Study on microsurgical anatomy of external branch of superior laryngeal nerve related to carotid endarterectomy

Abstract

Objective To discuss how to protect external branch of superior laryngeal nerve (EBSLN) during carotid endarterectomy (CEA) by studying on microsurgical anatomy of EBSLN in cadaver head specimens. Methods Ten cadaver heads [20 sides, average age (54.43 ± 4.08) years old] were studied by microsurgical anatomy. Skin as well as platysma was incised under the surgical microscope. Then sternocleidomastoid was retracted laterally. The origin of superior laryngeal nerve was found along the vagus nerve superiorly after it was discovered in the carotid sheath. The segment of superior laryngeal nerve from origin to bifurcation was carefully detached along the trunk of superior laryngeal nerve. Then EBSLN from bifurcation to the surface of inferior pharyngeal constrictor muscle where the nerve piercing in it was detached, and the thickness of the nerve was measured. Digastric muscle, common carotid artery (CCA), internal carotid artery (ICA), external carotid artery (ECA) and superior thyroid artery (SThA) were isolated to expose the triangle bounded superiorly by stylohyoid muscle, posteriorly by ECA, and anteriorly by SThA. The occurrence rate of EBSLN in this triangle was observed and recorded. The distance of this nerve segment with mastoid tip (MT) and angle of mandible (AM) as well as the bifurcation of common carotid artery (bCCA) was also measured. Results Nineteen sides of EBSLN were observed in the triangle, except one side. The occurrence rate of EBSLN in this triangle is 19/20, and the thickness of the nerve was (0.93 ± 0.83) mm (0.72-1.15 mm). This nerve segment was (0.34 ± 0.96) cm (-1.62-2.43 cm) posterior and (1.28 ± 0.93) cm (-1.33-3.42 cm) inferior to AM; (2.84 ± 1.09) cm (0.51-5.14 cm) anterior and (4.51 ± 0.76) cm (2.82-6.39 cm) inferior to MT; (1.64 ± 0.89) cm (0.57-3.78 cm) anterosuperior to bCCA (19/20). Conclusions This triangle and other 3 anatomical landmarks (MT, AM and bCCA) are significant to find and protect EBSLN during CEA.

doi：10.3969/j.issn.1672-6731.2014.01.004