Unique variation of digastric muscle: a confusing landmark for head and neck surgeons.

An anatomical variation of the left digastric muscle was found during the functional neck dissection of a patient with laryngeal carcinoma. This variant of the digastric muscle had three bellies including an accessory posterior belly. The anterior and posterior bellies had normal origin and course and were linked to each other by an intermediate tendon, whereas the accessory posterior belly took its origin from the mastoid notch of the temporal bone, together with the original posterior belly, sloped inferiorly and anteriorly, and inserted to the lateral border of the strap muscles by an evident tendon. This unique variation has not been reported in the literature. Presentation of this variation will guide surgical procedures, as well as anatomical dissections and medical imaging of the neck.