An anomalous belly of sternothyroid muscle and its significance.

The sternothyroid muscle and other infrahyoid muscles play a vital role in the process of vocalization, swallowing and mastication by mobilizing the hyoid bone and thyroid cartilage. During routine dissection of a 70-year-old male cadaver, we observed an anomalous sternothyroid muscle. It was arising from the posterior surface of the manubrium sterni and partly from the cartilage of the first rib. After a distance of 3.3 cm, the belly of sternothyroid muscle was divided into lateral and medial fibers. The lateral belly was inserted above the oblique line on the lamina of the thyroid cartilage, but the medial additional belly turned into a tendon, which was crossing over the thyroid artery and inserted to the hyoid bone and intermediate tendon of digastric muscles. The superior thyroid artery was below the above tendon on its way to the thyroid gland. The muscle was innervated by a branch from the ansa cervicalis.