Superior thyroid artery

Origin and course

The superior thyroid artery is found in the carotid triangle of the neck, and stems from the anterior surface of the external carotid artery, inferior to the greater horn/cornu of the hyoid bone. The artery then courses inferiorly along the lateral border of the thyrohyoid muscle and reaches the apex of the thyroid lobe.

The external laryngeal nerve lies posteromedial to the superior thyroid artery, being prone to ligation during surgical procedures on the gland.

Branches and supply

The superior thyroid artery has five branches;

• The glandular branches, which supply the upper half of the thyroid gland. They can be individually defined as the anterior, posterior and lateral branches, and anastomose with those of the inferior thyroid artery to complete the vascular network that feeds the whole gland.
• The infrahyoid branch supplies the infrahyoid strap muscles; the omohyoid, sternohyoid, sternothyroid and thyrohyoid.
• The sternocleidomastoid branch vascularizes the middle third of the sternocleidomastoid muscle
• The superior laryngeal artery supplies the structures of the upper part of the larynx. It anastomoses with the inferior laryngeal artery (from the inferior thyroid artery) to complete the vascular network of the larynx.
• The cricothyroid branch supplies the cricothyroid muscle.

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Anatomical variations

According to classical anatomical textbooks, the superior thyroid artery originates from the external carotid artery. However, certain noteworthy anatomical variations have been noted in the origin of this vessel. This artery arises from the external carotid artery in 35% of the cases, from the bifurcation of the common carotid artery in another 35% and from the common carotid artery in 20% of the cases.