Background: The anterior belly of the digastric muscle (ABDM) presents highly variable and frequent anatomical variations. Since the ABDM functions as a landmark for clinical procedures involving the submental region, it is important to have a comprehensive understanding of its variations. In this study, we sought to improve our knowledge of ABDM variations in the ethnically diverse whole-body donor population in Northern California. Specific aims were: (1) to determine the frequency of ABDM and anterior belly (AB) accessory muscle variations in cadavers donated to the UC Davis Body Donation Programme, (2) to classify these variations identified in this population using the previously proposed nomenclatures by Yamada (1935) and Zlabek (1933), and (3) to investigate the innervation and arterial supply to the representative ABDM and AB accessory muscle variations.
Materials and methods: During the 2018 and 2019 gross anatomy dissection laboratories at the UC Davis School of Medicine, the submental regions of 48 cadavers were examined and classified.
Results: Fifteen (31.2%) cadavers presented ABDM and AB accessory muscle variations. These variations were clearly categorised using the morphology of the ABDMs and attachments of the AB accessory muscles. We also identified three previously unreported types of variations, two of which presented the fusion of right and left ABDMs and one presenting an ectopic tubercle beneath the mandibular symphysis to which a pair of AB accessory muscles were attached.
Conclusions: Anterior belly of the digastric muscle variations were found in 1 in 3 individuals in the local Northern California population. Knowledge of the prevalence and common patterns of ABDM variations in the general population would be valuable information when an operation or examination is performed in the submental region.