The Cause of the Difference in the Submental Region

Abstract

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.

Symmetrical anatomical variant of the anterior belly of the digastric muscle: clinical implicat

“…Digastric muscle variants have been described more frequently as unilateral [3,12,14] then bilateral [10,11,21] and symmetrical variants of the anterior bellies of the digastric muscle are more rare [1,11,21]. Aktekin et al [1] described 2 accessory anterior bellies, each derived from the homolateral intermediate tendon, crossed together the midline, drawing an "X", and reached the mandible laterally to the mental symphysis.…”

“…According to this criterion, our case could be considered within the classification of the muscles that have their insertion both on the mandible (on the midline in the inner surface of the bone) and on the mylohyoid raphe. Another classification was suggested by Ozgur et al [14]. They divided the variations of the digastric anterior belly in two groups: Digastric fossa type, in which both origin and insertion (on mandible or hyoid bone) of the accessory bellies are homolateral; and Crossover type, in which the aberrant bellies crossed the midline to reach their insertion, with or without joining the mylohyoid muscle.…”

Variant Anterior Digastric Muscle Transfer for Marginal Mandibular Branch of Facial Nerve Palsy

“…22 Anterior digastric variants have been documented to occur unilaterally, bilaterally, symmetrically, and asymmetrically and insert both ipsilateral and contralateral to the origin of the muscle. 23,24 Variant anterior bellies have been reported to occur at a frequency ranging from 2.7% to 69.6%, respectively. 25,26 …”

“…Many variants meeting these criteria have been described, including additional muscle bellies spanning from the digastric fossa to the ipsilateral intermediate tendon/hyoid and additional muscle bellies spanning from the digastric fossa to the contralateral tendon/hyoid. 23,24 Anterior belly of digastric muscle variants have been identified via computed tomography and magnetic resonance imaging 25,28 ; therefore, screening for adequate variant musculature may be accomplished with advanced imaging techniques. Screening the submental region is also important in differentiating variant anterior digastric anatomy from submental lymph nodes, space occupying lesions, and muscular asymmetries due to trigeminal nerve lesion.…”

A morphological variant of anterior belly of digastric muscle: a cadaveric case report

“…In the former type the attachments of the accessory bellies are found to be on same side whereas in later type accessory bellies cross to the opposite side for the attachment. 5 Present case should be considered as combination of both types as the accessory bellies of right side are attached to the hyoid bone just left to the midline. It has been suggested that occurrence of accessory bellies of ABD could be due to the anomalous development of neural crest cells in the first bronchial arch.…”