neck dissections were performed in 36 fresh human adult cadavers. Every EBSLN was dissected and categorized using Cernea's classification. All data regarding gender, ethnicity, stature, side of the neck, and volume of hemi thyroid were collected and statistically analyzed by the χ 2 –test and analysis of variance. RESULTS: Although no statistical differences were observed between genders ( P = 0.3770), ethnicities ( P = 0.9780) or sides of the neck ( P = 0.2523), statistical significance was reached regarding the nerve type when the groups were divided by stature ( P = 0.0006) and glandular volume ( P = 0.0007). CONCLUSION: Individual stature and volume of the hemi thyroid gland are probably involved in risk of the surgical EBSLN injury. SIGNIFICANCE: Surgeons should be aware of these anatomic findings in order to obtain a good voice-related outcome in the thyroidectomies.

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Relation of the external branch of the superior laryngeal nerve to the superior pole of the thyroid gland: An anatomical study

Clinical Anatomy ◽

10.1002/ca.20463 ◽

2007 ◽

Vol 20 (5) ◽

pp. 516-520 ◽

Cited By ~ 14

Author(s):

D. Naidoo ◽

J.M. Boon ◽

C.J. Mieny ◽

P.J. Becker ◽

A.-N. van Schoor

Keyword(s):

Thyroid Gland ◽

Superior Laryngeal Nerve ◽

Anatomical Study ◽

Laryngeal Nerve ◽

External Branch ◽

Superior Pole

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VIRIATION OF THE EXTERNAL BRANCH OF THE SUPERIOR LARYNGEAL NERVE

Vestnik of Russian military medical Academy ◽

10.17816/brmma13053 ◽

2019 ◽

Vol 21 (1) ◽

pp. 84-88

Author(s):

V Y Malyuga ◽

A A Kuprin

Keyword(s):

Thyroid Gland ◽

Thyroid Cartilage ◽

Oblique Line ◽

Superior Laryngeal Nerve ◽

Laryngeal Nerve ◽

Type I ◽

Constrictor Muscle ◽

Point Of Entry ◽

External Branch ◽

Inferior Pharyngeal Constrictor

Till now, there is no universal clinical classification about variations of the external branch of the superior laryngeal nerve despite the multiple classifications that was proposed. The aim of this research is identification and systematization of topographic types of the external branch of the superior laryngeal nerve. The study is based on the autopsy material (21 complexes organs of the neck) and on identification of variations of 40 external branches of the superior laryngeal nerve. We identify two permanent landmark that are located at the minimum distance from nerve and on which we made metrical calculations: oblique line of thyroid cartilage, tendinous arch of the inferior pharyngeal constrictor muscle. The “entry” point of the nerve is always located on the inferior pharyngeal constrictor muscle,and not protruding beyond the oblique line of thyroid cartilage superiorly and tendinous arch of the inferior pharyngeal constrictor muscle anteriorly. The proposed topographic classification of the location of the external branch of the superior laryngeal nerve is based on localization of point of pierced of the nerve relating to the length of the oblique line of thyroid cartilage. In 64.2% of cases, the external branch of the superior laryngeal nerve was in close proximity to the upper pole of the thyroid gland, which could lead to its damage during surgery (type I and II). In type III and IV (35.8%) - the point of "entry" in the muscle was located as far as possible from the upper pole of the thyroid gland, and most of the nerve was covered by the fibers of the inferior pharyngeal constrictor muscle.

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Cernea's classification of the External Branch of the Superior Laryngeal Nerve during Microscopic Thyroidectomy at Gandaki Medical College, Pokhara

Journal of Gandaki Medical College-Nepal ◽

10.3126/jgmcn.v14i2.35893 ◽

2021 ◽

Vol 14 (2) ◽

pp. 133-136

Author(s):

Tulika Dubey ◽

Brihaspati Sigdel ◽

Rajendra Nepali ◽

Neeraj KC

Keyword(s):

Superior Laryngeal Nerve ◽

Neck Surgery ◽

Laryngeal Nerve ◽

Type I ◽

Medical College ◽

Risk Of Injury ◽

External Branch ◽

The Right ◽

Dissection Technique

Background: Preservation of the external branch of the superior laryngeal nerve (EBSLN) during thyroidectomy is important because its injury may lead to frequent occurrence of vocal fatigue and the inability to perform phonation. The objective of the study was to identify and classify the nerve as per Cernea's classification using operating microscope during thyroidectomy Method: Between January 2017 to December 2019, we evaluated 50 patients for the position of external branch of superior laryngeal nerve, who underwent microscopic thyroid surgeries in the department of ENT- head and neck surgery at Gandaki Medical College. Results: In our study, we dissected a total 59 superior poles of thyroid from 50 patients and identified the nerve in all the cases. Of the total superior poles, 36 (61.01%) had type IIa EBSLN among which 24 was on the right side and 12 on the left followed by 19 (32.20%) patients with type IIb EBSLN among which 8 on right and 11 on left side. There were only 4 poles (6.77%) of type I with 3 on the right and 1 on the left side. Conclusion: The EBSLN can be very efficaciously identified during a microscope assisted thyroidectomy. Cernea type 2a and 2b EBSLNs are in position to be at high risk of injury during ligation of the superior vascular pedicle, which can be avoided by prompt identification through a microscope and a meticulous extra capsular dissection technique.

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The Identification, Preservation and Classification of the External Branch of the Superior Laryngeal Nerve in Thyroidectomy

World Journal of Surgery ◽

10.1007/s00268-017-4046-z ◽

2017 ◽

Vol 41 (10) ◽

pp. 2521-2529 ◽

Cited By ~ 9

Author(s):

Kun Wang ◽

Huilan Cai ◽

Deguang Kong ◽

Qiuxia Cui ◽

Dan Zhang ◽

...

Keyword(s):

Superior Laryngeal Nerve ◽

Laryngeal Nerve ◽

External Branch

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Identification and Preservation of External Branch of Superior Laryngeal Nerve in Thyroidectomy

International Journal of Phonosurgery & Laryngology ◽

10.5005/jp-journals-10023-1059 ◽

2013 ◽

Vol 3 (2) ◽

pp. 39-41 ◽

Cited By ~ 2

Author(s):

Bhagyashree D Bokare ◽

Poorva K Athavale ◽

Vipin R Ekhar ◽

Devendra Meghraj Mahore

Keyword(s):

Thyroid Gland ◽

Total Thyroidectomy ◽

Superior Laryngeal Nerve ◽

Vocal Folds ◽

Laryngeal Nerve ◽

Superior Thyroid Artery ◽

Type I ◽

Care Hospital ◽

External Branch ◽

Superior Pole

ABSTRACT The basic principle of head and neck surgery is based on the identification and preservation of important structures, rather than avoidance. This principle is also applicable to identification and preservation of external branch of the superior laryngeal nerve (EBSLN) as a standard routine in all thyroid surgeries. During thyroid surgery, the EBSLN is clearly at risk due to its close proximity to the superior thyroid artery (STA) and its branches that need to be ligated during dissection of the superior pole of the thyroid gland. Injury is detrimental to the patient by causing paralysis of the cricothyroid muscle which is the main tensor and pitch controlling mechanism of the vocal folds. Injury to the EBSLN during surgery can result in the voice changes, loss of upper range and easy fatigability of voice, the severity of which varies according to the vocal demand of the patient. Total 45 cases of thyroid swellings were treated with surgery, in the Department of ENT at a tertiary care hospital during the period from 1st October 2009 to 30th October 2010. Hemithyroidectomy was the most common operative procedure implemented in 24 patients (53.33%) in which right sided was common. Next common procedure performed was that of total thyroidectomy in 14 patients (31.11%). Four patients underwent total thyroidectomy with neck dissection. The position of EBSLN was classified according the Cernea et al classification. In our study we found the EBSLN to be type I in 46.66%, type IIa in 73.33% and type IIb in 02.22%. The anatomical landmark taken into consideration to identify EBSLN was the Joll's triangle with its relation to the superior pole of the thyroid gland and STA. How to cite this article Athavale PK, Bokare BD, Ekhar VR, Mahore DM. Identification and Preservation of External Branch of Superior Laryngeal Nerve in Thyroidectomy. Int J Phonosurg Laryngol 2013;3(2):39-41.

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