Abstract
Sternohyoid, sternothyroid, omohyoid, and thyrohyoid muscles are collectively known as infrahyoid muscles. These muscles frequently show variations in their attachments. Here, an extremely rare variant muscle belonging to this group has been presented. During cadaveric dissection for undergraduate medical students, an additional muscle was found between sternohyoid and superior belly of omohyoid muscles bilaterally in a male cadaver aged approximately 70 years. This muscle took its origin from posterior surface of the manubrium sterni, capsule of the sternoclavicular joint and the posterior surface of the medial part of the clavicle. It was inserted to the hyoid bone between the attachments of sternohyoid and superior belly of omohyoid muscles and was supplied by a branch of ansa cervicalis profunda. There is no report on such a muscle in the literature and it could be named as “sternocleidohyoid muscle”. Knowledge of this muscle could be useful in neck surgeries.
Highlights
The infrahyoid muscles act on the thyroid cartilage of the larynx and the hyoid bone and their actions help in speech, swallowing and mastication
It was inserted to the hyoid bone between the attachments of sternohyoid and superior belly of omohyoid muscles and was supplied by a branch of ansa cervicalis profunda
Insertion, and morphology of the infrahyoid muscles including the cleidohyoideus accessorius have been reported in previous studies
Summary
The infrahyoid muscles act on the thyroid cartilage of the larynx and the hyoid bone and their actions help in speech, swallowing and mastication. Infrahyoid muscles include sternohyoid and omohyoid superficially and sternothyroid and thyrohyoid as deeper structures. One such variant of this muscle is a muscle presenting as an additional muscle belly extending between clavicle and hyoid bone [8] Other reported variants of the omohyoid muscle include absence of its superior belly [22], duplicated superior belly [11, 15] coursing deep to the internal jugular vein, short omohyoid [15] and existence as the variant cleidohyoideus muscle [3, 5]. It was placed in a superficial plane, with superior belly of omohyoid than the sternohyoid muscle This muscle took its origin from posterior surface of the manubrium sterni, capsule of the sternoclavicular joint and the posterior surface of the medial part of the clavicle. It was inserted to the hyoid bone between the attachments of sternohyoid and superior belly of omohyoid muscles and was supplied by a branch of ansa cervicalis profunda.
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