An accessory mylohyoid muscle.

During dissection of the submandibular region of a forty year old male a unilateral left accessory mylohyoid muscle was revealed. This muscle was located between the left anterior belly of the digastric and left mylohyoid muscles. It arose from the left mylohyoid line of the mandible and was inserted into the lower portion of the mylohyoid raphe and hyoid bone. This unilateral accessory mylohyoid muscle is a rare anomaly, which is thought to contribute to the functional support of the floor of the mouth.