Anomalies of digastric muscles: CT and MR demonstration.

Anomalies of the anterior bellies of the digastric muscles were described during the 19th century and have been of little clinical significance. However, new imaging modalities, such as ultrasound, CT, and magnetic resonance (MR) imaging, can easily depict muscle anatomy without having to rely on dissection studies. The anterior bellies of the digastric muscles were evaluated in 40 patients having CT and 35 patients having MR imaging of the oropharynx. An accessory muscle crossing the midline between two normal digastric muscles was found in a patient in the MR imaging group. In the CT group, one patient showed absence of one anterior belly; in its place a small muscle was seen passing from the hyoid bone to the midline raphe of the mylohyoid muscle. It is necessary to recognize that muscle variants of the digastric muscle occur, to avoid confusion with abnormal lesions of the floor of the mouth and the submental space.