Bilateral, asymmetric anomalies of the anterior bellies of digastric muscles.

Bilateral, asymmetric anomalies of the anterior bellies of digastric muscles were observed during dissection of the submental region. Specifically, four extra muscle bundles were found between the anterior bellies of the digastric muscle. Although anomalies of the anterior bellies of digastric muscles are often observed, this complicated pattern of digastric anomalies has not been previously reported. Our findings and previous observations illustrate the morphogenetic complexity of the anterior belly of the digastric muscle derived from the first pharyngeal arch, which gives rise to jaw musculature such as the mylohyoid muscle.