The biceps brachii muscle is a two-headed muscle located in the anterior compartment of the arm. Anatomical variations observed in the biceps brachii muscle are not uncommon. However, very few incidents are reported on a unilateral, rarely described accessory pectoral head in conjunction with the more commonly seen accessory humeral head. This anatomical variation was encountered during routine educational dissection and is the first case of this specific type of four-headed biceps brachii muscle to be described in detail. Variations in the biceps brachii morphology are linked to neurovascular compression, kinematic irregularities and variations in the musculocutaneous nerve. Knowledge of anatomical variations in the biceps brachii muscle is essential for understanding kinematic abnormalities, preventing surgical complications, and diagnosing symptoms of neurovascular compression.
Mosig et al. (Mon,) studied this question.