TRAPEZOID SHAPED OMOHYOIDEUS MUSCLE: An Anatomic Variation seen in Functional Neck Dissection

Omohyoid muscle (Om) is an important anatomical landmark in cervical lymph node partition, neck dissection for head and neck cancers and cervical spine surgery. It consists of two bellies united at an angle by an intermediate tendon. Variations in the origin and insertion of the muscle, absence or duplication of the superior or inferior bellies, aberrant position in relation to IJV and sternocleideomastoid muscle have been reported. We report a rare anatomical variation of the Om in this report. This variation was observed during neck dissection of a 58 years-old male patient with laryngeal carcinoma. It was noticed that, the superior belly of Om was in a trapezoid shaped unilaterally Introduction Omohyoid muscle (Om) is one of the infrahyoid muscle and consists of two bellies united at an angle by an intermediate tendon. The inferior belly arises from the upper border of the scapula, and ends there in the intermediate tendon. The superior belly begins at the intermediate tendon, passes almost vertically upwards near the lateral border of sternohyoid and is attached to the lower border of the body of the hyoid bone lateral to the insertion of sternohyoid [1]. It passed behind the sternocleidomastoid muscle and lies superficial to the internal jugular vein, the brachial plexus, phrenic nerve, and the transvers cervical artery and vein [2].