Purpose: Although anatomical variations were continuously found in the infrahyoid muscles, muscular variations of the sternothyroid muscle are still rare.
Materials and methods: We found an accessory belly of the sternothyroid muscle in a 46-year-old Korean male cadaver during routine dissection course, whose cause of death was 'chronic renal failure'.
Results: The accessory belly attached to the oblique line of the lamina of the thyroid cartilage, covered the thyroid gland anteriorly, and attached to posterior surface of left sternothyroid muscle and pretracheal layer of the cervical fascia from side to side. It was supplied by the inferior thyroid artery from the left thyrocervical trunk and innervated by the nerve to sternothyroid muscle from the left ansa cervicalis.
Conclusion: The present case is worth because it requires special attention performing procedures on the anterior neck.