The cause of the difference in the submental region: aberrant muscle bundles of the anterior belly of the digastric muscle.

The aberrant bundles' presence in the anterior belly of the digastric muscle is important in terms of causing asymmetry in the submental region, getting confused with some pathologic cases, radiologic examination, and aesthetic facial surgery. To provide data, aberrant bundles in the submental region were investigated in 30 cadaver heads. During the dissection of the submental region, origin, insertion, shape, and bilaterality of the anterior bellies of the digastric muscles and the aberrant bundles were investigated. The 20 heads with aberrant bundles were classified into two types based on the muscle arrangement: digastric fossa type and crossover type. The aberrant bundles, which did not cross the median line, were classified as being of the digastric fossa type, whereas those that crossed the line were of the crossover type. Fifteen of the heads contained bundles of the unilateral type and five heads contained the crossover type. In three heads, digastric fossa and crossover types coexisted. In this study, a wide range for incidence in the submental region was observed of variations. Some cases were not described in the classification of the previous studies of this muscle. It is also possible that the incidences may vary as a result of the ethnic differences of the populations studied. Bilaterality was frequently observed in this study. Anatomic variations of the anterior bellies of the digastric muscle can easily be confused with the pathologic conditions in ultrasonography, computed tomography, and magnetic resonance imaging; therefore, it is necessary to recognize that variants of the anterior belly of the digastric muscle occur to avoid confusion when diagnosis shows abnormal lesions in the floor of the mouth and submental region. Additionally, the possible occurrence of such anomalies should be remembered during the surgical procedures involving the submental region.