An abnormal digastric muscle with three bellies.

During the gross anatomy dissection of the submental region, an anatomical variation of the right digastric muscle was found. This muscle had three bellies. Whereas the anterior and posterior bellies had their normal origin and course and were joined by an intermediate tendon, the accessory anterior belly originated from the digastric fossa and a thin tendon together with the anterior belly was inserted onto the hyoid bone. This kind of variation can easily be confused with pathological conditions. For this reason, knowledge of the muscular anatomy and variations of the floor of the mouth is helpful when evaluating the base of the skull with CT and MR imaging.