Abstract
Anatomical considerations of the superior laryngeal nerve (SLN), a branch of the vagus, provides information to minimize the potential for iatrogenic intraoperative injury, thereby preventing motor and sensory dysfunctions of the larynx. The present study aims to assess the variation of the SLN and its relationship to the superior thyroid artery (STA) and superior laryngeal artery (SLA). The study was done on 35 formalin-fixed cadavers at Oakland University in 2018–2019. In our study, we found that out of 21 cadavers, 52.4% of the external laryngeal branches (ebSLN) are related posteromedial to the STA, while 47.6% are related anteromedial to it. Out of 14 cadavers, 64.3% of the internal laryngeal branches (ibSLN) are related superoposterior to the SLA, while 35.7% are inferoposterior to it. In most cases, the SLA crosses above the ebSLN while traveling to pierce the thyrohyoid membrane to reach the larynx. The data demonstrate that both the ebSLN and ibSLN display variation in their relationship with the STA and the SLA, respectively. Awareness of these variable relationships is critical for identification and isolation of these structures in order to prevent consequences of nerve injury, primarily a reduction in the highest attainable frequency of the voice and aspiration pneumonia.
Highlights
The superior laryngeal nerve (SLN), a branch of the vagus nerve, arises from the inferior vagal ganglion and descends posteromedial to the internal carotid artery (ICA)before branching distally into two nerves: The smaller external branch of the superior laryngeal nerve and the larger internal branch of the superior laryngeal nerve [1]
Anterior cervical deep dissection was performed on each cadaver with simultaneous identification and isolation of various structures, including the common carotid artery (CCA), external carotid artery (ECA), internal carotid artery (ICA), internal branch of the superior laryngeal nerve (ibSLN), external branch of the superior laryngeal nerve (ebSLN), superior thyroid artery (STA), superior laryngeal artery (SLA), thyroid gland, thyrohyoid membrane, and cricothyroid muscle, whenever possible
Out of 21 cadavers in whom the ebSLN was dissected, 52.4% of the ebSLN are related posteromedial to the STA, while 47.6% are related anteromedial to it (Figure 1)
Summary
The superior laryngeal nerve (SLN), a branch of the vagus nerve, arises from the inferior vagal ganglion and descends posteromedial to the internal carotid artery (ICA)before branching distally into two nerves: The smaller external branch of the superior laryngeal nerve (ebSLN) and the larger internal branch of the superior laryngeal nerve (ibSLN) [1]. Each branch of the SLN possesses a unique relationship with a respective artery: The ebSLN with the superior thyroid artery (STA) and the ibSLN with the superior laryngeal artery (SLA) [1,2]. While the STA provides blood supply to the superior pole of the thyroid gland, the ebSLN is responsible for motor innervation of the cricothyroid muscle, which acts to elongate and thin the true vocal folds during phonation, thereby elevating the pitch of the voice [1]. The ibSLN and the SLA pierce the thyrohyoid membrane, a membrane bounded superiorly by the hyoid bone and inferiorly by the thyroid cartilage, to enter the laryngeal vestibule for sensory innervation and blood supply to the laryngeal mucosa, respectively. The ibSLN commonly trifurcates in the laryngeal vestibule, providing sensory innervation to the epiglottis, anterior wall of the vallecula, aryepiglottic folds, and motor innervation to the interarytenoid muscle [2,4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
