Asymmetric Complex Variation of the Anterior Belly of the Digastric Muscle With Accessory Slips and Modified Intermediate Tendon Morphology

The anterior belly of the digastric muscle (ADB) is known for its marked morphologic variability, which may have important clinical and surgical implications in the submental region. During the educational dissection of a formalin-fixed adult male cadaver, a rare complex asymmetric variation of the ADB was identified. On the right side, the ADB was composed of 4 distinct muscular slips, including 2 deep slips originating from the digastric fossa and 2 superficial accessory slips arising from the inferior border of the mandible. These slips converged in a fan-like manner toward a flattened intermediate tendon (IMT). In contrast, the left ADB consisted of 2 compact slips originating predominantly from the digastric fossa. The IMT and posterior bellies were unremarkable, and no midline fusion was observed. This case demonstrates a complex, asymmetric type II anterior digastric variation and underscores the need to recognize such configurations during imaging interpretation and during surgical procedures involving the submental region.