A rare case of an accessory sternohyoid muscle: case report

Variability of the infrahyoid muscles is a well-known anatomical phenomenon; however, reports describing muscular variations and additional muscles remain limited, which may have clinical implications. The aim of our study was to describe a previously unreported infrahyoid muscle.

A routine anatomical dissection was performed on a 97-year old formalin- fixed female cadaver at the Department of Anatomy, Jagiellonian University Medical College. Morphometric measurements of the accessory muscle were obtained independently three times using a digital caliper. The course, attachments, and anatomical relationships of the muscle were documented. The muscle was identified in the deep layer of the right anterior region of the neck, lateral to the sternothyroid muscle. It originated from the right lateral surface of the hyoid bone, coursed beneath the superior belly of the omohyoid muscle, crossed anterior to the common carotid artery, and inserted onto the posterior surface of the manubrium of the sternum, beneath the origin of the sternohyoid muscle. The muscle measured 83.55 mm in length, 4.32 mm in width, and 0.95 mm in thickness. The anatomical arrangement did not correspond to any previously described anatomical variant.

This report presents a previously unreported accessory infrahyoid muscle. Descriptions of such anatomical variants are important for surgeons and radiologists, as these structures may complicate surgical procedures, increase the risk of iatrogenic injury, and be misinterpreted as lesions during diagnostic imaging.