A cadaveric analysis of anatomical variations of the anterior belly of the digastric muscle

Abstract

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 AB accessory muscle variations in cadavers donated to the UC Davis Body Donation Program, (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 cadavers (31.2%) presented ABDM and AB accessory muscle variations. These variations were clearly categorized 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: ABDM 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.

Bilateral and symmetrical accessory digastric muscles

“…Due to the highly variable anomaly, some classi cation systems had been made by researchers. As shown in the Anderson's study, the variation of ABDM could be classi ed into six types based on its origin and insertion, including atavistic, origin, insertion, mixed, complex and deletion types [2]. Kim and Loukas also used some pattern diagrams to describe the variations of the digastric muscle [8].…”