Abstract
Injury to the external branch of the superior laryngeal nerve (eSLN) can cause a hoarse or weak voice with dysergia of the cricothyroid. The present study provided the topographic information of the eSLN in the Asian and verified anatomical validity of the landmarks previously recruited to localize the eSLN. Thirty specimens were dissected from 16 human embalmed cadavers (12 men and four women; mean age: 80.5 years). The vertical distance between the eSLN and the apical pole of the thyroid gland (AP) was 8.2 ± 4.2 mm. It descended over the AP with <1 cm distance in 51.7%, >1 cm distance in 27.6% and under the AP in 20.7%. The piercing point (PP) of the eSLN to the muscles located 26.0 ± 5.5 mm posterior and 14.7 ± 5.0 mm inferior to the laryngeal prominence. Generally, the PP located superoposterior to the midpoint of the joint between the joint of inferior constrictor and cricothyroid (ICJ). The distance between the PP and the midpoint was 8.7 ± 5.1 mm. We found that 1) the Asian had the eSLN located over the AP with <1 cm distance about half cases, 2) the PP can be a consistent reference for the eSLN identification, 3) the ICJ can be a useful landmark to preserve the eSLN at the PP.
Highlights
The musculature and mucosa of the larynx play a key role in vocalization, respiration, and crucial glottic reflexes associated with deglutition, coughing, and vomiting[1]
The eSLN descended more than 1 cm from the AP in eight cases (27.6%), and this pattern was observed in approximately one quarter of both Korean and Thai samples
The branches of the vagus nerve that innervate the muscles of the larynx are responsible for the meticulous control of muscular movements involved in respiration, deglutition, and phonation. Most of these muscles are innervated by the recurrent laryngeal nerve (RLN), with the exception of the cricothyroid muscle (CT)
Summary
The musculature and mucosa of the larynx play a key role in vocalization, respiration, and crucial glottic reflexes associated with deglutition, coughing, and vomiting[1]. The SLN bifurcates into the internal branch, which conveys afferent fibers from the laryngeal mucosa, and the external branch (eSLN), which provides the only efferent fibers to the cricothyroid muscle (CT)[2]. These efferent fibers participate in meticulous control of the voice. Routine identification of eSLN anatomy has been hampered by topographic variation and difficulty in landmark recruitment. The aim of the present study was to provide topographic information regarding the course of the eSLN with reference to the STA, AP, and CT in the Asian population, and to verify the reliability of these www.nature.com/scientificreports/. We analyzed differences in eSLN topography between Asian specimens of the present study and Caucasian specimens described in previous studies
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